96 Annales Universitatis Paedagogicae Cracoviensis Studia Naturae, 5: 96–109, 2020, ISSN 2543-8832 DOI: 10.24917/25438832.5.7 Joanna Biel-Parzymięso Independent Research, Institute of Biology, Pedagogical University of Krakow, Podchorążych 2 St., 30-084 Kraków, Poland; jbp2@ onet.eu Effect of Morus alba L. leaf extracts on seeds germination and the seedlings growth of Sinapis alba L. and Cucumis sativus L. Introduction Hans Molisch (1937) was the �rst to introduce and apply the concept of allelopathy to biological systems. He de�ned the mutual – both adverse and bene�cial, biochemical interactions of all plants, including soil microorganisms as allelopathy (Wójcik-Wo- jtkowiak et al., 1998). �e concept of allelopathy (Harborne, 1997) was consolidated in the second half of the 20th century as a  result of pioneering research by Muller and Chou (1972), followed by Rice (1984). Currently, research on this phenomenon is growing because it is seen as an opportunity for more e�ective weed control; through learning about their allelopathic properties, natural compounds could be used to in- hibit weed development (Vyvyan, 2002; Możdżeń et al., 2018). Allelochemical substances that stimulate plant growth may actually act as inhib- itors at high concentrations, and compounds considered to be inhibitors at low con- centrations may stimulate some growth processes. �ere are more than 10,000 dif- ferent allelopathic compounds, and the main sources of their mass release are from crop plants, weeds, and soil microorganisms (Leather, Einhellig, 1988; Barazani, Fred- man, 2001; Weston, 2005; Kong et al., 2019). �ese compounds primarily belong to low-molecular-weight secondary metabolites (Rice, 1984; Einhelling, 1994). In the case of microorganisms, they can include enzymes involved in secondary metabolism pathways and antibiotics (Sturz, Christe, 2003). Most allelopathic substances are highly soluble in water, hence they easily pene- trate into the soil solution. �e most common allelo-inhibitors include: organic ac- ids, including phenolic acids; �avonoids; tannins; glycosides; terpenoids; alkaloids; unsaturated lactones; coumarins; and quinones. Allelopathins can be released into the immediate environment of plants through their various organs or parts: roots, seeds, fruits, �owers, and leaves. In the roots, inhibiting substances usually have weak 97 Effect of M orus alba L. leaf extracts on seeds germ ination and the seedlings grow th of Sinapis alba L. and Cucum is sativus L. properties and occur in lower concentrations. One example of an exception to this is the root of alfalfa (Medicago sativa L.), which is actually the primary source of sap- onin inhibitors. Roots usually contain large amounts of allelopathic substances with a  wide spectrum of activity. In seeds, inhibitors prevent rotting and control germi- nation by imposing absolute dormancy. Fruits contain inhibitors that play a  role in regulating seed germination. Some �owers also possess similar chemical substances (Gniazdowska, Bogatek, 2005). Most researchers believe that, under balanced natural conditions, allelopathins from seeds, fruits, and �owers are not released in amounts that could pose a  threat to nearby plants (Wójcik-Wojtkowiak et al., 1998). �e concentration of allelopathic compounds depends on the season, the age of the plant, and ecological and habitat factors. Allelopathins are released in the highest amounts by young plants in spring as compared to mature and aging plants in autumn (Wardle et al., 1993; Ahmed, Wardle, 1994). �e biological activity of allelopathic compounds is assessed relatively easily using biotests. �e simplest biotest is seed germination. A more accurate method may be to measure plant growth parameters (Oleszek, 1992). �e biotest that consists of measuring the mass of plants treated with allelopathic compounds is an order of mag- nitude more sensitive than the biotest based on seed germination, and the measure- ment of seedling growth is even �ve times more sensitive than that. �e aim of this study was to determine the e�ect of aqueous extracts of mulberry (Morus alba L.) leaves, with di�erent percentage