Photoprotection of Cotton in the Field

This chapter focuses on the mechanisms by which cotton leaves regulate and use incident light and dissipate the excess light energy when cotton suffers from drought in the field. The photoprotection of non-foliar organs, including bract, capsule wall and stem, will also be considered. This chapter includes a general description of photoprotection from the perspective of leaf movement, drought and non-foliar organs. Leaf diaheliotropic movement and wilting movement can regulate the excess light energy of the photosynthetic apparatus. Besides non-photochemical (heat) energy dissipation, the alternative electron sinks for the electron transport chains are of vital importance for resistance of the photosynthetic apparatus against excess light energy under drought. Thus, the functioning of both photosystem II (PSII) and the photosynthetic electron transport systems of cotton leaves shows a relatively high stability. Compared with leaf, bract mainly relies on high activities of thermal energy dissipation for photoprotection. Nevertheless, capsule wall of bolls is less able to dissipate energy via heat.