Impaginato 141 Adv. Hort. Sci., 2024 38(2): 141­153 DOI: 10.36253/ahsc­15535 Field evaluation of biostimulants on growth, flowering, yield, and quality of snap beans in subtropical environment S.H. Brengi 1, I.A. Abouelsaad 1, 2, (*), R.M. Mahdy 3, A.A. Khadr 1 1 Horticulture Department, Faculty of Agriculture, Damanhour University, Damanhour 22516, Egypt. 2 Faculty of Desert Agriculture, King Salman International University, Ras Sedr 46618, Egypt. 3 Horticulture Department, Faculty of Agriculture, Tanta University, Tanta 31527, Egypt. Key words: Chitosan, potassium silicate, 6­benzylaminopurine, snap bean, tria­ contanol. Abstract: The cultivation of snap beans (Phaseolus vulgaris L.) in subtropical regions faces environmental challenges leading to potential declines in yield. This study explores the efficacy of biostimulants as a solution, specifically inves­ tigating spraying treatments with 6­benzylaminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) on the snap bean cv. Paulista. Over two growing seasons with late sowing and elevated summer tempera­ tures, the research assesses growth, flowering, yield, and quality. Notably, 5 ppm TRIA demonstrates the most significant impact on plant growth and leaf nutrient content. Treatments with 40 ppm 6­BA, 5 ppm TRIA, or 200 ppm KSi exhibit notable effects on inflorescence flower count and flowers per plant. These treatments prove most effective for crucial green pod yield measures, including the number and weight of marketable pods. Moreover, 40 ppm 6­BA or 5 ppm TRIA significantly enhances pod characteristics, such as length, diame­ ter, and weight, consistently improving over both seasons. Particularly, 5 ppm TRIA outperforms in enhancing the chemical quality of pods throughout the study. Overall, the findings suggest that the application of 5 ppm TRIA offers the most favorable enhancements for the growth, flowering, productivity, and quality of snap bean plants in subtropical field conditions. 1. Introduction The global population is now and will continue to exert increased pres­ sure on the need for food. Hence, it is essential for farmers to annually increase food production with the existing resources to fulfill this demand. Common bean (Phaseolus vulgaris L.) is a common vegetable that includes both snap and dry beans (Lin et al., 2008). In Egypt, farmers dedicate 27363 hectares to green bean cultivation, yielding 284299 tons annually (FAOSTAT, 2021).However, snap beans have a notable suscepti­ (*) Corresponding author: ibrahim.abouelsaad@ksiu.edu.eg Citation: BRENGI S.H., ABOUELSAAD I.A., MAHDY R.M., KHADR A.A., 2024 ­ Influence of ground cover and tunnels on production of Red Russian kale in urban gardens. ­ Adv. Hort. Sci., 38(2): 141­153 Copyright: © 2024 Brengi S.H., Abouelsaad I.A., Mahdy R.M., Khadr A.A. This is an open access, peer reviewed article published by Firenze University Press (http://www.fupress.net/index.php/ahs/) and distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Competing Interests: The authors declare no competing interests. Received for publication 17 December 2023 Accepted for publication 7 March 2024 AHS Advances in Horticultural Science https://doi.org/10.36253/ahsc-15535 http://www.fupress.net/index.php/ahs/ http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ Adv. Hort. Sci., 2024 38(2): 141­153 142 bility to high summer temperatures, particularly when subjected to delayed planting, like in April and May under Egyptian field conditions (El­Bassiony et al., 2012). While it has been stated that the optimal temperature for bean plants is 23°C (Dickson and Boettger, 1984). Omae et al. (2006) observed that the occurrence of high summer temperatures (26°C Min and 30°C Max.) during the initiation of the blooming stage had an adverse impact on the quanti­ ty and the weight of pods. Along with this, climate models predict a 50% decrease in global cultivated area by 2050 due to global warming (Rippke et al., 2016; Rama Rao et al., 2022). One potential approach to enhancing snap bean production is through the breeding of new cultivars. However, it is important to note that this process often takes a significant amount of time and may provide limited results (Xiong et al. , 2022). Biostimulants provide a compelling alternative in the context of degraded agricultural regions and the risks associated with climate change. In recent times, there has been increased research focusin the utiliza­ tion of biostimulantsin the form of plant growth reg­ ulators (e.g., 6­benzylaminopurine; 6­BA as a synthet­ ic cytokinin, and triacontanol; TRIA), chitosan (Ch), and trace elements (e.g., silicon; Si) that have been found effective in improving plant productivity (Du Jardin, 2015; Yaghubi et al. , 2019; Islam and Mohammad, 2020; Hassan et al., 2021; Stasińska­ Jakubas and Hawrylak­Nowak, 2022). Although cytokinins (CKs) have vital function in controlling plant development, they have also been shown to confer other benefits, such as improving photosyn­ thetic rates, photosynthetic pigments, and nutrient uptake (Aremu et al., 2020; Li et al., 2021). In a study conducted by Mostafa and Brengi (2018), it was shown that the application of 6­BA solution on okra leaves resulted in improved yield and chemical com­ position. Furthermore, Yang et al. (2016) illustrated that the treatment with 6­BA resulted in an improve­ ment in several aspects of wheat grain development, including wheat grain filling and endosperm cell divi­ sion under heated growth conditions. It is a widely recognized that TRIA is plant growth regulator (Islam and Mohammad, 2020). Triacontanol is a saturated alcohol initially discovered in alfalfa (Ries et al., 1977) and is found naturally as a wax coating on a variety of plant species (Islam and Mohammad, 2020). In addi­ tion to its function in eliciting responses to stresses, TRIA is participated in plant growth, production, and vital physiological processes (Faiz et al., 2024). In this manner, Waqas et al. (2016) showed that both nor­ mal growth and heat stress conditions, TRIA treat­ ment of mung bean plants resulted in improved plant growth, leaf chlorophyll content, nutrients, and pro­ tein content. Chitosan is a naturally carbohydrate polymer that has been produced from chitin, a sub­ stance found in the shells of crustaceans (Hidangmayum et al., 2019). It is non­toxicand bio­ compatible, making it potentially useful in agriculture and biotechnology (Stasińska­Jakubas and Hawrylak­ Nowak, 2022). Basically, Ch improves physiological responses and reduces the negative effects of abiotic stressors through the secondary messengers (Hidangmayum et al., 2019). Therefore, Ch is thought to be a viable exogenous addition for increasing crop production and overcoming abiotic stress (Stasińska­ Jakubas and Hawrylak­Nowak, 2022). Apart from this, Ch also enhanced the productivity of many crops such as tomatoes (El­Tantawy, 2009), cowpea (Farouk and Amany, 2012) and cucumber (Ali et al., 2020). Generally, silicon (Si)ranks among the most abundant elements found in soil (Souri et al., 2021). Recently, the connections between Si and various biological processes in multiple crops were clarified, and silicon was recognized as one of the vital nutrients required by plants (Zargar et al., 2019). Silicon is engaged in many biological activities such as photo synthesis, nutrient uptake, and plant adaptation to stress (Zargar et al., 2019; Souri et al., 2021). Potassium sili­ cate (KSi) is usually used as biostimulant and a pro­ ducer of both soluble K and Si (Yaghubi et al., 2019). It is well recognized that K is a core element and par­ ticipates in a vital function in cell division, protein synthesis, the formation of sugars, and plant growth, as well as vital processes such as plant photosynthe­ sis and stomata movement (Ali et al., 2021). Although previous studies have examined the individual impacts of these elicitors on plant growth, a comprehensive investigation into their effects specifically on snap bean plants remains lacking. Moreover, these studies evaluated different parame­ ters and were conducted in different growing envi­ ronments; consequently, the field evaluation of these biostimulants under a particular subtropical summer conditions are required. Thus, this research was cre­ ated to test the beneficial impacts of 6­BA, Ch, TRIA, or KSi on the growth, blooming, productivity, and quality of snap bean plants grown in delayed summer cultivation in a subtropical environment. Abouelsaad ‐ Field evaluation of biostimulants 143 2. Materials and Methods Snap bean field conditions Field trials were undertaken in the Sidi Ghazy Region of Kafr El­Dawar city, located in the Beheira Governorate of Egypt. These experiments were done during the seasons of 2021 and 2022. The geographi­ cal coordinates of the study area are around 31°07ʹN latitude and 30°08ʹ E longitude. The region has an arid climatic condition characterized by an annual precipitation of about 90­110 mm, mostly in the form of ineffectual showers during the winter. Figure 1 presents a summary of the monthly temperatures, measured over the course of two cultivation seasons. The source of this data originates from the Egyptian Ministry of Agriculture and Reclamation of Soils, bul­ letin of agricultural meteorological data. Samples from the trial soil were subjected to drying and then sifted by a two­mm sieve. These samples were then analyzed using the protocols outlined by Page et al. (1982). Experimental soil had a clay texture (22.5% sand, 35.4% silt, and 42.1% clay) with a pH of 8.14, EC value of 1.19 dsm­1, and an organic material level of 1.75%, as an average over the two seasons. Plant material, experimental design, and treatments Seeds of the snap bean (Phaseolus vulgaris L.) cv. Paulista (Alsafwa company, Egypt) were planted on May 1st and May 2nd in the seasons of 2021 and 2022, respectively. The selection of this cultivar was based on its significant economic worth in both local and for­ eign markets. The experimental site was plowed and leveled adequately before plots were established in accordance with the experimental layout. The experi­ mental treatments were organized as stated by the Randomized Complete Block Design (RCBD). The trial consisted of 9 treatmentswith3replicates (plots). The seeds were manually cultivated on a single side of the ridge, with a spacing of 10 cm between each seed. The ridge itself had a dimension of 60 cm and 5 m long. Each plot consisted of three ridges, and the total size of each plot was 9 m2.Two guard ridges were present between each treatment to prevent spray drift. In this investigation, four biostimulants plus a con­ trol were examined, namely 6­benzylaminopurine (6­ BA, Sigma­Aldrich, USA) at 20 and 40 ppm, chitosan (Ch, Sigma­Aldrich, USA) at 100 and 200 ppm, triacon­ tanol (TRIA, Sigma­Aldrich, USA) at 2.5 and 5 ppm, potassium silicate (KSi, Sigma­Aldrich, USA) at 100 and 200 ppm, and a control group treated with distilled water. Former studies were employed to identify the suitabledose range of 6­BA (Abouelsaad and Brengi, 2022; Zarea and Karimi, 2023) Ch (Ibrahim and Ramadan, 2015; Stasińska­Jakubas and Hawrylak­ Nowak, 2022), TRIA (Islam and Mohammad, 2020), and KSi (Ibrahim et al., 2020). Foliar treatments were employed 3 times, 15 days after seed sowing, fol­ lowed by further applications every 15 days after­ wards. The plants were subjected to a foliar applica­ tion employing a knapsack sprayer throughout the afternoon until drop­off. All treatments were provided with an equal total quantity of 50 N, 60 P, and 60 K (kg ha−1) fertilizer for the duration of the season. These fertilizers(surface broadcast application) were given in two equal por­ tions, with the first dosage delivered during the third week after seed planting and the second dose applied during the seventh week. Nitrogen, P, and K were provided as ammonium nitrate, single superphos­ phate, and potassium sulfate, respectively. All the required practices for cultivating snap beans were properly conducted as required. Plant growth, flowering, chlorophyll content and min‐ eral analysis After 50 days of planting, three plants from each Fig. 1 ­ Monthly means of maximum (T Max.) and minimum (T Min.) temperature during the two studied seasons (sum­ mer 2021 and 2022) (Egyptian Ministry of Agriculture and Reclamation of Soils, bulletin of agricultural meteo­ rological data). Adv. Hort. Sci., 2024 38(2): 141­153 144 replicate (nine from each treatment) were taken for measuring the height (cm), branch number (plant­1), and number of leaves (plant­1). The relative content of chlorophyll in snap bean were assessed using the Chl meter instrument (SPAD­502) manufactured by Konica Minolta Sensing in Japan. The assessment included measuring the number of inflorescences plant­1, number of flowers in the inflorescence, total number of flowers plant­1, and evaluating the length of the inflorescence (cm) (at 50% flowering according to Schwartz and Langham, 2010) The fresh weight (g) of shoot was measured, and subsequently, the plants were subjected to oven­drying at a temperature of 60°C till their weights stabilized, leading to the deter­ mination of the dry weight (g) of the shoot. Plant leaves area (cm2) was conducted using a mathemati­ cal analysis that examined the relationship between the dry weight of leaves (plant­1) and the dry weight and area of 20 discs taken from fresh leaves using a borer with a known diameter. Wallace and Munger (1965) established this relationship and presented it in the following formula: Leaves area (cm2) = leaves dry weight (g) x 20 discs area (cm2)/20 discs dry weight (g) Micro­Kjeldahl was employed to assess Nin snap bean leaves (Sáez­Plaza et al., 2013), but P level was quantified by colorimetric techniques (Watanabe and Olsen, 1965). Zinc, Fe, Mg, and