Concentrations of oxygen and indole-3-acetic acid in cambial region during latewood formation and dormancy development in Picea abies stems |
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Authors: | Eklund L; Little C; Riding R |
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Institution: | Department of Engineering and Natural Science, Vaxjo University, S-351 95 Vaxjo, Sweden; Canadian Forest Service, PO Box 4000, Fredericton, New Brunswick, E3B 5P7 Canada; Department of Biology, University of New Brunswick, Fredericton, New Brunswick, E3B 6E1 Canada; Corresponding author e-mail: leif.eklund@itn.hv.se |
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Abstract: | To manipulate the occurrence of latewood formation and cambial dormancy in
Picea abies (L.) Karst. stems, potted seedlings were
transferred from the natural environment on 9 July, when tracheids early in
the transition between earlywood and latewood were being produced, and
cultured for up to 5 weeks in a controlled environment chamber having: (1)
Warm LD, (25/15 C during day/night) and long
(16 h) photoperiod, (2) Warm SD, (25/15 C)
and short (8 h) photoperiod, or (3) Cold SD, (18/8°C) and short (8
h) photoperiod. In Warm LD trees, the radial enlargement of primary-walled
derivatives on the xylem side of the cambium, as well as xylem production,
continued at the same magnitude throughout the experiment. In Warm SD and
Cold SD trees, the radial enlargement of primary-walled derivatives
declined and the cambium entered dormancy, both developments occurring
faster in the Warm SD trees. The concentrations of indole-3-acetic acid
(IAA) was higher in developing xylem tissue than in cambium+phloem tissues,
but did not vary with environmental treatment or decrease during the
experimental period. The O2 concentration in the cambial region followed
the order of Cold SD>Warm SD>Warm LD trees and was
<5%, the threshold for the inhibition of IAA-induced proton
secretion, for the first 3 weeks in Warm SD and Warm LD trees. Thus,
neither latewood formation nor cambial dormancy can be attributed to
decreased IAA in the cambial region. Nor does lower O2 concentration in the
cambial region appear to be inhibiting the IAA action that is associated
with cambial growth. |
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