Impaginato 535 Adv. Hort. Sci., 2018 32(4): 535-540 DOI: 10.13128/ahs-22474 Effect of a novel hydrogel amendment and seedling plugs volume on the quality of ornamental/miniature tomato R.A.C. Melo (*), M.H. Jorge, N. Botrel, L.S. Boiteux Brazilian Agricultural Research Corporation, Embrapa vegetables, Brasilia DF, Brazil. Key words: copolymer, pot plant, Solanum lycopersicum L., transplants. Abstract: The market for ornamental/miniature plants values aesthetic mor- phological characteristics, which give harmony to the potted plant. These traits depend on the growing media capacity to maintain quality and plant longevity. The use of hydrogels has increased recently in order to achieve visually attrac- tive and long-lasting plants. Thus, this study aimed to evaluate the effects of a novel hydrogel (H) amendment and seedling plugs volume (SPV) on the quality of ornamental/miniature tomato. Seedlings of tomato cv. BRS Finestra were produced in 200 and 162 plugs plastic trays - with 18 cm³ trapezium-shaped plugs and 50 cm³ conically shaped plugs, respectively. 18 cm³ plugs and H amendment presented several significant responses for plant characters - height, soluble solids, number of leaves, stem diameter, shoot dry matter and fruits weight per plant; making evident the advantages of using a growing medium of smaller volume and this copolymer amendement. Although consis- tent results were obtained, a combination of both these factors in terms of an optimal aesthetic value and considering all the morphological traits could not be accomplished. Therefore it’s necessary to study other elements such as plant nutrition and the use of plant growth regulators to complement them, aiming to promote better quality. 1. Introduction Miniature tomatoes can be grown singly in small pots, or more plants in larger hanging pots. They are also ideal for window boxes or garden borders because their plant canopy diameter is little (Scott and Harbaugh, 1995). These plants combine ornamental aspects of a well-proportioned, diminutive, tomato plant with tasting fruits that can be eaten. Small plant sizes are ideal for commercial growing, shipping, and retail selling (Scott and Harbaugh, 1995). The commercial success of the cultivation of miniature/ornamental potted plants such as tomatoes and peppers depends on consumer appeal conferred by the plant beauty, quality, vigor, color, shape, and size of leaves and fruits. In addition to that, the cultivars must present canopy harmony and be able to develop in relatively small pots (Costa et al., 2015). (*) Corresponding author: raphael.melo@embrapa.br Citation: MELO R.A.C., JORGE M.H., BOTREL N., BOITEUX L.S., 2018 - Effect of a novel hydrogel amendment and seedling plugs volume on the quality of orna- mental/miniature tomato. - Adv. Hort. Sci., 32(4): 535-540 Copyright: © 2018 Melo R.A.C., Jorge M.H., Botrel N., Boiteux L.S. 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 8 January 2018 Accepted for publication 28 June 2018 AHS Advances in Horticultural Science Adv. Hort. Sci., 2018 32(4): 535-540 536 Non-miniature tomato cultivars tend to overgrow small containers, and their plant size is restricted by the container size (Scott and Harbaugh, 1995), pro- ducing commercially unviable plants, requiring the use of plant growth regulators (PGR) to achieve attractive compact potted grown plants (Moraes et al., 2005). Another important feature of ornamental plants is the maintenance of interior quality and longevity, a never-ending effort by producers (Wang, 1992). Growing medium ability to prevent drying out is desirable, especially in peat-based substrates. Some growers report a benefit when plants are watered with a wetting agent prior to shipment, thus making it easier for retail clerks and consumers to thoroughly rewet the medium. Interest has increased recently among growers and mass market buyers in using water-absorbing gels (Nell, 1991). However, studies investigating the effects of hydrogel (H) application o n o r n a m e n t a l p l a n t s a r e s c a r c e a n d l i m i t e d (Ljubojević et al., 2017). Particularly to ornamental/ miniature vegetables, this scenario can be considered negligible. In regard to this matter, a promising nanocompos- ite hydrogel developed by an innovative technique using calcium montmorillonite showed great swelling degree, higher than 2000 times in water. The formu- lated H with high calcium montmorillonite content (approximately 50.0% wt) as well as featuring high loading capacity and individual and simultaneous release, denotes an interesting material for agricul- tural applications (Bortolin et al., 2016). Thus, the present study has the objective of evaluating the effects of a novel hydrogel amendment and seedling p l u g s v o l u m e ( S P V ) o n t h e q u a l i t y o f ornamental/miniature tomato. 