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(R_d),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,R_d,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.