不同光强条件下柠条锦鸡儿的种子萌发和幼苗生长特征

Characteristics of seed germination and seedling growth of Caragana korshinskii under different light intensities

在不同光照强度(自然全光照的55.4%、18.9%、5.5%、2.2%和0.5%)人工遮荫条件下,研究了柠条锦鸡儿(Caragana korshinskii)种子萌发和幼苗生长的特征。结果表明:柠条锦鸡儿种子的萌发率、萌发速率、萌发指数和萌发值均在18.9%光照处理最大,且随遮荫程度的增强逐渐减小;活力指数随着光照的减弱逐渐增大;尽管幼苗的株高随光照的减弱而增大,但基径、复叶数、主根长和总干质量均随着光照的减弱而持续减小或呈波动性减小趋势,表明遮荫不仅影响了幼苗基径的增大和复叶数的增加,而且限制了幼苗主根的伸长和干物质的积累;比叶面积随光照的减弱而增大,但根冠比随光照的减弱而减小。研究表明,柠条锦鸡儿种子的萌发对光强表现出一定程度的依赖,强光下的萌发抑制可能与强光引起的短期水分胁迫有关;光照对幼苗生长的促进作用反映了柠条锦鸡儿对自然分布区充足光照资源的适应,幼苗在不同光强下具有较高的形态学可塑性。

Under different light intensities [ 55.4%, 18.9%, 5.5%, 2.2%, 0.5% of natural sunlight （NS） ] created by shading, we examined the effects of light intensity on the seed germination and seedling growth of Caragana korshinskii. The results showed that the maximums of germination percentage, germination rate, germination index and germination value of C. korshinskii seeds were all observed under the treatment of 18.9% NS and all these four parameters decreased with the decrease of light intensity. The reduction of light intensity resulted in the gradual increase of vigor index. Basal stem diameter, paripinnate number, taproot length and total dry mass of C. korshinskii seedlings all declined continuously or with fluctuation, while shoot height increased when the light density decreased gradually, indicating that lower light intensity not only affect the growth of basal stem diameter and the increase of paripinnate number but also restrict the elongation of taproot and the accumulation of dry matter of seedlings. Increase in specific leaf area of seedlings was detected with the weakness of light intensity. Root/shoot ratio, however, decreased with the decline of irradianee. In summary, our results suggested that seed germination of C. korshinskii was in part dependent on the light intensity, and short-term water stress resulted from high light intensity could contribute to the inhibition of seed germination. The facilitation ofhigh light intensity to the growth of seedlings suggested the adaptation of C. korshinskii to sufficient light resource of its natural distribution regions, and seedlings had great morphological plasticity across different light regimes.