concentrations, on: (1) germination of mustard (Sinapis alba L.) and cucumber (Cucumis sativus L.) seeds – as crop plants, (2) their growth, and (3) the fresh and dry mass of underground and aboveground organs. Material and methods Plant material Mulberry leaves (Morus alba) were collected in southern Poland, and then dried in laboratory conditions. Mustard (Sinapis alba) and cucumber (Cucumis sativus) seeds were purchased from PlantiCo Zielonki Spółka z.o.o., POLAN Cultivation and Seed Plant. Extracts preparation Aqueous extracts of dry mulberry leaves were prepared at three di�erent percentage concentrations: 3, 5, and 10; for this purpose, 3 g of dry leaves were weighed and �ooded with 97 ml of distilled water, 5 g of leaves were �ooded with 95 ml of distilled water, and 10 g of leaves were �ooded with 90 ml of distilled water, respectively. A�er 24 hours of extraction at room temperature and in the dark, the extracts were �ltered Jo an na B ie l-P ar zy m ię so 98 through Whatman type �lter paper and stored in the 8°C temperature for the duration of the experiment. Seeds preparations and germination conditions Fi�y seeds, mustard or cucumber, were rinsed with running and distilled water and placed on sterilised Petri dishes with �lter paper, moistened with prepared extracts. �e control consisted of seeds on Petri dishes with distilled water. All seed dishes were placed in a  dark 25°C thermostat. �e percentages of germinated seeds were checked systematically a�er 24, 48, 72, and 96 h. To be considered a germinated seed, the sprout length was equal to or higher than 2 mm (Możdżeń et al., 2018). Plant growth Proceeding analogously as in the �rst stage of the experiment (germination), Petri dishes were prepared with �lter paper moistened with distilled water (control) and mulberry extracts. On each of the 7 Petri dishes 50 mustard or cucumber seeds were placed, a�er washing under running and distilled water. �e Petri dishes were placed in a dark, 25°C thermostat for 48 h. In the meantime, 70 pots were prepared with sand washed in running and distilled water. Morphologically similar mustard and cucumber seedlings were planted into 35 pots, from controls and extracts, previ- ously rinsed with distilled water. Seedlings were watered alternately every 48 h with 15 ml distilled water per plant and 10 ml Steiner medium per plant (Steiner, 1961). �e mustard and cucumber seedlings that were germinated in distilled water were planted in the remaining 35 pots. Seedlings were watered alternately every other day with distilled water (15 ml/plant) and mulberry extracts (5 ml/plant) and once a week with Steiner medium (10 ml/plant). All pots were placed in a growth chamber, with a light intensity of 200 μmol × m–2 × s–1, in the photoperiod 12 h/12 h, day temperature 25°C, night temperature 20°C, and relative humidity (RH) 70–80%. Biometric analysis Biometric analysis of mustard and cucumber organs was carried out on day 21 since planting the seedlings in the pots with sand. Plants were removed from pots and their roots were washed in water and dried with paper towel. Using a ruler, with an accuracy of 1 mm, the length of the root, hypocotyl, petioles and remaining part of the shoot, among other parts, was measured. Fresh and dry mass �e fresh mass of mustard and cucumber organs was determined using an electron- ic scale (Radwag 120 WPS, Poland). To obtain the dry mass, open Petri dishes with plants were placed in a dryer (WAMED SUP-100, Poland) for 48 h at a temperature 99 of 105°C. �e dried plant material was placed in a desiccator for 1.5 h. A�er this time, the dry mass of the plants was determined on an electronic scale, with an accuracy of 0.1 mg. Statistical analysis �e statistical analysis of signi�cance di�erences between the means ±SE were made by Tukey test at p ≤ 0.05 in StatSo�, Inc. (2018). Results Seeds germination A  much higher percentage of mustard seeds germinated under control conditions than on aqueous mulberry leaf extract (Tab. 1). 