Author Type

Graduate Student

Date of Award

1979

Document Type

Thesis

Publication Status

Version of Record

Submission Date

October 2026

Thesis/Dissertation Advisor [Chair]

Boss, Manley L.

Abstract

Intact sunflower plants were exposed to various lighting conditions, then detopped and the exudation rate determined at 1 hr intervals. The rhythm responded to the "lights-off" signal as evidenced when plants were cultured under different daylengths. A brief exposure given just before the cycle mini mum (circadian time 21) caused maximum phase shift. When irradiated with white light, a dosage of 7.5 min at 2500 fc was calculated to cause a minimum phase shift, while a dosage of 60 min at 2500 fc caused a maximum phase shift. The time necessary f or the stimulus messenger to travel from the receptor area (leaves) to the effector area (roots) was determined to be 1-2 hrs. Exposure to far-red or red light was found to be more effective for shifting the phase than blue or green light. This suggests that the rhythm may be governed by the High Energy Reaction of phytochrome.

Extent

66 p.

Comments

Charles E. Schmidt College of Science|Thesis (M.S.)--Florida Atlantic University, 1979.|FAU Electronic Theses and Dissertations Collection|Charles E. Schmidt College of Science

Identifier

FADT13974

Format

pdf

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