Mn were analyzed in leaves using the atomic absorption spectrophotome­ ter model Perkin Elmer 3100, while K and Ca levels of leaf tissue were quantified by a flame­photometer (CORNING M410) as employed by Munns et al. (2010). Green pod yield and quality At harvest time (65 days from sowing), observa­ tions were recorded for seven characters viz., the number of pods (plant­1), the weight of pods (g plant­ 1), the number of marketable pods (plant­1), the weight of marketable pods (g plant­1), the mean of pod weight (gm), pod length (cm) and pod diameter (mm). This research considers pods that possess sig­ nificant quality traits that are important for the export market, such as well­formedness, uniformity, straightness, and absence of flaws, as being consid­ ered marketable. Total N (%) was determined in green pods using the micro­Kjeldahl apparatus as defined by Sáez­Plaza et al. (2013). Subsequently, total protein (%) was calculated using N% (Mariotti et al., 2008). The detection of vitamin C in the green pods was carried out at a wavelength of 525 nm, uti­ lizing the methodology previously established by Srivastava and Singh (1988). To establish a standard curve, the utilization of ascorbic acid (Analytical Reagent, Solarbio) was employed. The quantification of vitamin C is presented in mg100 g­1 FW. The mea­ surements of crude fiber and soluble sugar in pods were conducted using the methodology established by Slavin (1987) and Rady et al. (2019), respectively. Data analysis The data underwent statistical analysis using a one­way factorial design within the framework of a Randomized Complete Block Design (RCBD). The COSTAT program (CoStat program version 6.311, 2005) was used to conduct a statistical analysis, namely the Duncan’s multiple range test, with a sig­ nificance threshold of P≤0.05, for the purpose of comparing the means. 3. Results and Discussion Snap bean growth and chlorophyll contents Changes in snap bean growth parameters caused by the foliar application of growth elicitors (6­BA, Ch, TRIA, or KSi) are presented in Tables 1 and 2. The application of all treatments boosted plant growth, as clarified by the increases in snap bean height, leaves area, shoot fresh and dry weights. In most instances, the applied treatments also resulted in boosted the number of leaves and branches, although in the case of the treatment with 100 ppm Ch, both seasons’ values were similar to the control treatment. Several studies have provided evidence suggesting that the applications of 6­BA, Ch, and KSi have the potential to increase the overall snap bean growth (Werner and Schmülling, 2009; Hidangmayum et al., 2019; Yaghubi et al., 2019; Gomaa et al., 2021). Cytokinins (CKs) are often char­ acterized as hormones that stimulate growth; howev­ er, it should be noted that several substances exhibit­ ing CK activity have been discovered to control many features of plant development (Haberer and Kieber, 2002). Cytokinins influence cell multiplication, that in turn influences plant development, and they also promote adventitious buds growth (Kieber and Schaller, 2014). Such substances, including exoge­ nous applications, were used to promote growth in crops and vegetables (Yang et al., 2016; Mostafa and Brengi, 2018; El­Areiny et al., 2019; Aremu et al., Abouelsaad ‐ Field evaluation of biostimulants 145 2020; Abouelsaad and Brengi, 2022). Additionally, Ch, a biopolymer, employed in crops production primari­ ly owing to its biocompatible and biodegradable nature, together with its notable biological activity (Hidangmayum et al., 2019). Despite not being a con­ stituent of plant tissues, Ch significantly boosts the development and growth of plants (Stasińska­ Jakubas and Hawrylak­Nowak, 2022). This was con­ firmed by El­Miniawy et al. (2013), who claimed that spraying Ch increased the growth (height, leaf area, and weight) of strawberry cv. Sweet Charlie. In another study, foliar application of Ch increased both the growth and nitrate reductase activity of okra (Mondal et al., 2012). Recently, ample evidence has shown that Si is a key nutrient for crops such as grains, legumes, and vegetables (Souri et al., 2021). Both in vitro and field investigations confirmed the favorable benefits of Si in boosting plant develop­ ment, especially in stressful situations (Zargar et al., 2019; Souri et al., 2021). According to Eneji et al. (2008), Si has been shown to act as a bioregulator and have the capacity to enhance plant develop­ ment. The usage of KSihas shown a substantial influ­ ence on the growth of several agricultural crops such as maize and strawberry (Yaghubi et al., 2019; Ibrahimet al., 2020; Gomaa et al., 2021). Nevertheless, within the range of applied treat­ ments, it was observed that the application of 5 ppm TRIA had a more pronounced impact on plant growth over both seasons. As average for the two growing seasons, with 5 ppm TRIA the snap bean height boosted by 17.23%, the leaf area expanded by Table 2 ­ The number of branches, number of leaves, and leaves area of snap beans affected by 6­benzylaminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the 2021 and 2022 seasons Table 1 ­ Plant height, shoot fresh weight, and shoot dry weight of snap beanas affected by 6­benzylaminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the 2021 and 2022 seasons Means with different letters for each plant parameter are considered significantly different (p<0.05) using the Duncan's multiple range test. Treatment Plant height (cm) Shoot fresh weight (g) Shoot dry weight (g) 2021 2022 2021 2022 2021 2022 Control 44.30 e 45.63 d 293.07 d 301.90 d 29.83 d 30.89 e 6­BA (20 ppm) 50.33 bc 52.33 ab 326.02 c 339.03 c 35.64 bc 37.30 cd 6­BA (40 ppm) 52.30 a 53.83 a 364.40 ab 375.09 ab 37.79 b 39.04 bc Ch (100 ppm) 48.43 cd 49.93 c 351.40 b 361.91 bc 34.77 c 35.99 d Ch (200 ppm) 47.97 d 51.67 bc 357.60 b 385.00 ab 35.48 bc 38.66 bc TRIA (2.5 ppm) 49.67 cd 52.80 ab 355.13 b 377.60 ab 36.62 bc 39.31 bc TRIA (5 ppm) 51.90 ab 53.53 a 373.93 a 386.23 a 41.31 a 42.84 a KSi (100 ppm) 48.17 d 52.17 ab 355.83 b 385.54 a 36.46 bc 40.00 b KSi (200 ppm) 50.10 bc 53.93 a 360.27 ab 387.89 a 35.94 bc 39.16 bc Means with different letters for each plant parameter are considered significantly different (p<0.05) using the Duncan's multiple range test. Treatment No. of branches plant­1 No. of leaves plant­1 Leaves area (cm2) 2021 2022 2021 2022 2021 2022 Control 6.67 c 6.67 b 20.00 f 20.67 c 2712.00 e 2793.67 e 6­BA (20 ppm) 7.33 abc 7.33 ab 21.33 cde 22.33 b 2901.33 d 3017.00 cd 6­BA (40 ppm) 8.33 a 8.33 a 23.33 a 24.00 a 3144.67 a 3292.67 a Ch (100 ppm) 7.00 bc 7.00 ab 20.33 ef 20.67 c 2845.00 d 2930.33 de Ch (200 ppm) 7.33 abc 8.00 ab 21.00 def 22.67 ab 2992.00 c 3222.00 ab TRIA (2.5 ppm) 7.67 abc 8.33 a 21.67 bcd 23.33 ab 3096.67 ab 3237.33 ab TRIA (5 ppm) 8.00 ab 8.33 a 22.67 ab 23.67 ab 3130.67 a 3230.67 ab KSi (100 ppm) 7.67 abc 8.33 a 21.33 cde 23.33 