| Lodging is one of the important factors that affect the wheat yield,wheat production reduction caused by lodging is very common all over the world every year.Plant growth regulators have wide application to enhance lodging resistance,so as to prevent wheat lodging and realize stable yield.Paclobutrazol is commonly used among growth regulator to control of wheat lodging.Spraying paclobutrazol can reduce plant heights,improve the ability of plant resistance,but there are few reports about physiological mechanism caused by paclobutrazol.In this study,the wheat varieties with different lodging resistance ability were selected out and lodging resistances about different spraying leaf period of paclobutrazol were studied,then paclobutrazol responses about different densities on lodging resistance significantly different wheat varieties were researched and lodging resistances about different spraying leaf period of paclobutrazol were further cleared,finally using verification test about paclobutrazol and gibberellin,we cleared the physiological mechanism on paclobutrazol to lodging resistance,the results of this study will provide certain theoretical basis and technical support for wheat lodging resistance.The main results of the study were listed below:1.Lodging resistance and yield diference and its response of paclobutrazol in wheat varietiesLodging resistance index were added under paclobutrazol treatment,and the increase of lodging resistance was biggest in reciprocal fifth leaf treatment,followed by reciprocal fourth leaf treatment,the increase of lodging resistance was minimum in reciprocal third leaf treatment.Internode external diameter and wall thickness and filling degree and mechanical strength had the biggest direct effect to the lodging resistance capability,the plant height and stem length and gravity center height and the stem anatomical structures had large indirect effect to the lodging resistance capability through influence internode external diameter and wall thickness and filling degree and mechanical strength.Principal component analysis showed that morphological structure including mechanical strength and intemode external diameter and wall thickness and filling degree,the stem anatomical structures including the thickness of mechanical tissue layer and the ratio of mechanictissue layer and small vascular bundle area have big contribution to the stem lodging resistance.Cluster analysis based on the indexs contributing larger on lodging resistance in principal component analysis,lodging resistance of AK58 and JM22 were best,lodging resistance of LX66 and YZ4110 and XM20 were the medium type,lodging resistance of WM29 and AN0305 andYN19 were the weaker type.Cluster analysis based on paclobutrazol sensitivity in different wheat varieties,AK58,YN19,WM29,JM22 and AN0305 were paclobutrazol sensitive wheat varieties,LX66,YZ4110 and XM20 were paclobutrazol sensitive common wheat varieties.2.The influence of lodging resistance affected by paclobutrazol under different densitySpraying paclobutrazol in reciprocal fifth leaf treatment,there had significant increase in the number and area of basal internode vascular bundle and the thickness of mechanical tissue layer and parenchymatous tissue layer and the width of a single cell,there had significant shorter in the length of the single cell,and there also had significant increase in cellulose,hemicellulose,lignin and soluble sugar concent,so as to the plant height and stem length and gravity center height of wheat stem were decreased largest,internode external diameter and wall thickness and filling degree were all increased largest,and then mechanical strength and lodging resistance index were added at most,so lodging rate of wheat was lowest.Correlation analysis showed that stem length and internode external diameter and wall thickness and filling degree and mechanical strength and small vascular bundle area and the thickness of mechanical tissue layer and cell length and width are the important factors affecting wheat lodging under different density.Using multiple stepwise regression analysis on the base of the second internode characters under different density,it concluded that small vascular bundle area,cell width and soluble sugar content all have great influence to the lodging resistance of wheat under different density,3.The physiological mechanism of lodging resistance improved by paclobutrazol in wheat plantUnder gibberellin treatment(R2),the plant height and gravity center height of wheat stem were increased,wall thickness and filling degree were all decreased,and hormone content of basal internode were increased,the number and area of basal internode vascular bundle and the thickness of mechanical tissue layer and parenchymatous tissue layer and the width of a single cell were reduced,the length of the single cell were increased,and stem assimilate composition in addition to the nitrogen content were decreased,then mechanical strength and lodging resistance index were reduced,so lodging rate of wheat was increased.Paclobutrazol treatment(R1)had the opposite effect.Spraying gibberellin treatment after paclobutrazol treatment(R3)reflected paclobutrazol effect because paclobutrazol lifted the gibberellin effect to reduce wheat lodging resistance,but the effect of wheat lodging resistance was less than paclobutrazol treatment(R1).Spraying paclobutrazol treatment after gibberellin treatment(R4)reflected gibberellin effect because gibberellin lifted the paclobutrazol effect to add wheat lodging resistance,but the effect of wheat lodging resistance was higher than gibberellin treatment(R2).Path analysis obtained the wheat morphological and assimilate composition have the biggest direct effect to the lodging resistance capability.Path analysis combining with correlation analysis,GAs and IAA content in the basal internode decreased suppressed execute outside of the internode assimilate composition,so as to improve the cellulose,hemicellulose,and lignin content and soluble sugar and potassium content of basal internodes,meanwhile the increase of Z+ZR content led to a decline of nitrogen content in basal internode,and indirectly reduced the output of the material in the stem,and benefited the accumulation of photosynthate in basal internode,made stem stronger.At the same time,the increasing of the number and area of basal internode vascular bundle chould added internode external diameter and wall thickness and vascular bundle channels for photosynthate transportation,enhanced photosynthate transportation ability,thus increased the accumulation and transportation of assimilate in stem and indirectly improve the ability of the lodging resistance of wheat.Moreover,high cellulose content,soluble sugar content and potassium content in the stem also improved the morphological structure,optimized the stem anatomical structures,and indirectly improved the lodging resistance of wheat.In conclusion,paclobutrazol treatment decreased GAs and IAA content of basal internodes,increased Z+ZR contents of basal internodes,and increased stem assimilate composition in addition to the nitrogen content,then improved wheat anatomic structure and morphological structure of basal internode,thus improved the ability of the lodging resistance of wheat.The increase of lodging resistance was biggest in reciprocal fifth leaf treatment.Path analysis obtained the wheat morphological and assimilate composition have the biggest direct effect to the lodging resistance capability.There had large indirect effect on the path of hormone level through influence morphological structure or assimilate composition and the path of anatomical structure through influence morphological structure or assimilate composition,meanwhile the path of morphological structure through influence assimilate composition and the path of assimilate composition through influence morphological structure also reached significant level.So the hormone level and morphological structure and anatomical structure and assimilate composition influenced each other could improved the ability of the lodging resistance of wheat. |
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