Browsing by Subject "Plant-water relationships"
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Item Determination of root diffusivity during water flow in root-soil systems(Texas Tech University, 1995-05) Bian, An-GwoWe are concerned with determining plant (cotton) root hydraulic diffusivity by measurement of the water flow from the region between two horizontal cross sections into the soil from root xylem through root epidermis over a period of time. The results of the experiment conducted by Yamauchi et al. [30] to measure the potential gradient in the root xylem of an intact, transpiring cotton plant are utilized to estimate the hydraulic difFusivity of the combined root tissues between root xylem and root epidermis. Figure 1.1 shows the cross-section of a root. Figure 1.2 is a schematic illustration of the laboratory setup used by Yamauchi et al. to collect water and measure the gradient in xylem water potential and water flow rate. The measurements were made in rigidly controlled environments. Temperature, soil moisture level, and lighting condition were all under control. The water potential of the xylem at a particular point along a root was measured while the plant was actively transpiring; the plant was still alive. There was no destruction of the root. This technique also allowed the xylem water potential at a particular point to be monitored dynamically. The water was collected by enclosing a small length of root in specially constructed Teflon psychrometer chambers. For a more detailed experimental description, refer to [30].Item Development and fecundity of the southwestern corn borer (Lepidoptera, Pyralidae) as affected by plant water stress and a secondary host(Texas Tech University, 1985-12) Aslam, MuhammadNot availableItem Effect of irrigation system, plastic mulch and antitranspirant on water use and yield of peppers (Capsicum annuum L.) and muskmelon (Curcurbita cantaloupensis L.)(Texas Tech University, 1980-05) Adedeji, Samson ANot availableItem Flammability-internal water status of shrubs(Texas Tech University, 1980-12) Peacock, George LouieIn Guadalupe Montains National Park (Texas) a study was conducted to determine the relationship between the internal water status of selected woody shrubs and their tendency to burn. Low correlations v/ere found between leaf relative water content and flammability, .652, .429 and .596, and xylem sap tension and flammability, .658, .665 and .787 for Cercocarpus montanus, Fallugia paradoxa and Quercus grisea, respectively. Leaf relative water content-xylem sap tension curves were developed for each species to determine if xylem sap tension could be used to estimate leaf relative water content. The low correlation coefficients indicated that no significant reliability could be placed on using these curves.Item Genotypic variability for rate and duration of grain fill in sorghum (Sorghum bicolor [L.] Moench) grown under two levels of water availability(Texas Tech University, 1983-06) Onwuka, Sebastine ObiNot availableItem Growth and development of cotton when released from osmotic stress(Texas Tech University, 1980-08) Prien, Samuel D.Not availableItem Impacts of water quality of plug production of gaillardia, salvia, and pepper(Texas Tech University, 1997-12) McGann, Linda S.The objectives of this study were to evaluate the effects of poor quality irrigation water fi-om two different water sources on the growth of Capsicum annuum fpepper), Gaillardia x grandiflora (gaillardia), and Salvia farinacea ("salvia) in plugs, to asses the feasibility of blending poor quality water with reverse osmosis treated water (RO) to remediate the potentially damaging effects of poor quality irrigation water on plant growth, and to empirically determine the most effective ratio of RO to poor quality water for each species. The study was a 2 x 5 factorial in a split plot design and was replicated over three runs. Two poor quality water sources (WS) were blended with RO in dilutions of 100 WS: 0 RO, 75 WS: 25 RO, 50 WS: 50 RO, 25 WS: 75 RO, and 0 WS: 100 RO. Seeds of each species were sown by hand into plug trays and measured volumes of each dilution were applied by hand. ANOVA analysis revealed that dilution of each water source significantly impacted dry weights for all three species. Pepper, a crop rated as moderately tolerant to soluble salts, generally produced more dry weight with 25 WS: 75 RO. However, visual evaluation scores for uniformity, quality, and salability of pepper revealed little difference between 0 WS: 100 RO, 25 WS: 75 RO, and 50 WS: 50 RO dilutions. Therefore, higher percentages of a poor quality water source and less RO may be tolerated in pepper plug production. Overall trends in gaillardia production revealed a trend for maximum dry weights with the 25 WS: 75 RO dilution. With few exceptions, the highest evaluation scores for uniformity, quality, and salability of gaillardia were with the 25 WS: 75 RO dilution. For salvia, a crop sensitive to soluble salts. 