Cotton leaf gas exchange responses to irradiance and leaf aging

Abstract

Cotton (Gossypium hirsutum L.) net photosynthetic rate (PN) decreased with leaf age and low irradiance, and the interaction of these factors might lead to decreased yields mainly in crops with a high plant density. Shade decreased leaf gas exchange, mainly in young leaves, which did not recover after exposure to an increasing irradiance. Old leaves reached PN saturation at a lower irradiance than young leaves. Also stomatal conductance decreased with leaf age and shading. Intercellular CO2 concentration and irradiance were inversely related. The responses of PN to irradiance decreased as leaf aged, and it did not interact with shade suggesting that self-shading is not primarily responsible for the decreased photosynthetic rate in older cotton leaves.

Keywords

• gossypium hirsutum
• intercellular co2 concentration
• pn
• shading
• stomatal conductance