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

Abstract

• Being a SD plant, photoperiodic manipulation is imperative to maintain year round availability of chrysanthemum. • The early planting treatment with application of artificial SDs contributed to early flower bud initiation and flower maturation. • However, because of early planting and blackout treatment, plants faced heat stress and the development from buds to flower was slower. • The variety Yellow Delight overcame heat stress, flowered in August and proved to be heat tolerant while the others viz. Reagan Emperor, Reagan White, Shova and Punjab Shyamli were found to be heat sensitive. Cluster analysis also grouped Yellow Delight in separate cluster than others on the basis of morpho physiological and biochemical parameters. • Hence, Yellow Delight could be used for the off- season flower production with artificial SD treatment in sub tropical region. 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 (P 1 ), Early Planting treated with artificial short days (P 2 ) and Normal Planting (P 3 )] 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 P 2 . 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 P 1 along with Reagan Emperor, Reagan White, Shova and Punjab Shyamli under P 2 were in Cluster I and all varieties under P 3 were in cluster III. Hence, Yellow Delight could be used for the off- season flower production with artificial SD treatment in Punjab region.