No description available.

[No abstract available] / Science, Faculty of / Botany, Department of / Graduate

No description available.

Many areas in the arid southwestern United States depend upon ground water for irrigation and municipal water supplies. The high transpiration rates of the extensive phreatophyte tamarisk (Tamarix pentandra Pall.) cause considerable depletion of ground water in this region. Eradication of tamarisk communities would appear to be a useful method for salvaging ground water; however, the vigorous reproduction and growth of tamarisk pose economic problems because of the re-treatment and maintenance work required. Also, the removal of tamarisk thickets may adversely affect wildlife habitat, esthetic values, and the ecosystem in general. The use of antitranspirant compounds on tamarisk was investigated in the laboratory, greenhouse, and field, to determine if transpiration could be reduced significantly without damaging the plant. Athel tree (Tamarix aphylla L.) was subjected to the same analyses as tamarisk to better evaluate treatment effects. Initially, several antitranspirants were tested in greenhouse studies from which the potentially useful compounds were selected for more detailed study. Phenylmercuric acetate was toxic to both species and was not used in further experiments with tamarisk. Daily transpiration rates of tamarisk, measured gravimetrically in a greenhouse, were reduced 28 to 36 percent for 20 days with spray applications of 0.01 M 8-hydroxyquinoline sulfate (8-HQS), and the combination of 150 ppm mono-methyl (MDSA) and 150 ppm mono-glyceryl (GDSA) esters of n-decenylsuccinic acid in Triton X-100 (0.5 percent) solutions. The MDSA-GDSA combination and 8_I-[QS significantly reduced stomatal apertures of tamarisk. Stomatal measurements were not obtained for athel tree, although daily transpiration rates of athel tree were reduced 31 percent for 32 days with the MDSA-GDSA combination. The addition of the filmforming Foli-gard (10 percent) did not enhance treatment effect. Treatment effects on net photosynthesis and respiration of both species were evaluated with an infrared gas analyzer. The net photosynthesis rates of tamarisk were significantly reduced 1 to 3 days by 8-HQS and MDSA-GDSA. Respiration rates, measured in the dark, were increased significantly only by 8-HQS. Net photosynthesis rates of athel tree were significantly reduced 13 days by MDSA-GDSA, but there were no effects on respiration. MDSA-GDSA and 8-HQS reduced tamarisk growth rates for 10 to 20 days following treaLment. These growth reductions may have contributed to the decrease in transpiration rates of treated plants. Analyses of foliage samples obtained from tamarisk after treatment indicated that chlorophyll and protein contents were not affected by 8-HQS or MDSA-GDSA. Similar results were noted for athel tree treated with MDSA-GDSA and MDSA-GDSA-Foli-gard. Transpiration rates of potted tamarisk in the field were reduced significantly for only five days by 8-HQS, MDSA-GDSA, and the reflective compound, kaolinite. Rainfall after the fifth day, and phenological phenomena may have contributed to the comparatively short duration of transpiration reduction. Increased foliage temperatures of 1.5 to 2.5 C were detected with a Barnes infrared thermometer 1 and 3 days after treatment. These were obtained under conditions of intense solar radiation, and high air and soil temperatures. This study indicated that tamarisk transpiration can be reduced substantially without lethal increases in foliage temperatures, but with reductions of growth. Additional studies with these antitranspirants may provide a useful management alternative for tamarisk dominated areas to salvage ground water and yet maintain plant cover for wildlife and other uses.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / I examined interactions between plants and the environment they live in along the soil-plant-atmospheric continuum and addressed the effects of drought and acid deposition on plant water use. Using a novel stable isotope technique, I showed that plant water source utilization can be modulated in some species based on the soil and atmospheric conditions they experience, whereas others only access a single subsurface water source. By modeling cuticular conductance in multiple plant species, I showed that the variability of cuticular conductance across species is largely related to the changes in leaf water potentials between pre-dawn and midday measurements collected in field studies. I also assessed the individual and combined effects of soil water stress and atmospheric water stress on plant productivity by developing a new methodology, which can be used across scales. In doing so, I found that in deciduous broad-leaf forests, periods of high vapor pressure deficit caused sufficient hydraulic stress to reduce plant productivity more than low soil water content alone, and often reduced productivity to levels equal to periods of both low soil water stress and high vapor pressure deficit. Utilizing historical data from a whole forest acidification experiment, I was able to link the stress of nutrient deficiencies caused by acid deposition (specifically calcium) to increases in plant water utilization. This was the first observation of such an effect at the ecosystem scale and could have significant implications for understanding water availability in the future. Finally, I assessed a common method for extracting cellulose from tree rings for isotope analyses, which is often used to determine the historical water use efficiency of plants. I was able to determine chemical alteration to the cellulose molecule using stable isotope measurements and spectroscopy. The chemical modification seems to be systemic and therefore could be addressed through mathematical corrections to existing data. Having accurate values of plant water use efficiency is extremely important for understanding how different stressors in the past changed the way plants used their water resources. My series of studies provide new insights and tools to evaluate the plant-environment interactions in current and future environments.

