Plant growth regulators preserved the longevity of cut stems of Chrysanthemum morifolium by orchestrating physio-biochemical and anatomical responses

The marketability of cut flowers is determined by their postharvest quality parameters. Among these parameters, vase life is most crucial and different plant growth regulators (PGRs) play a significant role in regulating vase life. With the objective, to regulate vase life and other quality parameters of commercially important cut stems of chrysanthemum cv. White Star, a study was planned to have an insight into the role of different PGRs in orchestrating underlying physio-biochemical and anatomical responses. Three PGRs viz., Benzyl adenine (50, 100, 150 and 200 mu M BA), Thidiazuron (5, 10, 15 and 20 mu M TDZ) and Salicylic acid (50, 100, 150 and 200 mu M SA) were used as pulsing solution. The results revealed that PGR especially 10 mu M TDZ delayed leaf and floret senescence as compared to control. The visual observations (retention of green colour of leaves and white of florets) were correlated to enhanced water absorption, relative water content, membrane stability index, total soluble sugars and total soluble proteins ; higher content of chlorophyll in leaves and lower content of carot-enoids and anthocyanins in florets. Further, the antioxidant enzymes (peroxidase and catalase) activities were also higher in PGR-treated stems than in control. These results were further supported by anatomical studies that indicated minimum blockage in xylem and maintenance in turgidity of cells as revealed through the size of tissues (radius of pith) of treated stems (control-118.48 mm and 10 mu M TDZ-177.94 mm). Although all PGR concentrations significantly maintained relative water content, membrane stability index, respiratory substrates and antioxidant activity for a longer time, the low concentrations of TDZ had the most relevant impact on longevity. The longevity of stems treated with10 mu M TDZ was up to 23 days as compared to 13 days in control. So 10 mu M TDZ could be used as a chemical tool to improve chrysanthemum longevity and increase its commercial potential.