Abstract: Climate change has been observed to increase the frequency and intensity of drought, which can adversely affect plant growth and development. Therefore, it is crucial to quantify plant xylem resistance to embolism, particularly in the context of global climate change, to study the process of plant response to drought. In this study, we aimed to evaluate the drought tolerance of Rhododendron cultivars and select those with strong drought resistance by using three species of shrub Rhododendron, namely Rhododendron × pulchrum ‘zihe', Rhododendron × hybridum ‘yangmeihong' and R. simsii, as the materials. We used optical techniques to construct embolism vulnerability curves in petal and leaf tissues, and measured petal and leaf anatomical structural traits, and also analyzed the correlation between xylem hydraulic function and anatomical structural traits. The results were as follows:(1)The P₁₂, P₅₀ and P₈₈ values(water potential values corresponding to the occurrence of 12%, 50% and 88% embolism)of petals in Rhododendron × pulchrum ‘zihe', Rhododendron × hybridum ‘yangmeihong' and R. simsii were higher than those of leaves.(2)The embolism vulnerability of petal and leaf tissues varied among the three species, and the speed of petal and leaf embolism occurrence did not coincide, which may be an important characteristic of hybridized horticultural flowering plants.(3)The correlation analysis between P₅₀ values and their morphological characteristics showed that the P₅₀ values of leaves were negatively correlated with leaf palisade tissue thickness, and the P₅₀ values of petals were positively correlated with petal thickness. In conclusion, the study suggests that the petal embolism vulnerability of the three shrubs of Rhododendron is higher than that of the leaves, and the plants preferentially sacrifice the petals to protect the leaves under drought stress. Furthermore, the embolism vulnerability may be related to the leaf palisade tissue thickness and petal thickness. Our findings provide scientific references for screening and cultivating drought-resistant Rhododendron varieties, and selecting and configuring tree species of Rhododendron plants in arid areas.

Key words: embolism vulnerability, drought resistance, vessel structure, morphological structure, optical

摘要： 气候变化引发的干旱频度和强度严重影响植物生长发育,在全球气候变化背景下,量化植物木质部抗栓塞的能力对评估植物耐旱性尤为重要。为评价杜鹃品种间的耐旱性及筛选强抗旱性品种,该文以锦绣杜鹃‘紫鹤'(Rhododendron × pulchrum ‘zihe')、西洋杜鹃‘杨梅红'(Rhododendron × hybridum ‘yangmeihong')、映山红(R. simsii)3种灌木杜鹃为材料,利用光学技术构建花瓣和叶片栓塞脆弱性曲线,测定花瓣和叶片解剖结构性状,并分析木质部水力功能和解剖结构性状的相关性。结果表明:(1)锦绣杜鹃‘紫鹤'、西洋杜鹃‘杨梅红'、映山红3种杜鹃花瓣的P₁₂、P₅₀和P₈₈值(分别发生12%、50%和88%栓塞时对应的水势值)大于叶片。(2)3种杜鹃的花瓣和叶片栓塞脆弱性存在一定的变异,花瓣和叶片发生栓塞的快慢不一致,这种变异可能是杂交园艺花卉植物的重要特征。(3)P₅₀值与其形态特征相关性分析显示,叶片P₅₀值与叶片栅栏组织厚度呈负相关,花瓣P₅₀值与花瓣厚度呈正相关。综上认为,3种杜鹃花瓣栓塞脆弱性高于叶片,干旱胁迫下植物优先牺牲花瓣从而保护叶片,栓塞脆弱性可能与叶片栅栏组织厚度和花瓣厚度相关。该研究为干旱地区筛选、培育抗旱性强的杜鹃品种及园林杜鹃植物选择和树种配置提供了科学依据。

关键词: 栓塞脆弱性, 抗旱性, 导管结构, 形态结构, 光学法