Autumn Features
Following is an article
about plants and
nutrients. This will be in four instalments over the next four issues
of the
Newsletter. The first part is an introduction, the second part will be
on root
adaptations, the third part symbiotic adaptations and the fourth part
on
parasitic and carnivorous plants.
An
overview of the
specialized mechanisms used by Australian plants for nutrient uptake
Introduction
Plants require nutrients in order to carry out
the physiological and biochemical processes necessary for growth and
reproduction. The soils of Australia
are generally low in nutrients particularly phosphorus and nitrogen.
Consequently plants utilise a number of mechanisms to overcome the
challenges
of nutrient deficient soils.
The root systems of plants are specialized
organs adapted for the function of nutrient up take. Plants living in
low
nutrient soil have evolved specific root morphologies and physiology to
overcome these deficiencies They may also form symbiotic relationships
in order
to enhance nutrient uptake, (such as mycorrhizal fungus or bacteria).
Some plants utilise even more specialized
strategies to obtain their nutrients. These are the parasitic plants
(which
parasitise other plants) and carnivorous plants (which obtain some or
most of
their nutrients from insect prey).
Nutrient
needs of plants
Apart from the intake of CO2,
and H2O during photosynthesis, plants also require other
nutrients
for the physiological and metabolic processes of growth, sustainability
and
reproduction. These are generally divided into the macronutrients
(nutrients
required in relatively large amounts) N, P, S, K, Mg, Ca and the
micronutrients
or trace elements, (nutrients required in relatively small amounts) Mn,
Zn, Cu,
Mo, B, Cl and Fe.
After C, O and H, Nitrogen is the most
abundant element in plants and growth is limited by its supply. In Australia,
phosphorus(P) is seen as most limiting as many Australian soils are low
in
phosphorus. P is unavailable to the plant from the parent soil. That
is, P is
either bound to other elements, insoluble in water or is bound to soil
particles. P must therefore be converted into forms available to the
plant, HPO42-
or H2PO4- (phosphate).
Apart from N and CO2
(which is
taken in via the leaves) mineral nutrients are derived from the soil
and
assimilated or ‘taken up’ by the roots of plants, which are
specifically
adapted for this process. Leaves can also take up nitrogen, but in
plants
growing in nitrate-poor soils most of the nitrogen is assimilated by
the roots.
Low
Nutrient Soil
Much of the Australian land mass is very
old and has been relatively untouched by the rejuvenating effects of
glaciation. As the last major period of glaciation occurred 250 Ma
during the
Permian, much of the soil has been leached of nutrients and
consequently
Australian soils are extremely infertile.
A distinguishing feature
of Australian
vegetation is its scleromorphy* and this is generally seen as an
adaptation to
soil nutrient deficiency rather than a lack of water. The low
phosphorus soil
levels in Australia are seen as limiting not only due to its essential
role in
the metabolism and structure of plants but also because soil
phosphorous levels
regulate nitrogen fixation.#
Aridity and acidity are
common conditions
experienced in Australian soils. The availability of many soil
nutrients is
dependent not only on water availability and temperature, but also on
pH. In
order to overcome these limitations the plants of Australia have adopted a
diverse
range of mechanisms to assist in nutrient uptake.
* Scleromorph: a plant whose leaves (or stems, if
leafless) are hard in texture, usually having a thick cuticle.
# Nitrogen fixation: the bacterial process which makes
soil nitrogen in a form which can be absorbed by the roots.
Table 1. Macro- and micronutirents essential for plant function.
|
Element
|
Taken up as
|
Function in Plant
|
|
Macronutrients
|
|
N
|
NO3-, NH4+
|
In amino acids, proteins, nucleic acids, nucleotides,
chlorophyll. Essential component of protoplasm and enzymes
|
|
P
|
HPO42-, H2PO4-
|
In ATP, ADP (molecules providing energy to cells),
Nucleic acids, necessary for phosphorylation
|
|
S
|
SO42-, SO2
|
In proteins, coenzymes, some amino acids
|
|
K
|
K+
|
In enzymes, amino acids, protein synthesis, regulation of
hydration, membrane potential, osmoregulation, enzyme activation,
stomatal movement
|
|
Mg
|
Mg2+
|
Part of chlorophyll and pectates, enzymes, ribosomes
|
|
Ca
|
Ca2+
|
In pectates, cell walls, enzymes, cell permeability,
regulator of membrane and enzymes activities
|
|
Fe
|
Fe2+, Fe3+
|
Component of enzymes
|
|
Micronutrients
|
|
Mn
|
Mn2+
|
Cofactor/activator of enzymes, stabilises chloroplast
structure
|
|
Zn
|
Zn2+
|
Component/activator of enzymes, shlorophyll formation
|
|
Cu
|
Cu2+
|
Component/activator of enzymes
|
|
Mo
|
MoO42-
|
Component of enzymes, in nitrogen fixation and reduction
|
|
B
|
HBO32-, H2BO3-
|
Influences Ca2+ utilization, bound to carbohydrates
|
|
Cl
|
Cl-
|
In photosynthesis, osmosis and ionic balance
|
Table 2. Abbreviations
|
Abbreviations
Macronutrients
|
Micronutrients
|
|
C
=
Carbon
|
Mn
=
Manganese
|
|
H
=
Hydrogen
|
Zn
=
Zinc
|
|
O
=
Oxygen
|
Cu
=
Copper
|
|
N
=
Nitrogen
|
Mo
=
Molybdenum
|
|
P
=
Phosphorus
|
B
=
Boron
|
|
S
=
Sulphur
|
Cl
=
Chlorine
|
|
K
=
Potassium
|
Fe
=
Iron
|
|
Mg
=
Magnesium
|
Ni
=
Nickel
|
|
Ca
=
Calcium
|
|
Back
to top
PRESS RELEASE
THE FLOWERS WILL BLOOM IN THE SPRING TRA LA
An unlikely shower has fallen on hundreds of native plants, many endangered from potential extinction through global warming, in the form of a ‘gift’ from the Federal Government.
The Federal Member for Macquarie, Kerry Bartlett M.P. recently advised the Committee and Volunteers of the wildplant and rescue organisation of some very welcome news.
The Katoomba based, Blue Mountains Wildplant Rescue Service Inc has been endorsed as a Deductible Gift Recipient by the Australian Taxation Office allowing all future donations to this essential service be tax deductible.
The fund to be known as the Blue Mountains Wildplant Rescue Fund will be chaired by local Katoomba resident, Geoffrey Weule.
‘This is a major breakthrough for the Wildplant Rescue Service’, Mr. Weule said. ‘For the past ten years it has been a real struggle making ends meet however this new Federal Government concession is a great boost for us and hopefully it will now attract a new level of funding, so vital for us to carry out our very important environmental and preservation work’.
Mr Weule, senior lecturer in Business Studies at the Western Sydney Institute of TAFE, Nirimba Campus, hopes that not only local businesses but businesses right across Australia together with members of the general public will now think seriously about supporting this major community enterprise that is a life-line for some of the world’s most beautiful native endangered plants in a World Heritage environment.
Ms Judy McLean, Treasurer of the B.M. Wildplant Rescue Service said initially they received a grant from the State Government but it fell a long way short in maintaining on-going sustainability, so this news is crucial in maintaining our financial security.
Tax deductible donations, made payable to the Blue Mountains Wildplant Rescue Fund, may be sent to the Fund‘s offices at 14 Oak Street Katoomba 2780.
For further information please contact;
Ms Judy McLean (02) 4782-6233
Email:
info@wildplantrescue.org.au
27th April, 2007
Back
to top
|