3种玉兰幼苗生长和生理特性对干旱胁迫的响应

Response of growth and physiological characteristics of three Magnolia spp.seedlings to drought stress

【目的】研究干旱胁迫下天女木兰、望春玉兰、红花玉兰‘娇红2号’的生长和生理变化,揭示3种玉兰幼苗对干旱胁迫的响应机理,评价3种玉兰的抗旱性,为干旱地区引种、推广提供参考。【方法】以3种玉兰的2年生盆栽播种苗为试验材料,设置4个处理水平(土壤相对含水量80%~90%(CK),60%~70%(T1),40%~50%(T2),20%~30%(T3)),干旱胁迫50 d后分析生长、生理等19个指标的变化。【结果】(1)中度和重度干旱胁迫(T2、T3)显著降低了3种玉兰的地径和各器官生物量增长量,显著增大了望春玉兰和红花玉兰‘娇红2号’的根冠比(P<0.05);重度干旱胁迫下(T3),红花玉兰‘娇红2号’的株高和各器官生物量增长量显著高于望春玉兰(P<0.05);(2)与CK相比,T1处理时红花玉兰‘娇红2号’叶绿素含量增加,其他干旱水平3种玉兰叶绿素含量逐渐降低;3种玉兰丙二醛含量、可溶性糖含量、可溶性蛋白含量、超氧化物歧化酶和过氧化氢酶活性随干旱加剧逐渐增加,T3与CK均存在显著差异;望春玉兰脯氨酸含量先降低后升高,天女木兰和红花玉兰‘娇红2号’脯氨酸含量随干旱加剧呈上升趋势;3种玉兰过氧化物酶活性随干旱加剧变化规律不同,天女木兰过氧化物酶活性T2处理最高,望春玉兰和红花玉兰‘娇红2号’T3处理最高。(3)红花玉兰‘娇红2号’T1处理净光合速率、胞间CO_(2)浓度、蒸腾速率最高,较CK分别高出2.67%、1.94%、3.09%,气孔导度和水分利用效率随干旱加剧逐渐降低;重度干旱胁迫(T3)显著降低了天女木兰和望春玉兰的净光合速率、胞间CO_(2)浓度、蒸腾速率、气孔导度、水分利用效率(P<0.05)。(4)隶属函数分析表明,3种玉兰抗旱性强弱为天女木兰>红花玉兰‘娇红2号’>望春玉兰。【结论】干旱胁迫影响了3种玉兰幼苗的生长和生理活性,使叶片细胞结构受损,植株生长缓慢,但植物能通过调节渗透调节物质含量和自身保护酶活性来抵御干旱,维持自身的正常生理代谢功能。综合各指标可知,天女木兰抗旱性最强,望春玉兰最弱。

[Objective]This study investigated the effects of drought stress on growth and physiological changes of Magnolia sieboldii,M.biondii,M.wufengensis‘Jiaohong No.2’to explore the influence mechanism of drought stress on three Magnolia spp.seedlings,evaluate the drought resistance of Magnolia spp.seedlings,and provide a basis for the introduction and promotion of seeds in arid areas.[Method]The 2-year-old potted seedlings of 3 kinds of Magnolia spp.seedlings were used as experimental materials,4 treatment levels(SWC80%−90%(CK),60%−70%(T1),40%−50%(T2),20%−30%(T3))were set,and the changes of 19 indexes,including growth and physiology were analyzed after 50 d of drought stress.[Result](1)Moderate and severe drought stress(T2,T3)significantly decreased the ground diameter increment and biomass increment of 3 kinds of Magnolia spp.seedlings,and significantly increased the rootshoot ratio of M.biondii and M.wufengensis‘Jiaohong No.2’(P<0.05).Under severe drought stress(T3),the increment of plant height and biomass of M.wufengensis‘Jiaohong No.2’was significantly higher than that of M.biondii(P<0.05).(2)Compared with CK,T1 increased the chlorophyll contents of M.wufengensis‘Jiaohong No.2’,and the content of chlorophyll in the 3 kinds of Magnolia spp.seedlings gradually decreased at other drought levels.With the intensification of drought,the content of malondialdehyde,soluble sugar,soluble protein and the activity of superoxide dismutase,catalase of the 3 kinds of Magnolia spp.seedlings gradually increased,and T3 and CK showed significant differences.Proline content of M.biondii decreased first and then increased,and the proline content of M.sieboldii and M.wufengensis‘Jiaohong No.2’showed an increasing trend with the intensification of drought.The peroxidase activity of 3 kinds of Magnolia spp.seedlings varied with the intensities of drought.The peroxidase activity of M.sieboldii was the highest at T2,and those of M.biondii and M.wufengensis‘Jiaohong No.2’were the highest at T3.(3)The net photosynthetic rate,intercellular CO_(2)concentration and transpiration rate of M.wufengensis‘Jiaohong No.2’were the highest at T1,which were 2.67%,1.94%and 3.09%higher than CK,respectively.The stomatal conductivity and water use efficiency decreased gradually with the worsening of drought.Severe drought stress(T3)significantly reduced the net photosynthetic rate,intercellular CO_(2)concentration,transpiration rate,stomatal conductivity and water use efficiency(P<0.05)of M.sieboldii and M.biondii.(4)The analysis of membership function showed that the drought resistance of 3 kinds of Magnolia spp.seedlings was M.sieboldii>M.wufengensis‘Jiaohong No.2’>M.biondii.[Conclusion]Drought stress affects the growth and physiological activities of the 3 kinds of Magnolia spp.seedlings,damages the leaf cell structure and slows plant growth,but the plants could resist drought and maintain their normal physiological metabolic functions by adjusting their own osmoregulatory substance content and protective enzyme activities.Based on the indicators,the drought resistance of M.sieboldii is the strongest,and the drought resistance of M.biondii is the weakest.