2. Materials and Methods Plant material and growth conditions An experiment was conducted from July 18 (sow- ing) to October 25 (harvest), 2017 at Embrapa Vegetables - 996 m altitude, 15° 56’ S, and 48° 08’ W - Brasília-DF, Brazil, in a glass-glazed greenhouse. A p h o t o s e l e c t i v e s h a d i n g n e t ( A l u m i n e t ® I C 5 0 - Ginegar Polysack®) was installed 2 m above the benches. The greenhouse presented an air tempera- ture of 15°C minimum and 44°C maximum, average DLI (daily light integral) of ≈ 11 mol.m-2.d-1 consider- ing a 12h period of sunlight and 81% maximum and 11% minimum of humidity. Measures were taking after seedlings transplantation 15 minutes apart by sensors connected to a Datalogger (Watchdog 1000 Series Micro Station - Spectrum Technologies®). Seedlings were produced in plastic trays with 200 and 162 plugs (JKS® - 18 cm³ trapezium shaped plugs and 50 cm³ conically shaped plugs, respectively) using a peat moss based substrate (Carolina Soil®) (Fig. 1 A). Solanum lycopersicum L. cv. BRS Finestra was selected, being the first Brazilian ornamental/miniature tomato cultivar released by Embrapa as a product for a very specific and demanding market (Giordano et al., 2001). They were transplanted at 36 DAS (days after sowing) to 1 dm³ pots (Nutriplan® NP14) filled with a pine bark-based substrate (Rohbacher®) with the fol- lowing characteristics: EC - 0.4; pH - 6.0; Water hold- ing capacity - 50%; Humidity - 60%; Density - 185 kg m³. Filling were complemented with 5 g of Bokashi compost per pot (Korin® - Garden Bokashi). Nutrients were supplied weekly during the experi- ment, with a solution developed for ornamental pep- pers containing 14.4, 1.95, 12.92, 2.5, 1.0, 2.44 mmol/L of N, P, K, Ca, Mg, S and 30, 5, 50, 40, 2 and Fig. 1 - (A) Seedling plugs volume and visual comparison - 50 cm³ (left) and 18 cm³ (right); (B) plants from 50 cm³ plugs with hydrogel amendment (left) and without (right); (C) plants from 18 cm³ plugs with hydrogel amendment (left) and without (right). Melo et al. - Quality of ornamental, miniature tomato 537 0.1 mol/L of B, Cu, Fe, Mn, Zn and Mo, respectively, according to Costa et al. (2015). Watering from seeding to the transplantation was performed twice daily with enough water to start the run off at the bottom of the trays. All other cultural practices were performed using technical recommen- dations for controlled environment miniature tomato cultivation (Schwarz et al., 2014). Plant morphological characteristics and fruit quality analysis All plant morphological characteristics were ana- lyzed when a commercial stage was reached, mean- ing that when 50% of the plant population of each treatment had at least 30% of fully ripe fruits or visu- ally marketable fruits with the maximum size and shape typical of growth for miniature/ornamental tomato. These agronomic characteristics are based on the morphological descriptors suggested by IPGRI (1995) and were validated by Costa et al. (2015) for ornamental peppers: (P) - Precocity - expressed by the number of days between transplantation and commercial stage; Dry matter content of shoot (SDM) - parts were dried in oven at 70°C until constant weight and values were obtained by equation: SDM% = {dry weight (g)/fresh weight (g) x 100}; (PH) Plant height (cm) - measured using a ruler, from the stem bottom until the last fully expanded leaf; (SD) Stem diameter (mm) - measured above the cotyledon leaves using a digital caliper; (CR) Plant canopy ratio - obtained from between the longitudinal (LD) and transverse diameters (TD), where the closer the value to 1, more circular is the canopy. (NL) Number of leaves - expressed by counting the number of leaves per plant; Number of fruits per plant (NFP); Number of fully ripe (NR); (FW) Fruit weight per plant (g) - expressed by the sum of different fruits ripening stages per plant; (FD) Ripe fruits diameter (cm) - obtained from the longitudinal diameter of 4 fruits from each treat- ment. The following fruit quality basic parameters were a n a l y z e d b y A O A C ( 2 0 1 0 ) a n d M c G u i r e ( 1 9 9 2 ) methodologies, utilizing 4 fruits from each