Relationship among light intensity, pigment compositions and photoinhibition in relation to rhodoxanthin accumulation in the gymnosperm Cryptomeria japonica

Abstract

ABSTRACT Some gymnosperms, including Cryptomeria japonica, exhibit needle reddening caused by red xanthophyll pigment, rhodoxanthin accumulation during long-term cold acclimation. Although photoprotective role of rhodoxanthin, serves as a “sunscreen”, was proposed, the key environmental and/or physiological factors involved in rhodoxanthin accumulation remain unclear. We exposed C. japonica trees to four different light intensities (13%, 39%, 64% and 100% of full sunlight) and measured some parameters (the nocturnal de-epoxidation state [DPS: ratio of the zeaxanthin + antheraxanthin to xanthophyll cycle pigments], the β-carotene level and the maximum photosystem II efficiency [Fv/Fm]) that have been suggested to play roles in rhodoxanthin accumulation. Rhodoxanthin was synthesised from autumn to winter, and less so in spring. Light intensity related to the maximum value of rhodoxanthin on chlorophyll (Chl) basis, but not to that on FW basis, because Chl content decreased with increasing light intensity. These results indicated that rhodoxanthin accumulation was accompanied with Chl decrease. In addition, the relationship between the rhodoxanthin content and the seasonal growth temperature was different among light treatments, reflecting differences in the amount of excess light among light treatments Furthermore, the rhodoxanthin content correlated significantly with the Fv/Fm, nocturnal DPS and β-carotene level in winter. Thus, rhodoxanthin accumulates in a photoinhibitory environment occurs with a decrease in Chl content and an increase in DPS.