Preparation of Radioactive Gibberellin A<sub>1</sub> and its Metabolism in Dwarf Peas

Kende, Hans

doi:10.1104/pp.42.11.1612

Cited by 63 publications

(27 citation statements)

References 13 publications

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“…Although conclusive identification was not made in our study, TLC and GLC evidence strongly suggested GA8 as a primary metabolite of GA1. This probable identification of GA8 suggests that the GA metabolic pathway in cucumber may be similar to that of other plant species (9,13,14,17). The conversion of GA4 to GA, by a single hydroxylation (4) seems relevant to cucumber as both GA, and GA4 occur in cucumber (7).…”

Section: Methodsmentioning

confidence: 98%

“…The metabolism of 3H-GA1 in barley half seeds (14), peas (9), and beans (15,17) resulted primarily in the production of GA8 and GA8-glycoside. Although conclusive identification was not made in our study, TLC and GLC evidence strongly suggested GA8 as a primary metabolite of GA1.…”

Section: Methodsmentioning

confidence: 99%

“…Two sources of 3H-GA1 were used. The first was received from H. Kende (9) and had a specific radioactivity of 420 mCi/mmole. The second was received from L. Rappaport (14) with a specific radioactivity of 48 Ci/mmole.…”

Section: Methodsmentioning

confidence: 99%

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Transport and Metabolism of ³H-Gibberellin A₁ in Dioecious Cucumber Seedlings

Rudich

Sell²,

Baker³

1976

Plant Physiol.

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The transport of 3H-GA1 through hypocotyl segments of cucumber (Cucumis sadivus L.) was found to be nonpolar. The transport of 3H-GA1 was increased by pretreatment with relatively high concentrations of either IAA or Ethephon (2-chloroethylphosphonic acid). Hypocotyl segments from plants of a gynoecious genotype transported more 3H-GA1 than those of an androecious. The metabolism of 3H-GA1 in hypocotyl segments was neither related to the sex genotype of the cucumber plant nor influenced by pretreatment with Ethephon. The primary metabolite of GA, was suggested to be GA8. Two other suspected metabolites were not identified. Differences in the endogenous GA of gynoecious and androecious plants could not be accounted for by transport differences.The sex expression of cucumber is influenced by the hormonal balance of auxin, ethylene, GA and ABA (1,5,6,18,20,21). Male flower production in cucumber is associated with endogenous GA levels (7,21,26). Exogenous application of GA3, GA4, GA7, and GA9 also increase the production of male flowers on both monoecious and gynoecious phenotypes (2, 26). Gynoecious phenotypes contain far less GA than monoecious (7,21), whereas the qualitative GA composition of both seeds and green plants is similar for all sex phenotypes. Most endogenous GA is present as GA, and GA3 with traces of GA4 and GA7 (7). Conjugated derivatives of GA have also been identified from cucumber seed (8), but appear to play no regulatory role in sex expression. The primary hormones associated with female flower production are ethylene (1,19,20) and auxin (5, 6). Treatment of cucumber plants with Ethephon actually decreases the endogenous GA activity (21).Accordingly, one possibility for the control of sex expression in cucumber is via ethylene biosynthesis and its effect on GA. Other possibilities (12) for hormonal control of sex expression might be a conversion from biologically active to inactive forms via conjugation or degradation, differences in biosynthesis, or differences in transport. We investigated the possibility that GA1 transport and/or metabolic differences as affected by ethylene might regulate the difference between male and female expression in cucumber. MATERIALS Hypobaric Ventilation. These experiments were conducted with explants under a reduced pressure of 0.2 atm to decrease internal ethylene concentration (1). Experiments were conducted over a 24-hr period with a gas mixture of 99.85% 02 and 0.15% C02. For ethylene treatments, the gas mixture was 99.85% 02, 3 ,u1/l C2H4, and 0.15% CO2. All experiments were conducted at a temperature of 25 C with continuous light (400 ft-c). All treatments were replicated three times in a completely randomized design.Radioactive 3H-GA1. Two sources of 3H-GA1 were used. The first was received from H. Kende (9) and had a specific radioactivity of 420 mCi/mmole. The second was received from L. Rappaport (14) with a specific radioactivity of 48 Ci/mmole. Experiments were conducted with 3H-GA1 concentrations of 1 iLM to 10 nM.Agar Block Preparation. ...