58% of seeds watered with distilled water began germination a�er 24 h. �is percentage subsequently increased and af- ter 72 h reached 92%. Germination of mustard seeds on 3% extract began a�er 48 h, when 4% of seeds had germinated; a�er 96 h, the seeds had germinated to a level of 40% less than control. Petri dishes saturated with 5 and 10% extracts exhibited germi- nation delayed by 2 and 3 days, respectively, from the time when the seeds were placed on the extracts. As a result, a�er 96 h, 14% of seeds germinated on the 5% extract and only 8% had germinated on the 10% extract. Tab. 1. Germination seeds capacity [%] of mustard (Sinapis alba L.) – A and cucumber (Cucumis sativus L.) – B, on the aqueous mulberry leaves extracts (Morus alba L.) Time [h] Control Concentration of Morus alba extracts [%] 3 5 10 A B A B A B A B 24 58 78 0 72 0 74 0 22 48 87 94 4 90 0 94 0 72 72 92 94 28 92 8 96 0 80 96 92 94 52 92 14 96 8 82 Cucumber seeds on Petri dishes with aqueous mulberry extract began to germi- nate a�er the �rst day (Tab. 1); a�er this time point, the percentage of germinated seeds was lower than in the control sample. Starting from day 2, the percentage of germinated seeds on the 3 and 10% extracts decreased. However, the percentage of germinated seeds on the 5% extract a�er the second day was the same as in the con- trol; a�er 3 and 4 days it remained at a level 2% higher than the control. �e use of an extract with a concentration of 10% most strongly inhibited the germination of cucumber seeds. Effect of M orus alba L. leaf extracts on seeds germ ination and the seedlings grow th of Sinapis alba L. and Cucum is sativus L. Jo an na B ie l-P ar zy m ię so 100 Tab. 2. Length of selected mustard organs (Sinapis alba L.) for plants watered with extracts of mul- berry leaves (Morus alba L.): A – during germination phase, B – during growth phase; mean ±SE values from 5 replicates marked with di�erent letters di�er signi�cantly according to Tukey test at p ≤ 0.05 Organ length [cm] Control Concentration of Morus alba extracts [%] 3 5 10 A B A B A B Root 5.6 a 4.6 ab 5.1 a 4.8 ab 3.5 b 0.0 cde 3.8 b Hypocotyl 5.5 a 4.4 b 4.8 b 4.4 b 4.5 b 0.0 cde 4.5 b Petioles of leaf 1.2 a 1.3 a 1.0 ab 1.0 ab 0.6 b 0.0 cde 0.3 b Remaining part of shoot 1.7 b 2.3 a 0.5 c 2.2 a 0.0 d 0.0 cde 0.0 d Biometric analysis Biometric analysis of mustard organs revealed an adverse e�ect on root growth and hypocotyls for plants grown from seeds watered with extracts for 48 h. �ese organs were shorter than similar organs grown in control plants (Tab. 2). Slight changes in length were observed for leaf petioles. Growth in 3 and 5% extracts resulted in in- creased lengths of the remaining parts of the shoot, relative to the control. �e 10% concentration extracts completely inhibited growth and development of the tested plants. Compared to control, the length of mustard plant organs from seedlings wa- tered with mulberry extracts during the growth period was signi�cantly inhibited. Regardless of the time point of watering, 10% extracts exerted the most adverse e�ect on plant growth. Tab. 3. Length of selected cucumber organs (Cucumis sativus L.) for plants watered with extracts of mulberry leaves (Morus alba L.): A  – during germination phase, B – during growth phase; mean ±SE values from 5 replicates marked with di�erent letters di�er signi�cantly according to Tukey test at p ≤ 0.05 Organ length [cm] Control Concentration of Morus alba extracts [%] 3 5 10 A B A B A B Root 15.8 b 23.8 a 7.6 c 21.1 a 6.1 cd 7.3 c 5.6 d Hypocotyl 5.1 a 5.1 a 4.0 b 5.3 a 4.1 b 4.5 b 5.7 a Petioles of leaf 2.1 a 2.2 a 1.4 b 2.3 a 1.4 b 2.1 a 1.5 b Remaining part of shoot 1.8 ab 2.0 a 1.3 b 2.4 a 1.1 b 0.6 c 1.2 b Fresh and dry mass Measurement of fresh and dry mustard organ masses revealed that 3% extract as a seed germination medium resulted in an increase in the value of all tested param- eters compared to control (Tab. 4–5). �e 5% extract resulted in an increase in fresh mass only for cotyledons and the remaining part of shoot. �e dry mass of the coty- ledons of plants watered with 3% and 5% extracts in germination phase, exceeded the dry mass of the control. Dry mass values for other organs were signi�cantly lower 101 than in the control. �e percentage of water content in mustard organs was lower