Embolism vulnerability analysis of petals and leaves in three species of shrub Rhododendron

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.

Keywords

• embolism vulnerability
• drought resistance
• vessel structure
• morphological structure
• optical