Effects Of Subdrought At Germination Stage On Cold Tolerance At Seedling Stage,Booting Stage And Flowering Stage In Rice

The effects of sub-drought pretreatment at the germination stage on cold tolerance at seedling stage,booting stage and flowering stage were studied using Zhonghua 11,Brazilian upland rice,Y Liang you 1and 9311 as materials in rice so as to improve the understanding of rice cold tolerance and provide reference for rice cold-tolerant cultivation.They are pretreated with 15% PEG6000 as simulated sub-drought during their germination period(the test group),and then they are treated with cold stress in artificial climate chamber at their seedling,booting and flowering stages.It was analyzed that the differences of the seedling survival rate,relative conductivity,leaf relative water content and water loss rate,photosynthetic pigment content,rubisco activity,gas exchange parameters,pollen fertility,and seed setting rate between sub-drought pretreatment group and control group(i.e.,when rice grows to germination stage,they did not sub-drought pretreatment).The results are as follows:1?The survival rates of Zhonghua 11,Brazilian upland rice,Y Liang you 1 and 9311 seedlings for sub-drought pretreatment group was 92%,25%,54%,and 2%,respectively after they were treated with cold stress of 5 °C for 4 days in dark at seedling stag and restoration of 7 days under suitable temperature,however,the survival rate of the control group was90%,8%,38%,and 1%,respectively under the same condition.2?The growth potential of seedlings in the sub-drought pretreatment group and the control group was significant difference.The plant height was increased from 16.35% to 26.68%,and the root length was increased from 7.11% to 19.18% compared to the control group,of which Y Liang you 1 and 9311 increased significantly.3?The test group was treated with cold for 4 days and recovered 3days.The relative conductivity of the leaves of Zhonghua 11,Brazil's upland rice and Y liangyou 1 was significantly lower than that of the control group,and there was no significant difference in 9311;The proline content of the other three rice varieties was significantly higher than that of the control group.4?The test group was treated with cold for 4 days and recovered 3days.The relative water content of leaves of Y Liangyou 1 and 9311 seedlings was significantly higher than that of the control group,and the difference of other materials was not significant;the water loss rate of leaves of 9311 seedlings Significantly lower than the control group,other materials were not significantly different.5?The test group was treated with cold for 4 days and recovered 3days.The chlorophyll content of all material seedlings was higher than the control group,of which Zhonghua 11 increased the most.Except for the carotenoid content of Brazilian upland rice,which was lower than the control group,other materials were higher than the control group.6 ? The test group were treated with the temperature of 18?(lighet,12h)and 16 °C(dark 12h)condition,for 7 days,at the booting stage.The pollen fertility of Brazilian upland rice and Y Liangyou 1 was significantly higher than the control group.The difference was not obvious,among Zhonghua 11 and the control group.The seed setting rate of Brazilian upland rice was also significantly higher than the control group,but there was not obviously difference among Y Liangyou 1 and Zhonghua 11.These indicators were not significantly different between the two groups,such as Photosynthetic pigment,rubisco activity,photosynthetic gas exchange parameters.7 ? he test group were treated with the temperature of 18?(lighet,12h)and 16 °C(dark 12h)condition,for 7 days,at the Flowering period stage.The seed setting rate of Brazilian upland rice was significantly higher than that of the control group,while the difference between Zhonghua 11 and its control group was not obvious.These indicators were not significantly different between the two groups,such as Photosynthetic pigment,rubisco activity,photosynthetic gas exchange parameters.The above preliminary results indicated that the sub-drought in germination stage can significantly enhance the cold tolerance of seedling stage and promoted the growth of seedlings;the sub-drought in germination stage also has some influence on the cold tolerance ofbooting stage and flowering stage,but it varies with phenotypes.