Discontinuous hydration alters seed germination under stress of two populations of cactus that occur in different ecosystems in Northeast Brazil

Abstract

The water uptake by the seed in arid and semi-arid ecosystems may not be continuous, but may occur in hydration and dehydration cycles (HD). In order to investigate the benefits of discontinuous hydration on seed germination of Pilosocereus catingicola subsp. salvadorensis subjected to environmental stresses, an imbibition curve was determined and times X, Y and Z selected, corresponding to 25, 50 and 75% of the first phase of imbibition, respectively. Seeds of two populations (Caatinga and Restinga) were subjected to 0, 1, 2 and 3 HD cycles, with 48 h of dehydration. Water and saline stress responses were tested at five osmotic potentials (0.0, –0.1, –0.3, –0.6 and –0.9 MPa). Discontinuous hydration provided greater tolerance to water and saline stress in the seeds from the Caatinga region. When the seeds were subjected to water stress, the reduction of the mean germination time (MGT) provided by HD cycles decreased with increasing concentration of the solution. In saline stress, the reduction of MGT was greater in the solutions with the highest concentrations. We conclude that the seeds of the same species collected from populations located in different ecosystems have different germination responses after passage through discontinuous hydration and HD cycles. This provides greater tolerance to environmental stresses but with different responses among populations.

Effect of hydration and dehydration cycles on Macroptilium atropurpureum seeds germination under water deficit conditions

“…In M. atropurpureum seeds, HD cycles may not have provided the germinative metabolism, inhibiting the positive effects that the HD cycles could confer during the seeds germination. Lima and Meiado (2017) demonstrated that the numbers and the hydration times had direct effects on seeds response to HD cycles. In this present study, hydration times and numbers of HD cycles may had interfered negatively on M. atropurpureum seed germination.…”

“…Each species germinates at a specific critical osmotic potential (Oliveira et al 2017). In addition, the environmental conditions from which the seeds were produced may influence the physiological responses to the abiotic conditions present during the germination of these seeds (Lima and Meiado 2017). Sevik and Cetin (2015), in germination experiments with Cupressus sempervirens L. (Cupressaceae), Koelreuteria paniculata Laxm.…”

“…For each treatment in this study, four replicates with 25 seeds were used, which were placed to germinate in 5 cm diameter Petri dishes containing two layers of filter http://cpsjournal.org paper moistened with 3 mL of PEG 6000 solution. The Petri dishes were sealed with parafilm plastic and maintained under white light (12 h photoperiod) and 25°C (Lima and Meiado 2017). The experiment took place in a growth chamber.…”

“…Lima and Meiado (2017) demonstrated in experiments with seeds of Pilosocereus catingicola (Gürke) Byles & G.D. Rowley subsp. salvadorensis (Werderm.)…”

“…Once this occurs, the seed has its germination process interrupted and loses the water absorbed to the environment (Fenner and Thompson 2005). These interruptions during germination process occur in arid and semi-arid environments, where water presents a limit of space and time in its availability, subjecting seeds to hydration and dehydration cycles (HD cycles) (Lima and Meiado 2017). Dubrovsky (1998) pointed that discontinuous hydration ensures a high survival rate during desiccation, demonstrating that seeds may present seed hydration memory, caused by the discontinuous imbibition process.…”