treat- ment: (SS) Soluble solids (°brix); (AC) Acidity; SS/AC ratio; Color (C) - evaluated by means of ripe fruits with the measurement of the colorimetric parameters L*, a*, b* C* and angle Hue (h°) in fruits. The L * coordinate expresses the degree of clarity of the measured color (L = 100 = white; L = 0 = black), C* the intensity of the color and h ° the saturation of the color. Statistical design and analysis The trial was conducted in a 2x2 factorial design in a complete randomized scheme, with six replications. The presence (amendment) and absence of H repre- sented the first factor. SPV- 18 cm³ plugs and 50 cm³ plugs - represented the second factor. Each replica- tion was composed of 10 plants. The rate of H per substrate consisted of 2.0% (on volume/volume basis) and followed previous studies recommenda- tions (Bortolin et al., 2016). Data were subjected to an analysis of variance (ANOVA). All computations were performed with ASSISTAT® software (Silva and Azevedo, 2016). Preliminary analysis indicated that PH, and NPP presented a skew and overdispersed distribution, and it was required a transformation to normalize data. Thus, their means were evaluated after square root transformation. Normality of resid- uals was tested using Shapiro-Wilk test (alpha 5%) and the distribution presented as normal subse- quently. 3. Results Plants grown utilizing 50 cm³ plugs required a shorter period of time to reach the ideal commercial stage - precocity (P). When 18 cm³ plugs were used, this stage was reached at the same time, indepen- dently of H amendment (Table 1). This differentiates the 50 cm³ plugs in 5 days (earlier) when compared to 18 cm³ plugs. A difference of 9 or 14 days when 50 cm³ plugs were amended or not with H, respectively, was also observed when comparing to 18 cm³ plugs. 50 cm³ plugs use resulted in plants with a very long stem (Fig. 1 B). Table 1 - Ornamental/miniature tomato precocity (P) stage reached according to hydrogel amendment and seedlings plugs volume P= when 50% of the plant population had at least 30% of fully ripe fruits or visually marketable fruits with the maximum size and shape typical of growth for miniature/ornamental tomato. Plug volume P (days after transplantation) With hydrogel Without hydrogel 18 cm³ 57 57 50 cm³ 43 48 Adv. Hort. Sci., 2018 32(4): 535-540 538 PH values were significant for both factors and their interaction (Tables 2 and 3), with 18 cm³ plugs and H combination reaching 19.63 cm. The general mean height value achieved in this trial (17.1 cm) is typical of the cv. BRS Finestra and is within the values quantified by Scott and Harbaugh (1995) evaluating different miniature tomatoes, ranging from 9 cm with cv. Micro-Tom to 25 cm with cv. Micro-Gold. Characters of aesthetic significance, such as plant architecture, number, position, and color of fruits, leaves shape and density are some of the reasons that ornamental species of the Solanaceae family are admired, being strictly related to plant longevity and to facilitate cultural handlings (Neitzke et al., 2016). One of these traits, NL, is consistent with the cultivar and growing conditions, presenting a significant response for all the studied factors. The interaction of 18 cm³ plugs and H enhanced the NL to 51.6 (Table 2) which can be perceived by the observation of leaves density in Fig. 2 D, but this response was not converted into a greater NFP. CR represents the aspect of the aerial parts of the plant, where the closer the value to 1, more circular it is the canopy. Therefore, when 50 cm³ plugs were used, a more circular shape was attained (LD/TD = 1.16) (Table 2). This format has a greater visual appeal, which is often decisive in the choice of the consumer to become more attractive and makes it easier to handle (Costa et al., 2015), although with plants being long-stemmed, a visual aspect uncom- mon for miniature tomatoes was observed, resem- bling a palm tree shape (Fig. 1 B). SDM and SD values were significant for both treatments (Table 3). Costa et al. (2015) evaluated the quality of ornamental pepper using two sub- strates and genotypes, founding distinct SDM con- tent responses, with values ranging from 20.58% to 26.54%, corroborating with the best results here found. SD results presented in this study (5.53 mm with H amendment and 5.55 mm from 18 cm³ plugs) Table 2 - Interaction between hydrogel and seedling plugs vol- ume for plant ornamental/miniature tomato charac- ters Means followed by the same lowercase