Stomata resistance

Figure 2. Intensity of photosynthesis (A), transpiration (B) and stomata resistance (C) of Arabidopsis thaliana L. plants exposed to Cd, and Ph ions in hydroponics culture for 22 and 29 days. Measurements were made using IRGA method with Photosynthesis System LICOR 6200, Lincoln, Nebraska. Data are expressed as % of control SE, n=5.

In cultures of the more resistant cell line, MDCK, the predominant effect of Tyv-specific monoclonal antibodies is to exclude larvae from the monolayer. This exclusion is associated with the formation of cap-like structures that cover the stoma of the larva. Such caps were first described... 

The pathway of least resistance for gases to cross an epidermis—and thus to enter or to exit from a leaf—is through the adjustable space between a pair of guard cells (Fig. 1-2). This pore, and its two surrounding guard cells, is called a stoma or stomate (plural stomata and stomates, respectively). When they are open, the stomatal pores allow for the entry of CO2 into the leaf and for the exit of photosynthetically produced O2. The inevitable loss of water vapor by transpiration also occurs mainly through the stomatal pores, as we will discuss in Chapter 8 (Section 8.1B). Stomata thus serve... 

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... 

There have been few measurements of cuticular resistance to gas transfer in succulent plants. By estimating water loss for cacti with stomata closed, Johnson estimated 619, 624, and 1022 s cm" for Opuntia basilaris, 0. acanthocarpa, and 0. bigelovii respectively (Ting and Szarek, 1975). These extremely high resistances to water loss must not only be due to the hermetically sealed stomata, but also to the heavy deposition of wax on the stoma-bearing surface (Fig. 5.24). 

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