黄瓜贴接苗砧木子叶淀粉代谢的动态变化特征

Dynamics of Starch Metabolism in the Rootstock Cotyledon of Cucumber/Pumpkin Grafted Seedlings

该研究以黄瓜品种‘中农18号’、南瓜砧木品种‘京欣砧5号’为试验材料,以南瓜自根苗(P)和去除1片子叶及生长点的南瓜苗(-/P)为对照,采用单子叶贴接法进行黄瓜/南瓜异体嫁接(C/P)和南瓜/南瓜自体嫁接(P/P),测定嫁接后砧木子叶形态指标和淀粉代谢的动态变化,分析嫁接后去除砧木子叶对嫁接苗生长发育的影响,以揭示砧木子叶淀粉代谢在黄瓜嫁接苗生长中的作用,为黄瓜嫁接苗的壮苗培育提供理论依据。结果显示:(1)贴接后,C/P、P/P和-/P砧木子叶鲜质量和面积显著增大,且增加量依次递减,表现为-/P>C/P>P/P>P。(2)贴接后,C/P和P/P砧木子叶中淀粉含量在嫁接后0~3 d时降低,之后迅速升高,至嫁接后13 d再次逐渐降低,且C/P砧木子叶淀粉含量及其淀粉分支酶(SBE)和水解酶(β-AL)活性均显著高于P/P。(3)在嫁接后0~10 d去除砧木子叶可显著抑制C/P嫁接苗接穗和根系生长,减弱根系活力,同时降低根系可溶性糖含量及其CWIN、HXK基因表达水平,并以嫁接后0 d去除砧木子叶的抑制效果最显著。研究表明,黄瓜C/P单子叶贴接苗中,砧木子叶作为贮存器官,在幼苗生长早期以淀粉形式储存光合产物,之后淀粉水解成单糖为嫁接苗接穗和根系快速生长提供物质和能量。

In this study,the cucumber cultivar‘Zhongnong 18’and pumpkin cultivar‘Jingxinzhen No.5’were used as materials,and the intact pumpkin seedlings(P)and the seedling with one cotyledon and apical meristem being removed(-/P)were used as control,two grafting combinations including cucumber/pumpkin(C/P)and pumpkin/pumpkin(P/P)were set up,using the one-cotyledon splice grafting method.The changes of the morphological indexes and starch metabolism in the rootstock cotyledon of grated seedlings were detected,and the effects of removing rootstock cotyledon on the growth of grafted seedlings were analyzed.The major purpose of this study is to reveal the role of starch metabolism of rootstock cotyledons in the growth of cucumber grafted seedlings,and thereby provide a theoretical basis for improving the quality of cucumber grafted seedlings.The results revealed that:(1)after grafting,the fresh weight and area of rootstock cotyledon of C/P and P/P seedlings increased rapidly,and the net increase in fresh weight and area decreased in this order:-/P>C/P>P/P>P.(2)After grafting,the starch content in the rootstock cotyledons of C/P and P/P seedlings decreased during the early healing stage[0-3 days after grafting(dag)].Then the starch accumulated rapidly until 13 dag,when starch was gradually decreased.The starch content and its starch branching enzyme(SBE,for starch synthesis)andβ-amylase(β-AL,for starch hydrolysis)activities in C/P rootstock cotyledon were significantly higher than that in P/P seedlings.(3)Removal of rootstock cotyledons at 0-10 day could significantly inhibit the growth of scion and roots in C/P grafted seedlings.Also,the root vigor,as well as the soluble sugar content and CWIN and HXK gene expression levels were significantly repressed.Removing the rootstock cotyledon at 0 dag led to the strongest inhibition effect.These results suggested that in the C/P grafted seedlings,rootstock cotyledon can serve as a storage organ.During early growth of grafted seedlings,the photosynthetic products can be stored as starch,and then the stored starch is hydrolyzed into monosaccharides,which can be used for the rapid growth of scion and roots of grafted seedlings.