Chilling Sensitivity of Photosynthesis in Maize

Abstract

Temperature is often a major determinant of the productivity of crops. In temperate regions the early growth and productivity of maize can be severely limited by low temperatures experienced in late spring and early summer. Photosynthetic productivity of a crop is determined by (1) the quantity of photosynthetically active radiation intercepted by the canopy, and (2) the efficiency with which the intercepted radiation is converted to dry matter. Interception of radiation by the crop canopy is dependent upon canopy and leaf structure and the density of the light-harvesting systems within the leaves. Clearly, low temperatures wilî affect many physiological processes associated with leaf growth and dry matter production (Miedema 1982). However, the small and chlorotic nature of leaves produced when maize experiences low temperatures (Miedema et al. 1987) suggests that the interception of light and photosynthetic competence of a crop are both likely to be markedly affected and have important consequences for photosynthetic productivity. Initially, this chapter will consider the importance of growth temperatures for the efficient development and functioning of the photosynthetic apparatus in maize. Chilling, particulariy in the presence of high light levels, can result in decreases in photosynthetic capacity of mature leaves (Long 1983; Powles 1984; Öquist et al. 1987). Consequently, we also examine the effects of chilling on photosynthesis in mature leaves. Finally, the relevance of low temperature-induced perturbations of photosynthesis identified in controlled environments to the photosynthetic productivity of maize crops in the field will be evaluated.