ab 2886.67 d 3127.00 bc KSi (200 ppm) 7.67 abc 8.33 a 22.33 abc 24.00 a 3018.00 bc 3250.00 ab 146 Adv. Hort. Sci., 2024 38(2): 141­153 15.54%, the snap bean fresh weight boosted by 27.76%, and the shoot dry weight boosted by 38.58% as compared to the control. Triacontanol (TRIA) is plant growth regulator that has a significant function in facilitating many plants metabolic processes, ulti­ mately resulting in enhanced growth and develop­ ment (Naeem et al., 2012; Islam and Mohammad, 2020). Its foliar application at low concentrations stimulates the plant biomass of the crops under both control and stressful circumstances (Naeem et al., 2012). A growing body of research has shown that TRIA is an important factor in controlling a wide range of plant morphological responses. One notable effect is its ability to promote many aspects of plant growth, such as increased height, enhanced biomass, greater leaf number, and expanded leaf area across multiple crop species (Naeem et al., 2012). This increase in plant growth might be because TRIA acti­ vates L (+)­adenosine, a second messenger that sends signals throughout the plant to boost growth by promoting cell expansion and proliferation (Masroor et al., 2006; Naeem et al., 2012). The growth of plants is greatly impacted by the level of photosynthetic pigments, that is critical for photosynthesis. In the current study, the use of spraying treatments has resulted in enhancements in chlorophyll contents, but these improvements were seen at comparable levels in most instances (Table 3). Studies have also shown the effect of CKs, Ch, TRIA, orKSi on increasing the content of photosyn­ thetic pigments. Cytokinins can impede or decelerate the process of plant senescence by inhibiting the degradation of chlorophyll, hence preserving the green color of the leaves (Werner and Schmülling, 2009; Kieber and Schaller, 2014). Meanwhile, treat­ ing wheat leaves with 6­BA has been shown to boost the production of the chlorophyll founder, D­ aminolevulinic acid (Wang et al., 2022). Also, the spray of Ch has been reported to boost the levels of photosynthetic pigments in rice plants (Pongprayoon et al., 2013) and creeping bentgrass plants suffering temperature stress conditions (Huang et al., 2021). In another study, TRIA shown a notable increase in pig­ ment content, namely chlorophyll a, b, and carotenoids, by 25.6, 33.9, and 13.0% respectively, in the leaves of basil plants, relative to the control (Hashmi et al., 2011). Also, Masroor et al. (2006) showed similar results in their study, where they noted a substantial rise in chlorophyll and carotenoid content in tomato seedlings that were treated with TRIA. Former research has also verified the beneficial influence of KSi on the chlorophyll levels in plant leaves (Yaghubi et al., 2019; Zargar et al., 2019; Tejada­Ruiz et al., 2020; Gomaa et al., 2021). Elemental analysis Nutrients are fundamental for the growth and productivity of agricultural crops. They are needed in varying quantities and play key functions in various biological processes. The application of 6­BA, Ch, TRIA, or KSi contributed to a higher level of macronu­ trients and micronutrients in snap bean leaves, with some exceptions (Tables 4 and 5). For instance, the treatments with 100 ppm Ch during the first season, 200 ppm Ch during the second season, and 100 ppm Si throughout both seasons demonstrated a P level comparable to that of the control. Additionally, the application of Ch at concentrations of 100 and 200 ppm resulted in limited changes to the Ca and Zn content of the leaves. Previous studies have also doc­ umented the positive effects of CKs and Si on the content and uptake of essential nutrients. Cytokinins regulate the plants’ capacity to uptake various ele­ ments, like N, P, and K (Argueso et al., 2009). In a study conducted by Abouelsaad and Brengi (2022), the application of CKs through foliar means led to a rise in the N and P levels in potato leaves, relative to the control. Haberer and Kieber (2002) reported that CKs regulate the expression of multiple transporter genes, thereby influencing the plant’s ability to uptake nutrients. From this perspective, some stud­ ies also showed that Si treatment boosts macronutri­ Table 3 ­ Relative chlorophyll content (SPAD value) of snap bean as affected by 6­benzylaminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the 2021 and 2022 seasons Means with different letters for each plant parameter are consi­ dered significantly different (p<0.05) using the Duncan's multiple range test. Treatment Relative chlorophyll content (SPAD value) 2021 2022 Control 41.33 c 41.67 c 6­BA (20 ppm) 41.67 bc 43.00 b 6­BA (40 ppm) 42.67 a 43.67 ab Ch (100 ppm) 41.67 bc 43.33 ab Ch (200 ppm) 42.33 ab 43.67 ab TRIA (2.5 ppm) 42.67 a 43.33 ab TRIA (5 ppm) 43.00 a 44.00 a KSi (100 ppm) 42.67 a 43.00 b KSi (200 ppm) 42.67 a 43.67 ab Abouelsaad ‐ Field evaluation of biostimulants 147 ent (e.g., P, K, and Ca) and micronutrient (e.g., Cu, and Fe) absorption in crops (Zargar et al., 2019). The results also showed that 5 ppm TRIA signifi­ cantly raised the average contents of N (9.10%), P (10.2%), K (32.73%), Ca (13.33%), Mg (38.66%), Zn (39.06%), Fe (26.8%), and Mn (14.23%), compared to the control, throughout the two successive growing seasons (Tables 4 and 5). Notably, this treatment was the most effective among the spraying treatments for all the examined nutrients. As previously reported, the use of TRIA demonstrated a significant influence on the levels of N, P, and K in some crops (Masroor et al., 2006; Naeem et al., 2012; Islam and Mohammad, 2020). Despite limited research on the impact of TRIA on micronutrient content, it may be inferred that TRIA induces modifications in plants, resulting in changed nutrient contents. In a manner similar to the 5 ppm TRIA treatment, the application of 40 ppm of 6­BA revealed the highest content of nutrients, but only for P, Fe, Zn, and Mn (Tables 4 and 5). Flowering characteristics Flowering characteristics (e.g., number of flowers and inflorescences) can have a great influence on the productivity of crops. In this study, the applied treatments had a beneficial effect on the length of the inflorescence in comparison to the control treatment, and the 40 ppm 6­BA treatment achieved Table 4 ­ Nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca) of snap bean leavesas affected by 6­benzylaminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the 2021 and 2022 seasons Means with different letters for each plant parameter are considered significantly different (p<0.05) using the Duncan's multiple range test. Treatment N (%) P (%) K (%) Ca (%) 2021 2022 2021 2022 2021 2022 2021 2022 Control 3.20 g 3.17 g 0.48 f 0.50 e 2.67 e 2.69 f 2.08 f 2.12 d 6­BA (20 ppm) 3.30 f 3.25 f 0.54 b 0.53 bcd 2.86 d 2.81 e 2.15 def 2.17 c 6­BA (40 ppm) 3.40 bc 3.36 c 0.58 a 0.56 a 3.06 b 2.99 c 2.27 bc 2.22 b Ch (100 ppm) 3.31 