Both xanthophyll cycle-dependent thermal dissipation and the antioxidant system are up-regulated in grape (Vitis labrusca L. cv. Concord) leaves in response to N limitation

• Author(s): Chen, Li-Song; Cheng, Lailiang;
• Abstract: One-year-old grapevines (Vitis labrusca L. cv. Concord) were supplied with 0, 5, 10, 15, or 20 mM nitrogen (N) in a modified Hoaglands solution twice weekly for 4 weeks. Effects of N supply on xanthophyll cycle and the antioxidant system in leaves were systematically investigated. As leaf N decreased in response to N limitation, leaf chlorophyll (Chl) decreased linearly whereas leaf absorptance declined curvilinearly. Compared with high N leaves, low N leaves had lower quantum efficiency of PSII as a result of both an increase in thermal energy dissipation, measured as non-photochemical quenching, NPQ, and an increase in closure of PSII reaction center at high photon flux density (PFD). Both the xanthophyll cycle pool size on a Chl basis and the conversion of violaxanthin (V) to antheraxanthin (A) and zeaxanthin (Z) were enhanced in low N leaves under high PFD. NPQ was closely related to A+Z expressed either on a Chl basis or as a percentage of the xanthophyll cycle pool. On a leaf Chl basis, superoxide dismutase (S OD) activity decreased linearly with increasing leaf N content; the activities of catalase (CAT) and glutathione-reductase (GR) increased linearly; and ascorbate-peroxidase (APX), monodehydroascorbate reductase (MDAR) and dehydroascorbate reductase (DHAR) decreased rapidly first, then gradually reached a low level. In response to N limitation, the contents of ascorbate (AsA), dehydroascorbate (DAsA), reduced glutathione (GSH), and oxidized glutathione (GSSG), expressed on a Chl basis, increased, whereas the ratios of both AsA to DAsA and GSH to GSSG decreased. It is concluded that in addition to decreasing light absorption, both xanthophyll cycle-dependent thermal energy dissipation and the total antioxidant system are up-regulated to protect low N leaves from photo-oxidative damage under high light.
• Publication Date: Aug 2003
• Journal: Hortscience