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Morpho-anatomical and Physiological Adaptations of Sweet Pepper (Capslcuum annuum L.) to Partial Shade
Dissertation Abstract:
This study characterized the morpho-anatomical and physiological adaptations of three sweet pepper cultivars ("Sinatala," "All Season," and "California Wonder") grown under increasing shade levels. The effects on morpho-anatomical, physiological, growth, and yield characteristics as well as the most suitable level of light intensity for the production of these cultivars in both dry and rainy growing seasons were also determined.
The experiments were conducted at the Institute of Plant Breeding and at the Department of Horticulture, College of Agriculture, University of the Philippines Los Banos. The first experiment was conducted from December 1991 to April 1992 and the second experiment, from April to August 1992.
Findings showed that the three sweet pepper cultivars had considerable morpho-anatomical and physiological adaptations to partial shade. Increasing shade levels had favorable effects on vegetative growth, subsequently contributing to growth and yield of the three cultivars. The morpho-anatomical adaptations of sweet pepper plants to low light intensity were: 1) increased total leaf area; 2) increased plant height; 3) longer internodes; 4) increased node number; 5) bigger canopy diameter; and 6) decreased leaf thickness. These were responsible for the plants' increased light interception and greater carbon dioxide assimilation, which consequently increased overall photosynthesis and dry matter production.
The decrease in leaf stomatal number on leaf area basis reduced the photosynthetic and transpiration rates on leaf area basis. Since total area and total chlorophyll content increased, plant growth measured in terms of dry weight, leaf area index, and crop growth rates consequently increased. Moreover, analysis for sugar and starch contents of the various parts revealed that the fruit was the priority sink and that photosynthates (from the leaves) were efficiently translocated to this plant part.
Fruit yield increased when shade level was increased up to 49 percent during the dry season and up to 43 percent during the rainy season. Fruit number, harvest index, and, to some extent, fruit size, were observed to be varietal characteristics and were not influenced by partial shade. "Sinagtala" produced the most number of fruits but were significantly smaller than those produced by "California Wonder" which were fewer but significantly bigger.
The most suitable shade level for the production of these three sweet pepper cultivars was 49 percent for dry season and 43 percent for the rainy season. Heavy shading (56% shade level), however, tended to have detrimental effects on growth, development, and yield of the three sweet pepper cultivars.