Photoinhibition, xanthophyll cycle and in vivo chlorophyll fluorescence quenching of chilling‐tolerant Oxyria digyna and chilling‐sensitive Zea mays

Abstract

The relationship between susceptibility to photoinhibition, zeaxanthin formation and chlorophyll fluorescence quenching at suboptimal temperatures was studied in chilling‐sensitive maize and in non‐acclimated and cold‐acclimated Oxyria digyna, a chilling‐tolerant plant of arctic and alpine habitats. In maize, zeaxanthin formation was strongly suppressed by chilling. Zeaxanthin formed during preillumination at 20°C did not protect maize leaves from photoinhibition during a subsequent high‐light, low‐temperature treatment, as judged from the ratios of variable to maximal fluorescence, Fv/Fm. However, such preillumination significantly increased non‐photochemical quenching (qN) at low temperatures, mainly due to an enhancement of the fast‐relaxing qN component (i.e., of energy‐dependent quenching. qE). In O. digyna, cold‐acclimation resulted in an increased zeaxanthin formation in the temperature range of 2.5–20°C. Cold‐acclimation substantially decreased the susceptibility towards photoinhibition at 4°C, but qN remained nearly unchanged between 2 and 38°C, as compared to control plants. Effects of cold acclimation on photosynthesis, photochemical quenching and quantum efficiency of photosystem II were small and indicated a slight amelioration only of the function of the photosynthetic apparatus at suboptimal temperatures (2–20°Ct. I) is concluded, that the xanthophyll cycle is strongly influenced by cold acclimation, while effects on the photosynthetic carbon assimilation only play a minor role in O. digyna.