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Reproductive development in Pisum : the role of genes Sn and Lf


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Duchene, Christiane 1984 , 'Reproductive development in Pisum : the role of genes Sn and Lf', Unspecified thesis, University of Tasmania.

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The influence of the flowering genes Sn/sn and Lfd/Lf/lf/lfa on postinitiation
reproductive events in Pisum was examined using pure lines and
two specially selected near-isogenic lines in the case of the Sn/sn difference
and pure lines and segregating progenies in the case of the Lf series.

From a comparison of lines 299+ (Sn, early photoperiodic) and 299- (sn,
early day neutral) in short day conditions, it was found that gene Sn
slowed the rate of flower bud, pod and seed development, prolonged flower
life-span and increased the number of pods per raceme. Sn also promoted
vegetative growth by delaying the onset of apical arrest and increasing the
tendency to produce lateral branches. The delay in growth of the proximal
pod at the first reproductive node remained even when the distal flower was
excised at this and all subsequent nodes. The delay was therefore not a
consequence of raceme ontogenesis. In contrast, removal of the apical bud
immediately above the node bearing the first pod partly eliminated the effect
of the Sn/sn difference on pod growth. By comparing genetically male sterile
with fertile plants in a segregating progeny, it was found that flower lifespan
was substantially extended in the absence of fertilisation. However,
when the growth of Sn and sn pollen tubes was examined in vivo with the aid
of fluorescence microscopy, no difference in the rate of growth could be
demonstrated for the two genotypes. Hence, the increased life-span in Sn
flowers does not appear to be a consequence of slower pollen tube growth.
Since short days increased the interval between flower initiation and open
flower in Sn plants but not sn plants, this interval is neither independent
of photoperiod nor genotype in Pisum.

The effect of the Lf series was examined on a day neutral background.
The rate of flower bud development and pod growth was slightly promoted as
the sequence lfa , lf, Lf and Lfd was ascended, i.e., as the time to flower
initiation was delayed, and the promotion in reproductive growth appears to
be a consequence of the delay in time to initiation. It is suggested that
the underlying metabolism is, at first, strongly geared toward vegetative
growth but that it becomes more favourable to reproductive growth with the
passage of time. In contrast, Sn appears to interfere with the metabolic
pathway, probably by delaying the time at which autonomous changes in the
underlying metabolism occur. Sn may act by controlling assimilate partitioning
within the shoot system.

One of the crosses used to examine the effect of an Lfd/lf segregation
also permitted the effect of segregation for the flowering gene pair Hr/hr
to be studied on an Lfd sn background for the first time. Although many
of the Lfd segregates initiated their first flower at node 20 or higher, no
significant effect of segregation for Hr/hr could be detected. It seems
therefore that sn remains epistatic to Hr in these circumstances.

Item Type: Thesis - Unspecified
Authors/Creators:Duchene, Christiane
Keywords: Peas
Copyright Holders: The Author
Copyright Information:

Copyright 1984 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 (M.Sc.) - University of Tasmania, 1985. Bibliography: leaves 108-116

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