Climate and seed size of a dry forest species: influence on seed production, physiological quality, and tolerance to abiotic stresses

Abstract: Seed production, quality and germination are likely to be affected by a drastic climate change in semi-arid areas predicted for the end of the century. We evaluated Anadenanthera colubrina var. cebil (Griseb.) Altschu (Fabaceae) seeds of different sizes, populations and harvest years for germination and tolerance to environmental stresses aiming to predict impacts of future climate. Seeds were accessed for germination temperature, salinity and osmotic limits and requirements. Germination of large and small seeds harvested in different populations was evaluated in optimum and stressful temperature, salinity and water deficit. A glasshouse pot assay tested weekly irrigation regimes and seedlings emergence and growth. Optimal temperature for seeds germination was 34.8 oC and limits were 5.6 oC and 50.9 oC. Large and small-sized seeds do not differ in germination, however small seeds are more efficient in stressful conditions. Seedlings can emerge and grow under small weekly irrigation for four months. The predicted increase in temperature will not impair germination, however, the time available for seedling establishment will decrease due to lacking rainfall. The increase in the amount of small-sized seeds produced in drought years is a strategy for coping with harsh environments, rather than a decrease in seed quality.

摘要：本世纪末半干旱地区预计将发生剧烈气候变化，该变化可能对种子生产、品质及萌发过程产生显著影响。本研究针对不同粒径、不同种群及不同收获年份的塞比尔弯荚金合欢（Anadenanthera colubrina var. cebil (Griseb.) Altschu，豆科Fabaceae）种子开展萌发试验与环境胁迫耐受性评估，旨在预测未来气候变化的影响。本研究测定了种子萌发的温度、盐度及渗透胁迫阈值与需求条件；针对不同种群收获的大、小粒径种子，分别在最优及胁迫性温度、盐度与水分亏缺条件下开展萌发评估；通过温室盆栽试验，探究了每周灌溉制度对幼苗出苗与生长的影响。该种子的最优萌发温度为34.8℃，温度耐受下限与上限分别为5.6℃与50.9℃。大、小粒径种子的萌发率并无显著差异，但小粒径种子在胁迫环境下的表现更优。幼苗可在每周少量灌溉的条件下存活并生长达四个月之久。未来预计的温度升高不会对种子萌发造成不利影响，但由于降雨量减少，幼苗建成的可用时间将会缩短。干旱年份产出的小粒径种子占比提升，是植物应对恶劣环境的一种生存策略，而非种子品质下降的表现。