杉木种子萌发及幼苗生长对光强的响应

设置不同光强梯度(透光率分别为100%、40%、20%、10%和5%,光照强度PPFD分别为201.3、77.0、37.5、19.2、9.8 μmol·m^-2·s^-1),研究光对杉木种子萌发和幼苗早期生长的影响,分析杉木种子萌发、幼苗存活、生长、形态响应、生物量积累及其分配格局对不同光环境的响应策略.结果表明: 杉木种子的萌发率、存活率、建植率和萌发指数在不同光强梯度下均有显著差异,且40%的透光率是种子最适萌发条件,萌发率最高,而全光照下存活率和建植率最高;随光照强度的减弱,杉木幼苗茎长增大,根长、子叶长、子叶厚、真叶数呈降低趋势,而基径在各光照强度间无显著差异;总生物量、根生物量、茎生物量、叶生物量均表现为全光照下最大.随着光照强度的减弱,光合组织与非光合组织生物量比、叶生物量比呈降低趋势,茎生物量比呈增加趋势,根冠比和根生物量比无显著差异.弱光环境促进杉木种子萌发,不利于杉木幼苗存活和生长.在弱光环境下,杉木幼苗通过增大茎生物量来提高对弱光环境的耐受力.

Response of seed germination and seedling growth of Chinese fir to different light intensities

The effect of light intensity on the seed germination and seedling growth of Chinese fir under different light intensities (100%, 40%, 20%, 10%, 5% of full light, and the PPFD was 201.3, 77.0, 37.5, 19.2, 9.8 μmol·m^-2·s^-1, respectively) was investigated, and the adaptive strategy of seed germination, seedling survival, growth, morphological plasticity, biomass accumulation and allocation under different light intensities was explored in this paper. The results showed that light intensity significantly affected the germination rate, survival rate, establishment rate and germination index. Germination rate reached the maximum under 40% light intensity, while survival rate and establishment rate reached the maximum at 100% light intensity. With the light intensity decreased, the stem length increased, while the root length, cotyledon length, cotyledon thickness and euphylla number declined, and basal stem diameter had no significant difference among diffe-rent light intensities. The total biomass, root biomass, stem biomass and leaf biomass were the highest under 100% light intensity. With the light intensity decreased, the photosynthesis non-photosynthesis biomass ratio and leaf biomass ratio declined, while stem biomass ratio increased, the root to shoot ratio and root biomass ratio had no significant difference among different light intensities. Low light promoted seed germination, but seedlings grew slowly with high mortality under low light. The accumulation of biomass in stem increased the plant tolerance to low light.