Effect of Ethylene and Gibberellic Acid on Auxin Synthesis in Plant Tissues " 2 Jack G . Valdovinos , Leland
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چکیده
Treatment of plant tissues with gibberellic acid leads to increased levels of auxin and stem elongation in several plant species (7,13). Pretreatment of plant tisstues with ethylene is known to decrease levels of diffusible auxin (5, 10, 20) as well as cell elongation (3, 4). Recent evidence has indicated that a significant influence of gibberellin on auxin levels and growth processes is ithrough its effect on auxin synthesis in plant tissues (8, 17). The possibility that ethylene may also regulate auxin levels in plant tissues by affecting the synthesis of auxin is suggested by the literature (4, 5, 10, 11, 20). Further support of this proposal is suggested by papers (1, 10, 20) which show ethylene to have no direct effect on the polar transport of auxin. Another indication that ethylene, in addition to gibberellin, may be involved in the regulation of auxin synthesis, lies in the fact that gibberellin and ethylene have opposing effects on the elongation of hypocotyls of lettuce seedlings (14). The possibility that ethylene affects the formation of auxin from itryptophan was investigated and the results of the experiments are presented in this paper. Pea seedlings (Pisum sativum L. varieties A,laska and Little Marvell) were grown under 14 hours per day of light at a temperature of 23 ± 20 during the day and 200 at night. The seedlings were grown in a medium of Perlite and vermiculite (1:1) saturated with half-strength Hoagland's nutrient medium. Eighteen hours before harvesting the tissue for tryptophan and auxin studies, the plants were placed in plastic or glass chambers and ethylene (25 jul/1) was added by means of a hypodermic syringe. Seedlings receiving gibberellic acid were treated in the apical region with 0.1 ml of 10 K-M gibberellic acid in 0.05 % Tween-20. Assays for tryptophan-14C conversion and IAA14'C destruction by cell free preparations of the
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تاریخ انتشار 2005