| This experiment is to study the physiological and biochemical indexes of three types of tobacco (Honghuadajinyuan, Yunyan87and k326) how to change in their seeding stage by the different temperatures. In details, continued low temperature and a brief high temperature will affect the period of growth stagnancy and the resume growth of three tobaccos. The results of the experiment provide theoretical basis for planting tobacco of Yunnan province in different elevations. Main research results are listed as following:1.Under the critical low temperature and short-term heat treatment, the growth targets three varieties aspect, the largest aspect ratio of leaf length and the biggest leaf area among these three tobaccos are both smaller than the ratio of the control group. As time passed, the gap of the ratio between the critical low temperature group and the control group become larger, but the gap of the ratio between the brief high temperature group and the control group become smaller, plant dry matter accumulation were decreased when compared to control group, the stems distribution rate increases significantly, temperature leads to large adjustment of tobacco growth structure, stem beccomes coarsening so that it can survive in the face of adversity, and high temperature has more significant impact than low temperature。The nitrate reductase activity decreases sharply and between these two are highly significant negative correlation.2.Under the critical low temperature and short-term heat treatment, the three varieties of physiological indicators, root vigor and chlorophyll of three tobaccos are both tend to decrease compared with the control group. As time passed, root vigor and chlorophyll go down markedly, and the extent of changes in the brief high temperature group is more than the extent of changes in the critical low temperature group;lipid peroxidation end products MDA content of three tobaccos are all increase distinctly compared with the control group. As time passed, MDA would decrease generally.3.Under the critical low temperature and short-term heat treatment, the content of endogenous hormones, GA, IAA and CTK contents of these three tobaccos are all decreasing dramatically. With the extended processing time, GA, IAA and CTK content goes up a little but still lower than the control group. It proves that endohormone contents need more time to adapt to the different temperatures; the effects of tobacco endogenous hormones contents which synthetize IAA and CTK are:temperature>variety and temperature interaction effect> variety; GA is temperature> variety> variety and temperature interaction effect. The trends of GA/IAA and GA/CTK are decreasing first and then after increasing, and the changes of GA/IAA and GA/CTK can affect the growth of tobacco external formation which would increase the aspect ratio of tobacco external shape and make the growth of tobacco trend to slender leaves.4.After the low night temperature management and the different growth time treatment, the time which leaves overall length required for stagnant growth and the processing has an inverse relationship. According to this experiment, the leaf stunted growth will exist when the seedling stage of tobacco K326affecting by critical low temperature accumulates36h;the content of endogenous GA in the leaf segment decreases dramatically during leaf length stunted growth process, and the contents of IAA and CTK sharp decline. The contents of endogenous GA, IAA and CTK in the root are higher than the hormone contents in the leaf. With the extension of processing time, these three hormone contents decline but not very significant.5.The number of days that stagnant tobacco seedlings needed to recover growth will increase by the extension of low temperature processing time. However, the relative growth rate of the leaves overall length finally can catch up with the average growth rate of control group and leaves gradually recover growth. |
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