Effect of light intensity on the gas exchange characteristics and total pigment content of Psidium guajava

Abstract

The gas exchange characteristics and photosynthetic pigments of a plant can be affected by the amount of light received by the plant. The objective of this research is to investigate the effect of light intensity on the gas exchange characteristics and total pigment content TPC of sun and shade leaves of Psidium guajava. Sun and shade leaves were studied, and their photosynthetic light response characteristics including light saturation point (LSP), light compensation point (LCP) and apparent quantum yield were estimated. Carotenoids (Car) and chlorophyll (Chl) contents were quantified spectrophotometrically, while total anthocyanin content (TAC) was determined using the pH differential method. The result of this study shows that high light intensity influence gas exchange, carotenoid content and total anthocyanin content while low light intensity influence chlorophyll content especially chlorophyll b of the studied plant. As the light intensity increases, Amax, light saturation point and light compensation point increases. There are significant differences between the photosynthetic light response characteristics and total pigment content of sun and shade leaves (P<0.05). The result leads to a conclusion that sun leaves of Psidium guajava contribute the greatest photosynthetic capacity to the plant than shade leaves. The high carotenoid and total anthocyanin contents of sun leaves provides photo protection to the plant.