Gas exchange and leaf water status of contrasting rice (Oryza sativa L.) genotypes as affected by salt stress

Abstract

Two genotypes of rice differing in salinity tolerance were used to investigate the effects of salinity on salt accumulation in plant tissue, photosynthesis, gas exchange characteristics and plant water status. Gas exchange measurements were made on the youngest fully expanded leaves of rice seedlings subjected to salt stress of 12 dS m-1 for 15 d. The salt-sensitive cultivar, IR29, showed significantly higher Na+ and lower K+ concentrations in the plant tissue than the salt-tolerant cultivar, IR65192-4B-10-3 (IR65192). IR29 also experienced greater reduction in its growth and gas exchange characteristics such as photosynthesis, transpiration and stomatal conductance, as the stress progresses. Salinity also affected the water balance of the plants as seen in the reduction of the leaf water potential in both genotypes but with IR29 showing a faster and greater reduction in leaf water potential than the tolerant genotype, IR65192, with the duration of the stress. These results imply that shoot salt accumulation exerts a negative effect on rice by lowering photosynthesis, transpiration and stomatal conductance as well as exerting an osmotic stress resulting in lower leaf water potential, and with greater detrimental effects on the intolerant genotype. A few mechanisms seem to underlie the tolerance of IR65192 of salt stress, such as greater capacity to store salt into roots as a consequence of greater root biomass, maintenance of higher K+ uptake and dilution of salt concentration in plant tissue through vigorous growth.

Source or Periodical Title

Philippine Agricultural Scientist

ISSN

317454

Page

40-48

Document Type

Article

Subject

Photosynthesis, Rice, Salt tolerance, Stomatal conductance, Transpiration, Water potential

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