Does discontinuous hydration of Senna spectabilis (DC.) H.S. Irwin & Barneby var. excelsa (Schrad.) H.S. Irwin & Barneby (Fabaceae) seeds confer tolerance to water stress during seed germination?

Abstract: Seed hydration memory is the ability of seeds to retain biochemical and physiological changes caused by discontinuous hydration. This study aimed to determine if Senna spectabilis (DC.) H.S. Irwin & Barneby var. excelsa (Schrad.) H.S.Irwin & Barneby (Fabaceae) present seed memory and evaluate the effects of hydration and dehydration cycles (HD) on the seed germination of this species when submitted to conditions of water stress. Seeds underwent HD cycles (0, 1, 2 and 3 cycles) corresponding to the hydration times X (6 hours), Y (16 hours) and Z (24 hours), determined from the imbibition curve, with 5 hours of dehydration and submitted to water stress conditions. Germination was evaluated at 0.0, -0.1, -0.3, -0.6 and -0.9 MPa, obtained with polyethylene glycol 6000 solution. Germinability (%), mean germination time (days) and hydrotime (MPa d-1) were calculated. The seeds of S. spectabilis var. excelsa are sensitive to the low osmotic potentials tested in this study, however, when submitted to the HD cycles of 16 hours hydration (time Y), the tolerance to water stress conditions is increased. In addition, the observed benefits on the evaluated germination parameters show that S. spectabilis var. excelsa present seed hydation memory.

摘要：种子水合记忆（Seed hydration memory）是指种子能够保留由间断性水合作用引发的生化与生理变化的能力。本研究旨在探明美丽决明（Senna spectabilis (DC.) H.S. Irwin & Barneby var. excelsa (Schrad.) H.S.Irwin & Barneby，豆科Fabaceae）是否存在种子水合记忆，并评估水分胁迫条件下，水合-脱水循环（HD循环）对该物种种子萌发的影响。供试种子接受了0、1、2、3轮次的水合-脱水循环处理：基于吸胀曲线确定的水合时长分别为X（6小时）、Y（16小时）与Z（24小时），脱水时长均为5小时，随后将种子置于水分胁迫环境中。本研究采用聚乙二醇6000（polyethylene glycol 6000，PEG 6000）溶液配制得到0.0、-0.1、-0.3、-0.6及-0.9 MPa的渗透势梯度，以此评估种子萌发情况，并计算了发芽率（%）、平均萌发时间（天）以及水时（hydrotime，单位：MPa·d）三项指标。本试验所用的美丽决明种子对本次测试的低渗透势环境较为敏感，但经16小时水合（时长Y）的水合-脱水循环处理后，其对水分胁迫的耐受性显著提升。此外，针对所评估萌发参数观测到的正向改善效应表明，美丽决明确实存在种子水合记忆。