Seeds of six pepper (Capsicum Anuum L.) cultivars were treated with tetcyclacis (TCY), an inhibitor of the oxidative steps from ent-kaurene to ent -kaurenoic acid in the gibberellin biosynthetic pathway. Seeds were soaked in TCY solutions for 24h in darkness at 25° to 30°C, washed with water and then air-dried. Various concentrations of TCY were needed to induce dormancy in `Yolo Wonder', `Cayenne', `California Wonder', `Sweet Banana', `El Paso' and `Anaheim'. TCY-treated seeds were germinated in water and in various concentrations of GA4+7 in darkness. Dormancy induced by TCY was released with 10 μM GA4+7. The germination inhibitor, abscisic acid (ABA), failed to induce dormancy in pepper seeds even when treated at a concentration of 400 μM for up to 14 d. Similar results were obtained with tomato seeds and will be reported elsewhere. The results indicate that the absence or the unavailability of GA rather than the presence of ABA determines the dormant state in pepper seeds.
Satriyas Ilyas, Claudinei Andreoli, and Anwar A. Khan
Anwar A. Khan, James D. Maguire, George S. Abawi, and Satriyas Ilyas
A matriconditioning procedure based on the matric properties of Micro-Cel E and expanded vermiculite #5 has proved effective in improving seedling emergence in growth chambers. The major objectives of this study were to examine some physical characteristics of the carriers and their effectiveness as preplant conditioning media in improving stand establishment of vegetable seeds in field plantings. Carrier characteristics included no detectable solute or osmotic potential, low electrical conductivity (0.48-0.04 mmho/cm), high water-retaining capacity (450% to 600%), a pH range of 7.0 to 8.4, and ability to effectively control seed hydration (conditioning) at low matric potential. The seed: carrier: water ratio for seed conditioning ranged from 1:0.3-0.5:1-2 (by weight). In a field trial, conditioning of `Long Imperator' and `Nantes' carrot (Daucus carota var. sativus Hoffm.) seeds reduced the time to 10% of final emergence (T10) by 2.6 to 2.8 days and to 50% of final emergence (T50) by 2.1 to 3.0 days. Conditioning increased the final emergence percentage by 39% in 1-year-old `Long Imperator' compared to 150% in 4-year-old `Nantes' seeds. In another field trial, the effect of conditioning on stand establishment was evaluated in `Jackpot' tomato (Lycopersicon esculentum Mill.), `California Wonder' pepper (Capsicum annuum L.), and `BBL 47' snap bean (Phaseolus vulgaris) seeds. In tomato, conditioning reduced the T10 by 0.9 day, had no effect on T50, and increased the emergence percentage by 86%. In pepper, conditioning reduced the T10 and T50 by 1.5 days and increased the percentage emergence by 30%. In snap bean seeds, conditioning in Micro-Ccl E reduced the T10 and T50 by 0.8 day but adversely affected the percentage emergence. Further reductions in T10 and T50 (1.2 and 1.6 days, respectively) and restoration of percentage emergence to control level occurred upon addition of 0.001 mM GA3 during conditioning. Fungicides added to carrot, tomato, and pepper seeds, with or without conditioning, showed no additional improvements and, in a few cases, adversely affected emergence. A preplant conditioning in Micro-Ccl E, alone or in combination with GA3, smears to be a viable alternative to conditioning! seeds in liquid carriers. Chemical name used: gibberellic acid (GA3)