In order to determine the best paclobutrazol spraying period to raise the capacity of wheat lodging resistance and find the response difference of varieties to paclobutrazol,eight wheat varieties have been studied to analyze the effects of paclobutrazol on stem lodging resistance,morphological and anatomical characters,and the response difference of different lodging resistant wheat types to paclobutrazol was studied. The result showed that plant height,center of gravity height and length of internodes were reduced,while filling degree of internodes,small vascular bundle number and mechanical tissue layer thickness were increased under paclobutrazol treatment,leading to the increased lodging resistant indices. The effect of paclobutrazol spraying was biggest under reciprocal fifth leaf treatment,followed by that of reciprocal fourth leaf treatment. Under reciprocal fifth leaf treatment,comparing with control,the reduce rate of plant heights,center of gravity height and length of internodes were 2.58%-6.45%,3.52%-10.18% and 6.64%-24.16%,respectively,and the increase rate of filling degree of internodes,small vascular bundle number and mechanical tissue layer thickness were 22.41%-109.49%,10.00%-16.98% and 12.76%-49.85%,respectively. The influence of paclobutrazol on different lodging resistant wheat types associated with paclobutrazol spraying periods,and the lodging resistance increase effect was larger for lodging medium types,compared with lodging resistance types and lodging susceptible types in reciprocal fifth leaf treatment,but the lodging resistance increase effect was larger for lodging susceptible types,compared with lodging resistance types and lodging medium types in reciprocal fourth leaf and third leaf treatments. In conclusion,the best paclobutrazol spraying period to raise the capacity of wheat lodging resistance is reciprocal fifth leaf period,followed by reciprocal fourth leaf treatment. The response of lodging medium types and lodging susceptible types to paclobutrazol were better,compared to that of lodging resistant wheat varieties. |