Memory or Reset? Transgenerational Water Stress in an Herbaceous Species from the Semiarid Region

Annual plants native to seasonally dry environments are exposed to fluctuating water availability across successive generations. Environmental conditions experienced by parental plants can influence offspring performance through a phenomenon known as transgenerational memory. This study examined drought-induced transgenerational memory in Macroptilium lathyroides, an annual Fabaceae native to the Caatinga, the largest tropical semiarid region in South America. Seeds from natural populations were cultivated over three consecutive generations under well-watered (FC100%; No Stress) and water-limited (FC40%; Stress) conditions. From third-generation (3G) progenies, germination was evaluated under different osmotic potentials, and plant performance was assessed under both FC100% and FC40% soil moisture regimes. Physiological responses in seeds and plants were analyzed using oxidative stress markers and hormonal profiling. No significant transgenerational effects were detected on germination or plant growth. However, changes in antioxidant and hormonal components were observed in the 3G-Stress progeny. Seeds from this group exhibited higher cytokinin and gibberellin concentrations, reflecting metabolic adjustments likely associated with the establishment of vigorous seedlings. In contrast, plants derived from the 3G-Stress progeny showed increased γ-tocopherol levels and reduced cytokinin and gibberellin concentrations. The absence of transgenerational effects on phenotypic traits of M. lathyroides indicates a high species resistance to transgenerational water stress, a key adaptive feature supporting survival under the irregular water availability characteristic of the Caatinga. The results underscore the remarkable adaptive capacity of species from the Brazilian semiarid region to marked hydric irregularity and highlight physiological adjustments in the progeny that may be triggered by parental drought history.