The climate, water loss, arid certain aspects of growth in semiarid-site ponderosa pine were measured from 1 February 1966 to 10 March 1967 to determine the environmental relationships governing transpiration, internal water balance, and tracheid production. Water loss from branches and from entire trees was measured by means of polyethylene enclosures. Changes In internal water status of the tree were ascertained from seasonal trends in loss of water from branches and diurnal as well as seasonal changes in the radius of the bole. The elongation of branches and needles, and the production of tracheids and their size and wall thickness were related to the coincident internal water status of the tree. The branch enclosure technique was found to be a convenient method by which the water loss process could be studied. The seasonal changes in transpiration undoubtedly were influenced by the elevated temperatures that developed within the enclosure during the day. However, the elevated temperatures did not appear to adversely influence branch and needle elongation within the chamber. Warm air temperatures and low soil moisture during June and early July increased internal water stress, reduced daytime water loss, and reduced elongation of branches and needles. Fewer tracheids were produced in the upper bole. They were small and had thick walls, Moisture from rains in July replenished soil moisture and larger, thin-walled tracheids were differentiated so that the intra-anntjlar band of small, thick-walled cells became apparent. Gradual shrinkage of the upper bole in June implied that the above changes in growth were due to changes in internal water deficits. There were no marked changes in tracheid sizes and wall thickness in the lower bole during 1966. Intra-annular bands of narrow, thick-walled tracheids occurred times during the last 10 years in the upper bole in the last 50 years in the lower bole. Graphical analysis showed that midday reductions in rates of xi transpiration during periods of low soil moisture and high air temperatures occurred in spite of steepening water vapor gradients and before stomates were closed. This evidence supports the hypothesis that reductions in water loss during midday may result directly from internal water deficits. Soil moisture, air temperature, and incident radiation appeared to influence transpiration by altering the availability of water, the vapor pressure gradient, and the energy available for evaporation.

The research described in this dissertation is predicated on the hypothesis that remotely sensed information from climatological satellites can be used to estimate the actual evapotranspiration from agricultural crops to improve irrigation scheduling and water use efficiency. The goal of the enabling research program described here was to facilitate and demonstrate the potential use of satellite data for the rapid and routine estimation of water use by irrigated crops in the Yaqui Valley irrigation scheme, an extensive irrigated area in Sonora, Mexico. The approach taken was first, to measure and model the evapotranspiration and crop factors for wheat and cotton, the most common irrigated crops in the Yaqui Valley scheme. Second, to develop and test a high-resolution (4 km x 4 km) method for determining cloud cover and solar radiation from GOES satellite data. Then third, to demonstrate the application of satellite data to calculate the actual evaporation for sample crops in the Yaqui Valley scheme by combining estimates of potential rate with relevant crop factors and information on crop management. Results show that it is feasible to provide routine estimates of evaporation for the most common crops in the Yaqui Valley irrigation scheme from satellite data. Accordingly, a system to provide such estimates has been established and the Water Users Association, the entity responsible for water distribution in Yaqui Valley, can now use them to decide whether specific fields need irrigation. A Web site (tekapucemitson. mx) is also being created which will allow individual farmers to have direct access to the evaporation estimates via the Internet.

No description available.

Würzburg, Univ., Diss., 2009. / Zsfassung in dt. Sprache.