Effect Of Water Deficit On Rice Seedling Growth And Its Regulation

With the development of China's economy and society,the planting area of mechanized transplanting is increasing year by year,and industrial seedling raising is becoming more and more popular,which has higher requirements for the quality of mechanized transplanting rice seedlings.Water management is particularly important in the process of raising seedlings.Too much water will cause the seedlings to weaken the packing force,poor blanket formation,high and thin seedlings are not conducive to machine insertion;too drought will cause the overall quality of the seedlings to decline,and seedling growth is inhibited.this study combines the hydroponic experiment and the seedling tray experiment to clarify the effect of water management on seedling quality during seedling raising,with a view to proposing the method of moisture management in the process of industrial seedling raising.The experiment used Huanghuazhan,IR36,Zhongzheyou 1,Tianyouhuazhan,Yongyou 538 and Zheyou 18as the materials,set light,moderate and severe water deficit treatments of three different degrees,study the effects of different degrees of water management on the quality of rice seedlings,and propose the most suitable water management methods At the same time,through the study of carbohydrate accumulation and metabolism,hormone changes,and root antioxidant system on water deficit,the physiological mechanism of water deficit affecting seedling quality is clarified.The main research shows:1.Under hydroponic mode,mild water deficit increases the leaf area of seedlings by 8.09%?23.01%,and the dry weight of the shoots above and below the ground increases by 7.42%?11.86%and2.95%?7.94%.There was no significant effect on plant height and root index.Moderate water deficit reduced the root length of the 6 varieties,and reduced the dry weight above ground and the dry weight below ground for most varieties,and had no significant effect on plant height,leaf area,root number,total root length,and total root volume,increasing the average root diameter.Severe water deficit significantly reduced the leaf area,longest root length,total root length,root surface area,and total root volume of the seedlings,significantly reduced the dry matter weight of the seedlings,and increased the average root diameter.It shows that the mild water deficit is generally conducive to the improvement of seedling quality,and the difference between varieties is not significant.2.The rice variety Zhongzheyou 1 was treated with different degrees of water deficit to analyze the effect of water deficit on carbohydrate metabolism of rice seedlings.The results showed that the mild water deficit had no significant effect on the net photosynthetic rate,significantly reduced the transpiration rate,increased the starch and sugar content of the seedlings,and significantly promoted sucrose synthase?SS?,sucrose phosphate synthase?SPS?,activity of soluble acid invertase?SAI?,pyruvate kinase?PK?and hexokinase?HK?.Moderate and severe water deficits significantly reduced photosynthetic parameters,starch,and sugar content,and weakened enzyme activities related to sugar metabolism.It shows that mild deficiency is beneficial to the synthesis and accumulation of carbohydrates in seedlings.3.The rice variety Zhongzheyou 1 was treated with different degrees of water deficit,and the effects of water deficit on hormone and root antioxidant system of rice seedlings were analyzed.The results showed that mild water deficit significantly increased the content of ABA,significantly reduced the content of ZR,had no significant effect on IAA and GA₃,increased the content of MDA,and increased the activity of SOD and POD,the difference was not significant.Moderate and severe water deficits significantly increased the content of ABA,significantly reduced the content of IAA,GA₃ and ZR,significantly increased the content of MDA,increased the activity of SOD,and reduced the activity of POD.4.Adopt greenhouse cultivation method,through controlling the substrate water potential and water content,different drought treatments were carried out on the rice varieties Huanghuazhan,Zhongzheyou 1 and Yongyou 538,and the effects of different drought treatments on the quality of mechanized transplanting seedlings quality were analyzed.The results showed that the mild drought significantly increased the plant height of Zhongzheyou 1 and Yongyou 538,and significantly increased the leaf area of the three varieties.It had no significant effect on the number of roots,the longest root length and the SPAD value,and significantly improved the root vitality,Dry weight above ground and dry weight below ground.Severe drought significantly reduced the plant height,leaf area,longest root length,SPAD value,root vitality,dry weight above and below ground of the three varieties,and had no significant effect on the number of roots.The results of the study show that the use of mild water deficits in the process of industrial seedling raising can improve the overall quality of seedlings and is conducive to the growth and development of mechanized transplanting.