Germination and seedling growth responses of the weed Sesbania cannabina to salinity and drought under iso-osmotic conditions

Sesbania cannabina (Retz.) is identified as a troublesome invasive weed in certain agricultural systems. This study quantified and compared its ecophysiological responses to iso-osmotic salinity (NaCl) and drought (PEG ۶۰۰۰) during germination and seedling establishment. Two independent experiments were conducted in a completely randomized design with osmotic potentials ranging from ۰ to −۱۰ bar at the Agronomy Laboratory of the University of Jiroft. Evaluated traits included germination indices, root and shoot length, and root and shoot dry weight. ANOVA revealed highly significant effects (P ≤ ۰.۰۱ p \le ۰.۰۱ P ≤ ۰.۰۱) for stress type, osmotic potential, and their interaction across all traits. Mean comparisons (P≤ ۰.۰۵p \le ۰.۰۵ P≤۰.۰۵) showed that mild stress (up to −۲ bar) had marginal impacts, whereas potentials below −۴-۴−۴ bar sharply reduced seedling growth. Non-linear regression models (Weibull, Logistic, and Gompertz) accurately fitted the stress-response curves (R۲ ≥ ۰.۹۷). To quantify tolerance limits, the EC۵۰ (osmotic potential causing a ۵۰% trait reduction) was calculated. An independent t-test confirmed a highly significant divergence (P ≤ ۰.۰۱) between the two stress regimes. Drought severely inhibited root elongation (EC۵۰ = −۵.۳ bar). Conversely, roots exhibited exceptional salt tolerance (EC۵۰ > −۱۰.۳۸ bar). In conclusion, under the tested laboratory conditions, S. cannabina seedlings demonstrate significantly greater physiological resilience to salt toxicity than to purely osmotic water deficit.

کلیدواژه ها:

Halophyte ، Non-linear modeling ، Osmotic stress ، Sesbania cannabina ، Tolerance thresholds