Plants encounter dynamic light environments in natural fieldconditions, and species differ in their physiological and biochemical mechanisms for acclimating to fluctuating light (FL). The manner in which soybean (Glycinemax(L.) Merr.) coordinates multiple physiological adjustments to FL remains poorly understood. This study assessed the effects of FL on soybean morphology and photosynthetic traits by examining changes in photosynthetic gas exchange parameters and chlorophyll (Chl) afluorescence under alternating high- and low-light conditions. Results indicated that soybeans exposed to FL exhibited reduced dry matter accumulation, smaller and thinner leaves, and a lower Chl a/Chl blevels-characteristics typically associated with plants grown under continuous low-light. Despite these morphological similarities, their photosynthetic gas exchange rates and photosynthetic capacity were maintained at levels comparable to those under steady high light, unlike plants grown under constant low-light. Thus, acclimation to FL is distinct from adaptation to sustained low-light conditions. Correlation analyses revealed that the decline in carbon assimilation under FL primarily stemmed from two factors: the slow recovery of stomatal conductance upon transition to high light and the delayed relaxation of nonphotochemical quenching when light intensity decreased. Therefore, the reduction in carbon assimilation under FL cannot be attributed to low-light phase adjustments but rather reflects a lag in photosynthetic responsiveness to changing light conditions.

high temperature stress  /  maize  /  seed setting stage  /  cell wall invertase  /  starch synthesis