干旱胁迫下华北驼绒藜种子大小及苞片对萌发和幼苗生长的影响

干旱是影响荒漠区植物种子萌发和幼苗生长的关键因素。以多年生强旱生半灌木华北驼绒藜为对象,研究了不同干旱程度(0、100、200、300和400 g·L^-1 PEG6000)下,种子大小及苞片有无对种子萌发及幼苗生长的影响。结果表明: 干旱胁迫显著抑制了种子萌发和幼苗地上部的生长。100和200 g·L^-1 PEG6000处理显著增加了幼苗根长,而300和400 g·L^-1 PEG6000处理显著降低了幼苗根长。与无苞片相比,有苞片使种子的发芽率显著降低12%,发芽指数显著降低50.5%,幼苗的地上部长度显著增加20.8%,幼苗根长显著增加6.3%。种子大小对种子发芽指数无显著影响,但与小种子相比,大种子发芽率显著提高3%,幼苗的地上部长度显著增加20.5%,幼苗根长显著增加33.0%。在干旱条件下,苞片能延缓种子的萌发速度,种子大小能影响后代的存活几率,二者共同影响华北驼绒藜对极端干旱环境的适应性。

Effects of seed size and bract of Ceratoides arborescens on germination and seedling growth under drought stress

Drought is a crucial factor affecting seed germination and seedling growth of desert plants. In the study, we examined the effects of seed size(large, small) and bract(without bracts, with bracts) on seed germination and seedling growth of Ceratoides arborescens, a perennial super xerophyte semi-shrub, under different drought levels(0, 100, 200, 300 and 400 g·L^-1 PEG6000). The results showed that drought stress significantly inhibited seed germination and reduced shoot length of seedlings. Under the 100 and 200 g·L^-1 PEG6000 stress conditions, root length of seedlings were significantly increased, whereas it was significantly reduced under the 300 and 400 g·L^-1 PEG6000 stress intensities. The presence of bract significantly reduced seed germination percentage by 12%, germination index by 50.5%, and shoot length by 20.8%, but increased root length by 6.3%. Seed size did not affect seed germination index. Compared with small seeds, germination percentage of large seeds was 3% higher, shoot length and root length of seedlings were 20.5% and 33.0% higher, respectively. In summary, seed bract in C. arborescens through delaying seed germination and seed size through influencing the survival of the early state of seedling were the most important strategies to adapt extremely arid environment.