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Scarcity
of sufficient amount of canal water for irrigation compelled the farmers to
irrigate their crops with tube well water. The quality of ground water is
deteriorating day by day due to rapid industrialization and urbanization.
According to estimation about 70-75% of ground water that is being pumped
out in Pakistan is brackish in nature.
The continuous use of this water for
irrigation leads to develop soil salinity which severely affects the
physiological processes of plants. These adverse effects of salinity may be
attributed to non-availability of water, disturbance in nutrient uptake
causing deficiency and ion-toxicity to plants. Salinity and sodicity
stresses are ever-present threats to crop yields, especially where tube well
irrigation is an essential aid to agriculture.
It has been noticed that when the
plant is under salinity stress then its ethylene (a growth hormone)
production is increased. No doubt it is required for the optimal production
of plant but up to certain limit. After that it has inhibitory effect on the
plant growth and development. Ethylene is produced in plants by the
following mechanism:
L-Methionine
Adenosylmethionine (SAM)
1-aminocyclo propane-1-carboxylate
(ACC)
Ethylene NH3
+ α-ketoglutaric acid
As plant has not any mechanism to stop
this excessive ethylene production during salt stress and ultimately yield
is reduced. But nature has gifted us certain soil microbes that have an
enzyme ACC-deaminase which utilize the ACC (an immediate precursor of
ethylene) as an energy source and cleavage it to NH3 and α-ketoglutaric
acid. Treating of such microbes with crops jut prior to planting
significantly reduced the salt stress in plants.
In an experiment on maize crop
irrigated with brackish water [EC, 5dSm-1; SAR, 10 (mmol L-1)1/2]
we have seen that plants treated with microbes having ACC-deaminase
activity, increased the crop yield up to 30 % over untreated plant. Thus
this is one of the promising techniques to use brackish water for
sustainable crop production in agriculture.
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