Abha Upadhyaya

In vitro production of flowering shoots in German Red carnation : effect of uniconazole and gibberellic acid

SummaryCallus regenerated near the base of senescing petals of flower bud explants of ‘German Red’ carnation (Dianthus caryophyllus L.) produced adventitious flowering microshoots on MS-medium containing benzylaminopurine (8.9 μM) and naphthaleneacetic acid (2.7 μM). When these microshoots were subcultured with some callus, additional adventitious flowering microshoots were produced from the callus. The production of adventitious flowering shoots continued for many subcultures spanning a period of more than two years. Uniconazole (6.9 μM) increased the number of adventitious shoots formed by as much as two-fold but decreased shoot length by about 50%. In contrast, GA3 (2.9 μM) decreased adventitious shoot formation and increased shoot length. Regardless of the growth regulator treatment, virtually all of the adventitious shoots produced flower buds. Thus, the growth regulators influenced flowering only indirectly by altering the number of adventitious shoots produced in vitro. These results demonstrate that the flowering habit of the adventitious shoots of ‘German Red’ carnation is highly persistent and the flowering stimulus continues to be transmitted to the newly formed microshoots through the callus.

Heat shock tolerance and antioxidant activity in moth bean seedlings treated with tetcyclacis

Moth bean (Vigna aconitifolia (Jacq.) Marechal cv. Jaadia) seeds were germinated in the presence of 0, 18, or 36 μM solutions of the gibberellin biosynthesis inhibitor, tetcyclacis. After 72 h, seedlings were exposed to 22 or 48°C for 90 min. The 48°C temperature dramatically increased total electrolyte and sugar leakage from the seedlings, particularly in the controls. Tetcyclacis reduced electrolyte and sugar leakage at 48°C by 15–35% compared to the 48°C controls. High temperature increased malondialdehyde concentration in control seedlings but not in treated seedlings indicating that tetcyclacis inhibited high temperature-induced lipid peroxidation. Relative to the control, tetcyclacis tended to increase the total activities of catalase and peroxidase in the seedlings. In contrast, tetcyclacis tended to decrease ascorbic acid oxidase activity, particularly at 48°C. These results suggest that tetcyclacis conferred at least some heat shock tolerance to moth bean seedlings. This increased tolerance was correlated with increased activities of some antioxidant systems.

Alleviation of Sulfur Dioxide-induced Phytotoxicity in Cucumber Plants by Uniconazole

Summary Cucumber (Cucumis sativus L. cv. Marketer) plants were treated with 0 or 100μg of soil-applied uniconazole (20 ml of 17μM solution) and then exposed to a gaseous sulfur dioxide pulse one week following treatment. Uniconazole-treated plants exhibited considerably less visible sulfur dioxideinduced phytotoxicity than untreated controls. Rates of net photosynthesis 24h following sulfur dioxide exposure were 0 and 5.6μmol CO2 m-2s-1 for the control and treated plants, respectively. Forty-eight hours following sulfur dioxide exposure, net photosynthesis in uniconazole-treated plants recovered to 10.4μmol CO2 m-2s-1 but remained near zero in controls. The foliar content of malondialdehyde, a by-product of lipid peroxidation, was about 30% less in uniconazole-treated plants compared to controls following exposure to sulfur dioxide. This indicates that uniconazole decreased sulfur dioxide-induced lipid peroxidation. Stomatal diffusive resistance measurements suggested that increased sulfur dioxide tolerance in uniconazole-treated plants was not due to stomatal closure. The content or activity of several antioxidant systems including glutathione, peroxidase, and catalase was increased in uniconazole-treated plants. These results suggest that uniconazole-induced sulfur dioxide tolerance may be due, at least in part, to increased antioxidant activity which reduces stress-related oxidative cellular damage.