Abstract:

【Objective】 Climate change-induced drought restricts the distribution, growth and productivity of southern poplar plantations in the south of China. To explore adaptability to drought and provide reference for future sex-based poplar clone selection, we studied physiological responses to short-term intermittent soil drought between different sexes. 【Method】 Based on pot experiments by setting short-term intermittent soil water deficiency, four female and three male clones of southern-type poplar were used to compare sex-specific changes in physiological traits, including leaf plasma membrane stability, osmotic regulation, antioxidant system, and photosynthetic pigments. 【Result】 Short-term drought induced increases in electrical conductivity of leaves, malondialdehyde (MDA) and proline (Pro) contents, and antioxidant enzyme activities, but decreases in leaf chlorophyll content, for both male and female poplar clones, which indicated damage to leaf membranes and photosynthesis system with membrane lipid peroxidation. After drought relief by rewatering, these physiological traits all returned to substantially the same level as the (normal watering/non-drought) control treatment. Differences existed in the level and pattern of physiological responses to short-term soil drought between male and female clones. For female clones, the activity of antioxidant enzymes in leaves fluctuated greatly, and the contents of chlorophyll and proline remained at a high level under draught treatment; after drought relief by rewatering, chlorophyll content recovered rapidly, while membrane lipid peroxidation remained high. For male clones exposed to short-term drought, however, we detected stable POD activity and reduced chlorophyll content; this indicated higher drought resistance. Male clones, by maintaining membrane stability and reducing water loss. Therefore, female poplar clones showed relatively lower drought tolerance, but maintained a certain level of photosynthesis and growth, while male clones presented relatively higher drought tolerance. In addition, during short-term soil drought, three male clones showed relatively consistent physiological responses, while male clones had greater inter-clone variation. 【Conclusion】 Male poplar clones had relatively high and stable drought resistance, while female clones had generally weak but varied inter-clone drought resistance. However, female clones displayed rapid recovery of leaf physiological conditions after rewatering between short-term drought.

Key words: drought stress, southern-type poplar, sexual difference, drought resistance strategy, antioxidant enzyme system