Resistance stomatal

Dorman, J. L. and Sellers, P. J. (1989). A global climatology of albedo, roughness length and stomatal resistance for atmospheric general circulation models as represented by the simple biosphere model (SiB), /. Appl. Meteorol. 28, 833-855. 

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. 

Transpiration rate and stomatal resistance are the most commonly measured plant gas exchange parameters using IRGA. Their behaviour in A. thaliana plants exposed to heavy metal ion stress is demonstrated in Figure 2 B and C. 

Figure 2.21 schematically depicts the dry deposition of a pollutant to a typical surface in the form of resistances (Lovett, 1994 Wesely and Hicks, 1999). In this case, the surface resistance rsurf has been broken down even further into a combination of parallel and series resistances (rs, rm, rct, rsoil, rwa(cl, etc.). Since leaves may absorb pollutants either through stomata or through the cuticles, the absorption into the leaf is represented by two parallel resistances, rcl for the cuticular resistance and rs for the stomatal resistance, which is in series with a mesophyllic resistance rm. Also shown are resistances for uptake into the lower part of the plant canopy and into water, soil, or other surfaces. 

All of the many biological transfer processes combine to determine a net surface resistance to transfer. Empirical relationships can be used to infer stomatal resistance from data on photosynthetically active radiation, water stress, temperature, atmospheric humidity and carbon dioxide levels. The resulting net surface resistance has been coupled with mathematical descriptions of aerodynamic and boundary-layer resistances in a "big leaf" model derived on the basis of agricultural and forest meteorology literature (4). At present, the big-leaf model is relatively coarse, permitting application only to areas dominated by maize, soybeans, grass, deciduous trees, and conifers. 

Coale, F. J., V. P. Evangelou, and J. H. Grove. 1984, Effects of saline-sodic soil chemistry on soybean mineral composition and stomatal resistance. J. Environ. Qual. 13 635-639. 

For our applications to transpiration and photosynthesis, we will define a stomatal conductance, and a stomatal resistance, r for the diffusion of species j using Equation 8.4 ... 

Stomatal resistance is a critical factor affecting pollutant uptake. The resistance is determined by stomatal number, size, anatomical characteristics, and the size of the stomatal aperture. Little or no uptake occurs when the stoma is closed. Stomatal opening is regulated by internal C02 content, temperature, humidity, light, water availability, and nutrient status, particularly potassium. Research shows that K+ ions in the guard cells regulate the guard... 

In Wesely s (1989) formulation what we have called the stomatal pore resistance rp is called just the stomatal resistance and given the symbol rst. As in Figure 19.4, it is assumed to act in series with the mesophyll resistance. 

The bulk canopy stomatal resistance is calculated from tabulated values of ry, the solar radiation (G in W m 2), and surface air temperature (Ts in °C between 0 and 40°C) using... 

All the formulas described above are for unstressed vegetation, which is the default vegetation status. Optionally, for vegetation stress due to lack of water, the stomatal resistance is increased by a factor of 10 and for inactive vegetation (winter deciduous), a stomatal resistance of 10,000sm 1 should be used, indicating a complete shutdown of this pathway. 

Baldocchi, D. D., Hicks, B. B., and Camara, P. (1987) A canopy stomatal resistance model for gaseous deposition to vegetated surfaces, Atmos. Environ. 21, 91-101. 

Fig. 4.22 Resistance model of dry deposition, — aerodynamic resistance, r — quasi-lami-nar resistance, — soil resistance, - soil resistance (water), - soil resistance (other ground), r f - fohar resistance (weighted by leaf area index), r s — stomatal resistance, r c cuticular resistance, mesophyhc resistance.

Table 4.18 Averaged surface resistances (in s m ) for different gases during daytime, with stomatal resistance also given after Erisman and Pul (1997).

The foliar resistance consists again of two parallel resistances the cuticular resistance and the stomatal resistance which is in series with the mesophyll resistance r . 

It is a common observation that under water stress, photosynthesis decreases. In air, water deficits smaller than 10% often cause a 90% inhibition of photosynthesis (Fig.l, ref.8). However, at external CO -concentrations high enough to completely overcome stomatal resistance (10 to 15%), photosynthesis is rather insensitive to even severe dehydration (Fig.l, also compare 9,10). The conclusion is that under water stress photosynthesis is limited mainly by stomatal resistance to CO, diffusion. 

Jasmonic acid treatment has been reported to result in the inhibition of Hill reaction activity and flash-Oj evolution [73], alteration of intra-chloroplast structure [74] and chlorophyll fluorescence parameters [75], a change in the polypeptide pattern of thylakoid membrane proteins [76] and ultimately a decreased photosynthetic rate [77]. An increase in the rate of dark respiration, photorespiration and stomatal resistance to COj diffusion has also been observed [77,78]. 

Mitchell EK, Davies PJ (1975) Evidence for three different systems of movement of indoleacetic acid in intact roots of Phaseolus coccineus. Physiol Plant 33 290-294 Mitchinson GJ (1980) The dynamics of auxin transport. Proc R Soc Lond B 209 489-511 Mittelheuser CJ, van Steveninck RFM (1971) Rapid action of abscisic acid on photosynthesis and stomatal resistance. Planta 97 83-86 Morath M (1972) Some early effects of auxin and of geotropic exposure on coleoptiles. In Kaldewey H, Vardar Y (eds) Hormonal regulation in plant growth and development. Verlag Chemie, Weinheim, pp 377-381 Morgan DG (1964) Influence of a-naphthylphthalamic acid on the movement of indolyl-3-acetic acid in plants. Nature 201 476-477... 

Fig. 5.20. Diurnal pattern of stomatal resistance for Opuntia basilaris growing in southwestern United States at the Boyd Desert Laboratory. The stomata are open at night and closed during the day. Estimates were made with a porometer after precipitation...

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