外源DA-6对UV-B辐射胁迫下紫花苜蓿幼苗生长调节及花青素合成代谢的影响

Effects of exogenous DA-6 on growth regulation and anthocyanin anabolism of alfalfa seedlings under UV-B radiation stress

为了解外源胺鲜脂(diethyl aminoethyl hexanoate,DA-6)对UV-B辐射胁迫下紫花苜蓿幼苗生长调节及花青素合成代谢的影响,试验采用营养液沙培法研究了叶面喷施或根施30 mg/L的DA-6溶液对UV-B辐射胁迫[在自然光照基础上增加UV-B辐射5 kJ/(m 2·d)]下紫花苜蓿幼苗生长、抗氧化能力、光合作用、叶绿素和花青素合成代谢的影响,处理15 d后取样进行各指标的测定。结果表明:UV-B辐射胁迫显著加剧了紫花苜蓿幼苗的细胞膜脂过氧化伤害,并抑制了幼苗的生长、叶绿素合成及光合作用。喷施或根施DA-6溶液能不同程度缓解UV-B辐射对紫花苜蓿幼苗的胁迫,且根施方式的综合缓解效果更为明显,具体表现为较喷施方式增加了幼苗的株高、根长、地上部干重及根部干重;提高了叶片过氧化物酶和过氧化氢酶活性,降低了超氧阴离子和过氧化氢含量;提升了叶片净光合速率,并通过改善UV-B辐射胁迫对叶绿素合成途径中胆色素原到尿卟啉原Ⅲ的转化受阻程度来促进叶绿素合成;增强了花青素合成代谢关键酶(苯丙氨酸解氨酶、查尔酮合成酶、查尔酮异构酶、花青素合成酶)的活性从而促进花青素的合成和累积。说明外源DA-6尤其根施方式能通过增强抗氧化酶(过氧化物酶、过氧化氢酶)活性、促进叶绿素和花青素合成代谢等方式缓解UV-B辐射胁迫对紫花苜蓿幼苗生长和光合作用的抑制效应,最终表现为促进幼苗地上部和根部的干物质积累。

In order to understand the effects of exogenous diethyl aminoethyl hexanoate(DA-6)on the growth regulation and anthocyanin anabolism of alfalfa seedlings under UV-B radiation stress,the effects of leaf spraying or root application of 30 mg/L DA-6 solution on the growth,antioxidant capacity,photosynthesis,chlorophyll and anthocyanin anabolism of alfalfa seedlings under UV-B radiation stress(added UV-B 5 kJ/(m 2·d)on the basis of the natural light)were studied by nutrient solution sand culture method.After 15 days of treatment,the samples were taken for the determination of each index.The results showed that UV-B radiation stress significantly aggravated the cell membrane lipid peroxidation injury of cell membrane of alfalfa seedlings,and inhibited the growth,chlorophyll synthesis and photosynthesis of the seedlings.DA-6 solution by leaf spraying or root application could alleviate the stress of UV-B radiation on alfalfa seedlings in varying degrees,and DA-6 by root application had a better comprehensive alleviation effect,which increased the plant height,root length,shoot dry weight,root dry weight,and root-shoot ratio of the seedlings,improved the activities of superoxide dismutase,peroxidase and catalase in leaves,decreased the contents of superoxide anion,hydrogen peroxide and malondialdehyde,and promoted the net photosynthetic rate.DA-6 by root application promoted chlorophyll synthesis by ameliorating the degree of transformation obstruction from porphobilinogen to uroporphyrinogenⅢin the chlorophyll synthesis pathway under UV-B radiation stress,and enhanced the key enzyme(phenylalanine ammonia lyase,chalcone synthase,chalcone isomerase,anthocyanin synthase)activities for anthocyanin anabolism such as phenylalanine ammonia lyase,thus promoting the synthesis and accumulation of anthocyanins.The results indicated that exogenous DA-6,especially root application,could alleviate the inhibitory effect of UV-B radiation stress on the growth and photosynthesis of alfalfa seedlings by enhancing antioxidant enzyme(peroxidase and catalase)activity and promoting chlorophyll and anthocyanin biosynthesis,and finally promoted the accumulation of dry matter in the shoot and root of the seedlings.