Response of Hydraulic and Photosynthetic Characteristics of Caroxylon passerinum (Bunge) Akhani and Roalson to Prolonged Drought and Short-Term Rehydration

Abstract

Hydraulic traits are essential functional characteristics of plants related to water absorption, transport, and loss, serving as indicators of a plant’s adaptability to prevailing environmental water conditions. However, the hydraulic traits of shrub, particularly desert plants in arid and semi-arid regions, have been underexplored. In this study, we conducted a pot experiment using Caroxylon passerinum (Bunge) Akhani and Roalson as the subject. Three treatment groups were established: adequate water supply, mild drought, and severe drought. After subjecting the shrub to drought and subsequent rehydration, we measured hydraulic conductivity, net photosynthetic rate, and stomatal conductance. We found that leaf water potential decreased and stomatal conductance and net photosynthesis decreased with increasing drought intensity. We found that leaf water potential and stomatal conductance decreased with increasing drought intensity. Although there was no significant change in hydraulic conductivity in the two drought groups, the values were greater in the drought group than in the control, and greater in the mild drought group than in the severe drought group. Meanwhile, the embolism resistance decreased with increasing drought intensity. After rehydration, hydraulic conductivity did not return to control levels in the severe drought group, as did embolism resistance in the two drought groups, and leaf water potential did not recover significantly. The results showed that drought stress increased the hydraulic conductivity of C. passerinum, and this effect was more pronounced under mild drought stress. After the stress was lifted, C. passerinum continued to maintain a lower leaf water potential to promote water uptake. This result provides a reference for us to study water use of desert shrubs under different drought stresses.