Drought is a major threat to global food security, with climate change enhancing its severity. Living organisms employ various adaptation strategies against loss of water, with desiccation tolerance representing the most extreme ones. The present study provides an analysis of dehydration response mechanisms in Pisum sativum, focusing on early seedling development. The experiments were carried out on 3‑day-old seedlings (with radicle up to 20 mm) and on similar seedlings with cotyledons removed, each subjected to 24 h of drying. Stress response was assessed through growth analysis, electrolyte leakage tests, and measurements of ascorbate content and lipid peroxidation products. The results demonstrated that, although dried seedlings underwent oxidative stress, those with cotyledons showed a superior recovery capacity upon rehydration. This was evidenced by their ability to regenerate adventitious roots, compensating for the damage to their primary root system. We further monitored the ABA-dependent stress response by registering the expression of key genes associated with ‘response to water deprivation’ (ABI3, ABI4, ABI5, HVA22, PER1, LEA14, RD22, LTI65, and LTP4). Drying followed by rehydration resulted in the 40-fold upregulation of ABI5 in the hypocotyls of both cotyledon-removed and intact seedlings, and the 108-fold upregulation of this gene specifically in the roots of seedlings with intact cotyledons. Our results demonstrate an extended role for cotyledons, which involves not only nutrient storage but also the coordination of developmental and stress adaptation under severe water deficit. We propose that the post-germination stage constitutes a ‘resilience window’ of plant development. During this period, desiccation-protective mechanisms remain partially active in the embryonic axis, supporting the survival of the developing seedling, whereas newly formed tissues derived from the meristems do not acquire the desiccation tolerance characteristic of seeds.
Smolikova et al. (Mon,) studied this question.