Abstract:

Abstract [Objective] The chlorophyll content is tightly related to the leaf senescence. High temperature and strong photoperiod affect the variation of chlorophyll content. However, the link between the variation of chlorophyll content and the thermo-photoperiodic responsiveness is yet to be known. Their relationships were analyzed here and the variation of chlorophyll content was also analyzed under different background level. [Method]Two groups with respective 35 and 133 varieties or breeding lines were grown in Guangzhou and Jingzhou, Hubei province. Their heading dates were investigated. The variation percentages in growth duration to heading between two areas were regarded as indicator for their thermo-photoperiodic responsiveness. The chlorophyll content was measured with chlorophyll meter and indicated by SPAD values. [Result] The reduction percentages of SPAD between 14 DAH (days after heading) and 18DAH were found to be positively related to their thermo-photoperiodic responsiveness. The correlative coefficients were respective 0.5093 and 0.3036 in 35 and 133 varieties. We also found that varieties/breeding lines with high background level of chlorophyll content displayed smaller chlorophyll reduction between 9DAH and 13DAH in comparison to those with low background level of chlorophyll content. In contrast, those lines with high background level of chlorophyll content would show bigger chlorophyll reduction between 14 DAH and 18 DAH. [Conclusion]The reduction percentages of SPAD between 14 DAH and 18DAH can be regarded as an indicator of their thermo-photoperiodic responsiveness.