Chin J Plan Ecolo ›› 2012, Vol. 36 ›› Issue (1): 19-29.

• Research Articles •

### Xylem hydraulic conductivity and embolism properties of desert riparian forest plants and its response to drought stress

ZHOU Hong-Hua1*, LI Wei-Hong1, AYUP Mubarek1, and XU Qian2

1. 1State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Ürümqi, 830011, China;
2College of Pratacultural and Environmental Sciences, Xinjiang Agricultural University, Ürümqi, 830052, China
• Received:2011-08-31 Revised:2011-12-07 Online:2012-01-01 Published:2012-01-05
• Contact: ZHOU Hong-Hua

Abstract:

Aims Xylem embolism is a physiological response of plant species to adverse environmental factors, such as water deficit. Desert riparian forest plays an important role in the inland river basin of China. Our objectives were to clarify how xylem embolism of desert plants responds to different drought stress and to understand their acclimation mechanism to drought environment.
Methods Desert species, Populus euphratica, Tamarix spp., Alhagi sparsifolia and Karelinia caspia were chosen to study the response of xylem hydraulic conductivity and embolism of the root and shoot to different drought stress in two riparian areas: Tikanlik, which is located in the lower reaches of the Tarim River, and Ulan Tug, which is located in the lower reaches of the Heihe River. We used a xylem embolism meter. We also examined the effects of soil moisture, groundwater depth and climatic factors in the two areas on the root and shoot xylem hydraulic conductivity and embolism of the desert plants at the same time.
Important findings Xylem hydraulic conductivities of the desert plants in Ulan Tug were significantly higher than those in Tikanlik. For example, the initial specific conductivity (Ks0) values in the root xylem of Tamarix spp., P. euphratica, A. sparsifolia and K. caspia increased 11.97, 6.74, 7.10 and 3.73 times, respectively, and the shoot xylem Ks0 values increased 9.48, 3.65, 2.07 and 1.88 times, respectively. The fundamental reason for the different xylem hydraulic conductivities of the plants was the difference in drought stress produced by different groundwater depths in the two regions. The drought resistance of Tamarix spp. was the strongest, meaning the genus could exist in a broad soil moisture environment, but A. sparsifolia and K. caspia only exist in a narrow soil moisture environment because of their weak drought resistance, which might be related to root distribution. The major resistance to water transportation of desert plants was shoot xylem when it encountered moderate drought stress, but it was root xylem when the plant encountered severe drought stress. Desert plants adapt to moderate drought stress through limiting shoot xylem hydraulic conductivity to coordinate the plant growth, but it adapted to severe drought stress through sacrificing inferior shoots and enhancing xylem hydraulic conductivity of the other shoots.