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Degree

Doctor of Philosophy, Ohio State University, Horticulture and Crop Science, 2004.

Abstract

Two plant species, Cuphea pulchra and Cuphea schumannii, native to Brazil and Mexico respectively, were evaluated for their potential as new ornamental crops. Both species are characteristic of the genus as suffrutescent sub-shrubs bearing intense orange, ribbed flowers. The objectives of the current research were to evaluate the species for ornamental qualities and begin developing information pertinent to commercial production. Initial greenhouse observations and three consecutive years of outdoor trials demonstrated that C. schumannii possess relatively little horticultural potential, due to an indeterminate growth habit, high susceptibility to green peach aphid infestation and development of leaf intumescence under greenhouse conditions. Conversely, C. pulchra holds much promise as an annual, landscape/garden bedding plant with its compact growth habit, sustained heavy production of attractive flowers, and resistance to greenhouse and outdoor insect pests. Continued studies of the species evaluated methods of growth regulation, production temperature, and photoperiodic requirements for flowering. Study testing growth regulation with chemicals daminozide, paclobutrazol, and chlormequat indicated that growth of C. schumannii could be effectively and uniformly controlled with a concentration of 5000 ppm daminozide. C. pulchra was successfully controlled by the non-chemical method of apex removal or “pinch”. Results of controlled temperature studies demonstrated that plant quality and floral evocation increased for both species when maintained under a day/night temperature regime of 21°C/18°C when compared to 13°C/10°C or 29°C/26°C temperature regime. Evaluation of photoperiodic response revealed that C. schumannii is a day-neutral or a very weak facultative long day plant, while C. pulchra is a facultative long-day plant. Preliminary investigations were conducted to determine the nature of insect resistance in C. pulchra. Choice and no-choice settling assays revealed that resistance is due in large part (if not all) to the presence of glandular trichomes on the stem and flower surfaces. Preliminary analysis by thin layer chromatography showed that the main component of the trichome exudate was a compound(s) that co-chromatographed with acyl esters of sucrose. Acyl esters of glucose and sucrose have been shown to be the primary compounds responsible for plant resistance to insect herbivores of wild species of tomato, potato, and tobacco.

Subject Headings

Agriculture, Plant Culture

Keywords

Cuphea; Species Evaluation; Production Information; Pest Deterrence; Sugar Esters

Advisor

James D. Metzger

Pages

xvii, 188 p. : ill (some col.)

Document number: osu1092587225
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=osu1092587225

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