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Photosynthetic rates, chlorophyll content, and activities of several photosynthetic enzymes were determined per cell, per unit DNA, and per unit leaf area in five ploidal levels of the C4 dicot Atriplex confertifolia. Volumes of bundle sheath and mesophyll protoplasts were measured in enzymatic digestions of leaf tissue. Photosynthetic rates per cell, contents of DNA per cell, and activities of the bundle sheath enzymes ribulose 1,5-bisphosphate carboxylase (RuBPC) and NAD-malic enzyme per cell were correlated with ploidal level at 99% or 95% confidence levels, and the results suggested a near proportional relationship between gene dosage and gene products. There was also a high correlation between volume of mesophyll...
Filamentous cyanobacteria are the main primary producers in biological desert sand crusts. The cells are exposed to extreme environmental conditions including temperature, light, and diurnal desiccation/rehydration cycles. We have studied the kinetics of activation of photosynthesis during rehydration of the cyanobacteria, primarily Microcoleus sp., within crust samples collected in the Negev desert, Israel. We also investigated their susceptibility to photoinhibition. Activation of the photosynthetic apparatus, measured by fluorescence kinetics, thermoluminescence, and low temperature fluorescence emission spectra, did not require de novo protein synthesis. Over 50% of the photosystem II (PSII) activity, assembled...
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These data were collected to evaluate if arrowweed (Pluchea sericea) individuals and genotypes collected from across a 5.3 degree Celsius temperature gradient and grown in a common greenhouse environment had different physiological and morphological responses to inundation. The objectives of the study were to assess if 1) individuals from climatically different provenances differ in their morphological and physiological phenotypes, 2) individuals from climatically different provenances differ in their response to inundation, and 3) phenotypes and inundation responses are partially controlled by genotype. These data represent measurements made on 248 plants that were grown in a greenhouse and, also in a greenhouse...
A field experiment using 2 patterns of irrigation and 1 level of nitrogen fertilizer (10 g-N m-2) was conducted in order to discern water and nitrogen interactions that may control production of creosotebush, (Larrea tridentata (D.C.) Cov. The 2 patterns of irrigation simulated precipitation from small, frequent events (6 mm water added weekly) or large, infrequent events (25 mm water added monthly). Understanding the factors controlling the production of this rangeland shrub may aid in the development of strategies for its management. Vegetative growth occurred mostly during March-May (spring) and August-October (summer-fall). Fruit production occurred mainly in the spring and root growth occurred mainly in the...
Human expansion into the Mojave Desert is a significant threat to rare desert plants. While immediate habitat loss is often the greatest concern, rare plants situated near areas where soil surfaces experience frequent disturbance may be indirectly impacted when fine particulate dust accumulates on leaf surfaces. Remaining populations of the federally listed Astragalus jaegerianus (Lane Mountain milkvetch) occur on land open to expanding military activities and on adjacent public land with increasing recreational use. This study was initiated to determine whether dust accumulation could decrease the vigor and fitness of A. jaegerianus through reduced growth. Beginning in early May 2004, plants located on Bureau of...
    map background search result map search result map Arrowweed (Pluchea sericea) morphological and physiological response data from a greenhouse inundation experiment Arrowweed (Pluchea sericea) morphological and physiological response data from a greenhouse inundation experiment