| Rhizosphere oxygen is an important environmental factor,it affects the rhizosphere environment and physiological metabolism of rice roots.To clarify the effects of different concentrations of rhizosphere oxygen on the growth,physiological characteristics and yield formation of rice at seedling stage,it can provide a reference for the cultivation of rice mechanical transplanting seedlings with high rhizogenic power,enrich rice cultivation theory and aerobic cultivation of rice.This study mainly includes three experiments:(1)Taking rice variety Huanghuazhan as material,the effects of short-term flooding on different leaf ages were studied in an artificial climate box,that is,the whole process of no flooding treatment(CK),one leaf stage to two leaf stage flooding treatment(T1),two leaf stage to three leaf stage flooding treatment(T3),three leaf stage to four leaf stage flooding treatment(T3),whole process flooding treatment(T4).(2)Taking rice variety Y Liangyou 957 as material,the effects of different oxygen concentrations in rhizosphere were studied under hydroponic conditions,i.e.low oxygen(0-1mg/L,Lo),medium oxygen(4-5mg/L,Mo)and high oxygen(7-8mg/L,Mo).(3)Rice variety Y Liangyou 957 was used as material,and three treatments were set under hydroponic condition,namely hypoxia(0-1mg/L,Lo),moderate oxygen(4-5mg/L,Mo)and hyperoxia(7-8 mg/L,Mo)The effects of different oxygen concentrations in Rhizosphere on Rice Yield and yield components were studied.The main results are as follows:1.No matter from which leaf age,the short-term flooding treatment before the three leaf stage promoted the growth of rice seedlings in a short time,and the fresh weight of the above ground and underground parts increased compared with the control,but the biomass of rice seedlings did not increase in the later stage of the experiment,on the contrary,it had a downward trend.2.The results showed that the oxygen concentration in rhizosphere of hydroponic culture had a significant effect on the rooting ability of rice seedlings,and the difference among treatments changed with the increase of leaf age.In one leaf one heart stage,the total length and number of hairy roots of rice seedlings under hypoxia treatment were better than those under medium oxygen and high oxygen treatment;in two leaf one heart stage,there was no significant difference in the total length and number of hairy roots among all treatments;in three leaf one heart stage,the total length of hairy roots of rice seedlings under medium oxygen treatment was the largest,and there was no significant difference in the number of hairy roots among treatments,but the medium oxygen treatment was the most.It can be seen that the short-term hypoxia treatment improved the rooting ability,but the medium oxygen treatment was better at the seedling stage.3.The soluble sugar content,soluble protein content and chlorophyll content in the shoot of rice seedlings did not change significantly at each leaf age,but the soluble sugar content in the shoot decreased sharply from the two leaf one heart stage to the three leaf one heart stage.Although the difference was not significant,the variation trend of soluble sugar content in aboveground and underground parts of rice seedlings at each leaf age was consistent with oxygen concentration,that is,the soluble sugar content in aboveground part was the lowest and the soluble sugar content in underground part was the highest under medium oxygen treatment,and there was a very significant negative correlation between the soluble sugar content in aboveground and underground parts of rice seedlings under each treatment.There was a significant positive correlation between rooting ability,root activity and root soluble sugar,and a significant negative correlation between them.4.Only abscisic acid content(ABA)in leaves of seedlings with different treatments was significantly different.In the leaves,the ABA content of low oxygen treatment increased by 19.5% and 29.3% compared with that of medium oxygen treatment and high oxygen treatment,respectively.With the increase of oxygen concentration,NR activity increased,while GS activity decreased;The activities of GOGAT,NADP-MDH and SOD in roots were the highest in the medium oxygen treatment,and the content of MDA in roots increased with the increase of oxygen concentration.5.Pot experiments were conducted to compare the growth after transplanting of rice seedlings cultured in different rhizosphere oxygen concentrations.It was found that there were no significant differences in panicle length and plant height among the treatments,but the effective panicles,grains per panicle,1000-grain weight and yield increased with the increase of oxygen concentration,and the low oxygen treatment was significantly lower,and seed setting rate in medium oxygen treatment was the highest and that in high oxygen treatment was the lowest.The results showed that it was feasible to control the oxygen concentration in rhizosphere at seedling stage to improve the growth and yield of rice in field.In conclusion,the short-term flooding treatment promoted the seedling growth,but the extension of flooding treatment time would make the seedling growth stagnate.Under the condition of hydroponic culture,medium oxygen(4-5 mg / L,Mo)treatment can improve the root ability by increasing the soluble sugar content and the activities of GOGAT,NADP-MDH and SOD,which is the most favorable for the growth of rice seedlings. |
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