外源水杨酸对低温胁迫下火龙果幼苗的形态及生理效应

Effects of exogenous salicylic acid on morphology and physiology of pitaya seedlings under low temperature stress

为探究外源水杨酸(SA)对低温胁迫下火龙果幼苗形态及生理的影响,该研究以‘紫红龙’火龙果幼苗为材料,将4个不同浓度的SA(0.1、0.3、0.5、0.7 mmol·L^(-1))喷施叶片,48 h后4℃低温培养,于第0、第3、第6、第9天观察火龙果幼苗形态及叶片组织结构的变化,并测定叶片相对电导率、丙二醛含量、渗透调节物(可溶性糖、可溶性蛋白、脯氨酸)含量及抗氧化酶(超氧化物歧化酶、过氧化物酶、过氧化氢酶、谷胱甘肽S-转移酶)活性等生理指标。结果表明:(1)低温胁迫下,火龙果幼苗呈现0级、Ⅰ级和Ⅱ级3个冷害等级,SA处理后的火龙果幼苗出现Ⅰ级冷害和Ⅱ级冷害的株数百分率均明显降低。(2)与低温对照相比,SA处理能降低火龙果幼苗叶片相对电导率和丙二醛含量并提高渗透调节物含量和抗氧化酶活性。(3)通过对不同SA处理结果进行比较分析,发现缓解冷害症状、降低相对电导率和丙二醛含量、提高可溶性糖和脯氨酸的含量、提高超氧化物歧化酶和谷胱甘肽S-转移酶的活性均以0.3 mmol·L^(-1) SA效果最好,提高可溶性蛋白含量、过氧化物酶活性、过氧化氢酶活性分别以0.7、0.1、0.5 mmol·L^(-1)的SA效果最好。综上表明,外源SA处理能缓解4℃低温胁迫下火龙果幼苗的冷害症状,对于提高幼苗抗冷性有正向生理效应,并且0.3 mmol·L^(-1)浓度较适宜。

Pitaya(Hylocereus undatus) is a typical tropical cash crop that is not chilling-tolerant.Low temperature stress seriously affects the quality and yield of pitaya.It is an efficient and safe method to apply exogenous natural substances to improve the chilling tolerance of plants.Salicylic acid(SA) not only regulates many physiological and biochemical processes such as seed germination,growth,fruiting and senescence,but also helps plants to cope with biotic and abiotic stresses.However,the role of exogenous SA in chilling tolerance of pitaya has not been reported.To explore the effect of exogenous SA on the morphology structure and physiology of pitaya seedlings under low temperature,the leaves of ‘Zihonglong' seedlings were sprayed with SA at four concentrations(0.1,0.3,0.5,0.7 mmol·L~(-1)).after spraying for 48 h,seedlings were incubated at 4 ℃.The change in the morphology and leaf tissue structure of pitaya seedlings were observed on 0,3,6,9 d.Physiological indexes such as relative electrical conductivity,contents of malondialdehyde,contents of osmotic regulators(soluble sugar,soluble protein,proline) and antioxidant enzyme(superoxide dismutase,peroxidase,catalase,glutathione S-transferase) activities in leaves were measured.The results were as follows:(1) Under low temperature stress,pitaya seedlings showed chilling injury of Grade 0,Grade Ⅰ and Grade Ⅱ.The leaf shape,color and cell structure of pitaya with different chilling injury symptoms were quite different.The percentages of Grade Ⅰ and Grade Ⅱ chilling injury of pitaya seedlings treated with SA were significantly reduced.(2) Compared with the low temperature control,SA treatment could reduce the relative conductivity and malondialdehyde contents of pitaya leaves,and increase the contents of osmotic regulators and antioxidant enzyme activities.(3) After comparing with different SA treatments,SA at 0.3 mmol·L~(-1) had the best effects on relieving chilling injury symptoms,reducing the relative conductivity and malondialdehyde content,increasing the soluble sugar and proline content,and increasing the activities of superoxide dismutase and glutathione S-transferase.The optimal SA concentrations for increasing soluble protein content,peroxidase activity and catalase activity were 0.7,0.1 and 0.5 mmol·L~(-1),respectively.In summary,exogenous SA could alleviate chilling injury of pitaya seedlings under 4 ℃,and has a positive physiological effect on improving chilling tolerance of seedlings,and exogenous SA at 0.3 mmol·L~(-1) is more suitable.