PLANT PHYSIOLOGY , Vol 113, Issue 3 981-985, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Diurnal Fluctuations in Ethylene Formation in Chenopodium rubrum
I. Machackova, N. Chauvaux, W. Dewitte and H. van Onckelen
De Montfort University, Norman Borlaug Centre for Plant Science, Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Ke dvoru 15, 166 00 Praha 6, Czech Republic (I.M.)
Ethylene formation was studied in 5- to 6-d-old Chenopodium rubrum
seedlings under the following light regimes: continuous light (CL),
continuous darkness (CD), and alternating light/darkness (12 h of each). No
significant regular oscillations in ethylene formation were found in either
the CL or CD groups. In the light/dark regime, pronounced diurnal
fluctuations in ethylene formation were observed. Activity of
1-aminocyclopropane-1-carboxylic acid (ACC) oxidase was transiently
increased on transfer from light to dark and vice versa. In CL, ACC oxidase
activity did not change significantly, whereas in CD, it decreased
continuously after the initial increase. The in vivo levels of ACC and
N-malonyl-ACC (MACC) were constant for the first few hours of darkness,
then decreased dramatically, but increased again in the light. In constant
darkness, the level of ACC displayed endogenous rhythm, with minimum values
at h 12 and 44, and a maximum value at h 32 to 36. The level of MACC in
both shoots and roots decreased in the CD group until h 12, and then
remained constant until h 30 before decreasing continuously. We conclude
that the photoperiodic regime affects both ACC and MACC levels, as well as
the conversion of ACC to ethylene. Correlation of the described changes in
ethylene formation to photoperiodic flower induction is discussed.
