青海云杉休眠前后非结构性碳水化合物含量随海拔变化

[目的]冬季低温是决定高山林线树种能否生存的重要生态因素。休眠前后树木体内碳水化合物的变化能够反映出其安全越冬的策略。但目前高山林线树种休眠前后体内碳水化合物的变化及机理尚不清楚。为了探讨林线树种越冬期间的生存策略,[方法]本文以祁连山林线青海云杉为对象,研究了不同海拔(2 900、3 000、3 100、3 200、3 300 m)成年树枝、叶休眠前后非结构性碳水化合物含量变化,包括可溶性糖(葡萄糖和果糖)、淀粉以及糖/淀粉比值的变化。[结果]表明:(1)休眠前青海云杉当年及1年生叶在高海拔处NSC含量高于中、低海拔处NSC含量,而在枝条中高、中、低海拔间没有显著差异。(2)休眠后叶中NSC含量最高值在中海拔3 100 m处,显著高于高海拔;不同组织中NSC含量高于休眠前,叶片中尤为明显。(3)与休眠前相比,休眠后可溶性糖及淀粉含量增加,淀粉含量增加幅度显著,引起可溶性糖/淀粉比值降低。[结论]青海云杉休眠前贮存足够的碳水化合物保证越冬期间的细胞渗透调节及能量代谢,并且休眠后气温升高时叶片和枝条的NSC能够得到迅速补充,为新枝条萌发提供充足的碳源,反映了青海云杉在越冬期间的生存策略。

Variation of Nonstructural Carbohydrates

[Objective] To study the survival strategy of treeline trees in winter. [Method] Nonstructural carbohydrates (NSC) and their components (glucose, fructose, and starch) in Picea crassifolia were investigated along five altitude gradients (2 900 m, 3 000 m, 3 100 m, 3 200 m, and 3 300 m) in the Qilian mountains. [Result] (1) Before dormancy, the NSC contents in leaves at high altitudes were significantly higher (P<0.05) than those in low altitudes, while no significant difference was found in branches. (2) After dormancy, the content of NSC at middle altitude (3 100 m) was significantly higher than those of other altitudes; moreover, the NSC contents in all the tissues, especially the leaves, were higher than those before dormancy. (3) After dormancy, the soluble carbohydrates increased, but starch increased more compared to those before dormancy, resulting in a decrease in the ratio of soluble sugar/starch. [Conclusion] These results reflects the adaptation strategy of Picea crassifolia near treeline that the reserved mobile carbon was enough to respiration metabolism and osmotic regulation during winter, and moreover, the NSC contents could have a quick compensation in the leaves and branches after dormancy, which provided the necessary carbon sources for the growth of new branches.