Wound-induced Gibberellins

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The effect of gibberellin A3 (10-4M) and abscisic acid (10-4 M), applied separately and together, on incorporation of 3H-thymidine and 3H-uridine into DNA and RNA of buds from freshly harvested potatoes was investigated. In some treatments apical buds in intact tubers were treated three times daily for 3 days with test solution before the buds were excised and treated an additional 12 hours in Petri dishes. In other treatments, untreated buds were excised and treated 12 hours. Irrespective of length of treatment, gibberellin A3 slightly promoted synthesis of DNA and RNA, and abscisic acid essentially blocked such synthesis, in both the presence and absence of gibberellin A3.Cumulative evidence favors the concept that the rest period of many buds and seeds is under control of growth promoters and inhibitors (1, 33). Thomas, Wareing, and Robinson (29) indicated that the dormancy of buds of Betula and Acer is regulated by a balance of ABA3 and gibberellin-like substances (GAs). Chrispeels and Varner (6) reported that ABA inhibited GA3-induced a-amylase synthesis, and Nitsch (19) and Khan (15) showed that GA3-induced germination of lettuce seeds was completely inhibited by ABA. Hemberg (11) was the first to suggest a direct correlation between the rest period and the occurrence of growth-inhibiting substances in the potato tuber. A later investigation (12) with extracts of potato peelings revealed that the concentration of inhibitor 3-complex decreased and essentially disappeared at the time rest terminated. In contrast, GAs in potato buds increased in concentration near the end of rest (26,27). Boo (3) reported a low concentration of GAs in freshly harvested potatoes but found that concentration increased to a maximum some weeks before rest terminated.In excised buds from resting potato tubers, prolonged inhibition of sprouting by inhibitor 13-complex or ABA was partly reversed by exogenous GA3 (2, 18). In intact tubers, GA3 only slightly reversed the inhibition by ABA (9).The emergence of potato buds from rest appears not to be controlled qualitatively by any environmental factor, but requires only the passage of time (24 (cv. White Rose) stored under favorable conditions sprout about 20 to 25 days after a harvest made 100 days after planting. Thus, emergence from rest is regulated by an internal timing mechanism, a conclusion indicated by results of Tuan and Bonner (30) and Rappaport and Wolf (22,23). This internal regulation was associated with the initiation of nucleic acid synthesis. Tuan and Bonner (30) showed that RNA and DNA increased prior to the increase in fresh weight of potato buds the rest period of which had been terminated with ethylene chlorhydrin. Deoxyadenosine, actinomycin D, and puromycin-inhibitors of nucleic acid and protein syntheses-reduced sprouting of buds in excised potato plugs, indicating that these syntheses are associated with the end of rest (18). Using histoautoradiographic techniques, Rappaport and Wolf (22, 24) related timing of GA3 action, changes in concentration of ...

Section: Resultsmentioning

confidence: 99%

Regulation of Bud Rest in Tubers of Potato, Solanum tuberosum L

Shih

Rappaport

1970

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“…Increased production of plant hormones in wounded tuber tissues has been observed in a few cases. An increase in content of auxin and gibberellin, at 4 and 12 hr after wounding, respectively, was found in potato tissue (9,20). If gibberellins synthesized after wounding should play an essential role in the induction of wound healing processes, application of growth retardants (12) should inhibit wound healing, since no gibberellin is present in resting potato tissue (20) and growth retardants are known to inhibit the biosynthesis of gibberellins.…”

mentioning

confidence: 99%

“…An increase in content of auxin and gibberellin, at 4 and 12 hr after wounding, respectively, was found in potato tissue (9,20). If gibberellins synthesized after wounding should play an essential role in the induction of wound healing processes, application of growth retardants (12) should inhibit wound healing, since no gibberellin is present in resting potato tissue (20) and growth retardants are known to inhibit the biosynthesis of gibberellins. Although various aspects of wound healing are found to be adversely affected by growth retardants, as shown in this study, no conclusions as to the possible role of gibberellins can be drawn, because the observed inhibitions are not reversed or prevented by application of gibberellin.…”

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confidence: 99%

Wound Healing in Potato Tuber Tissue

Borchert¹,

McChesney²,

Watson³

1974

“…However, it becomes more and more likely that plant growth-regulating substances play a role in all of these reactions. Actually, there is a rapid synthesis or activation of phytohormones of different kinds after wounding (4,27). Gibberellins occur naturally in potato tubers (3,31) and represent inducers of many biochemical changes (8).…”

mentioning

confidence: 99%

“…Total RNA was extracted using the phenol method of Kirby (23) (3,31) and wounding drastically influences their rate of synthesis (4,27). These hormones, if applied exogenously, stimulate the wound-induced nucleic acid synthesis at an optimal concentration of 0.1 mm (8).…”

mentioning

confidence: 99%

Enhancement of Polyribosome Formation and RNA Synthesis of Gibberellic Acid in Wounded Potato Tuber Tissue

Wielgat

Kahl²

1979

As part of a more detailed study on plant tumoigenesis, the acti of gibberellic acid (GAs) in wounded potato tuber tissues as a model system has been evaluated. GA, stimulates total RNA synthesis in wounded tissues, the optimal concentration being 0.1 micromolar. The responsiveness of the tissue toward the hormone develops with time after wounding.Wbereas freshly wounded tissue does not respond at all to the hormone, it becomes competent after about 6 hours, the competence being maximal after 1 day of wound heaig.GAs enhances the formation of poyribosomes in wounded tissues and stimulates the synthesis of both ribosomal RNAs, transfer RNAs, 5S RNA, and a fraction, which in sucrose density gradints sediments between 18S rRNA and 5S RNA. This fraction contains presumptive mRNA.The hormone, then, is somebow recognized by wounded potato tissue in a time-specific war, the sigal is transferd to the genome and triggers the synthesis of varous RNA species.