INVESTIGATIONS OF HYDRANGEA DISTORTION IN FLORISTS' HYDRANGEA (HYDRANGEA MACROPHYLLA (THUNB.))
Abstract
Studies were undertaken to (1) identify the environmental conditions that lead to hydrangea distortion; (2) describe both the macro- and micro-scopic symptoms of hydrangea distortion; (3) examine the relationship between foliar nutrition and hydrangea distortion; and (4) investigate the possibility of a pathogenic origin for hydrangea distortion. Results indicate hydrangea distortion is under thermal regulation. Foliar symptoms can be stimulated by ambient temperatures of 33/26(DEGREES)C (day/night), but the elevated temperatures must be maintained to sustain the production of distorted foliage. Higher photosynthetic photon flux results in a more rapid appearance of symptoms, but elevated leaf surface temperatures did not affect the appearance of distortion symptoms. Maintaining root zone temperatures of 20/18(DEGREES)C (day/night) in a distorting environment moderates but does not prevent hydrangea distortion. Distinct anatomical and morphological differences were documented for distorted and nondistorted leaves. It is not known whether these changes are the cause of or a result of hydrangea distortion. No apparent protein differences as determined by SDS-PAGE were associated with hydrangea distortion. Attempts to produce hydrangea distortion through nutrient imbalances were unsuccessful. Hydrangea distortion does not appear to be correlated with any nutrient deficiency or micronutrient toxicity. No pathogen could be associated with hydrangea distortion and symptoms appear to be nontransmittable. It is suggested that hydrangea distortion is strictly physiological and its expression is a genotype x environment interaction. Thermotolerant cultivars do exist and may offer an alternative to the production of present commercially popular cultivars.
Degree
Ph.D.
Subject Area
Botany
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