100% reverse osmosis treated irrigation water produced the highest dry weights with the best evaluation ratings for uniformity, quality, and salability.Item Photosynthesis and water use in honey mesquite(Texas Tech University, 1987-12) Wan, ChangguiSeasonal and diurnal patterns of photosynthesis in honey mesquite (Prosopis glandulosa) growing on a clay loam and a sandy loam were studied in Lubbock, Texas for two consecutive years. The highest photosynthetic rates were measured in June when soil moisture was adequate. Photosynthetic rate of mesquite is higher than either winter deciduous trees or desert shrubs. This high photosynthetic rate is associated with high leaf nitrogen content (27 mg/g) and high light saturation requirement (photosynthetic photon flux density greater than 1.8 mmol m^-2 s^-1). The optimum temperature for photosynthesis has shown a seasonal change, 27-31 °C in spring and summer and 14-18 °C in late fall. The thermostability of photosynthetic apparatus increases during May through September. Diurnal changes in photosynthetic rate has no unique relationship with xylem water potential. However, photosynthetic capacity is related to soil water potential. This may suggest that the primary sensor of water stress is located in the root system and root-shoot communication plays a significant role in regulating plant response to water stress. Photosynthesis of mesquite is mostly limited by nonstomatal factors rather than stomatal factors. In the drought period, the effect of stomatal closure on photosynthesis is mainly due to increased leaf temperature more than decreased intercellular CO2 concentration. Increased photorespiration under high temperature regimes is also responsible for the decreased net photosynthetic rates. The plants growing on the two sites are responding differently to water saturated soil. The mesquite trees on the sandy loam site tend to reach peak photosynthetic rates after soil recharge, while those on the clay loam site do not. Low soil temperature and/or poor aerobic conditions caused by slow percolation and root pruning caused by swelling and shrinking action of montmorillonitic clay may be the possible reasons for the poor response in the trees on the clay loam site. Root total nonstructural carbohydrate (TNC) concentration of honey mesquite shows a seasonal fluctuation. The root TNC recharge in honey mesquite is positively correlated with the rate of photosynthesis and root function. This recharge is not affected by a mild water stress, but is inhibited by a severe water stress. Spring drought in west Texas does not exert a great influence on the root TNC recharge, since it only represents a mild water stress. However, this recharge is negligible during midsummer for the trees growing on the xeric sandy loam site, since the severe summer drought reduces both source strength and sink (root) strength. The rate of root TNC recharge is regulated by relative sensitivity of photosynthesis and shoot growth to water stress and phenological development of the plant. It is also affected by sink activity. The rate of root TNC recharge is higher for trees on the sandy loam site than those on the clay loam site in spring because the soil conditions are more favorable for both photosynthesis and root growth. And the opposite holds true during the midsummer, since the plants on the clay loam site suffer less severe water stress than those on the sandy loam site. Transpiration of mesquite is regulated by strong stomatal response to internal and external factors. A close correlation between stomatal conductance and air-leaf vapor pressure difference (VPD) was found in mesquite. Stomata do not respond to bulk leaf water potential, indicating that water relation in the epidermis cells is independent of that in the mesophylls. Stomatal response to VPD is a desiccation avoidance mechanism, which allows the plant to succeed in the semiarid west Texas rangeland. Stomatal conductance is positively correlated with soil water status. This is another indication that water stress is sensed primarily by the root system. This root-shoot communication may be mediated by hydraulic resistance in soil-root-xylem system. It has been shown that hydraulic resistance is highly correlated with stomatal conductance on both sites. It is postulated that hydraulic resistance may influence the long distance transport of message from the roots to the shoots. Xylem water potential is a function of transpiration. During drought period, mesquite trees restrict transpiration so that soil water supply can be extended. As a result, photosynthesis is reduced due to insufficient transpirational cooling. The plant has evolved various means to reduce thermal load during drought periods. Water use efficiency (WUE, A/E) at leaf level is high in mesquite (2.5-3 mmol C02/niol H2O). However, WUE at plant level will be considerably lower because large amounts of carbon are allocated to belowground plant parts. WUE varies between the plants occupying the different habitats. This ecotypic differentiation in WUE is associated with anatomical modification. Intrinsic water use efficiency (A/g) and WUE tend to increase when the plant is growing on the more xeric sandy loam site. This provides another explanation for the widespread distribution of the plant in arid/semiarid areas. In mesquite plant, the early leaves and late leaves exhibit distinguishable characteristics in photosynthesis, leaf specific weight, leaf nitrogen content, leaf conductance and water use efficiency. The leaf morphology is also different. These changes reflect the environmental influence on leaf development