ef 3.29 e 0.49 ef 0.48 f 2.89 d 2.92 d 2.08 f 2.12 d Ch (200 ppm) 3.37 cd 3.36 c 0.51 cde 0.51 e 2.92 cd 2.94 cd 2.12 ef 2.10 d TRIA (2.5 ppm) 3.43 b 3.42 b 0.51 cde 0.53 cd 3.10 b 3.16 ab 2.31 b 2.33 a TRIA (5 ppm) 3.48 a 3.47 a 0.53 bc 0.55 ab 3.25 a 3.21 a 2.40 a 2.36 a KSi (100 ppm) 3.31 f 3.33 d 0.50 def 0.52 de 2.95 cd 2.93 cd 2.19 de 2.22 b KSi (200 ppm) 3.36 de 3.38 c 0.52 bcd 0.54 abc 3.02 bc 3.11 b 2.21 cd 2.24 b Table 5 ­ Manganese (Mn), iron (Fe), zinc (Zn), and manganese (Mn) of snap bean leavesas affected by 6­benzylaminopurine (6­BA), chi­ tosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the 2021 and 2022 seasons Means with different letters for each plant parameter are considered significantly different (p<0.05) using the Duncan's multiple range test. Treatment Mg (%) Fe (%) Zn (%) Mn (%) 2021 2022 2021 2022 2021 2022 2021 2022 Control 0.36 e 0.39 g 127.67 d 122.33f 37.33 e 40.33 e 48.33 d 50.00 e 6­BA (20 ppm) 0.41 d 0.43 f 151.33 ab 146.33 c 48.00 b 50.67 b 51.00 cd 52.67 d 6­BA (40 ppm) 0.49 ab 0.47 cd 159.00a 154.67 a 54.00 a 52.00 ab 55.33 ab 56.00 a Ch (100 ppm) 0.44 cd 0.45 e 137.00 cd 135.00 e 41.00 de 41.67 de 51.33 c 50.00 e Ch (200 ppm) 0.48 abc 0.49 bc 141.00 c 139.00 de 43.00 cd 42.00 de 55.67 a 54.00 abcd TRIA (2.5 ppm) 0.48 ab 0.49 bc 155.67 a 152.33 ab 48.67 b 50.33 b 52.33 c 53.00 cd TRIA (5 ppm) 0.51 a 0.53 a 160.67 a 156.67 a 53.67 a 54.33 a 57.00 a 55.33 ab KSi (100 ppm) 0.45 bc 0.47 de 139.33 c 142.00 cd 43.00 cd 44.00 cd 52.67 bc 53.67 bcd KSi (200 ppm) 0.49 a 0.50 b 145.67 bc 147.00 bc 47.00 bc 45.33 c 56.67 a 55.00 abc Adv. Hort. Sci., 2024 38(2): 141­153 148 the highest value in both seasons (Table 6). Additionally, except for 100 ppm Ch (first season) and 20 ppm 6­BA (second season), the foliar treatments had a stimulating impact on the number of inflorescences plant­1 (Table 6). While there is less documentation on the impact of Ch and KSi on promoting vegetable flowering, it has been shown to have positive effects on flower crops (Pichyangkura and Chadchawan, 2015; Amer, 2020). Among the applied treatments in this study, the use of 40 ppm 6­ BA, 5 ppm TRIA, and 200 ppm KSi resulted in the most significant increase in the number of flowers in the inflorescence and number of flowers plant­1, a trend that persisted over both seasons. Several studies have shown the role of CKs as pivotal regulators of inflorescence morphology in plants, primarily through regulating meristem activity (Kieber and Schaller, 2014). According to D’Aloia et al. (2011), flowering is induced in Arabidopsis plants by exogenous CKs applied during non­inductive short days. Similar findings were reported by Rylott and Smith (1990), who demonstrated that synthetic CKs enhance plant productivity and promote competition between generative and vegetative organs. In the current study, the number of flowers in the inflorescence and the number of flowers plant­1 exhibited respective increases of 22.8% and 50.15% in snap bean treated with 5 ppm TRIA, relative to the control treatment (Fig. 2). The application of TRIA has been found to exert a positive influence on the flow­ ering process of various crops. This was confirmed by Baba et al. (2017), who clarified that TRIA raised the number of flowers plant­1 while also influencing the timing of flowering in strawberry cv. Camarosa. In addition, Sharma et al. (2011) tested the effects of TRIA on olives and found that it enhanced the num­ ber of flowers in relation to the control. However, some treatments, such as the application of 100 ppm Ch and 20 ppm 6­BA, did not have any notable influ­ ence on the number of flowers for the inflorescence Table 6 ­ Number of inflorescences and length of inflorescenceof snap bean as affected by 6­benzylaminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the 2021 and 2022 seasons Means with different letters for each plant parameter are considered significantly different (p<0.05) using the Duncan's multiple range test. Treatment No. of inflorescences plant­1 Length of inflorescence (cm) 2021 2022 2021 2022 Control 9.00 c 9.33 c 7.50 f 7.96 f 6­BA (20 ppm) 10.33 ab 10.00 bc 10.63 cd 10.87 c 6­BA (40 ppm) 11.33 a 11.67 a 13.53 a 12.93 a Ch (100 ppm) 10.00 bc 10.33 b 8.83 e 9.53 de Ch (200 ppm) 10.67 ab 11.33 a 9.83 d 9.93 d TRIA (2.5 ppm) 11.00 ab 11.67 a 10.83 c 11.20 c TRIA (5 ppm) 11.33 a 11.67 a 12.43 b 11.77 b KSi (100 ppm) 10.33 ab 11.33 a 8.87 e 9.30 e KSi (200 ppm) 11.33 a 11.67 a 9.83 d 9.66 de Fig. 2 ­ The number of flowers in the inflorescence and number of flowers plant­1 of snap bean as affected by 6­benzy­ laminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the two studied seasons (summer 2021 and 2022). Means (bars) with different letters for each season are considered significantly differ­ ent (p<0.05) using the Duncan's multiple range test. Data are mean value ± SE. Abouelsaad ‐ Field evaluation of biostimulants 149 and number of flowers plant­1in relation to the con­ trol plants in both cultivation seasons (Table 6). Snap bean yield The value of crop yield is determined by the mar­ ketable yield, which is a crucial indicator of agricul­ tural productivity. In this study, relative to the con­ trol, it was noted that all the evaluated treatments had a positive impact on the total pod number plant ­ 1, except the treatments with Ch at 100 ppm or KSi at 100 ppm for only the first season (Table 7). Also, the implemented treatments caused a significant increase in the number of marketable pods plant ­1, the weight of total fresh pods plant ­1, and the weight of marketable pods plant ­1. Among the treatments used, applying 6­BA at a concentration of 40 ppm was the most effective treatment to achieve the highest yield parameters, a tendency that held across both seasons. This caused an increase in the total pod number by 36.67%, the number of marketable pods by 49.97%, the weight of total fresh pods by 38.23%, and the weight of mar­ ketable pods by 49.49% compared to the control treatment (Table 7). According to Jameson and Song (2016), an elevated concentration of CK throughout the developmental stages of pods and seeds has been identified as a constraining factor in their growth and maturation. A study by Nonokawa et al. (2012) also illustrated that CKfor both lupin and soy­ bean crops stopped flower abortion and improved pod set, which ultimately led to a higher yield. Nonetheless, the current data showed that the treat­ ments with 200 ppm Ch, 5 ppm TRIA, and 200 ppm KSi had comparable outcomes to the 40 ppm 6­BA treatment in terms of the number and weight of pods suitable for sale in both seasons (Table 7). Considering the data shown in Table 8, except for the application of 6­BA at 20 ppm and KSi at 200 ppm during the first season, all treatments exhibited enhancement in the weight of the pods. The applica­ tion of 6­BA (20 or 40 ppm) and TRIA at 5 ppm, resulted in statistically significant increases