西双版纳热带季节雨林四种珍稀濒危树种种子萌发对脱水和光的响应

Effect of dehydration and light on the germination of four rare and endangered tree species from a tropical seasonal rain forest in Xishuangbanna,SW China

绒毛番龙眼(Pometia tomentosa)、琴叶风吹楠(Horsfieldia pandurifolia)、箭毒木(Antiaris toxicaria)和思茅木姜子(Litseapierrei var. szemois)是西双版纳热带季节雨林乔木层的优势树种,也属于珍稀濒危物种。实验研究了4个树种的种子在经过不同脱水水平、人工遮荫条件下的不同光照水平以及热带季节雨林之林下和林窗的萌发特性。结果显示:脱水对于种子萌发特征具有显著影响,绒毛番龙眼和琴叶风吹楠经48h的连续脱水后丧失了萌发能力;箭毒木和思茅木姜子具较强的脱水耐性,经96h的连续脱水后仍具有较高的种子含水量,且种子萌发率分别为15%和33%。干旱季散布的种子比雨季散布的种子具有更强的脱水耐性。遮荫及森林种子萌发试验中,除绒毛番龙眼外,其它3个树种的种子萌发率以及平均萌发周期在不同光水平或生境下差异显著。琴叶风吹楠和思茅木姜子在30%的光照以及林窗中心的萌发率要显著低于低光处理(10%和3.5%光照)和林下,而箭毒木在30%和10%光水平以及林窗中心获得较高萌发率。雨季传播的具有干燥敏感性的种子,可以减少种子由于干燥而引起的死亡。试验结果可以为4种珍稀濒危植物的保护和人工繁育提供一定理论依据。

Pometia tomentosa, Horsfieldia pandurifolia, Antiaris toxicaria and Litsea pierrei var. szemois are dominant climax tree species in the tropical seasonal rain forest in Xishuangbanna, SW China. They are also listed as rare and endangered tree species in China. The seed germination ability of the four species was tested in response to different levels of dehydration, while their germination behavior was studied under different light regimes in shade houses, in the forest understory and in a forest gap. Seeds of P. tomentosa and H. pandurifolia lost their germination ability after 48 hours of continuous dehydration treatment, whereas Antiaris toxicaria and L. pierrei var. szemois showed strong dehydration tolerance and were able to maintain high seed moisture content after 96 hours of dehydration with a final germination percentage of 15% and 33%, respectively. In general, dry season dispersed seeds were more resistant to dehydration dispersed rainy season seeds. In the shade house and forest experiments, all species, except P. tomentosa, showed significant differences in germination under different light regimes and in different places in the forest. Final germination percentage of and L. pierrei var. szemois were very low under high light conditions （30% of full sunlight and in the centre of the forest gap） but were high under more shaded conditions （ 10% and 3.5% of full s the forest understory. In contrast, A. toxicaria exhibited higher t in the shade house） and in germination rates in 30% and 10% light in the shade house and at the center of the forest gap. It appears that, for the desiccation sensitive seeds, a have the advantage of minimizing losses from seed desiccation and subsequent death in wet season dispersal strategy may dry conditions. This study may provide useful information for the conservation and propagation of the four rare and endangered species.