Responses of sensitive and tolerant genotypes of rice (Oryza sativa L.) to salt stress

Date

10-2007

Degree

Bachelor of Science in Biology

Major Course

Major in Cell Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Merlyn S. Mendioro

Co-adviser

Abdelbagi M. Ismail

Abstract

The responses of one sensitive (IR29) and two tolerant (IR65192 and FL478) rice genotypes based on growth analysis(green leaf area, shoot length. root length). physiology (Na*, K', IC/Na+), biochemistry [GIutathione reductase(GR) activity. reduced ascorbate (AsA), malondialdehyde (MDA)] and gene expression of DHARI and RGRC2 were observed under salt stress condition (120mM NaCI or EC=12 dStn't ). Using the Standard Evaluating System (SES) of IRRI after 18 days of salinization, IR29 was indeed highly susceptible while FL478 and IR651 were tolerant. Salt stress decreased green leaf area, shoot length, and root length with 1R29 showing dramatic reduction. FL478 had the most superior growth and biomass production under NaCI stress which helped the plant in diluting the salts beyond its toxic level. IR29 had highest accumulation of Na' in the shoots (171% of the control). No significant increase in shoot Na' was noted in tolerant genotypes under 12dSm-I. However. IR651 (198.4% of the control) exhibited the highest increase in root Na'. Maintenance of lower Na' in the shoots and storage of higher Na' in the roots in the tolerant genotypes mitigates Na' toxic effects by means of exclusion. Salinity significantly reduced the K' in the roots. This may suggest that high Na' concentration displaces the K4 in the roots. K'/Na' in the shoots is positively associated with salt tolerance. 1R29 exhibited the most pronounced increase in malondialdehyde content (31.3% of the control). 1R651 showed the highest ascorbate content (159.3 ug FW) concentration and the lowest MDA increased (12.92% of the control). At 144 hours after salinization. 1R651 exhibited the highest increase in glutathione reductase activity (187.3% of the control).The inefficient GR activity of IR29 resulted in decrease AsA and increase membrane damage. Results showed that tolerant genotypes, particularly IR651, have more efficient antioxidative system and salt exclusion mechanism which protected them against the adverse effects of salt-induced oxidative stress.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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