in pod length in both growing seasons. Furthermore, the application of Ch at 200 ppm resulted in a notable enhancement of the pod diameter during both grow­ ing seasons. Moreover, the implementation of 6­BA (20 or 40 ppm), TRIA (2.5 or 5 ppm), and KSi (100 or 200 ppm) exhibited a significant increase in pod diameter, specifically during the first growing season (Table 8). Similar studies have shown strong evidence supporting the efficacy of Ch, TRIA, and KSi applica­ tions for improving the yield and yield components of both vegetable and grain crops (Artyszak, 2018; Kocięcka and Liberacki, 2021). Green pod quality The value of yield quality extends beyond mere productivity. It encompasses economic, environmen­ tal, social, and health aspects, making it a crucial fac­ tor for agricultural production (Abouelsaad et al., 2022). As shown in Table 9, the effects of treatments on the quality features (ascorbic acid, fiber, soluble Table 7 ­ Number of total pods, number of marketable pods, fresh pods weight, and marketable pods weight of snap bean as affected by 6­benzylaminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the 2021 and 2022 seasons Means with different letters for each plant parameter are considered significantly different (p<0.05) using the Duncan's multiple range test. Treatment No. of total pods plant­1 No. of marketable pods plant­1 Fresh pods weight (g plant­1) Marketable pods weight (g plant­1) 2021 2022 2021 2022 2021 2022 2021 2022 Control 19.00 f 17.67 e 9.43 e 9.33 d 100.08 g 92.69 e 49.71 d 48.95 d 6­BA (20 ppm) 22.33 bcd 21.00 d 12.67 bcd 11.67 c 118.65 bcd 110.61d 66.38 bc 61.45 c 6­BA (40 ppm) 25.67 a 24.33 a 14.00 a 14.00 a 137.06 a 129.13 a 73.20 a 74.29 a Ch (100 ppm) 20.00 ef 22 bcd 2.00 d 12.00 c 106.73 fg 116.9 bcd 64.04 c 63.76 c Ch (200 ppm) 21.00 cde 22 bcd 13.33 abc 13.67 ab 112.14 def 116.68 bcd 71.21 ab 72.48 ab TRIA (2.5 ppm) 22.67 bc 22.67 bc 12.33 cd 12.67 bc 121.11 bc 120.36 bc 65.90 bc 67.26 bc TRIA (5 ppm) 23.67 b 23.33 ab 13.67 ab 13.33 ab 126.77 b 123.98 ab 72.22 ab 70.84 ab KSi (100 ppm) 20.67 def 21.67 cd 12.00 d 12.67 bc 109.87 ef 115.19 cd 63.79 c 67.34 bc KSi (200 ppm) 22.00 bcd 23 abc 13.67 ab 13.33 ab 117.99 cde 122.36 abc 75.09 a 70.93 ab Adv. Hort. Sci., 2024 38(2): 141­153 150 sugar, and protein) of snap bean green pods were investigated. Except for plants treated with 6­BA at 20 ppm, the ascorbic acid content in the pods of treated plants was significantly increased with respect to the control in both cultivation seasons. Also, the treatments with 6­BA (40 ppm), TRIA (2.5 or 5 ppm), or KSi (200 ppm) significantly increased the amount of soluble sugar in the pods with respect to the control in both cultivation seasons. Moreover, it was observed that the application of 6­BA (20 and 40 ppm), Ch (200 ppm), TRIA (2.5 or 5 ppm), orKSi (200 ppm) resulted in enhancement of protein content within the pods, with respect to the control plants, across both seasons (Table 9).Comparable findings also demonstrated the beneficial effects of Cks, Ch, TRIA, orKSi on the levels of protein, soluble sugar, and ascorbic acid in cereal crops, vegetable, or legumes (Naeem et al., 2012; Artyszak, 2018; Hu et al., 2022). Moreover, snap beans should have fleshier green pods with little fiber content where immature pods are eaten as vegetables. In this study, the applied treatments significantly reduced the amount of fiber in the pods relative to the control group (Table 9). Overall, in both growth seasons, the TRIA (5 ppm) spraying treatment showed remarkable effi­ cacy across all quality criteria. Table 8 ­ Average of pod weight, pod length, fresh pods weight, and pods diameter of snap bean as affected by 6­benzylaminopurine (6­ BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the 2021 and 2022 seasons Means with different letters for each plant parameter are considered significantly different (p<0.05) using the Duncan's multiple range test. Treatment Average of pod weight (g) Pod length (cm) Pods diameter (mm) 2021 2022 2021 2022 2021 2022 Control 5.27 b 5.25 c 12.97 b 13.27 cd 6.67d 7.67 b 6­BA (20 ppm) 5.31 ab 5.27 b 13.57 a 13.70 ab 8.00 abc 8.00 ab 6­BA (40 ppm) 5.34 a 5.31 a 13.70 a 13.77 a 8.33 ab 8.33 ab Ch (100 ppm) 5.34 a 5.31 a 12.97 b 13.23 d 7.33 cd 8.33 ab Ch (200 ppm) 5.34 a 5.30 a 13.10 b 13.30 cd 8.33 ab 8.67 a TRIA (2.5 ppm) 5.34 a 5.31 a 13.40 ab 13.50 bc 8.00 abc 8.33 ab TRIA (5 ppm) 5.36 a 5.31 a 13.57 a 13.67 ab 8.33 ab 8.33 ab KSi (100 ppm) 5.32 ab 5.32 a 13.07 b 13.33 cd 7.67 ab 8.00 ab KSi (200 ppm) 5.36 a 5.32 a 13.37 ab 13.47 bcd 8.67a 8.33 ab Table 9 ­ The contents of ascorbic acid, fiber, soluble sugar, and protein in snap bean pods as affected by 6­benzylaminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), and potassium silicate (KSi) in the 2021 and 2022 seasons Means with different letters for each plant parameter are considered significantly different (p<0.05) using the Duncan's multiple range test. Treatment Ascorbic acid (mg 100 g FW­1) Fiber (g 100 g FW­1) Soluble sugar (g 100 g FW­1) Protein (%) 2021 2022 2021 2022 2021 2022 2021 2022 Control 17.43 d 18.60 c 3.51a 3.49 a 2.13 d 2.19 c 17.94 f 18.25 e 6­BA (20 ppm) 18.53 cd 19.73 bc 3.36 c 3.35 d 2.21 c 2.19 c 18.69 de 19.31 c 6­BA (40 ppm) 19.57 abc 20.38 ab 3.31 d 3.31 e 2.25 b 2.23 b 19.75 ab 19.44 c Ch (100 ppm) 19.70 abc 20.13 b 3.38 bc 3.36 d 2.20 c 2.21 bc 18.06 f 18.81 d Ch (200 ppm) 20.70 a 21.30 a 3.39 bc 3.37 cd 2.21 c 2.21 bc 19.13 cd 19.44 c TRIA (2.5 ppm) 19.31 bc 19.78 b 3.30 d 3.29 e 2.30 a 2.32 a 19.63 abc 19.88 b TRIA (5 ppm) 20.44 ab 20.61 ab 3.28 d 3.28 e 2.33 a 2.32 a 20.00 a 20.31 a KSi (100 ppm) 19.70 abc 20.07 b 3.40 bc 3.39 bc 2.20 c 2.21 bc 18.50 ef 18.81 d KSi (200 ppm) 19.87 abc 20.07 b 3.42 b 3.41 b 2.21 bc 2.23 b 19.13 cd 19.63 bc Abouelsaad ‐ Field evaluation of biostimulants 151 4. Conclusions The applications of 6­benzylaminopurine (6­BA), chitosan (Ch), triacontanol (TRIA), or potassium sili­ cate (KSi) by foliar spraying have the potential to enhance the development and agronomic characteris­ tics of snap bean plants.Specifically, the use of 5 ppm TRIA demonstrates the most advantageous improve­ ments in growth, blooming, yield, and overall quality. This study could potentially establish a theoretical framework for improving the commercial production of snap beans in summer conditions. Also, by demon­ strating the efficacy of biostimulants, sustainable agri­ cultural practices can enhance food production and environmental stewardship in subtropical regions. References ABOUELSAAD I.A., TEIBA I.I., El­BILAWY E.H., EL­ SHARKAWY I., 2022 ­ Artificial intelligence and reducing food waste during harvest and post‐harvest processes, pp. 63­ 82. ­ In: ACHARYA B., S. DEY, and M. ZIDAN (eds.) IoT‐based smart waste management for environ‐ mental sustainability. CRC Press, Boca Raton, FL, USA, pp. 196. ABOUELSAAD I., BRENGI S.H., 2022 ­ Effects of cytokinin types and concentrations on potato growth, yield, and quality under field conditions. ­ Alex. Sci. Exch. J., 43(4): 495­502. ALI M., AYYUB C.M., HUSSAIN Z., HUSSAIN R., RASHID S., 2020 ­ Optimization of chitosan level to alleviate the drastic effects of heat stress in cucumber (Cucumis sativus L.). ­ J. Pure Appl. Agric., 5(1): 30­38. ALI M.M.E., PETROPOULOS S.A., SELIM D.A.F.H., ELBAGO­ RY M., OTHMAN M.M., OMARA A.E.