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A study of some factors associated with aluminium uptake by three plant species

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Huett, DO (1979) A study of some factors associated with aluminium uptake by three plant species. PhD thesis, University of Tasmania.

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Abstract

Growth of many plant species may be limited in acid soils by
aluminium excess which may be alleviated by applications of lime
(calcitic or dolomitic) and phosphate fertilizers. The nature of
the aluminium response is not fully understood because the factors
associated with low pH-aluminium excess on plant growth and the
processes involved in aluminium uptake are not completely documented.
The aim of this project was to examine these factors and provide
evidence which would account for aluminium uptake and translocation
using three plant species, cabbage (Brassica oleracea var. capitata
(L.) Alef. cv. Ballhead hybrid), lettuce (Lactuca sativa L., cv.
Pennlake) and kikuyu (Pennisetum clandestinum Chiov. cv. Whittet).
Aluminium uptake by excised roots consisted of two phases, rapid
adsorption where most of the calcium was exchanged, followed by a slow
accumulation phase that was pronounced for cabbage and lettuce and
almost absent for kikuyu. Aluminium uptake in Phase I was considerably
higher at pH 4.2 than at 4.0; this could have resulted from a
decrease in net charge per aluminium atom, which could be expected
at the higher pH. Greater dissociation of carboxyl groups at the
higher pH may have also contributed to higher aluminium uptake.
The effect of temperature and a metabolic inhibitor indicated
that the entire uptake process was non-metabolic.
Succinic-tartaric acid buffer desorbed most of the aluminium
from roots. The small amount remaining was either associated with
the cytoplasm and/or irreversibly bound to exchange sites.
EDX-analyses (cell wall region) of freeze-fractured, dried
roots from all species demonstrated that aluminium was present in
all tissues throughout the epidermis, cortex and stele and along the entire length of roots. The highest concentrations were
recorded in the epidermis followed by the cortex. Aluminium
was also recorded in the stele and in the protoplasm of
cortical cells for all species. The distribution was consistent
with transport in the symplasm where aluminium was present in
the radial wall(cytoplasm) of the endodermis and also with
passive movement through meristematic cells hence pypassing
the barrier at the endodermis. High calcium application reduced
aluminium levels in the protoplasm of some xylem parenchyma
and cortical cells. There was a poor correlation between
aluminium and phosphorus levels in the cell walls of all
tissues.
Th~ yield of roots and tops of kikuyu, in contrast to
cabbage and lettuce, was relatively unaffected by low pH
(4.0 vs. 4.6) and aluminium compared with the yield of control
plants. The control treatment level of calcium was markedly
lower and the magnesium level markedly higher for kikuyu
compared with cabbage and lettuce.
The tolerance of kikuyu to aluminium was not associated
with lower alu~inium levels of roots than cabbage and lettuce
but was associated with significantly lower levels of tops.
Aluminium levels of roots were higher at pH 4.6 than 4.0 which
was consistent with the excised root results. Results for
tops were also consistent for all species where levels were
lower at the higher pH. High calcium application had no
effect on aluminium levels of roots but reduced levels of
tops. This supports the previous results where calcium had
little effect on aluminium adsorption during Phase I, but reduced accumulation during Phase II where passive movement
into the cytoplasm and transport to the stele occurs.
High calcium increased the root yield of cabbage and
lettuce and reduced top yield of kikuyu. This treatment
overcame the inhibitory effect of aluminium on the root
and top yield of cabbage and the root yield of lettuce.
The magnesium levels of roots and tops were reduced by
high calcium for all species.
Aluminium increased phosphate levels of roots for cabbage
and kikuyu, but had no consistent effect on levels of tops.

Item Type: Thesis (PhD)
Keywords: Plants, Soils, Botanical chemistry
Copyright Holders: The Author
Copyright Information:

Copyright 1979 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, 1980.

Date Deposited: 19 Dec 2014 02:24
Last Modified: 28 Mar 2017 05:48
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