Abstract:

In the northeastern Ulanbuh Desert, a water gradient experiment was conducted with seedlings of five provenances of Nitraria tangutorum according to the average annual precipitation, including extreme drought, drought, slight drought and normal precipitation. The physiological indices and growth indices of the five provenances were measured in response to the four water status. The results showed that net photosynthetic rate, transpiration rate, stomatal conductance, and stomatal limitation value were significantly affected by the different water status. There was significant differences in only net photosynthetic rate among the five provenances. There were difference in the water use efficiency, apparent light use efficiency and apparent CO₂ use efficiency, and seedling height and maximum new branch length existed among the water gradient or different provenances. Both of water gradient and different provenances had no remarkable influence upon the ground diameter of seedlings. In comparison with Linhe provenance (LH) and Urad houqi provenance (WH), Dengkou provenance (DK), Alxa League provenance (AM) and Minqin provenance (MQ) all showed the distinct differences in transpiration rate and resource use efficiency among the water gradients and had higher resource use efficiency. The differences in growth and gas exchange and resource use efficiency in responses to the water gradient among different provenances reflected the response difference of Nitraria tangutorum provenances.

Key words: Ulanbuh Desert, water gradient, photosynthetic physiology, plant growth, provenance, Nitraria tangutorum