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Abstract

A field study recognises three ways in which a forest canopy modifies the incoming
solar radiation to give the light climate on the forest floor. First, it attenuates the
intensity of light. Second , it alters the spectral quality of that light. Third , it
reduces the effective daylength. The ability of photosynthetic species to respond to
each of these was thus examined.
Atherosperma moschatum and Elaeocarpus holopetalus are both shown to
alter their development and carbon exchange characteristics in response to different
light intensities. The carbon exchange characteristics indicate that A. moschatum is
the more shade-tolerant of the two species, a conclusion supported by a field study of
a forest where the two species co-dominate.
A. moschatum is shown to be sensitive to nightbreaks of red/near infrared
irradiation. In the experiment only stem elongation was significantly affected.
Microcystis aeruginosa, a cyanobacterium, changes its carbon exchange and
carbohydrate partitioning characteristics in response to different photoperiods
and
light intensities. The changes seem to relate to light and carbon use efficiencies

under light limited conditions. A. mosqhaium is shown to respond in a similar way
when conditioned to different daylengths, nightlengths and light intensities.
Ananas comosus, pineapple, undergoing crassulacean acid metabolism is
shown to acclimaJe to nightlength in a similar way to A. moschatum. The acclimation
involves changes to both C3 and C4 photosynthetic metabolism.
Within a single sapling of A. moschatum leaves are shown to acclimate to
different light intensities in a manner similar to that shown earlier for comparisons
between plants.
The laboratory results are brought to bear on the developmental variation
shown by saplings of A. moschatum growing in the same forest from which the light
measurements which began this study were taken. The dimensions of leaves and
internodes indicate light to be a major determinant of form within this forest.

Item Type:	Thesis - PhD
Authors/Creators:	Olesen, Trevor(David)
Keywords:	Plants, Plants, Plants, Plant canopies
Copyright Holders:	The Author
Copyright Information:	Copyright 1992 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:	Includes bibliographical references (leaves 88-96). Thesis (Ph.D.)--University of Tasmania, 1993
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