The transduction of light signals controlling floral induction in Pharbitis nil
type: CreativeWork
description: The control of floral induction in the short day plant, Pharbitis nil, is based on a circadian rhythm. At certain times of the circadian (24 h) cycle, a brief light pulse, acting through the photoreceptor, phytochrome, can cause inhibition of induction, whilst at other time points, a brief light pulse promotes a change in phase of the rhythm. The aim of the research presented in this thesis was to investigate the signal transduction pathway linking perception of light by phytochrome to its physiological action on floral induction in Pharbitis nil, and how the circadian oscillator interacts with and influences this pathway. Experimental evidence has implicated calcium in both the regulation of circadian rhythms and in phytochrome action, and more specifically, in the control of floral induction. It was therefore decided to investigate whether the phosphatidylinositol cycle, which, via the key signalling component, l(l,4,5)P3, releases calcium from intracellular stores in animal cells, is involved in the transduction of light signals physiologically active in floral induction. In physiological studies, the calcium channel blocker Verapamil and the calcium chelator EGT A both enhanced the inhibition of floral induction by a sub-maximal light pulse at the ninth hour of an otherwise inductive period. EGT A applied before an inductive dark period significantly reduced the level of flowering, but did not affect flowering if applied at the end of induction. these findings imply that calcium is necessary for induction to take place. In studies investigating the metabolism of I( 1,4,S)P 3 by a soluble extract from Pharbitis nil cotyledons, elevated calcium levels were found to slow the metabolism of l(l,4,5)P3• Lithium, which blocks inositol-1-phosphatase activity in animal cells, causing inositol phosphates to accumulate and blocking the PI cycle, reduced the sensitivity of the response of inhibition to a night break, and caused a decrease in flowering when given before or a…
abstract: The control of floral induction in the short day plant, Pharbitis nil, is based on a circadian rhythm. At certain times of the circadian (24 h) cycle, a brief light pulse, acting through the photoreceptor, phytochrome, can cause inhibition of induction, whilst at other time points, a brief light pulse promotes a change in phase of the rhythm. The aim of the research presented in this thesis was to investigate the signal transduction pathway linking perception of light by phytochrome to its physiological action on floral induction in Pharbitis nil, and how the circadian oscillator interacts with and influences this pathway. Experimental evidence has implicated calcium in both the regulation of circadian rhythms and in phytochrome action, and more specifically, in the control of floral induction. It was therefore decided to investigate whether the phosphatidylinositol cycle, which, via the key signalling component, l(l,4,5)P3, releases calcium from intracellular stores in animal cells, is involved in the transduction of light signals physiologically active in floral induction. In physiological studies, the calcium channel blocker Verapamil and the calcium chelator EGT A both enhanced the inhibition of floral induction by a sub-maximal light pulse at the ninth hour of an otherwise inductive period. EGT A applied before an inductive dark period significantly reduced the level of flowering, but did not affect flowering if applied at the end of induction. these findings imply that calcium is necessary for induction to take place. In studies investigating the metabolism of I( 1,4,S)P 3 by a soluble extract from Pharbitis nil cotyledons, elevated calcium levels were found to slow the metabolism of l(l,4,5)P3• Lithium, which blocks inositol-1-phosphatase activity in animal cells, causing inositol phosphates to accumulate and blocking the PI cycle, reduced the sensitivity of the response of inhibition to a night break, and caused a decrease in flowering when given before or a…
author: Prior, Sarah Louise
language: en
keywords: H662 - Control by light systems
date published: 1992-08
date modified: 2026-07-24T01:35:56Z
provider: University of Central Lancashire
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Central Lancashire