| 1 Screening of tolerant rice and wheat genotypes to 1, 2, 4-trichlorobenzene stress at seedling stageIn order to evaluate the tolerance of fifty rice genotypes and fifteen wheat genotypes to 1, 2, 4-trichlorobenzene (1, 2, 4-TCB) stress and identify proper screening indices and concentration, the effects of 1, 2, 4-TCB on the rice and wheat seed germination and seedling growth were studied. Rice were treated with 0, 0.35, 6 mmo·kg-1 sand 1, 2, 4-TCB and wheat 0, 0.35, 6 mmo·kg-1 sand 1, 2, 4-TCB. Germination potential, germination rate, the longest root length, root number, plant height, coleoptile length, the dry weight of shoot and roots of different rice and wheat varieties at seedling stage were measured. Character relative values were got from measure values of treated groups and control groups. They were used as tolerance indices (TI) of early seedlings. Cluster analysis of different rice and wheat genotypes based on TI was adopted. The results showed that the fifty rice varieties and fifteen wheat varieties could be grouped into four types respectively, .i.e. TCB sensitive varieties, relatively sensitive varieties, tolerant varieties and relatively tolerant varieties. Comparatively speaking, the concentration of 0.35 mmo·kg-1 sand is better to rice screening and 3 mmo·kg-1 is better to wheat screening.2 The analysis of toxicity effect of 1, 2, 4-trichlorobenzene stress on rice and wheat seedlingsIn order to analyse the toxicity effect of 1, 2, 4-trichlorobenzene stress on rice and wheat seedlings. The influence of increasing concentration of 1, 2, 4-TCB on the germination rate and germination exponential of wheat seeds, the biomass of wheat seedling, soluble protein content in leaves and roots were measured. The results showed that the seed germination rate and germination exponential of rice were not obviously influenced by TCB, but the seedling biomass reduced with the increase of TCB concentration. TCB caused the increase of leaf soluble protein content of Xiangjing 2018, but the leaf soluble protein content of Siyang 1382 declined. Treated with TCB, root soluble protein content of Xiangjing 2018 and Siyang 1382 were lower than the control as a whole. Speaking of wheat, the change scopes of seed germination rate, germination exponential and seedling biomass of Yanfu 188 were smaller than those of Yangmai 16. With increasing of TCB concentration, the leaf soluble protein content of Yanfu 188 decreased firstly, then increased significantly, but that of Yangmai 16 was fluctuant. The root soluble protein content of Yanfu 188 increased, reaching the significantly higher level at the concentration of 1.0-2.0 mmol·kg-1 sand TCB.Whereas the root soluble protein content of Yangmai 16 decreased significantly except exceptional concentration. Obviously, the effects of 1, 2, 4-TCB stress on different crops are different, speaking of the identical crop, the change scopes of indexes of tolerant genotype are smaller than those of sensitive genotype. This manifests the tolerance of tolerant genotype3 The research on physiological and biochemical mechanism of response of rice and wheat seedlings to 1, 2, 4-trichlorobenzene stressWith sand culture, the physiological and biochemical mechanism of response of two rice genotypes ( Xiangjing 2018 and Siyang 1382 )as well as two wheat genotypes (Yanfu 188 and Yangmai 16) to 1, 2, 4-TCB stress were studied. The results showed: The influence of 0-0.8 mmo·kg-1 1, 2, 4-TCB on the rice leaf chlorophyll content is small. With the increase of 1, 2, 4-TCB concentration, Fv/Fm, Fv/Fo,φPSII, qP and ETR of the two rice varieties increased firstly, then reduced as a whole, qNP is smaller than the control all through. Under 1, 2, 4-TCB stress, the producing velocity of O2- in the two rice varieties leaves dropped firstly then rose, those in roots were higher than the control as a whole. MDA content in leaves were significantly higher than the control when 1, 2, 4-TCB reached high concentration, those in roots treated with 1, 2, 4-TCB were basically significantly higher than the control, this indicated 1, 2, 4-TCB caused active oxygen in rice accumulated more, led to the membrane lipid peroxidation aggravated, the cell membrane suffered finally. Under TCB stress, the activities of SOD in Xiangjing 2018 leaves and roots changed a little, while those in Siyang 1382 leaves and roots increased significantly. The activities of POD, CAT in Xiangjing 2018 leaves increased firstly then declined, while those in Siyang 1382 leaves and roots declined all through. The activity of POD in Xiangjing 2018 roots declined a bit, while that in Siyang 1382 roots increased significantly.Speaking of wheat, with the increase of 1, 2, 4-TCB concentration, the chlorophyll a, b as well as the total chlorophyll content in Yanfu 188 leaves assumed the trend of escalation, the chlorophyll a, b content in Yangmai 16 leaves dropped firstly, then rose. Fv/Fm and Fv/Fo of the two wheat varieties leaves were not changed remarkably, qP and qNP went up as a whole under TCB stress.ΦPS IIand ETR of Yanfu 188 basically rose with the increase of 1, 2, 4-TCB concentration, butΦPS IIand ETR of Yangmai 16 rose firstly, then dropped as a whole with the increase of 1, 2, 4-TCB concentration. Under TCB stress, the activities of SOD, POD in Yangmai 16 leaves were lower than control, and the activity of CAT was significantly lower than control. The activity of SOD in Yanfu 188 leaves was not significantly different with the control, POD and CAT activities were not significantly different with the control when the TCB concentration was low and were smaller than the control when the TCB concentration was high. Its MDA content was lower than Yangmai 16. The activities of SOD, POD in Yanfu 188 roots were not sensitive to TCB stress and changed a little, while those in Yangmai 16 roots increased with the concentration of TCB increasing, but its producing velocity of O2- was greater than Yanfu 188, so it could not eliminate excessive O2-·, this led its MDA content higher than Yanfu 188. |
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