圆柏属常绿木本植物叶片水分、渗透调节物质的季节变化与抗冷冻性的关系

以祁连圆柏（Sabina przewalskii）和圆柏（Sabina chinensis）为材料,研究了圆柏属植物的抗冷冻性与叶片水分和渗透调节物质季节变化的关系。结果表明，随秋季气温下降，叶片组织相对含水量（RWC）和自由水含量（FWC）下降，束缚水含量（BWC）、脯氨酸（Pro）、游离氨基酸（FAA）、可溶性蛋白质（SP）和可溶性糖（SS）含量增加，翌年春季气温回升，相对含水量和自由水含量增加，束缚水含量下降，有机渗透调节物再次增加。有机渗透调节物在秋末冬初及初春的增加正好与圆柏属植物抗冻锻炼及脱冻恢复生长的时间相吻合，因而是植物抗冻及脱冻适应的重要生理响应，在降低细胞冰点、防止细胞结冰引起的膜机械伤害、抑制膜脂过氧化、保护膜稳定性方面具有重要作用。祁连圆柏的相对含水量和自由水含量均低于圆柏，3种有机渗透调节物含量均高于圆柏，表明祁连圆柏在抗冷冻性诱导中具有更广泛的适应性策略。

The Relation of Seasonal Changes in Water and Organic Osmotica to Freezing Tolerance in the Leaves of Sabina

Seasonal changes in the contents of water and organic osmotica were examined in the leaves of Sabina przewalskii and Sabina chinensis, aimed to probe into their relationships with freezing tolerance. The results showed that the relative water content (RWC) and free water content (FWC) decreased during hardening in autumn, but bound water content (BWC) and organic osmotica accumulated and remained relatively higher level over winter. In spring, RWC and FWC increased, BWC decreased, and organic osmotica accumulated again. These seasonal patterns were consistent with winter hardening and dehardening. Organic osmotica may supply nutrients to regrowth in spring and contribute to the stabilization of the cell membrane by preventing lipid peroxidation and by binding the tissue water. The results also suggested that a better capacity for osmoregulation in S. przewalskii might account for its greater capacity for freezing tolerance than S. chinensis.