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  • Author or Editor: R. M. Sachs x
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Abstract

Although at each shoot apical meristem, vegetative and reproductive development represent alternative courses of differentiation, we wish to emphasize the quantitative interaction between these two processes particularly with regard to the potential for chemical control. Without exception the known flower promoting or inhibiting substances also have substantial influence on vegetative development (32).

Open Access
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Abstract

Although for an entire plant, vegetative and reproductive development may proceed concurrently, at each shoot apical meristem a transition occurs from leaf production to bract or sepal production at the time of flower initiation. Subsequent stages of reproductive development are equally differentiated from that of vegetative development. Hence, vegetative and reproductive development represent alternative courses of differentiation of apical meristematic tissues.

Open Access

Abstract

Ten compounds applied as foliar spray were screened for reducing and delaying bolting in fall-planted carrots (Daucus carota L.). Only butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) was effective; seedstalk height was reduced and root size was unaffected. Daminozide effectiveness was greatest in weak-bolting cultivars. Two sprays of 5000 ppm, 2 weeks apart at about 4 and 2 weeks prior to natural bolting were most effective, suggesting that daminozide does not interfere in the cold temperature induction process, but rather has a delaying and inhibitory effect on the initial seedstalk elongation. Two sprays of 500 liters/ha of daminozide solution of 5000 ppm gave promising results. Root quality was improved without influencing carrot yield or dry matter content. Although (2-chloroethyl)trimethymammonium chloride (chlormequat) suppressed bolting in some experiments, it was less effective than daminozide at comparable rates and higher rates decreased yield.

Open Access
Authors: and

Abstract

In ‘Bright Golden Anne’ chrysanthemums girdling below the treated leaves does not reduce, rather it may enhance, growth retarding activity of foliar applied ancymidol. Experimental evidence with 14C sucrose shows that the compound does not pass the girdle to enter the root system, and it is assumed that ancymidol transport is similarly restricted. Our results indicate that the major site of action of ancymidol is in the shoot tissues. One suggestion accounting for greater activity of soil, as compared to foliar, applications is that the chrysanthemum root system may absorb ancymidol more rapidly than the leaves.

Open Access

Abstract

Foliar applications of 2, 3, 4, 6-di-o-isopropyl-idene-2-keto-L-gulonate (dikegulac) at rates of 0.2-0.3% resulted in growth reductions comparable with l,2-dihydro-3,6-pyridazinedione (MH) or methyl-2-chloro-9-hydroxyfluorene-9-carboxylate (chlorflurenol). Where terminal leaf abscission occurs, tree appearance after treatment is sometimes better than that of trees treated with either MH or chlorflurenol. Growth reduction from trunk banding with dikegulac n-pentyl ester was observed only on Ulmus parvifolia Jacq.; chlorflurenol in trunk banding has a much wider species range and is effective at lower concn.

Open Access
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Abstract

Foliar application of 0.1 to 1% dikegulac-sodium [sodium 2,3:4,6-di-0-isopropyl-idene-2-keto-L-gulonate (Atrinal)] inhibited (shoot) elongation and axillary bud break for more than 3 months in field grown Xylosma congestum, (Lour.) Merr., Pyracantha coccinea (Roem.), Callistemon citrinus (Curt.), Cotoneaster pannosa (Franch.), and Nerium oleander L. Phytotoxic symptoms were minor in most species, but Nerium, chlorosis of young leaves and necrotic areas on tips of half expanded leaves were noted. Applications made immediately after pruning eliminated this problem. Fully expanded leaves were undamaged and their viability more than 5 months after treatment with 1% solutions were equal to that of control plants. Greenhouse trials with Eucalyptus globulus Labill., Fraxinus uhdei (Wenz.) lingelsh, and Ulmus parvifolia Jacq. indicated that this compound will also be a useful inhibitor for landscape tree species, although at 0.4%, phytotoxicity in Eucalyptus may be too severe for general application.

