Morphological and physiological responses of grafted Camellia oleifera seedlings with different rootstocks to drought stress

<bold>Objective</bold> This study aims to investigate the morphological and physiological responses of different rootstocks of <italic>Camellia oleifera</italic> grafting seedlings to drought stress，evaluate and screen drought-tolerant rootstock types，thus providing materials and technical support for the efficient cultivation of high-quality <italic>C. oleifera</italic> varieties. <bold>Method</bold> This study used seedlings propagated from seeds of the main promoted <italic>C. oleifera</italic> varieties in Jiangxi Province，including “Ganwu 1，” “Ganwu 2，” “Changlin 3，” and the high-ploidy <italic>C. oleifera</italic> “Gaozhou，” as rootstocks，and “Changlin 4” as the scion to cultivate 2-year-old grafted seedlings with the same scion but different rootstocks.A pot-controlled water experiment was conducted to study the effects of different levels of drought stress on the growth，root characteristics，and photosynthetic properties of <italic>C. oleifera</italic> grafting seedlings during the seedling stage.The differences in responses to drought stress among different rootstocks were analyzed，and the rootstock effects of <italic>C. oleifera</italic> grafting seedlings under drought stress were explored. <bold>Result</bold> Under mild drought conditions，the grafting seedlings with “Ganwu 1” as the rootstock exhibited higher growth increments，relative water content，and chlorophyll content.In contrast，“Ganwu 2” and “Gaozhou” were more significantly inhibited in terms of these indicators.Under moderate drought conditions，the growth increments，net photosynthetic rate，stomatal conductance，intercellular CO₂ concentration，and transpiration rate of all grafting seedlings significantly decreased.Under severe drought conditions，the grafting seedlings with “Ganwu 1” as the rootstock maintained higher stem height and ground diameter increments，and their chlorophyll a and total chlorophyll contents were significantly higher than those of other varieties.The grafting seedlings with “Gaozhou” showed the most significant decline in stem height and ground diameter increments，followed by “Ganwu 2.” Principal component analysis results indicated that the rootstock “Ganwu 1” exhibited higher resource utilization efficiency and drought tolerance under drought stress，while “Ganwu 2” and “Gaozhou” had relatively poorer drought tolerance，especially “Gaozhou，” which was most sensitive to water deficit. <bold>Conclusion</bold> Different rootstock types of grafting seedlings have different physiological responses to drought stress.The grafting seedlings with the rootstocks “Ganwu 1” and “Changlin 3” showed stronger drought tolerance under drought stress，while the grafting seedlings with the rootstocks “Ganwu 2” and “Gaozhou” were more sensitive to soil moisture.