Light acclimation of needle pigment composition in Sabina vulgaris seedlings under nurse plant canopy

In order to clarify the physiological mechanisms that allow establishment of Sabina vulgaris in different light conditions under a Salix cheilophila canopy in the frost-prone Mu Us Sandy Land of northern China, the photochemical efficiency of photosystem II at predawn (F_v/F_m) and the pigment composition of the needles of S. vulgaris seedlings in various light conditions were examined in late summer and winter. In the summer season, the F_v/F_m values of all seedlings were around 0.80. The ratio of chlorophyll (Chl)-a to Chl-b (Chl-a/Chl-b ratio) increased with growth light conditions. In the winter season, the F_v/F_m decreased considerably depending on growth light conditions. Although the Chl-a/Chl-b ratio remained the same in the summer season, changes in carotenoids such as lutein, the xanthophyll cycle pigments, and β-carotene were detected, particularly under high light conditions. These results suggest that changes in pigment composition against high light and/or low temperature may alleviate photodamage and contribute to establishment of the seedlings in a frost-prone semi-arid land.