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  • Author or Editor: James B. Shanks x
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Abstract

Trials over five consecutive winter seasons with ornamental crops growing in the greenhouse at split night and constant night temperatures (SNTs and CNTs) showed that a 5-hr period of 17°C minimum temperature during the dark period accelerated development over a CNT minimum of 12° to 13°. Maintaining 17° from 1700-2100 HR accelerated development over a 9° to 12° minimum CNT more than later periods of a 17° minimum with Euphorbia, Hydrangea, Kalanchoe, and Lilium. Continuation of 17° until 0100 or 0200 hr before a 9° to 12° minimum CNT was adequate for flower formation in Chrysanthemum. SNTs improved the bract : stem size ratio in Euphorbia and cyme size in Hydrangea relative to a 17° minimum CNT. Begonia × hiemalis, Begonia semperflorens, Brassaia, Coleus, Fuchsia, and Impatiens showed favorable growth responses or the potential for energy savings through the use of SNTs.

Open Access
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Abstract

Succinic acid-2,2-dimethylhydrazide (SADH) was ineffective but (2-chloroethyl)trimethylammonium chloride (chlormequat) and α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol) retarded growth of several cultivars of the Chinese hibiscus (Hibiscus rosa-sinensis Linn.) inducing shorter internodes and more and earlier flowering during summer months. (2-Chloroethyl)phosphonic acid (ethephon) also reduced the length of terminal snoots, but reduced flowering and stimulated the growth of lower axillary shoots of unpruned plants.

Open Access
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Abstract

Ethrel, a mixture of 2-chl-oroethanephosphonic acid and related compounds, has shown activity in dwarfing, inducing abscission, stimulating lateral or basal branching, and increasing the number of branches formed following topping. Examples of these effects on several flower crops are presented. Ethrel was shown to be absorbed and translocated by leaves, roots, or cut stems. Some of these effects were long-lasting in treated plants and of particular interest was the increase in number of branches formed when applied in conjunction with the chemical pinching agents.

Open Access

Abstract

Sixty-eight poinsettia cultivars (Euphorbia pulcherrima Willd.) were exposed to a population of greenhouse whitefly (Trialeurodes vaporariorum Westw.) for 9 weeks. Evaluation was based on 6 degrees of infestation by immature stages of whitefly on the bracts and upper and lower foliage. The upper foliage showed the heaviest infestation and was considered to be the best indicator of relative susceptibility. White bracts were more heavily infested than red bracts, while pink bracts were intermediate. A wide range in degree of whitefly infestation was found among poinsettia cultivars. Certain cultivars tested for 2 years showed appreciable resistance to infestation (‘U.S.D.A. 68-82-1’, ‘U.S.D.A. 68-160-2’, ‘Annette Hegg Maxi’, ‘Red Baron’, ‘Rudolph’).

Open Access

Abstract

The insect growth regulator (IGR) kinoprene reduced infestation by immature stages of greenhouse whitefly (Trialeurodes vaporariorum Westw.) on ‘Dramatic’ and ‘Puritan’ chrysanthemum (Chrysanthemum morifolium Ramat.) and ‘Annette Hegg Lady’ and ‘Eckespoint C-1’ poinsettia (Poinsettia pulcherrima Wild.). Three foliar applications at 2-week intervals were more effective than 1 or 2 applications. The plant growth regulators (PGR) ancymidol and chlormequat reduced whitefly infestation on both cultivars of chrysanthemum and ‘Annette Hegg Lady’ poinsettia.

Open Access

Abstract

Increasing levels of the systemic insecticide 2-methyl-2-(methylthio)propionaldehyde O-(methylcarbamoy)oxime (aldicarb) and a plant growth retardant (2-chloroethyl)trimethylammonium chloride (chlormequat) reduced the mean population of whitefly on poinsettia (Euphorbia pulcherrima Willd.). Chlormequat was effective only with the low level or with no aldicarb.

Open Access

Abstract

Following the termination of rest, 16-, 20-, or 24-hr photoperiods hastened flower development of 7 cultivars of hydrangeas [Hydrangea macrophylla (Thunb.) Ser.] compared to those at 8- or 12-hr photoperiods. The interruption of a 16-hr dark period with 4- or 8-hr incandescent illumination was as effective as continuous light. Stem elongation and cyme expansion increased with length of photoperiod, while the interruption of the dark period had an intermediate effect upon these parameters. Plants undergoing continuous development without defoliation or a rest treatment responded similarly to rested and defoliated plants in rate and extent of growth and initiated flowers more uniformly at an 8-hr photoperiod than at longer photoperiods.

Open Access

Abstract

Seven growth regulators representing ethylene-generating materials, auxins, gibberellins, cytokinins and inhibitors were applied prior to inoculation with selected pathogens of chrysanthemum (Chrysanthemum morifolium Ramat.), begonia (Begonia X hiemalis Fotech.), rose (Rosa hybrida L.), and poinsettia (Euphorbia pulcherrima Willd.). (2-ChloroethyI)phosphonic acid (ethephon) and 6-benzylamino purine (BA) increased the incidence of Ascochyta ray blight (incited by Ascochyta chrysanthemi Stevens) on ‘Ritz’ chrysanthemum but the other materials had no effect. None of the growth regulators influenced powdery mildrew [Sphaerotheca pannosa (Wallr.) Lev.] of rose, powdery mildew (Erysiphe cichoracearum DC.) of begonia, or grey mold (Botrytis cinerea Pers. ex Fr.) of poinsettia.

Open Access

Growth and flowering of chrysanthemum, poinsettia, fuchsia, hydrangea, and geranium grown on rotating shelves were compared with that of plants grown in full ambient sunlight on a stationary greenhouse bench. Ambient insolation reaching plants on the rotating shelves was ca. 55% of that on the stationary greenhouse bench on a sunny day and ca. 60% of full insolation on a cloudy day. Plants grown on the rotating shelves required two to six days longer to flower and were smaller in height, weight, and number of flowers compared to plants under full light. The lasting of chrysanthemum leaves and petals was lessened by growth on rotating shelves compared to plants grown in full light while there was no effect on the lasting of poinsettia bracts or of hydrangea leaves and sepals under simulated home conditions.

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