ISSN 10214437, Russian Journal of Plant Physiology, 2011, Vol. 58, No. 3, pp. 394–401. © Pleiades Publishing, Ltd., 2011.
Salinity is one of the major environmental stresses
that adversely affect plant growth and metabolism .
The problem becomes more acute where soil salt con
tent is naturally high because precipitation can be
insufficient for salt leaching, due to the irrigation with
saline water, or the usage of uncultivable saline/sodic
soils to fulfill the demand of the increasing population
all over the world. Salt stress affects plant physiology at
both wholeplant and cellular levels through osmotic
and ionic stress effects .
Growth of green plants is dependent on photosyn
thesis. However, the rate of photosynthesis varies with
the change in environmental factors, thereby affecting
plant growth . Salinity stress results in the suppres
sion of plant photosynthesis due to stomatal and non
stomatal factors, the latter are not yet fully understood
. At stomatal level, the plant reduces stomata aper
tures to prevent injuries. As a result, net photosynthe
sis is unavoidably reduced due to a decrease in
availability, which potentially damages the photosyn
thetic apparatus .
This text was submitted by the authors in English.
Maize, being preferably crosspollinated, has
become highly polymorphic in the course of natural
and domesticated evolution, and thus it manifests
enormous variability for salinity tolerance . Excess
leads to the appearance of symptoms
like those at nitrogen or potassium deficiency. Saline
environment is generally deficient in nitrogen .
Nitrogen, in one form or another, accounts for about
80% of total mineral nutrients absorbed by plants.
) and ammonium (
) ions are most
abundant nitrogen sources for higher plants, and their
availability usually constitutes a limiting factor for
plant growth . Salinity significantly suppresses dry
matter production. A significant negative correlation
between the concentrations of
in the shoots or roots. The reduction in
could occur due to the high
content in the saline
soil. However, supplementing soil with nitrogen
improved plant growth and yield and thus their salt
An increased N supply stimulates the photosyn
thetic capacity of leaves via increases in the contents of
stromal and thylakoid proteins in leaf chloroplasts.
The ability of plants to assimilate
is, in part, a
function of the rate of electron transfer, and therefore
Nitrogen Application Improves Gas Exchange
Characteristics and Chlorophyll Fluorescence
in Maize Hybrids under Salinity Conditions
, M. Y. Ashraf
, M. Jamil
, R. M. Iqbal
, M. Nafees
, and M. A. Khan
University College of Agriculture and Environmental Sciences, The Islamia University of Bahawalpur, Pakistan;
Nuclear Institute for Agriculture and Biology (NIAB), P.O. Box 128, Jhang Road Faisalabad, Pakistan
Received January 21, 2010
—The understanding of crop physiological responses to salinity stress is of paramount importance
for selection of genotypes with improved tolerance to this stress. Maize (
L.) hybrids Pioneer 32B33
and Dekalb 979 were grown in pots and subjected to three levels of salinity under four nitrogen levels to deter
mine the role of nitrogen under saline conditions. Salinity stress effects on gas exchange characteristics and
chlorophyll fluorescence of maize hybrids were evaluated under semicontrolled conditions. Under salinity
stress, the changes in the net photosynthetic rate (
), stomatal conductance (
), and transpiration rate (
were similarly directed: all decreased and were lower than in control at the higher salinity level (10 dS/m).
Water use efficiency was increased with increasing salinity since transpiration was stronger depressed by salt
than photosynthesis. Plants subjected to the lower level of salinity did not differ from control in tested char
acteristics. Nitrogen application ameliorated the effects of salinity.
Keywords: Zea mays
, salinity stress, nitrogen, leaf gas exchange, chlorophyll fluorescence.