Effects of single stress of enhanced UV-B radiation(2.5,5.0 and 7.5 kJ·m-2·d-1) and combined stress of enhanced UV-B radiation and inoculated Magnaporthe grisea(strain Y98-16T and Y99-63C) on three physiological indexes(relative conductivity,MDA content and SOD activity) in seedling leaf of two rice(Oryza sativa L.) cultivars('Huangkenuo' and 'Hexi-41') were studied by pot experiments.The results show that the three physiological indexes of seedling leaf of the two cultivars in low dose(2.5 and 5.0 kJ·m-2·d-1) of single stress of enhanced UV-B radiation all decrease compared with the control(natural light),while those all increase in high dose(7.5 kJ·m-2·d-1) of same UV-B stress.Compared with the control(only inoculated M.grisea),the three physiological indexes in seedling leaf of 'Huangkenuo' decrease generally in combined stress of first enhanced UV-B radiation with low dose(2.5 and 5.0 kJ·m-2·d-1) and then inoculated M.grisea,while those all increase in the same stress but treated with high dose(7.5 kJ·m-2·d-1).The three physiological indexes of 'Hexi-41' seedling increase generally in combined stress of first enhanced UV-B radiation with different doses and then inoculated M.grisea,and there are significant positive correlations between relative conductivity and SOD activity of the two cultivars(P0.05).In combined stress of first inoculated M.grisea and then enhanced UV-B radiation with different doses,the three physiological indexes in seedling leaf of 'Huangkenuo' all increase compared with the control(only inoculated M.grisea),while those of 'Hexi-41' seedling appear various changing trends.There are significant and extremely significant positive correlations among the three physiological indexes in seedling leaf of the two cultivars(P0.05 or P0.01) in combined stress of first inoculated M.grisea strain Y98-16T and then enhanced UV-B radiation,while there is no obvious correlation among those indexes in the same stress with M.grisea strain Y99-63C.It is suggested that because of different treating orders of the two stress factors,different strains of M.grisea,different radiation doses of UV-B and different rice cultivars,the relative conductivity,MDA content and SOD activity in leaf of rice seedling could appear various changing trends under the combined stress of inoculated M.grisea and enhanced UV-B radiation.
Effects of 4 nitrogen application rates on the quantity of soil microorganisms in Qiubei pepper field of Yunnan Province were studied by microbial cultivation in pepper′s bloom-growth,blossom and fruit period.The correlation analysis of quantity was carried out between different microorganisms.The results showed as follows: The quantity of different microorganisms was enhanced mostly when N application rate was 60 kg/hm2.The quantity of soil bacteria,actinomycetes,fungi,potassium bacteria and organic phosphate-dissolving bacteria in bloom-growth period,cellulose-decomposing bacteria and organic phosphate-dissolving bacteria in blossom period,azotobacter in the 3 growth period of Qiubei pepper were enhanced by nitrogen fertilization.The correlations between different physiological microorganisms were strengthened by nitrogen fertilization.There was a very significant positive correlation between the quantity of azotobacter and cellulose-decomposing bacteria,negative correlation between azotobacter,cellulose-decomposing bacteria and potassium bacteria,positive or negative correlation between organic phosphate-dissolving bacteria and other physiological microorganisms(P0.01).
[Objective] This study was to investigate the effect of atrazine stress on the growth of Pennisetum hydridum. [Method] Pot experiments were conducted to study the effects of atrazine stress (20, 50, 100, 200, 500 mg/kg) on plant height, biomass, root-shoot ratio and chlorophyll content of P. hydridum. [Results] Low level of atrazine stress (20 and 50 mg/kg) showed no significant effects on plant height and biomass of P. hydridum. Moderate level of atrazine stress (100 and 200 mg/kg) did not show significant effect on plant height, but did on the biomass of P. hydridum. Biomass of P. hydridum stressed by 100 and 200 mg/kg of atrazine was decreased by 34.1% and 36.4% compared with control, respectively. High level of atrazine stress (500 mg/kg) brought significant decrease in plant height(by 40.6%) and biomass(20.0%) of P. hydridum. All levels of atrazine stress showed no significant effects on root-shoot ratio and chlorophyll content of P. hydridum. [Conclusion] Pennisetum hydridum has strong tolerance to atrazine stress.
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