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Accueil du site → Doctorat → États-Unis → 1978 → PHYSIOLOGICAL RESPONSES TO SODIUM-CHLORIDE STRESSES BY TOLERANT AND SENSITIVE GENOTYPES OF AGROSTIS PALUSTRIS HUDS. AND HORDEUM VULGARE L.

University of Arizona (1978)

PHYSIOLOGICAL RESPONSES TO SODIUM-CHLORIDE STRESSES BY TOLERANT AND SENSITIVE GENOTYPES OF AGROSTIS PALUSTRIS HUDS. AND HORDEUM VULGARE L.

Bhola, Dharam Parkash

Titre : PHYSIOLOGICAL RESPONSES TO SODIUM-CHLORIDE STRESSES BY TOLERANT AND SENSITIVE GENOTYPES OF AGROSTIS PALUSTRIS HUDS. AND HORDEUM VULGARE L.

Auteur : Bhola, Dharam Parkash

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1978

Résumé
The degree of salt stress tolerance was determined for 65 clones of creeping bentgrass Agrostis palustris Huds., a relatively salt tolerant species. The clones were first rooted in tap water and later exposed directly to solutions containing sodium chloride (NaCl) equivalent to -20 bars for 6 days. Using criteria based on visual examinations, eight clones were placed in the least tolerant class and all others were classified as being intermediate. In a second experiment, plants were rooted and exposed to NaCl equivalent to -10 bars for 7 days and -20 bars for an additional 7 days. In this study, eight clones were classified as being tolerant, 20 were intermediate, and the balance was considered sensitive. Included in the least tolerant class were all sensitive clones found in the first study. These results together with those from a third more limited study showed that clones of bentgrass can differ widely in salt sensitivity.
Following the classification of bentgrass clones into salt stress tolerant and salt stress sensitive lines, bentgrass, barley (Hordeum vulgare L.), and other plant species were examined to determine their physiological responses to stress and whether response differences existed between tolerant and sensitive types. The physiological parameters studied at different levels of NaCl stress were proline levels, polyribosome content, nitrate uptake, and CO2 exchange rates. Short time exposure (0 to 4 hours) to NaCl equivalent to -10 bars did not alter proline levels in bentgrass, barley, Alaska peas and pumpkins. Exposure to NaCl for 8 or more hours, however, induced a significant accumulation of proline in both barley and bentgrass. Tolerant clones had higher proline levels than did sensitive clones. Measurements of growth rates using a photographic technique showed that salt stress effected rapid (within 5 minutes) reductions in growth, and relief of stress resulted in growth surge. In order to relate changes in polyribosome percentages to growth, a general extraction buffer containing sodium diethyldithiocarbamate and a procedure for separating polyribosomes on acrylamide gels were developed. These results showed that polyribosomes were reduced within 30 minutes in barley and bentgrass but growth rate changes during stress and relief of stress preceded changes in polyribosome percentages.
Absorption studies with N were conducted with one salt sensitive and two salt tolerant bentgrass clones. The N absorption study showed that increasing salinity resulted in reduced absorption in all plant types. Nitrogen absorption by the sensitive bentgrass clone was higher than that of the two tolerant clones in treatments receiving NaCl equivalent to 0 and -4 bars but not in treatments receiving -8 bars. Nitrogen uptake of all three clones was directly proportional to transpiration rate (r = 0.95).
Salinity also lowered rates of dark respiration, apparent photosynthesis and photorespiration in all three clones studied. These studies showed that all measurements were affected relatively little by salinity up to -7.5 bars. Treatments receiving the equivalent of -10 bars had lower rates of dark respiration, apparent photosynthesis, and photorespiration than controls and the sensitive clone was severely affected in all cases.

Mots clés : Plants — Effect of salt on. ; Agrostis. ; Barley.

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