for each of the extract concentrations used (Fig. 1A – Appendix 1). Tab. 4. Fresh mass of selected mustard organs (Sinapis alba L.) for plants watered with extracts of mulberry leaves (Morus alba L.): A  – during germination phase, B – during growth phase; mean ±SE values from 5 replicates marked with di�erent letters di�er signi�cantly according to Tukey test at p ≤ 0.05 Organ fresh mass [mg] Control Concentration of Morus alba extracts [%] 3 5 10 A B A B A B Root 496.6 ab 562.2 a 288.8 b 436.6 ab 174.4 c 0.0 e 120.0 cd Hypocotyl 944.4 a 1006.6 a 598.8 c 768.6 b 338.8 d 0.0 e 344.4 d Cotyledons 770.0 b 906.6 a 694.4 bc 1056.6 a 572.2 c 0.0 e 406.6 d Petioles of leaf 132.2 b 164.4 a 84.4 c 98.6 bc 24.4 d 0.0 e 16.6 de Leaf blades 740.0 a 762.2 a 446.6 b 468.8 b 138.8 c 0.0 e 114.4cd Remaining part of shoot 116.6 bc 298.8 a 16.6 c 148.8 b 0.0d 0.0 e 0.0 d �e fresh and dry mass of mustard organs from plants watered during the growth phase with the extracts were signi�cantly lower than the control values (Tab. 4–5). �e mass values varied depending on the concentration of the extract; as the concen- tration of allelopathins increased, a  decrease in the values of these parameters was observed. �e water content in plant organs decreased as the concentration of extracts increased (Fig. 1B – Appendix 1). �e fresh mass of cucumber organs grown from seeds germinating for 48 h on 3 and 5% extracts increased with an increase in the concentration of allelopathins in the extracts (Tab. 6). �e exception were leaf petioles and the remaining part of the shoot, whose masses were less than the fresh mass of control plants. Plants grown from seeds germinating on 10% mulberry extract had a  lower fresh mass for almost all organs, compared to the control. Similar results were obtained for cucumber dry mass (Tab. 7). �e water content of the cucumber organs was lower than the control. An in- crease in the water content value for organs watered with 10% mulberry extracts was observed (Fig. 1C – Appendix 1). �e fresh and dry mass of cucumber organs from plants watered with extracts dur- ing the growth phase was generally less than the masses of control plants (Tab. 6–7). Mulberry extracts with a concentration of 3 and 5% caused a signi�cant increase in fresh and dry mass of cotyledons and the 10% extract increased leaf mass. In the case of percentage water content, no statistically signi�cant di�erences were observed (Fig. 1D – Appendix 1). Tab. 5. Dry mass of selected mustard organs (Sinapis alba L.) for plants watered with extracts of Effect of M orus alba L. leaf extracts on seeds germ ination and the seedlings grow th of Sinapis alba L. and Cucum is sativus L. Jo an na B ie l-P ar zy m ię so 102 mulberry leaves (Morus alba L.): A  – during germination phase, B – during growth phase; mean ±SE values from 5 replicates marked with di�erent letters di�er signi�cantly according to Tukey test at p ≤ 0.05 Organ dry mass [mg] Control Concentration of Morus alba extracts [%] 3 5 10 A B A B A B Root 180.0 b 234.4 a 74.4 c 176.6 b 65.5 c 0.0 d 50.0 c Hypocotyl 40.0 ab 52.2 a 27.7 c 40.0 ab 25.5 c 0.0 d 24.4 c Cotyledons 48.8 b 54.4 ab 41.1 bc 60.0 a 40.0 bc 0.0 d 40.0 bc Petioles of leaf 6.0 b 14.4 a 4.4 b 6.6 b 2.2 c 0.0 d 0 d Leaf blades 74.4 a 80.0 a 45.5 b 46.6 b 30.0 c 0.0 d 20.0 cd Remaining part of shoot 16.6 b 34.4 a 2.2 c 16.6 b 0.0 d 0.0 d 0 d Tab. 6. Fresh mass of selected cucumber organs (Cucumis sativus L.) for plants watered wit–h extracts of mulberry leaves (Morus alba L.): A – during germination phase, B – during growth phase; mean ±SE values from 5 replicates marked with di�erent letters di�er signi�cantly according to Tukey test at p ≤ 0.05 Organ fresh mass [mg] Control Concentration of Morus alba extracts [%] 3 5 10 A B A B A B Root 579.6 b 803.4 a 408.8 bc 846.2 a 315.8 c 219.5 d 255.8 cd Hypocotyl 216.2 a 219.2 a 169.0 c 226.8 a 152.0 c 180.5 b 269.8 a Cotyledons 335.6 b 389.2 b 496.6 a 421.0 a 448.2 a 352.5 b 291.8 c Petioles of leaf 86.2 ab 70.4 b 35.4 d 101.0 a 39.0 c 45.0 c 72.4 b Leaf blades 435.6 b 496.8 a 93.8 e 545.8 a 154.6 d 292.0 c 470.0 a Remaining part of shoot 59.0 b 55.2 b 35.4 c 86.2 