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AN ENDOGENOUS RHYTHM IN THE HILL‐REACTION ACTIVITY OF TOMATO CHLOROPLASTS
Author(s) -
Hoffman Frank M.,
Miller John H.
Publication year - 1966
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1966.tb07369.x
Subject(s) - darkness , rhythm , biology , chloroplast , circadian rhythm , period (music) , light intensity , botany , biophysics , optics , biochemistry , physics , neuroscience , acoustics , gene
When tomato plants are grown under alternating light‐dark conditions there is a diurnal rhythm in the dichlorophenol indophenol–Hill‐reaction activity of chloroplasts isolated from the plants. The activity rises to a peak about 4 hr after the light period begins and then falls, and a second peak occurs during the dark period. When plants grown in alternating light‐dark are placed under conditions either of continuous darkness and constant temperature or of continuous low‐intensity light and constant temperature, the rhythm persists with a period of approximately 12 hr. This rhythm occurs only in plants up to about 4 weeks of age, and no rhythm in Hill‐reaction activity is found in chloroplasts isolated from plants grown under continuous light. However, when continuous‐light plants are placed in continuous darkness a rhythm is initiated which seems to be quite similar to the rhythm observed with chloroplasts from alternating light‐dark plants. Fluctuating temperatures do not replace light‐dark alternation in initiating the rhythm.