Carbon dioxide stomatal

Carbon Dioxide Stomatal activity is affected by carbon dioxide, and it may affect plant sensitivity to oxidants. Heck and Dunning reported a decrease in sensitivity of tobacco to ozone if the tobacco was exposed to added carbon dioxide at 500 ppm immediately before and during exposure to ozone (22% injury with added carbon dioxide, and 66% injury without). If this is a general plant response, the carbon dioxide now added to greenhouses to increase productivity may also increase resistance of the plants to oxidant pollutants. 

Akita, S. and Moss, D. N. (1973). Photosynthetic responses to carbon dioxide and light by maize and wheat leaves adjusted for constant stomatal apertures. Crop Sci. 13,234-237. 

Atrazine enters plants primarily by way of the roots and secondarily by way of the foliage, passively translocated in the xylem with the transpiration stream, and accumulates in the apical meristems and leaves (Hull 1967 Forney 1980 Reed 1982 Wolf and Jackson 1982). The main phytotoxic effect is the inhibition of photosynthesis by blocking the electron transport during Hill reaction of photosystem II. This blockage leads to inhibitory effects on the synthesis of carbohydrate, a reduction in the carbon pool, and a buildup of carbon dioxide within the leaf, which subsequently causes closure of the stomates, thus inhibiting transpiration (Stevenson et al. 1982 Jachetta et al. 1986 Shabana 1987). 

Todd and Todd and Probst also measured the effects of ozone (at 4 ppm for 40 min) on photosynthesis and found that development of symptoms was associated with inhibition of carbon dioxide fixation. This effect was also confirmed by Macdowall, who reported that the inhibition of photosynthesis was greater than that which could be accounted for by chlorophyll destruction. Hill and Littlefield associated decreased net photosynthesis caused by ozone (at 0.06 ppm for 1 h) with both stomatal opening and rates of transpiration. These studies have generally shown that net photosynthesis can decrease without visible injury. 

Figure 17.12 Stomatal conductance of potatoes grown at 400, 1000, and 10 000 ppm carbon dioxide. Conductance and transpiration were lowest at 1000 ppm and highest at 10 000 ppm. Super-elevated concentrations like 10 000 ppm might can occur in closed environments in space (source Wheeler et al., 1999).

McElwain JC, Chaloner WG (1995) Stomatal density and index of fossil plants track atmospheric carbon dioxide... 

McElwain JC, Mitchell FJG, Jones MB (1995) Relationship of stomatal density and index of Salix cinerea to atmospheric carbon dioxide concentrations in the Holocene. The Holocene 5 216-219 McElwain JC, Wade-Murphy J, Hesselbo SP (2005) Changes in carbon dioxide during an oceanic anoxic event linked to intrusion into Gondwana coals. Nature 435 479-482 Meyer HW (1992) Lapse rates and other variables applied to estimating paleoaltitudes from fossil floras. Palaeogeogr Palaeoclimatol Palaeoecol 99 71-99... 

Stomatal conductance numerical measure of the maximum rate of passage of either water vapor or carbon dioxide through the stomata (small pores on plant surfaces). 

During the late afternoon when the vapor pressure gradient declines, ponderosa pine stomata may open wider, resulting in greater oxidant uptake and simultaneous depression of carbon dioxide fixation. Some knowledge of stomatal function would be useful to see if there is any relationship between intraspecific oxidant tolerance and ability to close stomates in the presence of elevated ozone concentrations. This mechanism is an inherited characteristic of an ozone-resistant onion variety which closes its stomates when exposed to ozone (30). It is not known if this mechanism is involved in conditioning interspecific tolerance or sensitivity of the important conifer species. 

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. 

Beerling D. J. (1993) Changes in the stomatal density of Bcte/a nana leaves in response to increases in atmospheric carbon dioxide concentration since the late-glacial. Spec. Pap. Palaeontol. 49, 181-187. 

Figure 2. Effect of 24-epibrassinolide and ouabain on stomatal opening of Commelina epidermal strips in the light in the absence or presence of carbon dioxide in the air. Aperture of the control 11.6 pm (without CO2) 6.3 pm (with CO2).

Transpiration is a process that involves loss of water vapour through the stomata of plants. The loss of water vapour from the plant cools the plant down when the weather is very hot, and water from the stem and roots moves upwards or is pulled into the leaves. When less water is available for the plants, dehydrated mesophyll cells release the plant hormone abscisic acid, which causes the stomatal pores to close and reduce the loss of water during release of oxygen and intake of carbon dioxide. Fig. 2.7 (a) shows the transpiration effect in plants with open and closed stomata. 

Raschke,K. Simultaneous requirement of carbon dioxide and abscisic acid for stomatal closing in Xanthium strumarium L. Planta 125,243-259 (1975 b)... 

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