盐胁迫下番茄砧木对嫁接苗生物量、氨基酸含量和活性氧代谢的影响

Effects of Solanum lycopersicum rootstock on biomass,amnio acid content and reactive oxygen species metabolism of grafted seedlings under salt stress

为探讨砧木对提高番茄嫁接苗耐盐性的作用机理,以耐盐性较敏感的‘中杂9号’(S)为接穗,耐盐性较强的‘OZ-006’(R)为砧木,采用劈接法形成嫁接苗(RS)以及接穗自嫁接苗(SS)、砧木自嫁接苗(RR)3个试验材料,在175 mmol·L^(-1 )NaCl处理下测定植株生长、Na^+积累、氨基酸含量和活性氧代谢的变化。结果表明:NaCl胁迫导致番茄幼苗的盐害指数和Na^+含量均显著提高,幼苗生长速率和叶绿素含量显著降低,但不同嫁接苗的类型差异显著,在盐害表型上表现为SS>RS>RR的规律。NaCl胁迫诱导嫁接苗的叶片和根系总氨基酸含量显著提高,其中RR、RS叶片有9种、根系有8种氨基酸含量显著高于对照,以脯氨酸含量变化最为显著,而SS叶片中仅有2种、根系中仅有4种氨基酸含量显著高于对照;幼苗间的氨基酸含量呈现RR>RS>SS的规律,RR、RS叶片的氨基酸含量分别比SS叶片上升了32.8%、16.6%,根系分别比SS上升了53.1%和32.5%。NaCl胁迫造成活性氧代谢的变化,幼苗叶片和根系的抗氧化酶活性、超氧阴离子产生速率、丙二醛含量均显著提高,以RR叶片和根系中抗氧化酶活性的增幅最大,其次为RS;SS和抗氧化酶活性的增幅最小,品种间活性氧水平表现为SS>RS>RR。综上,砧木通过抑制Na^+向上运输、提高氨基酸水平和抗氧化酶活性缓解了盐胁迫对嫁接苗的伤害,但不同砧穗组合的耐盐性差异较大,以RR的耐盐性最强,其次为RS,SS最弱。因此,番茄嫁接苗的耐盐性主要受砧木耐盐性的影响,其次为接穗,同时,其与番茄体内的氨基酸和活性氧代谢调控密切相关。

To explore the mechanism of Solanum lycopersicum rootstock function in enhancing salt tolerance of grafted seedlings,we examined the growth,Na+accumulation,amino acid contents and active oxygen metabolism(ROS)in three grafted seedlings treated with and without 175 mmol·L-1 NaCl conditions.RS grafted seedlings were formed by split grafting using salt-sensitive variety‘Zhongza 9’(S)as scion and salt-tolerant variety‘OZ-006’(R)as rootstock,while the other two experiment materials were the scion self-grafted(SS)and rootstock self-grafted(RR)seedlings.The results showed that NaCl stress significantly increased the salt damage index and Na+content,concomitantly with substantial decrease in growth rate and chlorophyll content of seedlings.More-over,there were significant differences among the grafting combinations,with an order of SS>RS>RR.NaCl stress significantly increased total amino acid content in the leaves and roots of the grafted seedlings.The amino acid contents were significantly higher than those in the control.There were 9 kinds of amino acid in RR and RS leaves,and 8 kinds in RR and RS roots,with the most significant change in proline.Only 2 and 4 kinds of amino acids in leaves and roots of SS were significantly higher than those in control,respectively.Amino acid contents among three grafted seedlings showed RR>RS>SS under NaCl stress.The contents of amino acid in RR and RS leaves increased by 32.8%and 16.6%compared with SS,and those in RR and RS roots increased by 53.1%and 32.5%,respectively.The changes of ROS were caused by NaCl stress,which enhanced the activities of antioxidant enzymes,the production rate of O2-·and MDA content in both leaves and roots.Among different grafted seedlings,RR had the most prominent increase of antioxidant enzymes activities in leaves and roots,followed by RS,and SS showed the smallest.The active oxygen levels among the three grafted seedlings were show as SS>RS>RR.In summary,rootstock alleviated salt damage of grafted seedlings by inhibiting Na+transport upward,enhancing amino acid content and antioxidant enzyme activities.The salt tolerance ability showed remarkable difference among three different combinations of rootstock and scion,with a order of RR>RS>SS.Our results suggested that salt tolerance of S.lycopersicum grafted seedlings was mainly affected by the ability of rootstock salt tolerance,followed by scion,and also closely related to the regulation of both amino acid and active oxygen metabolism in seedlings.