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

Abstract

The imbibition process, which is essential for seed germination, can be interrupted due to lack of water in the environment. Once this occurs, seeds have its germination process interrupted and loses the water absorbed to the environment. The objective of this study was to evaluate the effects of hydration and dehydration cycles (HD cycles) on seed germination of Macroptilium atropurpureum under water deficit conditions. Seeds of M. atropurpureum were submitted to 0 (control), 1, 2 and 3 HD cycles at different hydration times. In addition, the seeds were also submitted to osmotic potentials of 0.0, -0.1, -0.3, -0.6 and -0.9 MPa for water deficit simulation. Although the seeds germinated in all of the osmotic potentials used, the seeds presented a reduction in the percentage of germination, independently of the number of HD cycles and the hydration time between each cycle. In addition, HD cycles also negatively affected the mean germination rate, promoting a reduction of this parameter as seeds were submitted to HD cycles and osmotic potentials. Thus, the results demonstrated that HD cycles did not provide an increase in water stress tolerance in M. atropurpureum seeds during germination. Highlighted Conclusions 1)Macroptilium atropurpureum seeds can germinate even in low osmotic potentials conditions. 2) Discontinuous hydration confers a negative effect on M. atropurpureum germination and does not provide a greater tolerance to water deficit.Seed imbibition is a key process in the plant life cycle determining whether seed germination and individual growth will be successful or not (Ribeiro et al. 2015). The imbibition process, which is essential for seed germination, can be interrupted due to lack of water in the environment. 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.In addition to the high survival rate during desiccation highlighted by Dubrovsky (1998), HD cycles may provide other advantages during the germination process of the seeds of some species. Rito et al. (2009) demonstrated that seeds of Cereus jamacaru DC. subsp. jamacaru (Cactaceae) present seed hydration memory, since, after being submitted to HD cycles, seeds had their percentage of seed germination increased. Pedrero-López et al. (2016), in experiments with seeds of Dodonaea viscosa Jacq. (Sapindaceae) also observed a significant increase of germinability after HD cycles from 22.5% to 63.3%. Discontinuous hydration may also provide greater tolerance to abiotic stress conditions, as observed by Li et ...

Envelhecimento acelerado em sementes de Mimosa tenuiflora (Willd.) Poir.

“…Acredita-se que estes fungos sejam inerentes às sementes da espécie, pois foram tomados todos os cuidados necessários em relação à assepsia do material utilizado. Garcia et al [7] e Caldeira e Perez [17] envelhecimento acelerado.…”

“…Dentre os aspectos a serem considerados quando se trabalha com qualidade de sementes e produção de mudas, a germinação e o vigor das sementes são os mais empregados, com destaque para o segundo que, de acordo com Souza et al [6], relaciona-se com o potencial de armazenamento e deterioração das sementes. Em geral, sementes com maior vigor apresentam germinação mais elevada e maior quantidade de plântulas normais, mesmo após terem sido submetidas a condições adversas ou armazenamento prolongado [7].…”

Interpopulational seed hydration memory does not affect seed germination of Xiquexique gounellei (F.A.C.Weber ex K.Schum) Lavor & Calvente subsp. gounellei (Cactaceae) under water deficit

“…After the start of imbibition, we weighed the seeds at 60 minute intervals until the germination process was completed with radicle protrusion. After establishing the imbibition curve, we selected a point on the curve named time X, which corresponded to half phase one of the imbibition process (Lima et al, 2018b). We chose this imbibition time because seed germination of most Caatinga cacti is favoured by discontinuous hydration in short hydration periods (Lima and Meiado, 2017; 2018b).…”

“…We kept the dishes at a temperature of 30°C during the period corresponding to the time X of the imbibition curve, which was previously determined. After hydration for a period equivalent to time X, we removed the seeds from contact with water, placed them to dry on dishes at 30°C and weighed them on an analytical balance at 60 minute intervals, until the samples returned to their initial weight (Lima et al, 2018b).…”

“…Seeds that undergo this discontinuous hydration can adapt as a survival strategy in adverse conditions, through biochemical regulations that confer resistance (López-Urrutia et al, 2014). Under laboratory conditions, HD cycles are simulated using the hydropriming technique, which consists of promoting hydration until the middle of the first phase of the imbibition process, with dehydration taking place in a forced-air dry oven at a temperature of 30°C, until the seeds return to their initial weight .…”