Studies on the Relationship Between Chlorophyll Fluorescence Parameters and Cold Tolerance of Cauliflower

The effects of cold stress on growth index,freezing injury index and chlorophyll fluorescence parameters in seven different genotype cauliflowers with different or same maturity were studied. The changes of chlorophyll fluorescence parameters in different genotype cauliflowers with same maturity under freezing injury stress were also examined. The correlations among growth,cold tolerance and chlorophyll fluorescence parameters were analyzed in cauliflower varieties with different or same maturity. The results showed that there were significant differences among the varieties with different maturity in freezing injury index and minimal fluorescence(Fo),and there were significant differences among the varieties with the same and different maturity in head weight,vegetative mass weight,SPAD value and conversion efficiency of primary light energy(Fv/Fm). Significant differences existed among the varieties with same maturity under freezing injury stress. Correlation analysis of growth index,freezing injury index and chlorophyll fluorescence parameters in different genotype varieties showed that freezing injury index which directly reflects cold tolerance were negatively correlated with SPAD and Fv/Fm. Head weight and vegetative mass weight which indirectly but externally reflects cold tolerance,were positively correlated with Fv/Fm in varieties with both same and different maturity,and positively correlated with SPAD only in varieties with different maturity. In conclusion,conversion efficiency of primary light energy closely related to cold tolerance,Fv/Fm could be used as index of cold tolerance identification in cauliflowers with both same and different maturity.