Effect of leachates on germination, seedling growth and vigour indices of Alternanthera sessilis
Leachates of all the tested sesame varieties showed significant reduction in the germination and growth attributes of
Alternanthera sessilis. The leachate of variety GT-10 showed lower germination percentage in
Alternanthera sessilis (16.67%) and it was statistically comparable with TMV-5 (23.33%). A reduction in germination percentage to an extent of 83.33 per cent was obtained with the application of leachate of GT 10, compared to control. Whereas, higher germination percentage was shown by the application of leachate of variety Thilak which was on par with Thilarani and Kayamkulam 1. The control treatment resulted in 100 per cent germination of
Alternanthera sessilis.
The root length of
Alternanthera sessilis was significantly inhibited by leachates of different sesame varieties and GT-10 (1.47 cm) exhibited shorter root length which was on par with TMV-5 (1.63 cm). Similarly, shorter seedling shoot length was observed in GT- 10 (1.10 cm) but was comparable with TMV-5 (1.20 cm). The results on plant weight also showed that lower seedling fresh and dry weight were noticed by the application of leachate of variety TMV-5 (0.22 g and 0.09 g respectively) which was on par with GT-10 leachate (0.23 and 0.11 g) (Table 1).
Similarly, whole plant leachate of GT- 10 resulted in lower SVI-I and SVI-II (43.00 and 1.81 respectively) and was statistically on par with TMV-5 (65.67 and 2.20 respectively (Fig 1 and 2). The SVI I and SVI II of seeds treated with GT 10 leachate were lower than control by 92.54% and 90.83% respectively.
The aqueous extracts of several allelopathic crops are found beneficial to suppress many weeds in the field conditions (
Irshad and Cheema, 2004). Inhibitory effects of sesame varieties might be owing to the presence of allelochemicals present in the whole plant leachates. Sesame contains several secondary metabolites, among which phenolic acids (18%), lipids (16%), flavonoids (14%), amino acid derivatives (9%) and alkaloids (5%) are the major chemical classes
(Dossou et al., 2021).
The phenolic compounds decrease germination by enhancing membrane damage, lipid peroxidation, electrolyte leakage and subsequent programmed cell death
(Bogatek et al., 2006).
Emulsion concentrate (EC) of sesame root exudate (240 µg/g) inhibited germination of broad leaved weeds
viz.,
Chenopodium album,
Anagalis arvensis and
Melilotus alba, by 80, 75 and 65%, respectively over control while, EC of sesame root exudates at 280 µg/g of soil inhibited the shoot and root biomass of
Chenopodium album by 86% and 89%,
Anagalis arvensis by 46% and 58% and
Melilotus alba by 42% and 72% respectively over control (
Kumar and Varshney, 2007).
Allelochemicals
viz., chlorogenic acid and iso-chlorogenic acid isolated from plant extracts of sunflower were found to possess inhibitory effect on seed germination
(Anjum et al., 2005). Aqueous extract of sunflower at 1:10 w/v inhibited the germination of broad leaved weed
Trianthema portulacastrum by 56.7%, shoot length by 25 % and root length by 31.82%
(Rashid et al., 2020).
Effect of leachates on germination, seedling growth and vigour indices of Setaria barbata
The germination of grassy weed,
Setaria barbata was markedly influenced by whole plant leachate of different sesame varieties. Leachates of all tested varieties inhibited the germination and growth of
Setaria barbata. Among the leachates, lower germination percentage was observed with the application of leachate of GT-10 (13.33%) and was on par with TMV-5 (16.67%). Compared to control, the germination percentage was lowered by 86.67% with the application of leachate of GT-10. The percentage inhibition of germination by leachates of other varieties were in the order; TMV 7 > GT 3 > GT 5 > VRI-1 > Thilathara > PKDS-8. While, higher germination percentage was observed with the application of leacahtes of varieties, Thilak, Thilarani and Kayamkulam 1.
Application of leachate of variety GT-10 resulted in shorter root length (1.40 cm) and was on par with leachate of variety TMV-5 (1.50 cm). The shoot length was also inhibited by leachates, among which, GT- 10 recorded the shortest shoot length (1.27 cm) which was statistically comparable with TMV-5 (1.28 cm). Application of GT-10 leachate registered lower fresh weight (0.20 g) and dry weight (0.08 g) of
Setaria seedlings and was on par with TMV-5 (0.19 g and 0.09 g respectively) (Table 2).
