Limitation to photosynthesis in leaves of eggplant under UVB according to anatomical changes and alterations on the antioxidant system

Abstract

The effects of increased ultraviolet radiation B (UVB) on the metabolism of agricultural plants depends on the species and its tolerance level. Ultraviolet radiation B can change plant photosynthesis and biochemistry, which reduces commercial production levels. This study investigated leaf changes due to alterations in gas exchange, chlorophyll a fluorescence, anatomy, and the activities of antioxidant enzymes SOD, CAT, and APX in eggplants (Solanum melongena L.) after exposure to UVB radiation. Eggplants (variety Nápoli) were subjected to two treatments: with and without UVB. After 49 days, photosynthesis levels decreased by more than 50% and the carboxylation rate by 80% in plants under UVB. The UVB radiation decreased the electron transport rate and the ability of the photosystems to convert energy to photochemical products. However, there was minimal degradation of the adaxial epidermis. Palisade parenchyma became the first barrier against UVB radiation. It became smaller and more compressed in order to decrease radiation effects on the spongy parenchyma, which maintained its photosynthetic activity. The SOD and APX activities increased, whereas CAT decreased. The lipid peroxidation results showed that there was no cell destruction, which confirmed that there was an operational biochemical system. The UVB affected several essential parameters eggplants need to survive and the increased incidence of UVB reaching the surface of the earth may affect their commercial production.