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Accueil du site → Doctorat → États-Unis → 1985 → VEGETATIVE GROWTH AND ITS LIMITATION BY MODERATE SALT STRESS IN KENAF (HIBISCUS CANNABINUS L.) (PLANT ANALYSIS, NEW CROPS, PHOTOSYNTHESIS, CARBOHYDRATES, WATER RELATIONS)

University of California, Davis (1985)

VEGETATIVE GROWTH AND ITS LIMITATION BY MODERATE SALT STRESS IN KENAF (HIBISCUS CANNABINUS L.) (PLANT ANALYSIS, NEW CROPS, PHOTOSYNTHESIS, CARBOHYDRATES, WATER RELATIONS)

CURTIS, PETER SMITH

Titre : VEGETATIVE GROWTH AND ITS LIMITATION BY MODERATE SALT STRESS IN KENAF (HIBISCUS CANNABINUS L.) (PLANT ANALYSIS, NEW CROPS, PHOTOSYNTHESIS, CARBOHYDRATES, WATER RELATIONS)

Auteur : CURTIS, PETER SMITH

Université de soutenance : University of California, Davis

Grade : Doctor of Philosophy (PhD) 1985

Résumé
Kenaf (Hibiscus cannabinus L., Malvaceae), a stem fiber and pulp crop, was investigated as to its suitability for introduction into regions of the arid southwest with access to saline irrigation water. Quantitative plant growth analysis was combined with the analysis of germination response, tissue ion content, plant water relations, leaf gas exchange, carbohydrate status, and leaf anatomy to evaluate the relative salinity tolerance of kenaf and to determine the physiological causes of the observed growth reduction under moderate salt stress. Selected cultivars and one experimental breeding line were grown in nutrient solution culture (0.5X Hoagland’s solution amended to 4 mM Ca(’2+)) at 1, 37, 75, and 150 mM NaCl under greenhouse conditions. Germination was tested at 50 mM increments up to 250 mM NaCl. Kenaf was determined to be a moderately salt tolerant non-halophyte with a threshold of approximately 37 mM NaCl (5 dS m(’-1)) after which biomass accumulation declined at the rate of 10% with each additional 10 mM NaCl. Germination was delayed although otherwise unaffected by NaCl concentrations up to 150 mM. Sodium was excluded from the shoot relative to Cl(’-) with expanding leaves significantly lower in both ions than mature leaves. Leaf tissue K(’+) and Ca(’2+) contents were unaffected by the salt treatments. Leaf expansive growth was very sensitive to salinity. In the cultivar Cuba-108, whole plant leaf area development was affected to a greater degree and more rapidly at 37 and 75 mM NaCl than was biomass accumulation. Conversely, stomatal conductance, CO(,2) exchange rate, and net assimilation rate were not adversely affected. Although final leaf area declined with salt stress, carbohydrate pool size (soluble plus starch) remained constant in mature leaves and doubled in expanding leaves. Growth was therefore not limited by photosynthetic capacity or available carbohydrates. Pressure-volume analysis of newly expanded leaves showed that kenaf was unable to adequately adjust osmotically to lowered plant water potentials under salt stress. Consequently, turgor was lower in stressed plants relative to controls, falling to near 0 MPa during midday. Epidermal cell size was also reduced. The decline in plant water status and cellular expansive growth were considered to be of major importance in causing the reduction in leaf area development. Ionic effects on carbon metabolism and cell division were also implicated.

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