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Desensitization and recovery of phototropic responsiveness in Arabidopsis thalianaPhototropism is induced by blue light, which also induces desensitization, a partial or total loss of phototropic responsiveness. The fluence and fluence-rate dependence of desensitization and recovery from desensitization have been measured for etiolated and red light (669-nm) preirradiated Arabidopsis thaliana seedlings. The extent of desensitization increased as the fluence of the desensitizing 450-nm light was increased from 0.3 to 60 micromoles m-2 s-1. At equal fluences, blue light caused more desensitization when given at a fluence rate of 1.0 micromole m-2 s-1 than at 0.3 micromole m-2 s-1. In addition, seedlings irradiated with blue light at the higher fluence rate required a longer recovery time than seedlings irradiated at the lower fluence rate. A red light preirradiation, probably mediated via phytochrome, decreased the time required for recovery from desensitization. The minimum time for detectable recovery was about 65 s, and the maximum time observed was about 10 min. It is proposed that the descending arm of the fluence-response relationship for first positive phototropism is a consequence of desensitization, and that the time threshold for second positive phototropism establishes a period during which recovery from desensitization occurs.
Document ID
Document Type
Reprint (Version printed in journal)
Janoudi, A. K. (Michigan State University-Department of Energy Plant Research Laboratory East Lansing 48824-1312)
Poff, K. L.
Date Acquired
August 21, 2013
Publication Date
January 1, 1993
Publication Information
Publication: Plant physiology
Volume: 101
ISSN: 0032-0889
Subject Category
Life Sciences (General)
Funding Number(s)
Distribution Limits
NASA Program Space Biology
NASA Discipline Number 40-50
NASA Discipline Plant Biology
Non-NASA Center