林线树种太白红杉种子萌发的生理生态特性

 太白红杉(Larix chinensis)是太白山的高山林线树种。通过在人工气候室内的试验，研究了太白红杉种子在6种不同的光照与温度组合处理条件下的萌发特性。结果表明：在恒温和变温两种条件下，交替光照对于种子吸胀后的脱落酸（ABA）和赤霉素 (GA)有刺激作用。在恒温条件下，持续光照对于种子吸胀后的生长素 (IAA)有刺激作用，而变温条件下交替光照对生长素有刺激作用。细胞分裂素（CTK）的变化情况与IAA相反。光照条件相同时，恒温条件下的植物激素含量要高于变温条件下的含量，说明恒温对于各种激素有刺激作用。在25 ℃环境下种子的萌发率高于在12 ℃环境下的萌发率，说明温度对于种子的萌发有重要作用。太白红杉种子的萌发受交替光照（12 h光照/12 h黑暗）的刺激；恒温（25 ℃）条件下的种子萌发率高于变温（12 ℃/25 ℃）条件下的种子萌发率。实验结果反映了内源激素在太白红杉种子萌发过程中起着重要作用。

ECO-PHYSIOLOGICAL CHARACTERISTICS OF SEED GERMINATION OF LARIX CHINENSIS, A TIMBERLINE TREE

Larix chinensis is a timberline tree species on Mt. Taibai in the Qinling mountains. To better understand climatic and physiological processes that control timberline formation, the eco-physiological characteristics of L. chinensis seeds were investigated in the laboratory by exposing seeds to different treatments of illumination and temperature. The major results are summarized below. An alternating photoperiod of 12 h light∶12 h dark increased phytohormone levels of ABA and GA in imbibed seeds during germination. Under conditions of constant temperatures of 25 ℃ or 12 ℃, constant illumination had a positive affect on phytohormone levels of IAA in imbibed seeds. Under alternating temperatures of 25 ℃ for 12 h and 12 ℃ for 12 h, alternating illumination did not affect phytohormone contents of IAA. Changes in phytohormone levels of CTK showed an opposite response as IAA. Constant temperatures had a positive effect on phytohormone contents in imbibed seeds. Temperature was crucial for seed germination, and the rate of seed germination at a constant temperature of 25 ℃ was greater than at a constant temperature of 12 ℃. Alternating illumination (12 h light∶12 h dark) also had a strong, positive effect on seed germination. Otherwise the results showed that endogenous phytohormone levels were important for seed germination. The results indicated that temperature affected the germination rate and success of L. chinensis seeds, which is crucial for regeneration of L. chinensis, while illumination impacts were weak. Further studies are needed to better understand the underlying mechanisms of how temperature affects timberline formation on Mt. Taibai, Qinling mountains.