Assimilative Branches and Leaves of Alhagi sparsifolia Shap. Possesses a different Adaptation Mechanism to Shade

As the energy source for carbon fixation by plants, light is one of the most important environmental factors regulating the development of the photosynthetic apparatus. Further, light also regulates plant growth. The leaves of plants respond differently depending on light availability.

Alhagi sparsifolia Shap. (Fabaceae), considered as a desert sun plant, grows in high-irradiance environments and is the dominant vegetation of the forelands of the Taklamakan Desert, Xinjiang, northwest China. The plant plays an important role in wind protection and sand fixation at the transition zone of oasis to desert. Leaves and assimilative branches are crucial to the life cycle of A. sparsifolia, especially in arid regions.

To characterize the development of leaves and assimilative branches of A. sparsifolia and determine whether the assimilative branches adapt to low-light conditions in the same way that leaves do, researchers investigated the morphology, physiology, and photosynthesis of A. sparsifolia leaves growing under low-light conditions.

The results indicated that low-light conditions limited the normal growth of A. sparsifolia. The fraction of biomass allocated to leaves increased, whereas that to assimilative branches decreased. In addition, leaf thickness and assimilative branch diameter decreased, resulting in higher specific leaf area, specific assimilative branch length, and area for higher light absorbing and higher efficiency of light-usage. The assimilative branches and leaves were responded oppositely under low-light conditions in that leaves had lower photosystem II activity and assimilative branches had higher light-use efficiency to maximize light energy absorption for growth of A. sparsifolia. The result was published in Plant Physiology and Biochemistry in January 2014.