The aim of this study was to determine the relationship between extractable chlorophyll and SPAD readings in chrysanthemum leaves. Chlorophyll breakdown during leaf senescence was measured by chlorophyll meter, SPAD-502, and diversity of chlorophyll declination was evaluated among varieties.

　　SPAD readings were significantly related to extracted chlorophyll of chrysanthemum leaves both on a fresh weight and leaf area basis. The linear regression relationship between the SPAD readings of leaves in different stage of senescence induced in 25 ℃ in the dark and chlorophyll contents analysed by spectrophotometry was described. T he R² value for total chlorophyll on a leaf area basis was 0.820 , while on a fresh weight basis was 0.660. The SPAD readings of 18 varieties with different greenness and their extractable chlorophyll contents were also correlated. The R² of linear regression equation on a leaf area basis was 0.795, while on a fresh weight basis was 0.635.

　　Senescence of leaf discs of three varieties in 6 temperatures in the dark was investigated. The higher the temperatures, the faster the SPAD readings declined. Initial SPAD of 18 chrysanthemums were between 42.0 and 60.8. The speeds of chlorophyll declination in 25 ℃ in the dark among 18 varieties were calculated by regression analysis. The highest speed was SPAD –6.51 daily, and the lowest speed was –2.13. The estimated days to leaf yellowing of 18 varieties was correlated with the initial SPAD readings (r=0.662) and with declining speeds (r=0.718) of chlorophyll breakdown. It was suggested that chlorophyll content and its declination of leaf could be a selecting indicator of breeding program.

Key words: chrysanthemum, leaf senescence, SPAD, chlorophyll breakdown .