­D., MOHAMED M.H., 2021 ­ Plant growth, yield and quality of potato crop in relation to potassium fertilization. ­ Agronomy, 11(4): 675. AMER E.E.A., 2020 ­ Influence of irrigation levels, in pres‐ ence of potassium silicate sprays treatments on growth, flowering and chemical constituents of marigold (Tagetes erecta L.) plant. ­ Ann. Agric. Sci. Moshtohor, 58(4): 977­988. AREMU A.O., FAWOLE O.A., MAKUNGA N.P., MASONDO N.A., MOYO M., BUTHELEZI N.M.D., AMOO S.O., SPÍCHAL L., DOLEŽAL K., 2020 ­ Applications of cytokinins in horticultural fruit crops: Trends and future prospects. ­ Biomolecules, 10(9): 1222. ARGUESO C.T., FERREIRA F.J., KIEBER J.J., 2009 ­ Environmental perception avenues: the interaction of cytokinin and environmental response pathways. ­ Plant Cell Environ., 32(9): 1147­1160. ARTYSZAK A., 2018 ­ Effect of silicon fertilization on crop yield quantity and quality ‐ A literature review in Europe. ­ Plants, 7(3): 54. BABA T., ALI A., KUMAR A., WANI A.W., 2017 ­ Periodic response of vegetative growth of strawberry to salicylic acid and Triacontanol. ­ Int. J. Chem. Stud., 5(5): 2414­ 2417. D’ALOIA M., BONHOMME D., BOUCHÉ F., TAMSEDDAK K., ORMENESE S., TORTI S., COUPLAND G., PÉRILLEUX C., 2011 ­ Cytokinin promotes flowering of Arabidopsis via transcriptional activation of the FT paralogue TSF. ­ Plant J., 65(6): 972­979. DICKSON M.H., BOETTGER M.A., 1984 ­ Emergence, growth, and blossoming of Bean (Phaseolus vulgaris) at suboptimal temperatures. ­ J. Am. Soc. Hortic. Sci., 109(2): 257­260. DU JARDIN P., 2015 ­ Plant biostimulants: Definition, con‐ cept, main categories and regulation. ­ Sci. Hortic., 196: 3­14. EL­AREINY A.A., ALKHARPOTLY A.A., GABAL A.A., ABIDO A.I., 2019 ­ Potato yield and quality as affected by foliar application with cytokinin and salicylic acid. ­ J. Adv. Agric. Res., 24(1): 52­77. EL­BASSIONY A.M., GHONAME A.A., EL­AWADI M.E., FAWZY Z.F., GRUDA N., 2012 ­ Die positive Wirkung von Brassinosteroiden auf das Wachstum und die Produktivität von grünen Bohnen, gewachsenunterho‐ hen Temperaturen. ­ Gesunde Pflanz., 64(4): 175­182. EL­MINIAWY S.M., RAGAB E.M., YOUSSEF M.S., METWALLY A.A., 2013 ­ Response of strawberry plants to foliar spraying of chitosan. ­ Res. J. Agric. Biol. Sci., 9(6): 366­ 372. EL­TANTAWY E.M., 2009 ­ Behavior of tomato plants as affected by spraying with chitosan and aminofort as natural stimulator substances under application of soil organic amendments. ­ Pak. J. Biol. Sci., 12(17): 1164­ 1173. ENEJI A.E., INANAGA S., MURANAKA S., LI J., HATTORI T., AN P., TSUJI W., 2008 ­ Growth and nutrient use in four grasses under drought stress as mediated by silicon fertilizers. ­ J. Plant Nutr., 31(2): 355­365. FAIZ H., KHAN O., ALI I., HUSSAIN T., HAIDER S.T., SIDDIQUE T., LIAQUAT M., NOOR A., KHAN R.W., ASHRAF S., RASHID S., NOREEN A., ASGHAR S., ANJUM Q.S., 2024 ­ Foliar application of triacontanol ameliorates heat stress through regulation of the antioxidant defense system and improves yield of eggplant Title in the second language of the article: Amelioration of heat stress in eggplant through application of tricontanol. ­ Braz. J. Biol., 84: 1­10. FAOSTAT, 2021 ­ Statistical pocketbook world food and agriculture 2015. ­ FAO, Rome, Italy, pp. 232. FAROUK S., AMANY A., 2012 ­ Improving growth and yield of cowpea by foliar application of chitosan under water stress. ‐ Egypt. J. Biol., 14(1): 14­26. GOMAA M.A., KANDIL E.E., EL­DEIN A.A.M.Z., ABOU­ Adv. Hort. Sci., 2024 38(2): 141­153 152 DONIA M.E.M., ALI H.M., ABDELSALAM N.R., 2021 ­ Increase maize productivity and water use efficiency through application of potassium silicate under water stress. ­ Sci. Rep., 11(1): 224. HABERER G., KIEBER J.J., 2002 ­ Cytokinins. New insights into a classic phytohormone. ­ Plant Physiol., 128(2): 354­362. HASHMI N., KHAN M.M.A., NAEEM M., IDREES M., AFTAB T., MOINUDDIN A., 2011 ­ Ameliorative effect of tria‐ contanol on the growth, photosynthetic pigments, enzyme activities and active constituents of essential oil of Ocimum basilicum L. ‐ Med. Arom. Plant Sci. Biotechnol., 5(1): 20­24. HASSAN M.U., CHATTHA M.U., KHAN I., CHATTHA M.B., BARBANTI L., AAMER M., IQBAL M.M., NAWAZ M., MAHMOOD A., ALI A., ASLAM M.T., 2021 ­ Heat stress in cultivated plants: nature, impact, mechanisms, and mitigation strategies ‐ A review. ­ Plant Biosyst., 155(2): 211­234. HIDANGMAYUM A., DWIVEDI P., KATIYAR D., HEMAN­ TARANJAN A., 2019 ­ Application of chitosan on plant responses with special reference to abiotic stress. ‐ Physiol. Mol. Biol. Plants, 25(2): 313­326. HU W., SU Y., ZHOU J., ZHU H., GUO J., HUO H., GONG H., 2022 ­ Foliar application of silicon and selenium improves the growth, yield and quality characteristics of cucumber in field conditions. ­ Sci. Hortic., 294. HUANG C., TIAN Y., ZHANG B., HASSAN M.J., LI Z., ZHU Y., 2021 ­ Chitosan (Cts) alleviates heat‐induced leaf senes‐ cence in creeping bentgrass by regulating chlorophyll metabolism, antioxidant defense, and the heat shock pathway. ­ Molecules, 26(17): 5317. IBRAHIM E.A., RAMADAN W.A., 2015 ­ Effect of zinc foliar spray alone and combined with humic acid or/and chi‐ tosan on growth, nutrient elements content and yield of dry bean (Phaseolus vulgaris L.) plants sown at dif‐ ferent dates. ‐ Sci. Hortic., 184: 101­105. IBRAHIM M.F.M., ABD EL­SAMAD G., ASHOUR H., EL­SAWY A.M., HIKAl M., ELKELISH A., EL­GAWAD H.A., EL­ YAZIED A.A., HOZZEIN W.N., FARAG R., 2020 ­ Regulation of agronomic traits, nutrient uptake, osmolytes and antioxidants of maize as influenced by exogenous potassium silicate under deficit irrigation and semiarid conditions. ­ Agronomy, 10(8): 1212. ISLAM S., MOHAMMAD F., 2020 ­ Triacontanol as a dynamic growth regulator for plants under diverse environmental conditions. ­ Physiol. Mol. Biol. Plants, 26(5): 871­883. JAMESON P.E., SONG J., 2016 ­ Cytokinin: A key driver of seed yield. ­ J. Exp. Bot., 67(3): 593­606. KIEBER J.J., SCHALLER G.E., 2014 ­ Cytokinins. ­ The Arabidopsis Book, 12: 1­35. KOCIĘCKA J., LIBERACKI D., 2021 ­ The potential of using chitosan on cereal crops in the face of climate change. ­ Plants, 10(6): 1160. LI S.M., ZHENG H.X., ZHANG X.S., SUI N., 2021 ­ Cytokinins as central regulators during plant growth and stress response. ­ Plant Cell Rep., 40(2): 271­282. LIN L.