ABSTRACT
Chilling temperatures are a major factor in depressing the yields of many crops. The majority of studies on the effects of low temperatures on photosynthesis have involved chilling of mature leaves. Chilling inevitably has immediate and major consequences for the photosynthetic performance of leaves, via thermodynamic effects on the constituent physicochemical and metabolic reactions, photoinhibition, and possibly photodamage. When the rate of excitation of the photosynthetic apparatus exceeds the rate at which energy can be dissipated by photochemical and nonphotochemical processes associated with the thylakoids, damage to photosystem II reaction centers can occur. In maize, low growth temperatures not only result in a decrease in the amount of photosynthetic apparatus per leaf area, but also in the preferential loss of specific thylakoid proteins. The deficiency in chloroplast-encoded, relative to the nuclear-encoded, proteins in the thylakoids of leaves grown at suboptimal growth temperatures has important implications for the quantum efficiency of photosynthesis.