Similarly, lower SVI-I in
Setaria barbata was observed by the application of leachate of GT-10 (36.00) which was statistically on par with TMV-5 (46.33) (Fig 1 and 2). The SVI-II also exhibited the same trend and the lowest SVI-II in GT- 10 (1.05) was statistically comparable with TMV-5 (1.44). Application of GT 10 leachate lessened SVI I and SVI II to the tune of 93.89 and 93.59 % respectively, compared to control.
Unique allelochemicals in sesame like 9, 12-octadecadienoic acid (Z, Z) - methyl ester and hydroquinone inhibit the germination of seeds
(Verma et al., 2021). Aqueous extract of different plant parts of sesame (root, stem and leaf) at 100 mg/ mL delayed seed germination and reduced the shoot and root length of moso bamboo (
Phyllostachys edulis)
(Zhao et al., 2022). The allelochemicals
viz., flavonoids, alkaloids, tannins and phenols in the leachate of sesame might have inhibited the expression and elongation of bud cells and cell division.
Root extract of soybean (46%) inhibited seed germination of
Sorghum halepense by 50% (Mahmoodzadeh and Mahmoodzadeh, 2013). Aqueous extract of sunflower (10%) inhibited the germination of
Phalaris minor by 85.5%
(Sarvadamana et al., 2019). Nadeem et al., (2020) reported that application of aqueous fruit extract of safflower (8%) recorded the lowest germination percentage (53.33%) of
Echinochloa crusgalli while the shortest shoot length (5.82 cm) and root length (1.91 cm) were observed with the application of safflower leaf extract (8%).
Effect of leachates on germination, seedling growth and vigour indices of Cyperus rotundus
Whole plant leachates of different sesame varieties had significant inhibitory effect on the germination and growth of
Cyperus rotundus. Lower germination per cent in
Cyperus rotundus was observed with the application of leachate of variety GT-10 (10.00%) and was on par with TMV-5 (16.67%). Compared to control, the application of leachate of GT-10 l reduced the germination percentage by 90 per cent.
Significant inhibition in growth parameters of
Cyperus rotundus were also observed with the application of sesame whole plant leachates. The root length and shoot length of
Cyperus rotundus were also inhibited with application of leachate of GT-10 (2.17 cm and 1.87 cm) which was on par with TMV 5 (2.67 cm and 2.20 cm). Similarly the fresh and dry weight of
Cyperus rotundus were also decreased significantly with the application of leachate of variety GT-10 (0.30 g and 0.11 g respectively) (Table 3).
The same trend was observed in SVI I and SVI II. Lower values for SVI I and SVI II were observed by the application of leachate of GT 10 (40.33 and 1.11 respectively) which was statistically on par with TMV-5 (79.67 and 2.50 respectively) (Fig 1 and 2). The leachate of GT- 10 lowered SVI I and SVI II to a tune of 95.79 and 96.73 per cent compared to control.
Leaves of sesame contains specific chemicals like epigallocatechin, 3-epibartogenic acid and kaempferol derivatives that hinder the activity of α- amylase, involved in germination
(Dat et al., 2016). Leachate of sesame leaves (100% concentration) inhibited sprouting of
Cyperus rotundus rhizomes by 53.33% compared to control
(Hussain et al., 2017).
Application of EC formulation of sesame root exudates at 240 µg/g concentration of soil decreased the shoot and root biomass of
Cyperus rotundus by 81.30 and 91.9% respectively over control (
Kumar and Varshney, 2008).
Iqbal and Cheema (2009) reported that water and methanol extracts of sunflower (50%) was effective in suppressing the shoot length and dry weight of purple nutsedge.
Hussain et al., (2017) found that shoot length and dry weight of
Cyperus rotundus were reduced by 53.01 and 83% respectively with the application of sesame leachate at 100% concentration compared to control.
Geethika et al., (2022) observed a reduction in density and dry weight of
Cyperus rotundus with the application of sunflower aqueous extract (15 L/ha).