and plant response to this influence. The common response of mesquite to soil water deficit is to restrict initiation of late leaves so that the plant canopy size is adjusted to match the soil water availability. The reduction in transpiring area is another effective mechanism to avoid desiccation in a drought environment. Although no difference in photosynthetic rates between the populations growing on the two sites, the productivity of mesquite trees on the clay loam site is greater than that on the sandy loam site, because of greater contribution of late leaves to the aboveground organic carbon pool.Item Photosynthetic variation in sorghum as affected by water stress(Texas Tech University, 1979-05) Morrisset, Barbara LouiseNot availableItem Physiological and morphological effects of film-forming antitranspirants on herbaceous ornamentals(Texas Tech University, 1986-12) McKenney, Cynthia B.Suppression of transpiration by film-forming antitranspirants on Petunia x hybrida and Salvia splendens was evaluated as a method of reducing water stress in retail and landscape conditions. Cloud Cover and Folicote antitranspirants were tested at three dilutions of their recommended rate under greenhouse and garden conditions. Transpiration, stomatal conductance and leaf temperature were measured using a Licor 1600 steady state porometer and were found to be not statistically altered by varying treatment concentration. Merrill leaf cutter psychrometers were used to determine the effects of the films on the water potential of both crops. Neither species was found to be affected significantly. However, high concentrations of antitranspirant did significantly improve the relative water content of Petunias in a garden environment. The effect of antitranspirant treatment on growth and development was also tested. Leaf number, leaf area, area per leaf, flower size, and number of flowers per plant were evaluated throughout the experiment. Some phytotoxicity, possibly due to the carriers in Cloud Cover and Folicote antitranspirants, were noted on both crops. A considerable gain in plant appearance or growth must result from application of these films to warrant the expense of the application.Item Plant and soil water relationships following sand shin oak control(Texas Tech University, 1983-05) Galbraith, John MichaelStudies of soil water use by forage and competitive deep-rooted brush species are needed to make brush management decisions in the seiaiarid southwestern United States. A study was conducted on a sandy soil in west Texas supporting a dense stand of sand shin oak (Quercus havardii) and an adjacent area treated with tebuthiuron in 1978 to control the shin oak. Root and rhizome distributions were estimated by auger extraction and washing, and forage yield was estimated by clipping. Both total and available soil water, water use, and water use efficiency were estimated by neutron scattering in 1981 and 1982. Measurable soil water savings began at the first herbicide-induced resprouting cycle of shin oak. Available water tended to be higher in the grass-forb community which remained after herbicide removal of the shin oak than in the shin oak-grass community. Water use efficiency was higher in shin oak-grass vegetation than in the grass-forb vegetation. Clipping, or simulated grazing, had minimal effect on water use efficiency of vegetation in the grass-forb community. Although sand shin oak efficiently uses water, the water used could be used by more desirable vegetation. Shin oak has a deeper effective rooting depth than most associated herbaceous plants. The grasses and forbs remaining after shin oak control extended their effective rooting depths to take advantage of additional available water. Soil water potentials were higher below 137 cm (effective rooting depth of herbaceous plants) in the herbicide- treated area than in the untreated area. Shin oak developed and maintained more negative midday leaf water potentials than associated plants (-25 to -30 bars). Most plants had more negative midday leaf water potentials in shin oak areas than in herbicidetreated areas because less soil water was available to them. Shin oak is the dominant plant on sandy soils within its range because of its morphological and physiological adaptations. To simulate short-duration grazing, or when the oak-grass vegetation was compared to shin oak alone after all understory species had been removed by hand. Therefore, sand shin oak can be considered an efficient user of rainfall for aboveground biomass production in its native environment in west Texas.Item Root growth and water uptake patterns of cotton, sunflower and kochia, and their relationship to caliche(Texas Tech University, 1986-08) Georgen, Paul GNot availableItem Soil-plant water relations in the Altiplano of Peru(Texas Tech University, 1985-12) Aguirre, LucreciaThe growth patterns of key range species and forage production on two major range sites, and the influence of soil water on plant water status and growth were measured. The research was conducted at La Raya Research Station, Department of Cusco (highlands of southern Peru) during June 1984 to May 1985- Site II (light sandy loam soil) had higher mean forage production (2,417 kg/ha) than Site I (heavy sandy loam soil (1,436 kg/ha). Site I was dominated