­Z., HARNLY J.M., PASTOR­CORRALES M.S., LUTHRIA D.L., 2008 ­ The polyphenolic profiles of common bean (Phaseolus vulgaris L.). ­ Food Chem., 107(1): 399­410. MARIOTTI F., TOMÉ D., MIRAND P.P., 2008 ­ Converting nitrogen into protein‐beyond 6.25 and Jones’ factors. ­ Crit. Rev. Food Sci. Nutr., 48(2): 177­184. MASROOR M., KHAN A.A., NAEEM M., MOHAMMAD F., MASROOR M., KHAN A., MUJIBUR­RAHMAN M., SID­ DIQUI M.H., NASIR KHAN M., 2006 ­ Triacontanol‐ induced changes in growth, yield and quality of tomato (Lycopersicon esculentum Mill.). ­ Electron. J. Environ., Agric. Food Chem., 5(2): 1492­1499. MONDAL M.M.A., MALEK M.A., PUTEH A.B., ISMAIL M.R., ASHRAFUZZAMAN M., NAHER L., 2012 ­ Effect of foliar application of chitosan on growth and yield in okra. ­ Aust. J. Crop Sci., 6(5): 918­921. MOSTAFA S.H., BRENGI A., 2018 ­ Growth, yield and chemi‐ cal composition of okra as affected by three types and levels of synthetic cytokinins under high temperature conditions. ­ Alex. J. Agric. Res., 63(6): 365­372. MUNNS R., WALLACE P.A., TEAKLE N.L., COLMER T.D., 2010 ­ Measuring soluble ion concentrations (Na+, K+, Cl−) in salt‐treated plants, pp. 371­382. ­ In: SUNKAR R. (ed.) Plant stress tolerance. Methods and Protocols. Humana Press, Springer, Germany, pp. 376. NAEEM M., KHAN M.M.A., MOINUDDIN, 2012 ­ Triacontanol: A potent plant growth regulator in agri‐ culture. ­ J. Plant Interact., 7(2): 129­142. NONOKAWA K., NAKAJIMA T., NAKAMURA T., KOKUBUN M., 2012 ­ Effect of synthetic cytokinin application on pod setting of individual florets within raceme in soy‐ bean. ­ Plant Prod. Sci., 15(2): 79­81. OMAE H., KUMAR A., KASHIWABA K., SHONO M., 2006 ­ Influence of high temperature on morphological char­ acters, biomass allocation, and yield components in snap bean (Phaseolus vulgaris L.). ­ Plant Prod. Sci., 9(3): 200­205. PAGE A.L., MILLER R.H., KEENEY D.R., 1982 ­ Methods of soil analysis. Part 2. Chemical and Microbiological Properties. ­ Amer. Soc. Agron., Soil Sci. Soc. Amer, Madison, WI, USA, CABI, pp. 1159. PICHYANGKURA R., CHADCHAWAN S., 2015 ­ Biostimulant activity of chitosan in horticulture. ­ Sci. Hortic., 196: 49­65. PONGPRAYOON W., ROYTRAKUL S., PICHAYANGKURA R., CHADCHAWAN S., 2013 ­ The role of hydrogen peroxide in chitosan‐induced resistance to osmotic stress in rice (Oryza sativa L.). ­ Plant Growth Regul., 70(2): 159­173. RADY M.M., ELRYS A.S., ABO EL­MAATI M.F., DESOKY E.­ S.M., 2019 ­ Interplaying roles of silicon and proline effectively improve salt and cadmium stress tolerance in Phaseolus vulgaris plant. ­ Plant Physiol. Biochem., 139: 558­568. RAMA RAO C.A., RAJU B.M.K., JOSILY S., RAO A.V.M.S., Abouelsaad ‐ Field evaluation of biostimulants 153 NAGARJUNA KUMAR R., SRINIVASA RAO M., SWAPNA N., SAMBA SIVA G., MEGHANA Y.L., PRABHAKAR M., SINGH V.K., 2022 ­ Impact of climate change on produc‐ tivity of food crops: a sub‐national level assessment for India. ­ Environ. Res. Commun., 4(9): 095001. RIES S.K., WERT V., SWEELEY C.C., LEAVITT R.A., 1977 ­ Triacontanol: A new naturally occurring plant growth regulator. ‐ Science, 195(4284): 1339­1341. RIPPKE U., RAMIREZ­VILLEGAS J., JARVIS A., VERMEULEN S.J., PARKER L., MER F., DIEKKRÜGER B., CHALLINOR A.J., HOWDEN M., 2016 ­ Timescales of transformation‐ al climate change adaptation in sub‐Saharan African agriculture. ‐ Nat. Clim. Change, 6(6): 605­609. RYLOTT P.D., SMITH M.L., 1990 ­ Effects of applied plant growth substances on pod set in broad beans (Vicia faba var. major). ­ J. Agric. Sci., 114(1): 41­47. SÁEZ­PLAZA P., NAVAS M.J., WYBRANIEC S., MICHAŁOWSKI T., ASUERO A.G., 2013 ­ An overview of the Kjeldahl method of nitrogen determination. Part II. Sample preparation, working scale, instrumental finish, and quality control. ­ Crit. Rev. Anal. Chem., 43(4): 224­272. SCHWARTZ H.F., LANGHAM M.A.C., 2010 ­ Common bean growth stages . ­ Bean IPM https://Beanipm. Pbgworks.Org/Common­Bean. SHARMA N., SINGH K., THAKUR A., 2011 ­ Growth, fruit set, yield and fruit quality of olives (Olea europaea L.) as influenced by nutrients and bio‐stimulants under rain‐ fed condition. ­ Acta Horticulturae, 890: 385­392. SLAVIN J.L., 1987 ­ Dietary fiber: classification, chemical analyses, and food sources. ­ J. Am. Diet. Assoc., 87(9): 1164­1171. SOURI Z., KHANNA K., KARIMI N., AHMAD P., 2021 ­ Silicon and plants: Current knowledge and future prospects.­ J. Plant Growth Regul., 40(3): 906­925. SRIVASTAVA A., SINGH S.K., 1988 ­ Determination of vita‐ min C in chemical, pharmaceutical and biological sam‐ ples by spectrophotometric titrimetry with o‐diace‐ toxyiodobenzoate. Analysis of mixtures of vitamin C with methionine and cysteine or glutathione. ­ Analyst, 113(2): 259­262. STASIŃSKA­JAKUBAS M., HAWRYLAK­NOWAK B., 2022 ­ Protective, biostimulating, and eliciting effects of chi‐ tosan and its derivatives on crop plants. ­ Molecules, 27(9): 2801. TEJADA­RUIZ S., GONZALEZ­LOPEZ C., ROJAS E., JIMÉNEZ­ BECKER S., 2020 ­ Effect of the foliar application of microalgae hydrolysate (Arthrospira platensis) and sili‐ con on the growth of pelargonium hortorum L.H. Bailey under salinity conditions. ­ Agronomy, 10(11): 103390. WALLACE D.H., MUNGER H.M., 1965 ­ Studies of the physi‐ ological basis for yield differences. I. Growth analysis of six dry bean varieties. ­ Crop Sci., 5(4): 343­348. WANG K., SHEN Y., WANG H., HE S., KIM W.S., SHANG W., WANG Z., SHI L., 2022 ‐ Effects of exogenous Salicylic acid (SA), 6‐Benzylaminopurine (6‐BA), or Abscisic Acid (ABA) on the physiology of Rosa hybrida ‘Carolla’ under high‐temperature stress. ­ Horticulturae, 8(9): 851. WAQAS M., SHAHZAD R., KHAN A.L., ASAF S., KIM Y.­H., KANG S.­M., BILAL S., HAMAYUN M., LEE I.­J., 2016 ­ Salvaging effect of triacontanol on plant growth, ther‐ motolerance, macro‐nutrient content, amino acid con‐ centration and modulation of defense hormonal levels under heat stress. ­ Plant Physiol. Biochem., 99: 118­ 125. WATANABE F.S., OLSEN S.R., 1965 ­ Test of an ascorbic acid method for determining phosphorus in water and NaHCO3 extracts from Soil. ‐ Soil Sci. Soc. Am. J., 29(6): 677­678. WERNER T., SCHMÜLLING T., 2009 ­ Cytokinin action in plant development. ­ Curr. Opin. Plant Biol., 12(5): 527­ 538. XIONG W., REYNOLDS M., XU Y., 2022 ­ Climate change challenges plant breeding. ‐ Curr. Opin. Plant Biol., 70: 102308. YAGHUBI K., VAFAEE Y., GHADERI N., JAVADI T., 2019 ­ Potassium silicate improves salinity resistant and affects fruit quality in two strawberry cultivars grown under salt stress. ­ Commun. Soil. Sci. Plant Anal., 50(12): 1439­1451. YANG D., LI Y., SHI Y., CUI Z., LUO Y., ZHENG M., CHEN J., LI Y., YIN Y., WANG Z., 2016 ­ Exogenous Cytokinins increase grain yield of winter wheat cultivars by improving stay‐green characteristics under heat stress. ­ PLOS ONE, 11(5): e0155437. ZAREA M.J., KARIMI N., 2023 ­ Grain yield and quality of wheat are improved through post‐flowering foliar application of zinc and 6‐benzylaminopurine under water deficit condition. ­ Front. Plant Sci. 13. ZARGAR S.M., MAHAJAN R., BHAT J.A., NAZIR M., DESH­ MUKH R., 2019 ­ Role of silicon in plant stress toler‐ ance: opportunities to achieve a sustainable cropping system. ‐ 3 Biotech, 9(3): 73.