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The involvement of gibberellins with the internode length and flowering genotypes of Pisum


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Potts, Wendy Carmel 1982 , 'The involvement of gibberellins with the internode length and flowering genotypes of Pisum', PhD thesis, University of Tasmania.

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This study was primarily concerned with the involvement of
gibberellins in the control of internode length in a range of genotypes
of Pisum sativum L. Shoots of tall peas (Le) are shown by lettuce
hypocotyl and rice seedling bioassays to contain a relatively large
amount of a polar gibberellin-like substance which is either absent from
or present in only small amounts in dwarf peas (Ls). This biochemical
difference can be attributed to a genetic difference at the Le locus.
Preliminary results using unrelated pure breeding tall and dwarf lines
were confirmed by the use of an F2 progeny segregating for the Le/le
pair of alleles. The polar gibberellin-like substance in shoots of tall
peas is tentatively identified by GCMS-MIM as GA1. In tall peas, the
GA1-like substance is located mainly in the actively growing and
elongating apical region of the shoot. Its level is much reduced in
mature leaf and stem tissue, perhaps explaining the lack of a graft
transmissible effect of the tall and dwarf phenotypes. GA20 is the
major active gibberellin in dwarf peas and the GA20-like substance is
also shown to be located mainly in the apical region of the shoot of
both tall and dwarf peas.
Shoots of the extremely short plants with mutant na are found by
bioassay to contain undetectable levels of gibberellin-like substances.
This is confirmed by the use of near isogenic lines differing at the Na
locus. Results from graft and feed experiments using the gibberellin
deficient na Le and na is plants suggest that the Le gene controls the
conversion of GA20 to the GA1-like compound by promoting
31β-hydroxylation (as evidenced by high activity in the rice seedling
bioassay using cv. Waito C). In contrast to their action in the shoot,
the na and Le genes do not influence the gibberellin-like content of
immature seed, suggesting that the action of genes controlling gibberellin
biosynthesis or metabolism can be organ or tissue specific.
In an F2 progeny, shoots of slender and dwarf segregates show no
large differences in gibberellin content that would explain the large
phenotypic difference. The slender phenotype (la cry8 ) can be mimicked
in dwarf peas with the application of non-limiting quantities of GA3 .
However, as slender peas appear insensitive to changes in gibberellin
levels, it is suggested that genes at the La and Cry loci are influencing
some process at or beyond the activation of the gibberellin receptor
The gibberellin content of a range of different flowering genotypes
was examined to provide evidence for or against a reported link between
the flowering genes Sn and Hr and gibberellin metabolism. The results
do not support the theory that the primary action of these genes is to
control gibberellin metabolism. The results do show an apparent drop in
the level of the GA20-like substance with the onset of apical senescence
in some lines making the comparison of early flowering to later flowering
genotypes difficult.

Item Type: Thesis - PhD
Authors/Creators:Potts, Wendy Carmel
Keywords: Plant hormones, Plant genetics, Growth (Plants), Pisum
Copyright Holders: The Author
Copyright Information:

Copyright 1982 the author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1983. Bibliography: l. 158-170

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