KINETIC SEPARATION OF PHOTOTROPISM FROM BLUE‐LIGHT INHIBITION OF STEM ELONGATION

Research output: Contribution to journalArticle

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Abstract

Abstract— These experiments tested the hypothesis that phototropic bending arises when a light gradient across the stem differentially inhibits cell elongation because of direct inhibition of cell elongation by light (the Blaauw hypothesis). Continuous irradiation of dark‐grown cucumber seedlings (Cucumis sativus L.) with unilateral blue light inhibited hypocotyl elongation within 30 s, but did not induce phototropic curvature until 4.5 h after the start of irradiation. Marking experiments showed that curvature began simultaneously at the top and bottom of the growing region. In situ measurements of the light gradient across the stem with a glass fiber optic indicated that a 5‐ to 6‐fold difference in fluence rate was established on the two sides of the stem. The light gradient established at the start of irradiation was the same as that after 6 h of irradiation. Changes in gravitropic responsiveness during this period were also ruled out. Calculations show that the light gradient should have caused curvature which would be detectable within 30 to 60 min and which would extrapolate to the start of irradiation–if the Blaauw hypothesis were correct. The long lag for phototropism in this case indicates that rapid inhibition of cell elongation by blue light does not cause the asymmetrical growth of phototropism. Rather, phototropism is superimposed upon this separate light growth response.

Original languageEnglish (US)
Pages (from-to)745-751
Number of pages7
JournalPhotochemistry and Photobiology
Volume42
Issue number6
DOIs
StatePublished - Jan 1 1985

Fingerprint

phototropism
Phototropism
Scanning Transmission Electron Microscopy
stems
elongation
Elongation
Light
Kinetics
kinetics
Irradiation
Cucumis sativus
gradients
irradiation
curvature
Cells
Hypocotyl
glass fibers
Growth
in situ measurement
Seedlings

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physical and Theoretical Chemistry

Cite this

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abstract = "Abstract— These experiments tested the hypothesis that phototropic bending arises when a light gradient across the stem differentially inhibits cell elongation because of direct inhibition of cell elongation by light (the Blaauw hypothesis). Continuous irradiation of dark‐grown cucumber seedlings (Cucumis sativus L.) with unilateral blue light inhibited hypocotyl elongation within 30 s, but did not induce phototropic curvature until 4.5 h after the start of irradiation. Marking experiments showed that curvature began simultaneously at the top and bottom of the growing region. In situ measurements of the light gradient across the stem with a glass fiber optic indicated that a 5‐ to 6‐fold difference in fluence rate was established on the two sides of the stem. The light gradient established at the start of irradiation was the same as that after 6 h of irradiation. Changes in gravitropic responsiveness during this period were also ruled out. Calculations show that the light gradient should have caused curvature which would be detectable within 30 to 60 min and which would extrapolate to the start of irradiation–if the Blaauw hypothesis were correct. The long lag for phototropism in this case indicates that rapid inhibition of cell elongation by blue light does not cause the asymmetrical growth of phototropism. Rather, phototropism is superimposed upon this separate light growth response.",
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KINETIC SEPARATION OF PHOTOTROPISM FROM BLUE‐LIGHT INHIBITION OF STEM ELONGATION. / Cosgrove, Daniel J.

In: Photochemistry and Photobiology, Vol. 42, No. 6, 01.01.1985, p. 745-751.

Research output: Contribution to journalArticle

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