Journal of Experimental Botany, Vol. 54, No. 381, pp. 385-393,
January 2, 2003
© 2003 Oxford University Press
Xanthophyll cycle pool size and composition in relation to the nitrogen content of apple leaves
Received 22 March 2002; Accepted 2 August 2002
1 Department of Horticulture, 134A Plant Science Bldg., Cornell University, Ithaca, NY 14853-4203, USA
1 Fax: +1 607 255 0599. E-mail: LC89{at}Cornell.edu
The objective of this study was to determine xanthophyll cycle pool size and composition in response to N status and their relationships to non-photochemical quenching in apple leaves. Bench-grafted Fuji/M.26 trees were fertilized with different N concentrations (0–20 mM) in a modified Hoagland’s solution for 6 weeks to create a wide range of leaf N status (1–4.4 g m–2). Chlorophyll content, xanthophyll cycle pool size, lutein, total carotene, and neoxanthin on a leaf area basis all increased linearly with increasing leaf N. However, only the ratios of the xanthophyll cycle pool and of lutein to chlorophyll were higher in low N leaves than in high N leaves. Under high light at midday, both zeaxanthin (Z), expressed on a chlorophyll basis, and the percentage of the xanthophyll cycle pool present as Z, increased as leaf N decreased. Thermal dissipation of excitation energy, measured as non-photochemical quenching of chlorophyll fluorescence, was positively related to, whereas efficiency of excitation transfer and photosystem II quantum efficiency were negatively related to, Z, expressed on a chlorophyll basis or on a xanthophyll cycle pool basis. It is concluded that both xanthophyll cycle pool size (on a chlorophyll basis) and conversion of violaxanthin to zeaxanthin are enhanced in response to N limitation to dissipate excessive absorbed light under high irradiance.
Key words: Apple, chlorophyll, excess absorbed light, leaf nitrogen, Malus domestica, non-photochemical quenching, photosystem II quantum efficiency, thermal dissipation, xanthophyll cycle.
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