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Manoj G. Kulkarni, Glendon D. Ascough and Johannes Van Staden

Smoke shows promising results in stimulating germination and vigor. The biologically active butenolide compound isolated from smoke has potential to become a valuable tool in horticulture. ‘Heinz-1370’ tomato (Solanum lycopersicum) seedlings showed a positive response to smoke and were therefore tested with smoke-water and butenolide for growth, yield, and nutritional composition. Smoke-water (1:500, by volume) treatment showed the maximum height, number of leaves, and stem thickness from 57 to 78 days after sowing. The percentage of plants with fruit from 85 to 95 days after sowing was much higher with the application of smoke-water and butenolide solution than in the control. The total number of marketable fruit was significantly greater (P ≤ 0.05) for smoke-water–treated (1:500, by volume) tomato plants (168) than for the control (124). Butenolide and the lower concentration of smoke-water (1:2000, by volume) yielded more fruit, but was not significantly (P ≥ 0.05) different from the control. In spite of achieving a greater number of fruit, smoke treatments did not significantly (P ≤ 0.05) change the size, weight, and nutritional composition (ascorbic acid, β-carotene, lycopene, and total soluble solids) of fruit. The harvest indices of smoke-water– and butenolide-treated plants significantly improved (P ≤ 0.05), suggesting the possible use of smoke technology for tomato cultivation.

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Manoj G. Kulkarni, Glendon D. Ascough and Johannes Van Staden

The ecologic significance of smoke-related seed germination is now well recognized. Consequently, smoke solutions and a pure butenolide, the active compound from smoke that stimulates germination of a number of plant species, show great potential for enhancing the growth of vegetable crops. Achieving maximum production and better and faster growth of the seedlings has always been a priority for vegetable growers. This study therefore highlights the effects of foliar application of smoke-water and a butenolide on seedling growth of okra [Abelmoschus esculentus (L.) Moench] and tomato (Lycopersicon esculentum Mill.). Treating okra seedlings with smoke-water (1:500 v/v) showed a significant (P < 0.05) increase in shoot/root length, shoot fresh/dry weight, number of leaves, total leaf area, and stem thickness compared with the control treatment. Treatment of okra seedlings with smoke-water significantly (P < 0.05) increased the absolute growth rate (AGR) per week. However, the seedling vigor index (SVI) did not improve as a result of no change in root fresh weight. On the other hand, foliar application of smoke-water and butenolide showed a pronounced effect on the seedling growth of tomato. Most of the growth parameters examined for both the treatments were significantly (P < 0.05) increased, resulting in a significantly (P < 0.05) higher SVI and AGR than the control. This study indicates that the foliar application of smoke-water or butenolide may be a useful and inexpensive technique for enhancing seedling growth of vegetable crops.

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Glendon D. Ascough, Johannes van Staden and John E. Erwin

Genetic modification and manipulation offers the possibility of introducing novel traits into existing plants, thereby increasing marketability. Polyploid induction has in the past produced plants that are more compact and have larger flowers, leaves, and fruit, making them more desirable to consumers. The effect of pulse treatments (0, 24, 48, and 72 h) of colchicine (25, 50, 125, and 250 μm) or oryzalin (30, 60, 90, and 120 μm) on in vitro-grown Watsonia lepida N.E. Brown shoots was investigated. Explant survival was higher and more consistent with oryzalin treatment compared with treatment with colchicine. More mixoploids than tetraploids were produced with both compounds. The optimum treatment for producing tetraploids was 120 μm oryzalin for 24 h. Of the 30% explants that survived this treatment, 33% were found to be stable tetraploids.