[Changes of non-structural carbohydrates of Pinus sylvestris var. mongolica seedlings in the process of drought-induced mortality].

To understand the distribution of non-structural carbohydrates (NSC) and adaptive mechanism in the process of drought-induced mortality, two-year-old Pinus sylvestris var. mongolica seedlings were grown under continuous natural drought condition. Needle water potential and the contents of soluble sugar, starch and total NSC in different organs (current-year-old needles, one-year-old needles, stems, coarse roots and fine roots) of the seedlings were measured when soil water content decreased to 60%, 40%, 30%, 20% and 15% of the soil field water capacity (SFC). The results showed that when the soil water content decreased from 40% SFC to 15% SFC, there was no significant change in needle water potential at predawn and midday. When soil water content decreased from 60% SFC to 30% SFC, the contents of soluble sugar, starch, total NSC and the ratio of soluble sugar and starch first decreased and then increased in all organs. When soil water content dropped from 30% SFC to 20% SFC, the soluble sugar, starch and total NSC contents decreased in the current-year-old needles, one-year-old needles, stems and fine roots. The soluble sugar content increased, but the starch and total NSC contents decreased in the coarse roots. When soil water content decreased from 20% SFC to 15% SFC, the contents of soluble sugar, starch and total NSC decreased in the current-year-old needles, one-year-old needles and stems, and the soluble sugar and total NSC contents decreased, but the starch content increased in the coarse roots, the soluble sugar content decreased, but the starch and total NSC contents increased in fine roots. The results indicated that NSC content in different organs of P. sylvestris var. mongolica seedlings varied in their adaptation to different degrees of drought. The contents of soluble sugar and total NSC in seedlings decreased under less than 30% of the soil field water capacity, with the starch being accumulated in the coarse roots and fine roots. The seedlings might be died due to carbon depletion.以2年生沙地樟子松幼苗为对象,通过持续自然干旱处理,研究当土壤含水量下降到田间持水量的60%、40%、30%、20%和15%时幼苗叶片水势及不同器官(一年生叶、当年生叶、茎、粗根和细根)的可溶性糖、淀粉和非结构性碳水化合物(NSC)的含量,分析沙地樟子松幼苗在干旱致死过程中各器官NSC的分配规律及其适应机制.结果表明: 土壤含水量从田间持水量的40%下降到15%,幼苗叶片凌晨及正午水势无显著变化.当土壤含水量从田间持水量的60%下降到30%,各器官可溶性糖、淀粉、NSC含量和可溶性糖/淀粉先下降后上升.从30%下降到20%,当年生叶、一年生叶、茎和细根可溶性糖、淀粉和NSC含量降低,而粗根可溶性糖含量增加,淀粉和NSC含量减少.从20%下降到15%,当年生叶、一年生叶和茎可溶性糖、淀粉和NSC含量降低,粗根可溶性糖和NSC含量下降,淀粉含量上升,细根可溶性糖含量减少,淀粉和NSC含量增加.沙地樟子松幼苗通过不断调整各器官NSC及其组分含量变化以适应不同干旱环境,土壤含水量下降到田间持水量的30%后,幼苗可溶性糖和NSC含量总体呈下降趋势,淀粉在粗根和细根中积累,幼苗可能因碳耗竭而死亡.