Open Access

Abstract

Morphactins, mixed with non-phytotoxic paraffinic, low molecular weight oil, were applied as bark bands and tested for growth inhibition of trees growing under field conditions. Three species were tested: Monterey pine (Pinus radiata D. Don.), olive (Olea europaea L. cv. Manzanillo) and eucalyptus (Eucalyptus globulus Labill). Shoot elongation was inhibited in all three species, but sensitivity to the treatment varied.

Open Access

Abstract

A new formulation of maleic hydrazide (Royal Slo-Gro), containing the surfactant polyoxyethylene trimethylnonyl ether (TMN-10), was superior to the maleic hydrazide formulation, containing polyoxyethylene nonyl surfactant (X-77) for inhibiting shoot elongation of Pinus radiata L., Xylosma congestum (Lour.) Merr., Viburnum japonicum (Thunb.) Spreng., and Coprosma repens A. Rich. The X-77 formulation was superior to the one containing TMN-10 for inhibiting growth of Juniperus sabina L. ‘Tamariscifolia’, Pyracantha coccinea (Roem.), and Callistemon citrinus (Curt.). There was little difference between the two formulations in tests with Cotoneaster pannosa (Franch.) and mixed results were obtained with Nerium oleander L. The greatest advantage of the TMN-10 formulation was manifested in Pinus where inhibition occurred without severe foliar discoloration, necrosis, or tip dieback which are characteristic of other maleic hydrazide formulations.

Open Access

Abstract

Pea root tips were pre-incubated for 2 hr in the presence of Alar, Amo–1618, or Cycocel after which a quantity of 2-14C-mevalonic acid was added to the medium. The incorporation of mevalonic acid subsequent to decarboxylation into 3 gibberellic acid precursors, trans-geranylgeraniol, kauren-19-ol, and kauren-19-al was ascertained by paper and thin layer chromatography. The amount incorporated into a fourth acidic fraction containing kaurenoic acid was also estimated.

In the presence of Alar, the amount of radioactivity in trans-geranylgeraniol increased while that in kauren-19-al decreased simultaneously; the radioactivity in the acidic and kauren-19-ol fractions remained unchanged. Amo-1618 at 125 ppm induced an accumulation of radioactive acidic materials and concurrent decreases in the other 3 fractions. With Cycocel, the incorporation of 14C in kauren-19-ol and kauren-19-al remained unchanged while that in the acidic fraction increased and trans-geranylageraniol decreased. Amo-1618 was 100-fold more effective than Cycocel in altering the levels of GA precursors. The Alar concentration required to affect the biosynthesis of GA precursors was the same as that which inhibited epicotyl elongation of intact pea seedlings. The findings support the hypothesis that these growth retardants disrupt GA biosynthesis which in turn affects subapical meristematic activity, thereby inhibiting internodal elongation.

Open Access

Abstract

Several field-established broadleaved and coniferous evergreen shrubs and 2 ground covers, Carpobrotus sp. and Hedera helix L., survived, and maintained adequate appearance with greatly restricted growth, without supplemental irrigation from May through September on deep soils at San Jose and Santa Ana, CA. Eugenia uniflora L. at Santa Ana required 1 irrigation (9.4 cm) in July to insure survival and both Coprosma baueri Endl. and Cotoneaster pannosa Franch. required 1 or 2 irrigations to insure adequate foliar density. At San Jose only Nerium oleander L. lost leaves or lost leaf color and turgidity in the non-irrigated plot. The plantings at both locations had viable roots down to 1 m and probably deeper. Non-irrigated and bimonthly irrigated soils were at or below the permanent wilting percentage down to 1 m. Leaf temp in the non-irrigated Xylosma congestum (Lour.) Merr. and Carpobrotus plots were 6 and 15° C, respectively, above ambient and yet no permanent foliar injury was observed. We suggest that leaf temp may be used to measure critical water stress in landscape plants. Our findings indicate that substantial savings in water costs and in controlling vegetative overgrowth can be realized by reducing irrigation frequency in established landscape plantings.

Open Access