Morpho-physiological and Biochemical Characterization of Chrysanthemum Varieties For Early Flowering under Heat Stress

Chrysanthemum morifolium Ramat. is a short day plant, with commercial significance in floriculture industry. Using photoperiod as a tool, flowering can be regulated throughout the year. The present study evaluated five spray varieties (Yellow Delight, Reagan Emperor, Reagan White, Shova and Punjab Shyamli) under different planting treatments [Early Planting (P₁), Early Planting treated with artificial short days (P₂) and Normal Planting (P₃)] for morpho-physiological and biochemical characterization of flowering under heat stress. The plants of all varieties took least days to bud initiation and flowering under normal planting whereas plants under early planting took maximum days for bud initiation and flowering. The plants treated with artificial SDs initiated buds earlier than early planting but due to sub-optimal temperature further development of buds to flower was slower. The plants of all varieties under early planting exhibited maximum vegetative growth as they took more days to bud initiation. Yellow Delight exhibited optimum vegetative growth, minimum days to bud initiation (87.98 days) and flower maturation (141.93 days) under P₂. The membrane stability index, relative water content, total soluble sugars, total soluble proteins, sucrose and proline content, along with peroxidase activity supported early bud initiation, heat tolerance and flower development in Yellow Delight. The varieties Reagan Emperor, Reagan White, Shova and Punjab Shyamli were found to be heat sensitive. Further, the cluster analysis supported our results as Yellow Delight under early planting with SDs was in cluster II, all varieties under P₁ along with Reagan Emperor, Reagan White, Shova and Punjab Shyamli under P₂ were in Cluster I and all varieties under P₃ were in cluster III. Hence, Yellow Delight could be used for the off- season flower production with artificial SD treatment in Punjab region.