Physiological Mechanism Of Salicylic Acid And N-Acetyl-L-Cysteine On The Recovery Stage Regulation Of Machine-Transplanted Rice

Rice is the staple food of over 60 percent of population in China.Therefore,obtaining stable and high yield is a prominent problem that needs to be solved at present.Recently,with the rapid development of the economy,the transfer of land and the loss of quality labor in county,the rice-planting mechanization has become an inevitable trend and the significance of mechanical transplanting witch is regarded as dominant technology is becoming increasingly prominent.Due to planting injury,the growth and development of machine-transplanted rice was inhibited and resulting in a 2-3 days longer recovery stage than hand-planted rice,and its tillers usually begin to grow at 10-15d after transplanting.So it is of great significance for tapping yield’s potential to improve the growth,shorten recover period and promote the rapid growth of tillers.In this study,two plant growth regulators(Salicylic Acid and N-acetyl-L Cysteine)with better growth effects after mechanical planting were screened through preliminary experiment.The key results are as follows:1、The affect SA and NAC on tillering of rice seeding after planting during recover periodFoliar application of SA or NAC can promote the occurrence of tillers after transplanting with cutting roots.Compared with CK,the 15 μM SA treatment significantly increased the number of tiller at 7d after planting and increased the number of panicles by 16.1%at mature period.And the 2000 μM NAC treatment increased the number of tiller and increased the number of panicles by 12.8%at mature period.Soaking seeds with SA or NAC can improve the ability of low tillering after transplanting.Compared with CK,the 1500μM SA treatment increased the number of tiller and increased the number of panicles by 12.5%at mature period.And the 20μM NAC treatment increased the number of tiller and increased the number of panicles by 6.3%at mature period.2、The affect SA and NAC on root growth after planting during recover periodFoliar application of SA significantly increased root diameter,volume and surface area of seeding on 5d after transplanting.The 15μM SA treatment compared with CK,significantly increased root volume by 20.2%,and the root surface area by 44.3%.Foliar application of NAC significantly promoted root tips number,root length,root diameter and surface area during recover period.Compared with CK,2000μM treatment increased root surface area by 81.7%.Soaking seeds with S A or NAC could also significantly effect the root tips number,root length and root surface area during recovery stage.Compared with CK,the 1500 μM treatment increased the root surface area by 29.7%,and the 20μM treatment increased the root surface area by 48.5%.3、The affect SA and NAC on photosynthetic capacity of rice seeding after planting during recover periodFoliar application of SA or NAC extremely significantly decreased the chlorophyll content.,significantly decreased the carotenoid content due to the damage to the leaves,but S A or NAC could reduce the decomposition rate of chlorophyll after transplanting and then promote photosynthesis.At 2d after transplanting,the 15μM SA spray treatment reduced the chl(a+b)by 33.8%and the Chl a/b by 29.4%,and 2000μM NAC treatment increased chl(a+b)by 19.3%,Chl a/b reached 1.54,which was higher than CK 43.6%.Soaking seeds with SA or NAC reduced the decomposition of chlorophyll after transplanting,increased Chl(a+b)during recovery stage,and then enhanced the photosynthetic capacity.The content of chlorophyll(a+b)decreased only 22.3%after 1500μM S A soaking treatment at 2d after transpanting.The value of Chl a/b was significantly higher than that of CK,and the Fv/Fm of 7d after transplanting was increased,and gs,Ci and Tr were decreased.The content of chl(a+b)in the 20μM NAC treatment was only 17.4%lower than that before transplanting.At the same time,the Fv/Fm of 7d was increased,and gs,Ci and Tr were decreased,and Pn was increased by 80.8%compared with CK.4、The affect SA and NAC on Antioxidative system of rice seeding leaves after planting during recover periodFoliar application of SA could significantly increase POD activity in 5d after tranplanting,and APX activity at 2d,promote the increase of AsA content and AsA/DHA ratio,and then reduce H2O2 content and extremely reduce MDA.Compared with CK,15μM treatment reduced H2O2 content by 13.8%,MDA content by 21%.Foliar application of NAC can activate SOD activity in leaves of seedlings in advance,and highly significantly increase the activity of CAT,POD and GR,promote the accumulation of AsA and GSH,and then reduce the content of H2O2 and MDA at 2d after transplanting.Compared with CK,the 2000μM treatment reduced H2O2 content by 25.7%,MDA content by 26.3%.Soaking seeds with SA treatment signicigantly inhibited POD activity in 5d after transplanting,extremely significantly increased GR activity at 2d and significantly decreased H2O2 and MDA.At 2d after transplanting,compared with CK，1500μM treatment decreased H2O2 content by 11.8%,MDA content by 16.6%.Soaking seeds with NAC could signifigantly increase CAT,APX,GR activity,extremely significantly inhibit POD activity,increase GSH content and GSH/GSSG,and reduce the accumulation of H2O2 and MDA.Compared with CK,20μM treatment reduced H2O2 content by 4.9%，MDA content by 16.6%.5、The affect SA and NAC on endogenous hormone of rice seeding after planting during recover periodSoaking seeds with SA had no significant effect on GA3,IAA,(Z+ZR)and ABA contents in leaves.In the root,compared with CK,the 1500μM treatment extremely significantly increased the GA3 content by 26.7%at 2d after transplanting,and the IAA content of 4d increased by 3.5%.But there was no significant effect on ABA and(Z+ZR).Soaking seeds with NAC had no significant effect on GA3,IAA,(Z+ZR)and ABA contents in leaves.In the root,compared with CK,the 20μM treatment highly significantly increased the IAA content by 5.8%and the rate of increase of(Z+ZR)content get to 86.4%at 2d.However,the effect on ABA content was not significant.