Journal of Experimental Botany, Vol 49, 547-553, Copyright © 1998 by Oxford University Press
L Miguel, N Longnecker, W Ma, L Osborne and C Atkins
Although the basal and uppermost lateral branches of Lupinus
angustifolius L. frequently grow and contribute to yield, buds
formed in the axils of leaves 6-12 (referred to as middle buds) rarely
grow. This may be due to an inherent limitation of these buds, or some form
of apical dominance or competition imposed by the plant. The hypothesis
that middle buds have the full capacity to grow, but remain suppressed on
intact plants was tested. The main stem apex and buds from the axils of
leaves 1 and 8 (bud 1 and bud 8) were excised and cultured on sterile agar.
The buds were removed from culture and weighed every 2-3 d for 21 d. The
growth rate of apices from the main stem was approximately 5.8 mg
d-1, compared to 2.4 mg d-1
for bud 1 and 0.9 mg d-1 for bud 8. Buds in the
axils of leaves 6-10 on intact plants were painted six times with a
synthetic cytokinin, benzylaminopurine, from 40 d after sowing. This
promoted rapid elongation and thickening of these buds, visible as early as
5 d after painting began. The rapid growth of these branches was associated
with a reduction in the length of the remaining branches on the plant.
However, excision of lower branches did not increase the growth of the
middle buds. It is concluded that buds 6-12 of Lupinus
angustifolius L. have a partial potential to grow. This
potential appears to be limited by innate factors in the bud, and may be
structural and/or hormonal. The limitation appears to develop very early in
the plant, and potential growth is not modified by subsequent nutrition of
the plant.Keywords: Apical dominance, cytokinin,
branching, Lupinus angustifolius.
ARTICLES
Branch development in Lupinus angustifolius L.#I. Not all branches have the same potential growth rate
Centre for Legumes in Mediterranean Agriculture, University of Western Australia, Nedlands, WA 6907, Australia; Soil Science and Plant Nutrition, University of Western Australia, Nedlands, WA 6907, Australia; Botany Department, University of Western Australia, Nedlands, WA 6907, Australia; Corresponding author; E-mail: Imiguel@cyllene.uwa.edu.au
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