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Section: Methodsmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

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Transport and Metabolism of ³H-Gibberellin A₁ in Dioecious Cucumber Seedlings

Rudich

Sell²,

Baker³

1976

Plant Physiol.

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“…It should be noted that an increased growth rate is not necessarily associated with increased GA metabolism. For example, dwarf peas show marked differences in growth when kept in light or darkness, while metabolism of`H-GA1 was the same (10), and that of 'H-GA5 only slightly different (15) under the two conditions. If GAs are biologically active in the chemically unchanged form as shown for GA1 and GA, in peas (10,15), metabolism of GA per se will not contribute to growth.…”

Section: Gibberellins and Growth Inispinachmentioning

confidence: 99%

“…For example, dwarf peas show marked differences in growth when kept in light or darkness, while metabolism of`H-GA1 was the same (10), and that of 'H-GA5 only slightly different (15) under the two conditions. If GAs are biologically active in the chemically unchanged form as shown for GA1 and GA, in peas (10,15), metabolism of GA per se will not contribute to growth. However, more GA will be available to spinach plants under LD because of increased GA biosynthesis, and this, combined with the increased sensitivity to GA, could be responsible for increased petiole growth and stem elongation under LD.…”

Section: Gibberellins and Growth Inispinachmentioning

confidence: 99%

Effects of Photoperiod on Growth Rate and Endogenous Gibberellins in the Long-Day Rosette Plant Spinach

Zeevaart

1971

Plant Physiol.

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The earliest visible responses of spinach plants (Spinacia oleracea L., cv. Savoy Hybrid 612) transferred from short to long days (8 hours of high intensity light supplemented with 16 hours of low intensity illumination from incandescent lamps) were upright leaf orientation and increased elongation of the petioles. The effect of long days on growth rate was direct; i.e., there was no after-effect if the plants were transferred to short days. Gibberellin A3 applied to plants under short days had an effect similar to that of long days, whereas application of the growth retardant AMO-1618 [2'-isopropyl-4'-(trimethylammonium chloride)-5'-methylphenyl piperidine-I-carboxylate] under long days caused a growth habit typical of short-day conditions. Gibberellin A3 caused more stem growth in plants under long days in which the endogenous gibberellin content had been reduced by AMO-1618 than in plants under short days not treated with the growth retardant.Three gibberellin-like substances, called I, II, and III in order of increasing RF value, were present in acidic extracts of spinach under short days. After transfer to long days, II increased, whereas I and III decreased, the latter below the level of detection in the d5 corn assay. Following application of AMO-1618 the gibberellin content of plants under long days fell off more rapidly than in those under short days, indicating that gibberellin turnover was markedly higher under long days. This increased rate of gibberellin metabolism was established after 2 long days. When plants were returned to short days, the turnover of gibberellins declined. It is suggested that a higher rate of gibberellin biosynthesis combined with increased sensitivity to gibberellin is responsible for the observed growth responses in spinach under long days.In many rosette LDP,1 application of GA under SD conditions causes stem elongation and flower formation (4, 11, 26). These observations have led to the idea that rosette plants on SD are deficient in GAs, while LD would raise the level of endogenous GAs which in turn would stimulate stem growth e.g., Ref. crease over the SD control by more than a factor of 2. However, results of diffusion experiments suggested that just prior to the onset of stem elongation both the biosynthesis of GA and its metabolism had increased.Working with spinach, Radley (16) reported a sharp although transient increase in GA content after 1 LD. She suggested that the decrease in GA level after more LD cycles was due to greatly increased turnover of GA. In view of this marked increase in the GA content after 1 LD, the levels of native GAs in spinach have been reinvestigated under different photoperiods, as well as the decrease in GA content following the application of the growth retardant AMO-1618. The results in this communication provide experimental support for the notion that the turnover of GAs in spinach is much higher under LD than under SD conditions. Preliminary reports of this investigation have been presented earlier (26, 27). MATERIALS AND METH...

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