The hydraulic architecture of three Caragana species and its relationship with environmental factors in different habitats of the Inner Mongolia Plateau
内蒙古高原不同生境三种锦鸡儿属植物的水力结构特征及其对环境因子的响应

We studied the diurnal dynamics of the hydraulic architecture parameters of Caragana microphylla Lam., C.davazamcii Sancz and C.korshinskii Kom., which grew in different habitats of the Inner Mongolia plateau, and their relationship with environmental factors affecting water relations. The research was conducted on 1-year-old twigs in situ in order to compare the hydraulic efficiency and regulating abilities of the three Caragana species. We also analyzed how plants, subjected to drought stress, regulated water transportation to cope with variable environments. The relationship between hydraulic architecture parameters and air temperature followed a linear function with negative slope, while the relationships between these parameters with atmospheric humidity were positive. Comparing the hydraulic efficiency among the three seasons, the descending order was summer>spring>autumn. In the same season, the hydraulic efficiency of C.korshinskii was higher than that of C. microphylla which was in turn higher than C. microphylla. It can be concluded from the range of Ks, and the slope of two linear functions, that there were significant differences in the sensitivity of specific conductivity to environmental factors, both among species and in different seasons, with the sensitivity order being summer>spring>autumn. In the same season, C.korshinskii was the most sensitive to the changes of environment, and the sensitivity of C.davazamcii was higher than C. microphylla. The results also supported the view that the reduction of hydraulic efficiency due to embolism in xylem could benefit the plants subjected to water deficit, by means of limiting water loss.