Masters Theses

Date of Award

5-2001

Degree Type

Thesis

Degree Name

Master of Science

Major

Landscape Architecture

Major Professor

Terri W. Starman

Committee Members

Mary Albrecht, Susan Hamilton

Abstract

There is an economic need for a more a diverse palette of plants to produce for the small to mid-size commercial flower grower. The objective of our research was to establish the vegetative and reproductive responses to photoperiod, light intensity, and plant growth regulators for three vegetatively propagated annual crop species, Angelonia angustifolia Benth. ‘Blue Pacific' Asteriscus maritimus L. (Lem.) cultivars and Heliotropium aborescens L. 'Fragrant Delight'.

Neither flower initiation nor flower number in A. angustifolia 'Blue Pacific' were affected by photoperiod. High intensity discharge (HID) supplemental lighting decreased time to flower development and increased overall plant weight; flower number and axillary branching compared to ambient and shade conditions. In a plant growth regulator experiment, uniconazole drench reduced plant weight and resulted in stunted plants. Daminozide decreased foliage stem height but had no effect on inflorescence height or plant weight. HID day length extension decreased time to flower, increased overall plant weight and number of flowers. Other methods of long day treatment caused stem elongation unless daminozide treatment was used. Plants grown under HID lighting and treated with daminozide were the most marketable of all the treatments.

Asteriscus maritimus Gold Coin' was found to be a day neutral plant with regards to flowering, but photomorphogenicNode numbers and plant weight increased with short day (SD) photoperiod. Asteriscus maritimus 'Compact Gold Coin' was found to be a facultative long day (LD) plant for flowering and also photomorphogenic producing more compact plants under SD photoperiod. The increased vegetative growth of both cultivars of this crop species under SD photoperiod may be a useful tool for stock plant production.

High intensity discharge (HID) supplemental lighting decreased time to flower and increased number of flowers, while increasing plant compactness and weight compared to ambient and shade conditions for A. maritimus 'Gold Coin'. Ancymidol, daminozide and uniconazole were all effective in reducing plant size parameters, and especially useful when producing plants during LD photoperiod. As a method of applying LD photoperiod to 'Compact Gold Coin', HID daylength extension decreased time to flower, increased overall plant weight and number of flowers. Methods of LD treatment using incandescent lamps caused stem elongation unless daminozide treatment was used. Continuous LD for decreasing time to flower and continuous SD for bulking vegetative growth proved to be more effective than limited inductive photoperiod for Asteriscus maritimus 'Compact Gold Coin'.

Heliotropium aborescens 'Fragrant Delight' was found to be a day-neutral plant. Neither flower initiation nor flower number was affected by photoperiod. High intensity discharge (HID) supplemental lighting was found to decrease time to flower development, increase overall plant weight, flower size and axillary branching compared to ambient and shade conditions. Ethephon at 500 and 1000 mg.L-1 were effective in controlling plant growth, but reduced overall plant mass and delayed flower development. Daminozide gave limited control of plant height without affecting overall plant weight. Uniconazole drench at 1 and 2 mg.L-1 controlled plant height, reduced internode length and peduncle length, however it also reduced leaf width and overall plant weight. Daminozide reduced. plant height under all methods of photoperiod applicationPlants grown under HID/Ext. with daminozide were the most marketable of all treatments.

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