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Evidence of the morphological range, transition and evolution of stomatal protection mechanisms in some selected Proteaceae

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Ratnawati, 2001 , 'Evidence of the morphological range, transition and evolution of stomatal protection mechanisms in some selected Proteaceae', Unspecified thesis, University of Tasmania.

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Abstract

Xero- and scleromorphic adaptations are obviously shown by Australian plants, in
response to the Australian climate and edaphic factors. Since these adaptations
overlap, there are problems separating the two. Some qualitative hypotheses about
the distinction between xero- and scleromorphic characters have been proposed. This
research is an effort to quantitatively determine xeromorphic characters in some
members of the Proteaceae, in order to elaborate upon some of the existing
hypotheses about these characters.
Twenty three species of Banksia, 16 species of Grevillea and 6 species of Orites were
sectioned and observed under the light micrscope and measurements were made of
the stomata! depressions, margin recurvations, cuticle thickness and hair dimensions.
Cuticle peels were made in order to count the number of stomates and hairs on the
leaf surface. From the characters measured the following were calculated: the
depression index (Id), recurved margin index (Irm), epidermis index (le), hair. index
_ (Ih) and cuticle components. The sum totals of the calculations were called the
stomata! protection component (Spc). These data were then analysed using an
analysis of variance with five replicates per species, in order to investigate whether
there were any differences in characters determined .among species observed. Every
index calculated (Id, Irm, Ih, le) and the cuticle components were analysed
separately, with the aim of determining the intensity of the association between the
characters observed and the minimum of the range of habitat annual rainfall, the
maximum of the range ·of habitat annual temperature, the maximum of the range of
habitat daily radiation and the maximum of the range of maximum daily wind run.
An analysis of correlation was applied to these data. A similar method was applied
for observations on juvenile and adult leaves. On the basis of these results the
possible evolution of Banksia is reconstructed.
Results showed that in Banksia species stomata! depression seems to have an
important role protecting the stomates from the effect of habitat climatic factors,
especially from temperature and radiation effects. The presence of recurved margins
and hairs, however, were not as important as stomata! depressions. In Grevillea
species, cuticle characters had a significant role in stomata! protection, particularly
the stomata! and lower epidermis cuticle. A _contradictory finding to that of Banksia
in this genus was that stomata! depression did not contribute to the stomata!
depression. In comparison to the two genera already discussed, Orites was quite
different. However, the hairs had a significant contribution in protecting stomates
from temperature and radiation effects. -
The phenomenon of leaf transition from juvenile to adult in some species observed
showed some performance similarities to plants grown in harsh environments. Banksia
blechnifolia leaves exhibited more intense stomata! depression and denser leaf hairs in
adult leaves. It was assumed that these structures increased stomatal protection from
excessive radiation. Similar growing phenomena were displayed by leaves of Grevillea
pyramidalis. Stomata! depression in this species developed from being not present to
being present and then deepened in later leaves. In addition, leaf hairs showed a
gradual alteration in density from seedling through juvenile and adult leaves.
However, leaves of B. marginata did not show the presence of stomata! depressions
either in juvenile or adult stage. The leaf hairs, however, exhibited similar phenomena
to those found in B. blechnifolia and G. pyramidalis.
The results suggest that stomatal depression, margin recurvation, leaf hairs and
cuticle characters increase stomata! protection either individually or collectively. It
thus can be concluded that there is a possibility that these characters are
xeromorphic when expressed by Banksia, Grevillea and Orites species .

Item Type: Thesis - Unspecified
Authors/Creators:Ratnawati,
Keywords: Proteaceae, Stomata
Copyright Holders: The Author
Additional Information:

For consultation only. No loan or photocopying permitted until December 2003. Thesis (M.Sc.)--University of Tasmania, 2003. Includes bibliographical references

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