Plant water status

Jones, H.G. (1979). Visual estimation of plant water status in cereals. Journal of Agricultural Science, Cambridge, 92, 83-9. 

The dry weights (104 C, 48 hr) of ten plants from each treatment group were taken at the termination of each experiment in order to compare growth effects with plant water status. Dry weight data were analyzed using analysis of variance (ANOVA) and Duncan s multiple-range test. Diffusive resistance and water potential were evaluated using the t-test. Each of these and subsequent experiments was replicated. 

Plant water status is affected by environmental pollution and consequently influences plant function at every level of biological organisation. It can be characterized by measurements of the relative water content (RWC), the water deficit, the water potential ( P ) and the osmotic potential ( Fq), along with transpiration rate and stomatal resistance. Since for the latter four parameters, tissue samples are removed from the plant, they are usually determined in the end of an experiment. If several sampling times are needed, then additional plants/replicates must be included. 

The two remaining of plant water status parameters (water and osmotic potential) reflect free water availability. These can be measured with a Dew Point Microvoltmeter (e.g., the WESCOR HR 33T [Logan, Utah]), but other methods and equipment can be applied. Osmotic potential can be determined from either fresh or frozen plant samples, but water potential requires fresh tissue. The water potential of leaf discs, strips or roots of the same size/weight can be measured with the WESCOR device (for detailed methods see http //www.wescor.com/environmental/index.phtml). Osmotic... 

Oliveira, C., Silva Ferreira, A. C., Mendes Pinto, M., Hogg, T., Alves, F., and Guedes de Pinho, P. (2003). Carotenoid compounds in grapes and their relationship to plant water status. J. Agric. Food Chem. 51, 5967-5971. 

Verslues, P.E., M. Agarwal, S. Katiyar-Agarwal, J. Zhu, and J.K. Zhu. 2006. Methods and concept in quantifying resistance to drought, salt and freezing, abiotic stress that affect plant water status. Plant J. 45 523-539. 

B. Klepper, V. D. Browning, and H. M. Taylor, Stem Diameter in Relation to Plant Water Status, Plant Physiol. 48, 683-685 (1971). 

Besides light and nutrition, plant water status is an additional important environmental factor influencing the rate of CO2 uptake. In general, the initial phase of this response is a response of stomata, which are more sensitive to water stress than the photosynthetic metabolism. If plant water status decreases further, also photosynthesis is reduced. In laboratory experiments it has been shown, that it is not the leaf water status but hormonal and ionic relations between root and shoot which regulate stomatal opening and photosynthesis under soil water stress (Gollan et al., 1988). 

Gollan, T., Passioura, J.B. Munns, R. (1986). Soil water status affects the stomatal conductance of fully turgid wheat and sunflower leaves. Australian Journal of Plant Physiology, 13, 459-64. 

Zhang, J. Davies, W.J. (1989). Abscisic acid produced in dehydrating roots may enable the plant to measure the water status of the soil. Plant, Cell and Environment, 12, 73-81. 

Water status of the seedlings was determined each afternoon by obtaining leaf diffusive resistance, water potential, and osmotic potential. Diffusive resistance was measured on both the adaxial and abaxial surfaces of the youngest fully expanded leaf for six randomly selected plants in each treatment using a Lambda Model LI-60 meter and a narrow aperture sensor. Total leaf resistance (R) was calculated from the component resistances (r) as follows ... 

Data summarizing the effects of the inhibitory weed extracts on sorghum water status was taken from the second trial in each case (Table V). All of these extract treatments had reduced sorghum growth, and all but one had some effect on plant water balance. 

Both of them require at least limited model calibration. They do not stochastically estimate daily climate data for model evaluations or long-term changes in plant nutrient status and the resulting changes in plant growth and water balance. HYDRUS and UNSAT-H would be very useful and accurate if used in research however, they are difficult to use in engineering design of ET landfill covers and provide incomplete estimates of performance. 

In conclusion, it is our view that K+ plays a dominant role in maintaining a favorable plant cell water status and that the deleterious effects of ozone occur primarily due to disruption of this normal ionic balance. We currently visualize the following scheme of ozone damage (a) ozone attack of an SH group or fatty acid residue (b) permeability changes of the membrane leading to loss of both K" " and osmotic water (c) inhibition or loss of K" " pump activity for reacquisition of lost K+ (d) loss of a critical level of ion and (e) gross disruption of cellular metabolism. 

Boyer, J.S., and Kramer, P.J. 1995. Measuring the Water Status of Plants and Soils. Academic Press, San Diego, CA. 

Water status, temperature, and PPF all affect stomatal opening (Section 8.1B) and hence the photosynthetic rates of leaves. Sometimes such environmental effects are incorporated into photosynthetic models by their influences on (Eq. 8.5) or Fmax (Eq. 8.27). Indices have also been proposed relating Jcoi to rainfall and the water status of the plants, to the... 

In general, the chemical composition of plants closely reflects the chemical properties of whole environments, soils, waters, and air. Using plant chemical status for geochemical prospecting is very old practice (Kabata-Pendias and Pendias 2001), but recently it has been used broadly for the bioindication of contaminated sites and for the environmental biomonitoring (see Part I, Chapter 12). 

As basic information in plant science increases additional markers will be identified for which immunoassays can be developed. Rapid determination of the nutrient status of the growing crop will allow crop managers to select fertilization that produces maximum return based on the specific needs of the crop as it grows in a specific location (29). Similarly, detection of water stress markers will permit irrigation scheduling based on crop water status rather than on soil moisture levels or other environmental measures. 

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