by Festuca dolichophylla and Muhlenbergia fastigiata. Vegetative composition included grasses, 87%, sedges and reeds, 7%, and forbs, 5%. Site II was dominated by F^. rigida and Stipa obtusa. The vegetation was composed of grasses, 93%, forbs, 6%, and sedges, 1%. Festuca dolichophylla and Festuca rigida started regrowing in September; although Festuca rigida grew at a faster rate than Festuca dolichophylla and produced a greater amount of dry matter, it started decreasing earlier (May-June) than Festuca dolichophylla (July). Soil water content increased as the wet season progressed. The soil water content was higher on Site I (heavy sandy loam) 26% than at Site II (light sandy loam) 20% from September to April. The greatest water content occurred in November (36% and 34%, Site I and Site II, respectively). The water content was lowest (10% and 8%, Site I and Site II, respectively) in September. Soil water potential averaged across month and time of day (dry season and early wet season) was higher on Site II (light sandy loam), -47 bars, than at Site I (heavy sandy loam), -54 bars. During the dry season, the potentials were -70 and -69 bars, on Site I and Site II, respectively. Plant water potentials also increased as the wet season progressed. Festuca dolichophylla had lower plant water potentials than Festuca rigida throughout the day. Festuca dolichophylla attained higher conductance rates than Festuca rigida during November; conductances at mid-day were 0.3727 and 0.2900 cm.sec respectively.Item The Effect of Water Stress on Sorghum Bicolor L. Moench: A Stereological Study of Bundle Sheath Cells(Texas Tech University, 1982-12) Vishnoi, UshaSorghum leaves from plants grown under irrigated and dryland field conditions were used. The leaves from stressed plants had smaller leaf areas and they were thicker than the leaves from nonstressed plants. The bundle sheath cells occupied about 13% of the leaf area in both nonstressed and stressed plants. Leaves from stressed plants had smaller but more numerous bundle sheath cells. It was concluded that the reduced leaf area in the stressed plants was due to a sensitivity of cell enlargement to water stress and that cell division was not affected. Stereological analysis of bundle sheath cells from nonstressed and stressed plants was used to study differences in the cell wall, cytoplasm, chloroplasts, starch granules, chloroplast lipid bodies, mitochondria and central vacuole. The total volumes showed a decrease in the cell wall, cytoplasm and central vacuole of the bundle sheath cells of stressed plants. In the same cells the chloroplasts were reduced in number but individual chloroplasts showed no change in volume. In stressed plants the starch granules were both smaller and fewer in number whereas the chloroplast lipid bodies were the same size but fewer in number. The mitochondria were both smaller and fewer in the leaves from the stressed plants. On a per leaf basis the chloroplasts were reduced both in volume and number but only mitochondrial volume was reduced.Item The effect of water stress on the leaf area of Cucumis melo(Texas Tech University, 1986-08) Matthews, Lisa RGreenhouse and field-grown Cucumis melo, cantaloupe vines were grown under irrigated and water stressed conditions. In addition, the stressed plants were rewatered after stress had resulted in a reduction in leaf area, providing a water stressed/recovered condition. The upper surface of the leaves was examined with a scanning electron microscope to determine if the primary cause of reduced leaf area was a decrease in cell number or cell size. The reduction in leaf area induced by water stress was due to a decrease in mitotic activity of the epidermal cells, which caused a reduction in the total number of cells per leaf. Leaves that first appeared during water stressed conditions exhibited the most severe decrease in cell division. Leaves that first appeared under irrigated conditions but developed under stressed conditions exhibited relatively normal cell division as well as normal leaf size. This indicated that most cell division occurred during and immediately following leaf initiation. Cell size did not appear to be affected by water stress, but was affected by the age of the leaf. There was a recovery of leaf area after the stressed plants were rewatered that resulted from a corresponding recovery of cell division and a concomitant increase in the total number of cells per leaf. This finding contradicts the majority of the literature which suggests that cell turgor is most affected by water stress which, therefore, causes a decrease in cell expansion. Measurements of plant water status of the greenhouse grown plants revealed an increase in diffusive resistance during water stress and a decrease in relative water content during water stress with a recovery of both upon rewatering. It is concluded that, under the conditions used in this study, cell division was more sensitive to water stress than was cell enlargement. Further, cell differentiation, as judged by the relative number of upper leaf surface cells, was found to be increased in the guard cells but unaltered in the epidermal cells and trichomes.Item Water stress and Russian wheat aphid interactions in wheat(Texas Tech University, 1995-12) Nalbant, DemetNot available