四种热带雨林树种光合和形态解剖特征对不同生长光强的适应

研究了西双版纳热带雨林2种喜光树种中平树(Macaranga denticulata)、倒樱木(Pnravallaris macrophylla)和2种耐荫树种云南肉豆蔻(Myristica yunnanensis)、金丝李(Garcinia paucinervis)幼苗叶片光合和形态解剖特征对3种不同生长光强(5％、25%和50％相对光强)的适应。研究结果表明，与强光下相比，弱光下生长的4种植物最大净光合速率、光饱和点、光补偿点、暗呼吸速率、叶绿素a／b、叶片和栅栏组织厚度、气孔密度和比叶重都降低，而海绵组织／栅栏组织和叶绿素含量升高。在相同光强下，与2种耐荫树种相比，2种喜光树种有较大的最大净光合速率、暗呼吸速率、气孔密度和较低的叶绿素含量。在不同光强下，4种植物均表现出了对光适应有利的生理和形态解剖可塑性，而喜光树种比耐荫树种有较大的生理和形态可塑性，表明喜光树种具有比耐荫树种对强光有更强的适应能力。4种植物的生理指标的可塑性均大于叶片解剖结构的可塑性。

Leaf Photosynthetic and Anatomic Acclimation of Four Tropical Rainforest Tree Species to Different Growth Light Conditions

Leaf morphological and physiological acclimation to three irradiance levels (5%, 25% and 50% daylight) were investigated in seedlings of the following four tropical rainforest tree species. Macaranga denticulata and Paravallaris macrophylla are light-demanding species, and Myristica yunnanensis and Garcinia paucinervis are shade-tolerant species. The results showed that, with decreasing irradiance, all of four species displayed decreasing maximum net photosynthetic rate (Pmax), saturation irradiance, light compensation point, dark respiration rate (Rd), Chl a/b ratios, leaf thickness, stomatal density and lamina mass per area, and increasing spongy/palisade ratio and chlorophyll content. Under the same light levels, the light-demanding species had higher Pmax, Rd, stomatal density and lower Chl content compared to the shade-tolerant species. The shade-tolerant species had lower morphological and physiological plasticity, suggesting that their weaker abilities to acclimate to strong light. The physiological plasticity of the four species is greater than that of leaf anatomy. Our results supported that light-demanding species have greater abilities of acclimation to strong light conditions than shade-tolerant species.