Research On Effects Of Waterlogging Stress On Rice Growth At Tilling Stage And Its Application

Flooding is a major threat to agricultural production. Most studies have focused on the lower water storage limit in rice fields, whereas few studies have examined the upper water storage limit. This study aimed to explore the effect of waterlogging at the rice tillering stage on rice growth and yields. The early-ripening late japonica Yangjing 4227 was selected for this study. The treatments included different submergence depths (submergence depth/plant height: 1/2 (waist submergence),2/3 (neck submergence), and 1/1 (complete submergence) and durations (1,3,5d and 7d). The control group was treated using the conventional alternation of drying and wetting. The effects of waterlogging at the rice tillering stage on the root characteristics,dry matter production, nitrogen and phosphorus accumulation physiological characteristic,yield, and yield components were explored.The main conclusions are as follows:1) Compared with the control group, the 1/2,2/3 and 1/1 group showed more adventitious root, larger root volume and wider root diameter after 1d of submergence. The grain number per panicle, lenth of the longest root,root volume and root diameter increased or significantly increased after 3d,5d and 7d of submergence, the 1/2 and 2/3 group had significant increase and the 1/1 group showed no difference in the average percentage of dry root weight after 1d of submergence in 0～5 cm soil layer. the 1/1-1 treatment showed the largest in dry weight of the aboveground and belowground parts,and was moderate in root-shoot ratio. Correlation analysis revealed a significant positive correlation between the yield and the dry root weight in 0-5 cm soil layer (r=0.664*), root number, length of the longest root,root volum, dry root weight, root-shoot ratio (r=0.589*～0.698*),and dry weight of the aboveground (r=0.835**)2) Compared with the control group, with the extension of flooded days, the 1/2 group showed decrease or significant decrease in inverted 3 leaf area and photosynthetically effective leaf area, the 2/3 group showed significant decrease in inverted 1,2 and 3 leaf area and photosynthetically effective leaf area except for 2/3-1 treatment. The complete submergence after 1-d submergence showed increases in plant height, spike length, inverted 1 and inverted 2 internode length, inverted 1 to inverted 4 leaf length, inverted 1 to inverted 3 leaf area and efficient leaf area. With the increase of submergence days, compared with the control, the complete submergence after 3 d,5 d and 7 d became shorter and shorter in plant height, spike length, inverted 1 and inverted 2 internode length, inverted 4 and inverted 5 internode length, inverted 3 and inverted 4 leaf length were gradually getting shorter and shorter than the control, and inverted 1 leaf length and inverted 1 leaf width got gradually longer and wider than the control, inverted 2 to inverted 5 leaf width gradually narrowed, inverted 3 leaf area, effective leaf area and yield are less than control, and reduce the amplitude becomes larger, the more days flooded, the more higher plant height during the flooding stage. Inverted 1, inverted 2 leaf area and effective leaf area showed in parabolic curve relationship with the yield.3) Compared with the control group, the 1/2-1 and 2/3-1 treatments showed higher MDA content but 1/1-1 treatment had no difference in MDA conten of leaf. With the extension of flooded days,the other treatments all showed a trend of increased significantly in MDA content and the activity of POD and CAT of leaf.Correlation analysis revealed a significant positive correlation between the MDA content and conductivity(r=0.724**); however, significant negative correlation(r=-0.821**、-0.748**、and-0.857**) were found with yield, seed-setting rate and 1000-grain weight.4) Compared with the control group, with the extension of flooded days, the 1/2 and 2/3 group showed decrease or significant decrease in nitrogen content, nitrogen accumulation amount, phosphorus content and phosphorus accumulation amount except for 1/2-1 treatment. The 1/1 group had the first increase and then decrease in nitrogen content, and showed increases or significant increases in the nitrogen accumulation amount after Id and 3d of submergence, but significant decrease were found in the phosphorus content and phosphorus accumulation amount after 5d and 7d of submergence.Correlation analysis revealed a significant positive correlation between the panicle number and the nitrogen content(r=0.775**); however, no significant correlation was found with the phosphorus content(r=-0.045).5)Compared with the control group, the 1/1 group showed significant increases in yield, seed-setting rate, and photosynthetically efficient leaf area after 1 d of submergence. The grain number per panicle also increased. With the extension of flooded days,the other treatments showed increases or significant increases in yield, seed-setting rate and the grain number per panicle, the ear number had a tendency to increase. The decrease in rice yield can be controlled within 5% or 10% after the plants suffer from half,2/3, and complete submergence for 1 d or 1-3 d. This treatment can be expanded for rice field water control and to improve rainfall resource utilization.