Unveiling the influence of stress memory: enhancing stress tolerance in seedlings through seed stage stress exposure

Plants leverage past stress experiences, whether occurring individually or in sequential combinations, to bolster their responses to future stressful situations, a phenomenon known as stress memory. Hydration cycles imitate a natural process within the environment when seeds are integrated into the soil seed bank, and experience numerous hydration and dehydration cycles due to inconsistent water supply. This study investigates the potential for stress exposure during the seed stage to enhance stress tolerance in subsequent seedlings, shedding light on the potential transfer of stress-related memories between various life stages following multiple stress-inducing experiences. We specifically employed hydration (soaking) and dehydration (simulating drought stress) cycles (0, 1, and 2 HD cycles) as stimuli to activate stress memory in seeds. Following germination, a randomized experiment was conducted, subjecting the seedlings to various water treatments, including control conditions, 50% and 75% reductions in soil humidity, and rewatering, with a focus on assessing recovery. Remarkably, all germinative parameters exhibited similar responses irrespective of the number of HD cycles. However, notable variations in plant growth and biomass accumulation were observed in seedlings subjected to HD cycles. These plants displayed reduced sensitivity to drought-induced damage, maintaining growth rates even under stressful conditions. Importantly, the relative water content remained unaltered in plants subjected to stress resulting from HD cycles. Consistently, the results highlight that intermittent hydration supports plant survival under stress by mitigating drought-induced damage. Stress memory acquired through stress exposure during the seed stage stress enhances drought resistance by delaying dehydration and reducing water loss, ultimately preserving growth.