Photosystem II activity of typical desert plant Alhagi sparsifolia Sharp.: response to exposure to natural light after being kept in shade

Abstract

Alhagi sparsifolia Sharp. is commonly considered as a type of sun plant, but shade-grown plants cannot acclimate to the strong irradiance which is normal for plant in a short time when kept in low-light conditions for a while. Alhagi sparsifolia Sharp., commonly considered as a type of sun plant, is the main vegetation found in the forelands of Taklamakan desert; this plant has an important function in wind prevention and sand fixation at the transition zone. A. sparsifolia could adapt to shaded conditions after a period of exposure to low-light conditions. However, whether or not the sun plant A. sparsifolia can adapt to natural light intensity after initial exposure to shaded conditions remains unknown. The specific light adaptation mechanism of this species is yet to be identified. In this study, the characteristics of the photosystem II (PSII) of A. sparsifolia exposed to natural light after the initial treatment under shaded lighting conditions were examined. Our results indicated that the PSII activity of A. sparsifolia under the specified condition was low; the thickness of leaves was reduced and occurred as an adaptive response to capture high amounts of light and exhibit high intensity of light-use efficiency. Shade leaves differed in terms of chlorophyll. Furthermore, the excess excitation energy has been converted to thermal dissipation energy to maintain energy balance. Shade-grown plants cannot adapt to strong irradiance, which is normal in plants for a short period when they are initially maintained under low-light conditions. Therefore, A. sparsifolia should not be considered as a typical sun plant.