Determination of Relative Auxin Content in Hermaphrodite and Andromonoecious <i>Cucumis sativus</i> L.

Galun, Esra; Izhar, S.; Atsmon, Dan

doi:10.1104/pp.40.2.321

Cited by 37 publications

(17 citation statements)

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“…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).…”

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“…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).…”

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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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confidence: 99%

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

Rudich

Sell²,

Baker³

1976

Plant Physiol.

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“…Femaleness of cucumbers has been increased by application of auxin (9,19). When homologous sections of hermaphrodite and andromonoecious cucumber plants were compared, higher levels of auxin were found in the hermaphrodite type (10). The role of auxin in the development of female flowers in cucumbers has been demonstrated (11) by growing, in tissue culture, flower buds of cucumber plants from nodes which produce only male flowers.…”

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The Level of Phytohormones in Monoecious and Gynoecious Cucumbers as Affected by Photoperiod and Ethephon

1972

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The endogenous levels of auxin, gibberellin, and inhibitors were followed in monoecious and gynoecious cucumber (Cucumis sativus L.) plants, and in plants treated with the ethylene-releasing compound Ethephon (2-chloroethyl phosphonic acid). Higher auxin inhibitor and lower gibberellin levels were associated with female tendency. The endogenous level of gibberellin and auxin decreased in Ethephon-treated plants. Appli (33). When ethylene evolution from cucumber plants was examined, more ethylene was evolved from apices of the gynoecious than from those of monoecious type (28).The interactions between auxin and ethylene are complex. Many studies have shown that auxins hasten the production of ethylene (1,6,8), that ethylene enhances the decomposition of auxin (3), and that it also inhibits the movement of auxin in the plant (3). A number of effects, in the past attributed to high levels of auxin, are now considered to be a result of ethylene production under the influence of auxin (5, 7).Little is known about the interaction between ethylene and gibberellin. Antagonism between them has been found in germination of wheat and the production of both a-amylase and invertase (31). Their action is also antagonistic in fruit ripening and in sex expression of flowers (13, 26). We are not aware of any publication on the effect of ethylene on endogenous gibberellin levels. Kang et al. (18) found that gibberellin had no effect on ethylene production in bean seedlings. They concluded that GA and ethylene effects in the development of the seedlings were independent.Since sex expression in cucumbers is influenced by Ethephon as well as by auxin and gibberellin, we tried to determine in the present work the effect of Ethephon on the level of the above phytohormones as well as on ABA and other native inhibitors, in an attempt to gain additional knowledge on the relation of these phytohormones to sex expression.MATERIALS AND METHODS Plant Material. Endogenous levels of growth substances were determined in the monoecious and gynoecious 'Bet Alpha' 2 lines of cucumber (Cucuinis sativus L.) plants. The gynoecious line was bred from the monoecious one and differs from it in the gene for femaleness (2). Under short day conditions it produces female flowers from the first or second node, under long day conditions male flowers are produced at the first six nodes, all the rest being female. In one experiment andromonoecious muskmelon plants (cv. Ananas PMR) were used.In most experiments plants were grown in growth chambers at 8-hr photoperiod under mixed fluorescent and incandescent lamp light of 3500 ft-c. Long day treatments were given by incandescent lamps of 70 to 80 ft-c. Temperature during the day, 8 hr, was 28 C, at all other times it was 18 C. In some experiments CO2 level was also controlled in the chambers.In a few experiments plants were grown in a phytotron under natural light intensities. Long days were given by extending the natural day to 16 hr by incandescent lamps of 100 ft-c.

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“…High endogenous auxin levels (2) are associated with female tendency, and exogenous auxin treatments (5) enhance the femaleness of cucumber plants, whereas high endogenous gibberellin levels are associated with maleness (1). Ethephon [(2-chloroethyl) phosphonic acid], which releases ethylene in plant tissues (11), also changes the sex expression of cucumbers, enhancing femaleness (6,10 Ethylene evolution was determined by gas chromatography using a Packard gas chromatograph equipped with a flame ionization detector and 36-X ¼-inch alumina column.…”

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Ethylene Evolution from Cucumber Plants as Related to Sex Expression

1972

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Sex expression is also influenced by growth regulators (8, 9). High endogenous auxin levels (2) are associated with female tendency, and exogenous auxin treatments (5) enhance the femaleness of cucumber plants, whereas high endogenous gibberellin levels are associated with maleness (1). Ethephon [(2-chloroethyl) Ethylene evolution was determined by gas chromatography using a Packard gas chromatograph equipped with a flame ionization detector and 36-X ¼-inch alumina column. Ethylene was determined in a 2-ml sample removed from a 30-or 100-ml vessel in which the tissue was incubated for 2 hr at 25 C at a light intensity of 600 ft-c. The vessels containing 1 ml of water were sealed with rubber stoppers through which the sample was drawn. The instrument was calibrated with a 1 ,ud/l ethylene standard. The data presented are from different experiments for each table.RESULTS AND DISCUSSION Ethylene evolved from young seedlings was determined in explants cut from the hypocotyl region 1 cm below the cotyledons. The data in Table I show that 11-day-old explants of the monoecious and gynoecious types evolve similar quantities of ethylene. In plant apices tested 19 days after germination, more ethylene was evolved by the gynoecious type (Table II), and the quantities were especially large under short day conditions which promote femaleness.

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Determination of Relative Auxin Content in Hermaphrodite and Andromonoecious Cucumis sativus L.

Cited by 37 publications

References 19 publications

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

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

The Level of Phytohormones in Monoecious and Gynoecious Cucumbers as Affected by Photoperiod and Ethephon

Ethylene Evolution from Cucumber Plants as Related to Sex Expression

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Determination of Relative Auxin Content in Hermaphrodite and Andromonoecious Cucumis sativus L.

Cited by 37 publications

References 19 publications

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

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

The Level of Phytohormones in Monoecious and Gynoecious Cucumbers as Affected by Photoperiod and Ethephon

Ethylene Evolution from Cucumber Plants as Related to Sex Expression

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

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