Optical and physiological properties of a leaf

Abstract

The most important role of a leaf is capturing light energy and fixing CO2 into carbohydrates (i.e., photosynthesis). Fundamental knowledge on the optical and physiological properties of an individual leaf of a C3 plant is summarized below. A leaf adjusts light absorption, at the scales of both whole-leaf and intra-leaf, in order to efficiently capture light energy and to avoid photodamage caused by excessive light energy. Several interacting factors involved in orchestrating these optical properties, such as leaf orientation, mesophyll structure, chloroplast movement, and the absorption properties of phytopigments, are outlined. Photosynthesis consists of two reactions that are spatially separated within the chloroplast. Light energy is converted into reducing power and chemical energy via the electron transport chain. These are then consumed during CO2 fixation in the carbon assimilation process. The electron transport reaction is affected significantly by the spectral distribution of light due to the optical properties of the leaf. Photosynthesis is closely related to other physiological processes. CO2 uptake accompanies water vapor release (transpiration). Produced photosynthates are transported to the other plant organs (translocation). Brief information about the significance and the machinery of these photosynthesis-related processes is provided.