a 32.2 c 24.2 d 39.0 c Tab. 7. Dry mass of selected cucumber organs (Cucumis sativus L.) for plants watered with extracts of mulberry leaves (Morus alba L.): A – during germination phase, B – during growth phase; mean ±SE values from 5 replicates marked with di�erent letters di�er signi�cantly according to Tukey test at p ≤ 0.05 Organ dry mass [mg] Control Concentration of Morus alba extracts [%] 3 5 10 A B A B A B Root 43.2 b 116.2 a 45.6 b 123.6 a 43.6 b 33.2 c 42.4 b Hypocotyl 11.2 a 11.8 a 8.6 b 12.2 a 7.8 c 8.5 b 10.8 b Cotyledons 25.4 c 29.2 b 48.0 a 30.8 b 37.8 ab 26.2 bc 22.0 c Petioles of leaf 4.0 ab 3.6 b 1.8 d 4.8 a 1.8 d 2.5 c 3.8 b Leaf blades 45.4 b 52.0 a 9.2 de 54 a 14.2 d 30.2 c 48.0 b Remaining part of shoot 4.2 b 4.2 b 2.8 c 5.6 a 2.6 c 2.0 d 2.8 c 103 Discussion �is experiment demonstrated the adverse e�ects of mulberry leaf extracts on the germination and growth of mustard and cucumber (Tab. 1–7). Considering the fact that most allelopathics are phenolic compounds that belong to secondary metab- olites (Grześkowiak, Łochyńska, 2017), it can be assumed that, to a  large extent, they could be responsible for inhibiting the germination process of the analysed species. Allelopathic substances already exert negative e�ects during the seed swelling process and then disrupt the metabolic processes that occur in the germinating seed. In this study, each concentration signi�cantly inhibited mustard seed germination (Tab. 1). However, for cucumber the reactions were slightly di�erent and likely related to the size of seeds and other structures of the seed coat (Możdżeń, Rzepka, 2017; Mazur, 2019). �e percentage of germinated cucumber seeds, for low concen- trations of mulberry extracts (3 and 5%), did not di�er greatly from the percentage of germinated seeds for distilled water (Tab. 1). Only at a 10% concentration of mulberry extract was a signi�cant germination delay observed. Zandi et al. (2018) showed that aqueous extracts from Stellaria media L. (Vill.) at low concentrations stimulated seed germination of Raphanus sativus var. radicula, and extracts from Helianthus annuus L., regardless of concentration, inhibited growth of Sinapis alba L. cv. Barka (Puła et al., 2020). �e negative e�ect of 10% mulberry extract on seed germination was prob- ably due to the higher content of allelochemical compounds in the extracts. �ese re- sults suggest that mulberry extracts caused oxidative stress due to allelopathins. A�er use of allelopathic compounds, plant tissues increased the production of reactive oxygen species which caused lipid peroxidation and oxidative damage (Ding et al., 2020). Inhibition of germination is a secondary e�ect of allelopathics. Before their ef- fects become visible, allelopathic substances �rst a�ect metabolic changes and physio- logical processes (Możdżeń et al., 2018; Szafraniec et al., 2019), such as cell membrane permeability and water-ion balance (Skrzypek et al., 2015). In this experiment, the action of 10% mulberry extract was the most apparent; wa- tering mustard seeds with it for 48 h completely inhibited their development and simi- larly to cucumbers caused a reduction in the length of individual organs and their fresh and dry mass (Tab. 2–7). �is e�ect was probably associated with a high concentra- tion of allelo-inhibitors (Możdżeń et al., 2020). Inhibition of plant growth may result from the delay or incubation of mitotic divisions and reduction of cell elongation (Vaughan, Ord, 1991). Rice (1984) believed that allelopathic substances inhibit cell division and elongation by deforming the nucleus and strong cell vacuolisation. Inhibition of plant growth may also be associated with a reduction in nutrient uptake due to impaired membrane integrity (Klein, Blum, 1990; Baziramakenga et al., 1995; Możdżeń et al., 2016), inhibition of plasmolemic proton pump activity, which plays Effect of M orus alba L. leaf extracts on seeds germ ination and the seedlings grow th of Sinapis alba L. and Cucum is sativus L. Jo an na B ie l-P ar zy m ię so 104 a key role in the growth of plant cells (Janicka-Russak et al., 2004), or with changes in hormonal balance (Rice, 