letters in the columns and capital letters in the lines do not differ by Tukey test at 5% proba- bility. Fig. 2 - Ornamental/miniature tomato plants visual aspect when precocity stage was reached. (A) from 50 cm³ plugs with hydrogel amendment; (B) from 50 cm³ plugs without hydrogel amendment; (C) from 18 cm³ plugs without hydrogel amendment; (D) from 18 cm³ plugs with hydro- gel amendment. Table 3 - Hydrogel amendment and seedlings plug volume effect on ornamental/miniature tomato plant charac- ters Means followed by the same lowercase letters in the columns and capital letters in the lines do not differ by Tukey test at 5% proba- bility. Plug volume 50 cm³ 18 cm³ Plant height (cm) With hydrogel 16.49 aB 19.63 aA Without hydrogel 16.30 aA 16.02 bA Soluble solids (°Brix) With hydrogel 4.65 aB 5.35 aA Without hydrogel 4.50 aB 5.20 aA Number of leaves (per plant) With hydrogel 37.41 aB 51.60 aA Without hydrogel 37.45 aB 43.88 bA Canopy ratio With hydrogel 1.16 aB 1.32 aA Without hydrogel 1.23 aA 1.26 aA Plant characters Hydrogel Plug volume With Without 50 cm³ 18 cm³ Stem diameter (mm) 5.53 a 5.31 b 5.29 b 5.55 a Shoot dry matter (%) 19.49 a 18.37 b 18.31 b 19.55 a Fruit weight per plant (g) 68.39 a 67.17 b 77.39 a 58.17 b Number of fully ripe fruits 3.08 a 2.43 b Number of fruits per plant 9.90 a 6.01 b Melo et al. - Quality of ornamental, miniature tomato 539 (Table 3) are inferior but consistent with the ones found in the work of Backes et al. (2007) with orna- mental pepper. They obtained an SD of 6.42 mm as the best result using controlled release fertilizer mixed to a commercial substrate. Even though SD values in this study were significant to H and SPV, only a slight increase was observed amongst treat- ments. NFP, NR, and FW values were superior with the use of 50 cm³ plugs (Table 3). With a compact canopy and well-distributed leaves, the photosynthetic process that depends on the interception of light energy most likely was converted into chemical ener- gy in an efficient way, resulting in this positive response. SS and AC values were significant for SPV and also for the interaction of 18 cm³ plugs with H. The values of 5.35 and 0.61 achieved for SS and AC, respectively, are comparable to 5.37 and 0.65 from cv. Micro-Gold bred by Scott and Harbaugh (1995), ensuring that cv. BRS Finestra produces mild tasting fruits that can be appreciated/consumed. NI (general mean value of 1.52), FD (general mean value of 3.1 cm), SS/SC ratio (general mean value of 8.38) and C (general mean value of L* 40.67; C* 51.05 and h° 48.51) were not significant (NS) to both treatments. For C values, although being NS, ripe fruits exhibited an intense red coloration (Fig. 1B). This color is favored by consumers, a point which is believed to possess the highest carotenoids content such as β-carotene and lycopene (Kader et al., 1977). 4. Discussion and Conclusions Plants grown with 50 cm³ plugs, in the presence or absence of H amendment, demanded a shorter period of time to reach the ideal commercial stage - precocity (P). Precocity is a very important attribute, as it would allow the grower to commercialize plants earlier and to reutilize the spaces emptied in the greenhouse benches. But for its recommendation, the fact that PH in this plug volume resulted in an undesired visual aspect displaying a very long stem, needs to be taking in to account. The 50 cm³ plugs were significant for NFP, NR, NG, and FW characters as well. An efficient interception of light with plants produced using this plugs made most likely converted chemical energy into fruits, being a response of a compact canopy with well-dis- tributed leaves. 18 cm³ plugs were significant for SD, SDM and FW, making evident the advantages of using a smaller volume of substrate, which can be fully employed for the growing of ornamental/minia- ture tomatoes in 1 dm³ pots. The use of H resulted in higher SD, SDM and FW values, considered fundamental in the aspect of the plant canopy and its longevity. H and SPV interaction responded differently to the analyzed plant character- istics, with 18 cm³ plugs and H amendment together showing significant responses only for PH and NL. In conclusion, although several consistent results for plant characters were obtained when 18 cm³ plugs and H were used solely, a combination of both in terms of an optimal aesthetic value and consider- ing all the morphological traits could not be accom- plished. 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