Photosynthesis and photoinhibition

Characterization of Stomatal Closure Caused by Ultraviolet-B Radiation

“…After the pea seeds were sown, pots were placed in a transparent UV-exposure cabinet within the greenhouse, as described by Allen et al (1997). The UV-C radiation was screened out by cellulose diacetate film, and the control treatments were under the same configuration of lamps as the UV-B treatments, but the UV-B was screened out with Mylar-D film.…”

“…The UV-C radiation was screened out by cellulose diacetate film, and the control treatments were under the same configuration of lamps as the UV-B treatments, but the UV-B was screened out with Mylar-D film. The UV spectrum at the top of the plants was measured with a scanning spectroradiometer (SR 991-PC, Macam Photometrics, Livingston, UK) and was the same as that previously described (Allen et al, 1997). Greenhouse and cabinet transmission of UV-A radiation, supplemented by the UV fluorescent lamps, ensured that UV-A exposure was maintained for photorepair and flavonoid biosynthesis (Teramura and Ziska, 1996).…”

“…High UV-B irradiance has been shown to inhibit photosynthesis in pea (Nogués and Baker, 1995), oilseed rape (Allen et al, 1997), soybean (Middleton and Teramura, 1993), rice (Ziska and Teramura, 1992), and algae (Lesser, 1996). Such inhibition of photosynthetic competence primarily involves the loss of both Rubisco activity and content (Allen et al, 1997), but is also associated with the loss of activity of sedoheptulose 1,7-biphosphatase (Allen et al, 1998), and probably that of other Calvin cycle enzymes, and is sometimes associated with damage to PSII photochemistry (Nogués and Baker, 1995;Baker et al, 1997;Allen et al, 1998).It is not clear whether changes in stomatal function play a major role in the UV-B-induced inhibition of CO 2 assimilation. An increase in stomatal limitation observed in oilseed rape (Allen et al, 1997) and soybean (Middleton and Teramura, 1993), together with a reduction in the intercellular CO 2 concentration (c i ) in pea (Day and Vogelmann, 1995), suggests that there may be a direct UV-B effect on stomatal function.…”

“…High UV-B irradiance has been shown to inhibit photosynthesis in pea (Nogués and Baker, 1995), oilseed rape (Allen et al, 1997), soybean (Middleton and Teramura, 1993), rice (Ziska and Teramura, 1992), and algae (Lesser, 1996). Such inhibition of photosynthetic competence primarily involves the loss of both Rubisco activity and content (Allen et al, 1997), but is also associated with the loss of activity of sedoheptulose 1,7-biphosphatase (Allen et al, 1998), and probably that of other Calvin cycle enzymes, and is sometimes associated with damage to PSII photochemistry (Nogués and Baker, 1995;Baker et al, 1997;Allen et al, 1998).…”

“…An increase in stomatal limitation observed in oilseed rape (Allen et al, 1997) and soybean (Middleton and Teramura, 1993), together with a reduction in the intercellular CO 2 concentration (c i ) in pea (Day and Vogelmann, 1995), suggests that there may be a direct UV-B effect on stomatal function. However, it is widely reported that any UV-B effects on stomata do not affect CO 2 assimilation (Murali and Teramura, 1986;Sullivan and Teramura, 1989;Teramura et al, 1991;Ziska and Teramura, 1992).…”