Seed Germination of Tropical Trees under Polyethylene Glycol-Induced Osmotic Stress: A Comprehensive Study for Early Screening of Drought Tolerance
Abstract
Drought-induced water stress is a major environmental factor affecting seed germination and plant establishment in tropical forest ecosystems. This study examined the effects of polyethylene glycol (PEG)-induced osmotic stress on the germination of seven tropical tree species: Hardwickia binnata, Butea monosperma, Acacia catechu, Acacia nilotica, Holoptelea integrifolia, Diospyros melanoxylon, and Pithecellobium dulce. Seeds were subjected to three osmotic levels: 0 MPa (control), −0.5 MPa (moderate stress), and −1.0 MPa (severe stress). Germination experiments were conducted under controlled laboratory conditions using a factorial completely randomized design. Results showed that increasing osmotic stress significantly reduced germination in all species. Under control conditions, Hardwickia binnata showed the highest germination (90%), while other species exhibited moderate germination rates. Under moderate stress (−0.5 MPa), germination declined substantially, though Hardwickia binnata and Butea monosperma maintained relatively higher tolerance. Severe stress (−1.0 MPa) almost completely inhibited germination in most species. Statistical analysis confirmed significant effects of species, treatment, and their interaction on germination response. The findings indicate strong species-specific differences in drought tolerance during the germination stage. Hardwickia binnata and Butea monosperma demonstrated greater resilience to water stress and may be suitable for afforestation and restoration programs in drought-prone regions.
