溃疡病影响杨树根部淀粉的年度积累

Impact of Canker Disease on Annual Starch Accumulation in Poplar Roots

为了了解新发生的溃疡病的严重程度对杨树根部淀粉积累的影响,通过根部淀粉积累的变化初步探索溃疡病对杨树树势的影响,笔者按照溃疡病发病指数的大小,选取5年生中林46杨,采用固定样株取根和碘-淀粉比色法,测量了2008年休眠期、2009年生长期和2009年休眠期杨树根部淀粉含量的变化。结果表明,2008年休眠期感病植株的淀粉含量与健康植株的差异不显著。持续发病显著降低了发病指数>60%,即发病严重植株2009年生长期(F=3.668,P=0.02)和2009年休眠期(F=3.335,P=0.035)的淀粉含量,但使发病中等树木2009年休眠期的淀粉含量显著高于发病轻和严重发病树木。t检验结果证实,只有发病指数>60%的植株自身的淀粉含量在2009年生长期(t=5.197,P=0.001)和休眠期(t=3.219,P=0.008)分别显著低于2008年休眠期。健康和发病轻的树木淀粉含量虽然均有所下降,但差异均不显著;而发病中等树木2009年生长期根部的淀粉含量较2008年休眠期高,同时2009年休眠期的淀粉含量较2008年休眠期高,但均未达显著水平。本研究初步揭示,当杨树罹患溃疡病后,其根部淀粉含量的变化受发病指数的影响呈现出不同的变化趋势:当发病指数>60%,即严重发病时,根部淀粉积累呈现极显著的下降趋势,因而其生长势受到较大的负面影响;轻度发病不会影响树木生长势;而发病中等的树木经过2年生长,其淀粉含量显著高于发病轻和发病重的树木,其树势可能增强。

In order to better understand the impact of newly occurred cankers on soluble starch accumulations in poplar roots,and to further assess trees＇vigor along to the change of starch reserves in roots,Populus euramerican＇zhonglin 46＇with new canker were selected during 2008 growing season and marked according to disease severity indices and their roots were collected at dormancy period in 2008,growing season in 2009 and dormancy in 2009 from 6 temporary plots in Qingfeng County,respectively.Starch in roots was determined using iodine colorimetric method.Starch of diseased trees was not significantly different compared to that of healthy trees at 2008 dormancy（F =0.535,P =0.660）.Starch content was significantly different among roots of healthy,slightly diseased,intermediately diseased and severely diseased trees in 2009 growing season（F = 3.668,P =0.02）and 2009 dormancy（F =3.335,P =0.035）,particularly a significant reduce of starch was found among those severely diseased trees;while starch content in intermediately diseased trees was significantly higher than that of slightly diseased and severely diseased trees in 2009 dormancy.Thet-test indicated that starch content of severely diseased trees significantly decreased during 2009 growing season（t =5.197,P = 0.001）and dormancy period（t =3.219,P =0.008）compared to 2008 dormancy.At the same time,no significant difference of starch content change was found in healthy and slightly diseased trees.Interestingly,an increment of starch content was found in intermediately diseased trees,while the change was not significantly.This study revealed that the change of starch content was affected by severities of canker in different ways.Starch content in severely diseased trees reduced significantly and further reduced trees＇vigor,while slightly disease trees＇ vigor was not affected due to insignificant decreases of starch reserves.A slightly increase of starch reserve was observed in those intermediately diseased trees which most likely meant a slight increase of vigor.