Abscisic acid and other hormonal effects on growth in Spirodela.
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Date
1969
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Abstract
The effects of abscisic acid In particular, as well well as gibberellic acid and the cytoklnlns, 6-benzyladenine,
kinetin, and 6-dlmethylal lalylamlnopurine, on the growth of
Spirodela oligorrhiza were investigated.
Abscisic acid effectively arrested growth permanently
at concentrations down to 10¯¹ mg/I. Normal
growth tended to be resumed at concentrations of 10¯² and
10¯³ mg/l between nine and twelve days after treatment.
A concentration of 10[-8] mg/l, however, resulted in a significant
increase in dry weight at both eight, nine and twelve
days after introduction into the culture medium. It is
suggested that the resumption of growth twelve days after
treatment at those concentrations which inhibit growth up
to nine days, was due to a possible progressive inactivation
of abscisic acid resulting in a lowering of its concentration
to a level that is promotive.
It was furthermore found that the growth response
of Spirodela in terms of dry weight production over a period of eight days is proportional to the log[10] concentration of
abscisic acid. It is suggested that this curve can be used
as a relatively reliable and easily performed bioassay to
detect amounts of abscisic acid as low as 10[-5] μg. The
assay is more reliable over the range 0.01 to 10,000 μg and
appears not to be affected by gibberellin, benzyladenine and
kinetin.
The inhibitory effect of abscisic acid on growth
in Spirodela was shown to be reversed by benzyladenine,
kinetin and dimethylallalylaminopurine, although they were
not equally effective in doing so. Benzyladenine at 1.0 mg/l
was the most effective In overcoming growth inhibition by
abscisic acid. Gibberellic acid, however, proved ineffective
in reversing the inhibitory effect of abscisic acid on
Spirodela oligorrhiza. The apparent Increases in growth
obtained in some cases may have resulted more directly from
gibberellic acid stimulation than from the Interaction of
gibberel lie acid with abscisic acid.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1969
Keywords
Growth (Plants), Plant hormones., Theses--Botany.