CHLOROPHYLL LOSS AND GAS-EXCHANGE IN TOMATO LEAVES AFTER FEEDING INJURY BY BEMISIA-TABACI (HOMOPTERA, ALEYRODIDAE)

Feeding injury caused by larvae and adults of the sweetpotato whitefly, Bemisia tabaci (Gennadius), reduced rates of net photosynthesis and transpiration of tomato, Lycopersicon esculentum Mill., leaflets. Leaf stomatal resistance increased with larval and adult injury, which indicated that gas exchange was restricted because of increased stomatal closure. Furthermore, larval injury reduced leaf chlorophyll content, photosynthetic capacity per unit of remaining chlorophyll, chlorophyll a:b, and specific leaf weight. Adult feeding also significantly reduced leaf chlorophyll content and, in one trial photosynthetic capacity of remaining chlorophyll, but it did not affect chlorophyll a:b and specific leaf weight. Net photosynthesis was positively correlated with leaf stomatal resistance, chlorophyll content, and photosynthetic capacity per unit of chlorophyll in both larval and adult trials. These results indicate that larval injury reduced tomato leaf gas exchange more than adult injury. Furthermore, feeding by B. tabaci reduced leaf photosynthesis in tomato by restricting gas exchange through stomata and by reducing content and photosynthetic capacity of chlorophyll.