1984; Vaughan, Ord, 1991; Wójcik-Wojtkowiak, 1998). �e e�ects of phenolic compounds can be observed in this study, as mentioned previous- ly (Grześkowiak, Łochyńska, 2017). Phenols reduce protein biosynthesis, disrupt lipid metabolism, and inhibit the synthesis of porphyrin compounds, including chlorophyll synthesis (Wójcik-Wojtkowiak, 1998). In this experiment, symptoms of chlorosis were noted in mustard plants watered with 10% extracts. Bright patches on the leaf surface indicated a chlorophyll de�ciency and most likely a�ected photosynthesis and dark res- piration (Einhelling, 1994; Hussain, Reigosa, 2011; Możdżeń, Repka, 2014; Skrzypek et al., 2015). Inhibitory activity of allelopathic compounds includes disorders of oxidative phosphorylation, reduction of ATP levels, and reduction of oxygen uptake. Energy de- �ciency interferes with active transport of substances within the plant and functioning of cytoplasmic membranes for which a constant supply of metabolic energy is neces- sary (Barkosky, Einhelling, 2003; Einhelling, 1994). Many studies (e.g. Wójcik-Wojtkowiak, 1998; Hussain, Reigosa, 2011; Możdżeń et al., 2018, 2020) indicate that allelochemical compounds interfere with water intake, its transport, and cause its gradual loss. As a result of these phenomena, they reduce the intensity of transpiration, induce the closing of stomata, and reduce the overall and active sorption surface of the roots. In studies with mulberry leaf aqueous extracts, di�erences were found in the water content of mustard and cucumber organs treated with this type of extracts (Fig. 1 – Appendix 1). �e withering of mustard plants watered with 10% mulberry extract may have been a sign of irregularities in the uptake of water by the roots and reduction of their sorption surface. It is not known whether the production of plant allelopathic substances is a  de- liberate strategy developed to counter competition or an accidental occurrence, pre- served in subsequent generations, allowing the plant to synthesise an advantage over other plants in a  particular ecosystem (King, 2003). Whittaker (1972) put forward the theory that allelopathic interactions of chemical compounds present in plants are created as a result of pressure from herbivores. It was intended to be a reaction that repelled herbivores by releasing plant secretions from leaves, stems, and roots into the environment. �ese types of substances may have accidentally played a  role in plant-plant interactions. Because they gave the plant the bene�t of reduced com- petition, their synthesis was maintained. �e need to reduce the use of chemicals in horticulture and agriculture, due to the high costs of synthetic plant protection prod- ucts and the emergence of herbicide-resistant weeds, provides an opportunity to use allelopathy as a source of safer substances that improve the quality of agricultural pro- duction (Cheng, Cheng, 2015). �is is why plant-based chemicals are constantly being sought as a basis for synthesising natural herbicides (Duke et al., 2000; Vyvyan, 2002; Gniazdowska, Bogatek, 2005). 105 Conclusion (1) �e aqueous extracts of mulberry leaves (Morus alba L.) inhibited the germina- tion of mustard seeds (Sinapis alba L.); as the concentration of extract increased, the time of seed germination was delayed and number of germinating seeds signi�cantly decreased; for cucumber (Cucumis sativus L.) signi�cant inhibition of the seed germi- nation process was only observed with 10% mulberry extract, as compared to control. (2) Regardless of the concentration of extracts and the time point of watering, a neg- ative e�ect of mulberry leaf extracts on mustard and cucumber growth was demon- strated; mustard plants were more sensitive to extracts than cucumber plants. (3) Fresh and dry mass of organs grown from seeds germinated on substrates with mulberry extracts in low concentrations was higher than in the control; with increas- ing extract concentration, regardless of the time point of watering with extracts, the tested plants were characterised by a smaller increase in fresh and dry mass for almost every organ compared to control; di�erences in percentage water content depended on the plant organ, extract concentration, and watering time. Con�ict of interest �e author declares no con�ict of interest related to this article. References Ahmed, M., Wardle, D.A. (1994). Allelopathic potential of vegetative and �owering ragwort (Senecio jacobaea L.) plants against associated pasture species. 