Journal of the Department of
Agriculture, Western Australia,
Series 4
Volume 31
Number 2 1990
Article 6
1-1-1990
Plant growth and survival in saline, waterlogged
soils
Ed Barrett-Lennard
[email protected]
Neil Davidson
Richard Galloway
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Recommended Citation
Barrett-Lennard, Ed; Davidson, Neil; and Galloway, Richard (1990) "Plant growth and survival in saline, waterlogged soils," Journal of the
Department of Agriculture, Western Australia, Series 4: Vol. 31 : No. 2 , Article 6.
Available at: http://researchlibrary.agric.wa.gov.au/journal_agriculture4/vol31/iss2/6
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Plant growth and
survival in saline,
waterlogged soils
By Ed Barrett-Lennard1,
Neil Davidson 2 and
Richard Galloway 2 ,
Division of Resource
Management
1
Research Officer, Albany
Research and Technical
Officers respectively,
South Perth
2
Waterlogged soils in Western Australia are often
These saltbushes were growing in a paddock at Narrogin. In the
foreground, a marsh saltbush fAtriplex paludosa.) has become
salt-affected. Recent research has shown that the
interaction between waterlogging and salinity has a bleached and died. In the background, a grey saltbush (A.
cinerea) has survived.
far greater adverse effect on plant groivth and
survival than either of these two factors individually.
Plants need oxygen to break down carbohydrate
reserves within their roots to produce the
The consequences of the combined effects of salt and
energy
needed for exclusion of salt, root
waterlogging for most plant species are increased
growth
and absorption of nutrients.
salt uptake, reduced growth, chlorosis (yellowing of
leaves), defoliation, and death.
The most important effect of waterlogging is to
greatly decrease the oxygen concentrations in
Salt sensitive agricultural species (nonhalophytes)
the root zone. Lack of oxygen at the roots leads
are more severely affected by this interaction than
to anaerobic respiration of these carbohydrates
salt tolerant species (halophytes).
and a 95 per cent decrease in the production of
energy. This causes increases in salt uptake and
decreases in:
•
•
•
root growth and survival;
nutrient uptake; and
water uptake
Increased salt uptake and decreased water
absorption play a crucial role in the death of
plants growing on waterlogged saline land.
This will be discussed more fully below. For
further information on the effects of waterlogging on root growth and survival, and decreases in nutrient uptake, see 'Waterlogging:
how it reduces plant growth and how plants
can overcome its effects' on page 51.
56
W./4 JOURNAL OF AGRICULTURE Vol31,1990
Salt sensitive (nonhalophyte) species
Agricultural plants survive and grow in mildly
saline soils by excluding salt from their tissues,
but the roots need energy to do so.
Wheat roots growing in mildly saline soils use
about 2 to 3 per cent of their total energy
requirements to exclude the sodium in salt
from the root tissues. However, in waterlogged
conditions (when the available energy declines
by 95 per cent) there is insufficient energy to
exclude the sodium. Sodium concentrations
build u p to toxic levels in the shoots.
Rice is one of the few crop species that grows
in a mildly saline, waterlogged environment
and has not shown increased salt uptake. In
rice, maintenance of salt exclusion coincides
with the formation of air channels
(aerenchyma) inside the root which enables it
to avoid an oxygen deficiency.
An increase in the amount of salt reaching the
plant shoot can have dramatic adverse effects
on the growth and survival of nonhalophytes.
In the short term, there is a decrease in growth
followed by chlorosis (yellowing) of the leaf
and leaf senescence.
In the longer term, the accumulation of salt
results in progressive shoot death.
In wheat, a combination of mild levels of
salinity (electrical conductivity 200 milliSiemens per metre) which would not normally
have any adverse effect on yield and waterlogging was sufficient to kill plants after 33 days.
Lack of oxygen to the roots results in death of
root tips and a progressive decline of the whole
root system. At the same time the roots absorb
less water and the shoot dehydrates.
Salt tolerant (halophyte) species
weeks of waterlogging. A. nummularia (old
man saltbush) died after five weeks, while A.
amnicola (river saltbush) and a hybrid between
A. amnicola and A. nummularia were still apparently undamaged after eight weeks of waterlogging. It appears that saltbushes are more
efficient at regulating salt uptake under
waterlogged conditions than many nonhalophytes.
However, saltbushes do not develop
aerenchyma and the root tips eventually die in
waterlogged soils. When the root tips stop
working properly they take up less water, and
water deficit (physiological drought) develops
in the shoots. At the same time there is a rapid
decrease in shoot growth, closure of leaf
stomata, decreases in transpiration and photosynthesis, wilting of the leaves, and finally,
death of the plant.
Further reading
Barrett-Lennard, E.G.
(1986). Effects of waterlogging on the growth and
sodium chloride uptake by
vascular plants under saline
conditions. Reclam. Reveg.
Res. 5:245-261.
Barrett-Lennard, E.G.
(1986). Wheat growth on
saline waterlogged soils. /.
Agric. W. Aust. 27(4): 118119.
There is some evidence to suggest that the
more sensitive species also become bleached
(lose their chlorophyll) before death. This may
be caused by photo-oxidation of the chlorophyll once stomata close. In this case, loss of
photosynthesis and depletion of carbohydrate
reserves may hasten death.
Lane, L. and George, R.
(1986). Drainage of saline
and waterlogged soils. W.
Aust. Dept Agric. Farmnote
No.45/86.
Malcolm, C. V. (1986).
Saltbush management selecting forage plants for
saltland. W. Aust. Dept.
Agric. Farmnote No. 32/86.
Productivity and waterlogging
Productivity of both nonhalophytes and
halophytes can be improved substantially by
reducing waterlogging. This can be done by:
• reducing water flow onto saltland (using
interceptor drains and increasing water use on
hillsides planted with perennial pastures,
shrubs and trees);
• improving the drainage of saltland (using
drains and groundwater pumping);
• maximizing water use on saltland (growing
vigorous pastures and shrubs); and
• growing plants in elevated positions (on
beds).
Halophytes do not exclude all salt. They absorb
some salt and store it in compartments within
their cells. This reduces the desiccating effect of
high salt concentrations in the external environment and enables them to grow in soils
more saline than seawater.
Piggott, M. (1988). Saltbush
gives new hope for salt
scalds. Farm, June 1988. pp
15-17.
Effects of waterlogging and
salinity on wheat.
Although halophytes often grow naturally in
waterlogged environments, little is known of
their growth in saline, waterlogged soils.
Our research indicates that saltbush (Atriplex)
species are relatively tolerant of waterlogging
in mildly saline soils.
Considerable differences exist between species.
Atriplex paludosa (marsh saltbush) and A. bunburyana (silver saltbush) were killed after four
W.A. IOURNAL OF AGRICULTURE Vol. 31.1990
57