切除上胚轴对绿豆子叶衰老逆转及其核酸和蛋白质代谢的效应

在绿豆子叶衰老达到不归点(萌发后5～6d)前切除上胚轴可使开始衰老的子叶中核酸和蛋白质含量回升,衰老短期逆转。衰老不归点后的子叶中核酸和蛋白质变化的主要特征是:丧失了较多的核主带DNA、25S、18S rRNA以及大部分可溶性蛋白质组分,一种小分子DNA 组分完全消失。不归点前切除上胚轴可使上述核酸和蛋白质组分明显增加,表明子叶衰老的逆转可能与这些重要功能物质的回升有关。在切除上胚轴的茎顶涂抹IAA,能阻止子叶核酸和蛋白质回升,也消除了切除上胚轴对子叶裹老的逆转作用。

Effects of Epicotyl Removal on the Reversion of Senescence and Related Metabolism of Nucleic Acids and Protein in Mung Bean Cotyledons

The decline of the contents of nu-cleic acids and protein in senescingcotyledons of mung bean (Plaseolus ra-diatus) was reverted to an increase, andhence the process of senescence was re-versed, when the epicotyl was removedbefore the point of no-return (betweenday 5 and day 6). Epicotyl removalafter the point of no-return had no ef-fect in reversing the senescence ofcotyledons and in recovering the loss ofnucleic acids and proteins. By compar-ing the cotyledons before and after thepoint of no-return, and the senes-cence-reversed cotyledons, differencesin the patterns of changes of differentcomponents of DNA, RNA and solubleproteins were observed. The cotyledonsafter the point of no-return had lost allof its low molecular weight DNA com-ponents, larger amount of nuclearmain-band DNA, 25 S. and 18 SrRNA and most of its soluble proteins.The cotyledons of a seedling fromwhich the epicotyl was removed beforethe point of no-return, showed signifi-cant increase in the amount of all theDNA and RNA component and almostall of the soluble proteins. Epicotyl re-moval prevented the low molecularweight DNA compeonent from degra-dation and stimulated the synthesis ofnew proteins. The results indicate thatthe irreversibility of cotyledon senes-cence may be related to the loss of theabove mentioned DNAs, RNAs andproeins, and that the reversion of thecotyledon senescence by epicotyl re-moval may be related to the recoveryof those components. Application onthe cotyledons of 6-BA could retard theprogress of cotyledon senescence, butdid not have the same effect as epicotylremoval. While the application of IAAon the top of a seedling ftom which theepicotyl had been removed could inhib-it the recovering effect of epicotyl re-moval on the contents of nucleic acidsand protein. This indicates that thesenescence of mung bean cotyledons isrelated to hormone, especially auxin,distribution.