10-March-2008 SEARCA News Release
One may ask, why salt (NaCl)? This is because salt stress or salinity is one of the major soil problems arising due to climate change and bad agricultural practices.
Rice, being a staple crop in the country, was studied to characterize
its responses to salt stress. Sixteen varieties of rice were initially
studied to find out the effects of salt stress. The study used 14-21
day-old seedlings since earlier studies showed that these are the ones
most sensitive to salinity.
The seedlings were observed in terms of their metabolic and growth
responses after two weeks of salt introduction. Results divided the 16
varieties into two categories: 1) salt-tolerant varieties (e.g.,
Pokkali, IR651, IR4630, and others) and 2) salt-sensitive varieties
(e.g., IR29, Hitomebore, Bankat).
It was found that salt-sensitive varieties suffer from nutrient
imbalance because of high sodium (Na) and potassium (K) content. There
was also a decrease in superoxide dismutase, an enzyme which acts as
scavenger of superoxide radical. Superoxide can cause damage to lipids
and protein which leads to membrane damage. The high salt
concentrations also decreased water potential thus seedlings are not
able to absorb water.
On the other hand, in the salt-tolerant varieties, it was found that
their stomata closed preventing them to absorb the salt. This
phenomenon occurred because of a chemical signal in the root known as
the abscisic acid. The abscisic acid acts as a trigger to close the
stomata during initial salt introduction thus, protecting these rice
varieties from salinity.
In light of current challenges in climate change, it is really
important to study and develop rice varieties tolerant to salinity. The
Philippines is after all, a rice-eating country. (Ranell Martin M.
Dedicatoria, KMU)
______________
1 Paper presented by Dr.
Maribel L. Dionisio-Sese, Institute of Biological Sciences, College of
Arts and Sciences, University of the Philippines Los Baņos during the
SEARCA Agriculture and Development Seminar Series (ADSS): Sustaining
Rice Agriculture through Physiological Profiling of Rice Cultivars for
Salt Tolerance. 4 March 2008
