干旱胁迫下白刺花种子大小与萌发对策

种子大小与种子萌发及其与环境因子的关系是植物种子萌发对策研究中的重要科学问题之一。采用PEG模拟干旱法研究不同干旱胁迫强度(0,5%,10%,15%,20%)下,白刺花(Sophora davidii)种子萌发进程、种子大小与种子萌发及种子命运的关系。结果表明:不同干旱胁迫下,白刺花种子具有相似的萌发进程,但中度干旱处理(10%PEG)萌发率显著高于零干旱(0%PEG)和重度干旱处理(P0.05),重度干旱处理(20%PEG)种子萌发开始时间晚于零干旱和中度干旱处理;种子大小与种子萌发开始时间的关系表现为零干旱处理下呈极显著负线性关系,中度干旱处理(5%PEG,10%PEG)下无相关关系,重度干旱处理(15%PEG,20%PEG)下呈负二次曲线关系;种子大小对种子命运的影响表现为零干旱处理有利于大、小种子萌发和小种子休眠,中度干旱处理(10%PEG)增加中等种子萌发、大种子休眠和小种子死亡风险,重度干旱处理(15%PEG,20%PEG)增加大种子死亡风险、中等种子和小种子休眠。综合分析表明,白刺花种子大小与萌发行为及种子命运的关系具有较强的环境依赖性,即种子萌发行为表现为顺境下种子越大萌发越快,逆境下小种子和大种子较中等种子萌发更快;种子命运表现为顺境增加种子死亡的风险,中度干扰有利于种子萌发,逆境则有利于种子休眠。

Seed size and germination strategy of Sophora davidii under drought stress

Sophora davidii is an important leguminous shrub that is widely used for revegetating areas experiencing karst rocky desertification in southwest China. Karst is a fragile environment that is very sensitive to environmental and climate change, and is often under considerable drought stress. Seed size is a prominent life history trait of plants. Experiments were conducted in the laboratory to evaluate the effect of osmotic potential and seed size on germination, dormancy and mortality. The effect of drought stress on seed germination was examined by using different concentrations of polyethylene glycol treatments(0, 5%, 10%, 15%, and 20%) to provide designated osmotic potentials. The results showed that S. davidii seeds had a similar germination process under different degrees of drought stress. Seed germination percentage under moderate drought stress(10% PEG) was significantly higher than under non-stress and severe stress treatment(P < 0.05). The initiation of seed germination under severe drought stress(20% PEG) was slower than under non-stress and moderate stress. Seed size had a significant negative linear correlation with the initiation time for seed germination under non-stress treatment and a negative curve correlation for treatments under severe stress treatments(15% PEG, 20% PEG), while there was no correlation for moderate drought stress(5% PEG, 10% PEG). The relationship between seed size and seed fate of S. davidii showed that non-stress conditions may beneficial to germination for large or small seeds and dormancy for small seeds; moderate drought stress can drive medium seed germination, large seed dormancy and small seed mortality, and severe drought stress(15% PEG, 20% PEG) can lead to large seed mortality, and medium and small seed dormancy. Seed size, germination behavior and seed fate were heavily dependent on environmental factors. The germination strategy had a diverse pattern, that is, the larger seed size, the earlier seeds germination; in non-stress conditions, but larger and smaller seeds germinate earlier than medium seeds in adversity. The seed fate of S. davidii showed that seed mortality increased in non-stress conditions, seed germination was facilitated under moderate stress, and that seed dormancy was expedited in adversity. The information in this study may help land managers develop effective and sustainable revegetation management strategies.