The absence of light during discontinuous hydration affects the viability of a cactus species

Abstract

Seeds maintained on seed banks are submitted to two conditions of light during discontinuous hydration: presence or absence. We aimed to investigate the influence of light during discontinuous hydration and its relationship with the establishment of the cacti species. We raised two hypotheses: discontinuous hydration increases the longevity of seeds, and the presence and the absence of light during hydration/dehydration cycles (HD cycles) present different benefits in maintaining their viability in the soil seed bank for a longer time. We subjected seeds to HD cycles in the presence and absence of light. After that, we established a soil seed bank and analyzed the germinative behavior and biochemical compounds at intervals of 0, 3, 6, 9, 12, and 15 months. HD cycles prolonged seed longevity, confirming our first hypothesis. Treatments of HD cycles in the darkness provided the maintenance of seed viability for a period longer than 9 months, which corroborates our second hypothesis. HD cycles in the presence of light only favor the germination behavior of fresh seeds. Reducing sugars are consumed during the first months in seeds buried in the soil. However, protein concentration remains higher in seeds not submitted to HD cycles after 12 months. Our study proposes the existence of a “seed dark hydration memory” related to seed longevity and a “seed light hydration memory” related to the germination of fresh seeds. Thus, the response to light incidence during discontinuous hydration represents an important strategy for the reproductive success of positive photoblastic species in their natural environment.