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A  w at er c on te nt o f o rg an s i n m us ta rd (S in ap is al ba L .) – A , B a nd c uc um be r ( C uc um is sa tiv us L .) – C , D , f or p la nt s w at er ed w ith e xt ra ct s o f m ul be rr y le av es (M or us a lb a L. ): A , C – d ur in g ge rm in at io n ph as e, B , D – d ur in g gr ow th p ha se (m ea n va lu es fr om 5 re pl ic at es ) 109 Abstract Plant growth and development can be modi�ed, including modi�cation by chemical processes that result from neighbouring plants. If interactions in the natural environment between one plant and another are of a chemical nature, then this phenomenon is called allelopathy. �e aim of the study was to determine the e�ect of aqueous extracts of Morus alba L., at concentrations of 3%, 5% and 10%, on the germination and growth of Sinapis alba L. (mustard) and Cucumis sativus L. (cucumber). It was found that allelopathins contained in the extracts slowed the germination of both species. �e highest, 10%, extracts signi�cantly inhibited germination. It was found that with an increase in allelopathin concentration, there was a signif- icant inhibition of the growth of underground and above-ground plant organs. A complete lack of growth was observed for mustard plants grown from seeds watered with extracts during germination for 48 hours. Compared to the control plants, a di�erences in the growth of fresh and dry mass in plants watered with extracts during the germination and growth phases were found. Depending on the timing of treatment and the type of organ tested, aqueous mulberry leaf extracts at lower concentrations had a  positive e�ect on the growth and development of the analysed species. Extracts with a higher concentration of chemical compounds had a negative impact on both mustard and cucumber. Key words: aqueous extract, Cucumis sativus L., fresh and dry mass, plants length, Sinapis alba L. Received: [2020.04.07] Accepted: [2020.06.20] Wpływ wyciągów z liści Morus alba L. na kiełkowanie oraz wzrost Sinapis alba L. i Cucumis sativus L. Streszczenie Wzrost i rozwój roślin jest mody�kowany, m.in. przez procesy chemiczne, wynikające z sąsiedztwa innych roślin. Jeśli oddziaływania w  środowisku naturalnym jednej rośliny na drugą mają charakter rywalizacji chemicznej, to zjawisko określa się mianem allelopatii. Celem przeprowadzonych tu eksperymentów było zbadanie wpływu wodnych wyciągów z  liści Morus alba L., o  stężeniach 3%, 5% i  10%, na kiełkowanie i  wzrost Sinapis alba L. oraz Cucumis sativus L. Okazało się, że zawarte w  ekstraktach allelopatiny spo- walniały kiełkowanie nasion obydwu gatunków. Najwyższe, 10% ekstrakty, wyraźnie ograniczały zdolność kiełkowania. Stwierdzono, że wraz ze wzrostem koncentracji allelopatin następowało istotne zahamowanie wzrostu organów podziemnych i nadziemnych badanych roślin. Całkowity brak wzrostu wykazano dla ro- ślin gorczycy wyrosłych z nasion podlewanych wyciągami w czasie kiełkowania przez 48 h. W porównaniu z roślinami z kontroli, wykazano zróżnicowanie przyrostu świeżej i suchej masy u roślin podlewanych eks- traktami w  fazach: kiełkowania oraz wzrostu. W  zależności od czasu traktowania i  od rodzaju badanego organu, wodne wyciągi z  liści morwy w  niższych stężeniach miały pozytywny wpływ na wzrost i  rozwój analizowanych gatunków. Ekstrakty o większej koncentracji związków chemicznych wpływały negatywnie, zarówno na gorczycę, jak i na ogórka. Słowa kluczowe: wyciągi wodne, Cucumis sativus L., świeża i sucha masa, wzrost roślin, Sinapis alba L. Information on the author Joanna Biel-Parzymięso She is interested in an allelopathic interaction between weeds and crop plants. Effect of M orus alba L. leaf extracts on seeds germ ination and the seedlings grow th of Sinapis alba L. and Cucum is sativus L.