Alterations in light‐induced stomatal opening in a starch‐deficient mutant of Arabidopsis thaliana L. deficient in chloroplast phosphoglucomutase activity

Abstract

Stomatal responses to light oi Arabidopsis thaiiana wildtype plants and mutant plants deficient in starch (phosphoglucomutase deficient) were compared in gas exchange experiments. Stomatal density, size and ultrastructure were identical for the two phenotypes, but no starch was observed in guard cells of the mutant plants whatever the time of day. The overall extent of changes in stomatal conductance during 14 h light-10 h dark cycles was similar for the two phenotypes. However, the slow endogenous stomatai opening occurring in darkness in the wild type was not observed in the mutant plants. Stomata in the mutant plants responded much more slowly to blue light (70 ;Umol m~^ s~*) though the response to red light (250 /imol m~^ s~') was similar to that of wild-type plants. In paradermal sections, stomatal responses to red light (300 ^mol m""^ s~^) were weak for wild-type plants as well as for mutant plants. Stomatal opening was greater under low blue light (75 /imol m"^ s~*) than under red light for the two genotypes. However, in mutant plants, a high chloride concentration (50 mol m~^) was necessary to achieve the same stomatal aperture as observed for the wild-type plants. These results suggest that starch metabolism, via the synthesis of a counter-ion to potassium (probably malate), is required for full stomatal response to blue light but is not involved in the stomatal response to red light.

The ATP Binding Cassette Transporter AtMRP5 Modulates Anion and Calcium Channel Activities in Arabidopsis Guard Cells

“…Analysis of Stomatal Apertures-For experiments at the University of Zurich stomatal apertures of rosette leaves of 7-to 8-week-old plants were measured according to the method of Lascève et al (27). Measurements were started in the morning after 15-16 h of darkness.…”

Control of stomatal aperture

“…97 However, this blue-light response was restored in the presence of high concentrations of Cl -, possibly because Cl -replaced malate as a necessary counterion for K + highlighting the complexity of the mechanisms responsible for the stomatal control.…”

The plant multidrug resistance ABC transporter AtMRP5 is involved in guard cell hormonal signalling and water use

“…Continuous recording of the mean leaf conductance and whole-plant CO 2¯u xes in a dedicated chamber (Lasce Á ve et al, 1997) showed that both genotypes normally reacted to a day±night cycle by closing the stomata during the dark period, pre-opening in the second part of night period and opening under light (Figure 4d). No signi®cant difference was observed for CO 2 ®xation at ambient CO 2 partial pressure, whereas a signi®cant reduction of the mean leaf conductance was observed in mrp5-1 plants, a result consistent with the one observed in stomatal bioassays (see Figure 4.…”

“…Stomatal apertures and density of 4±5-week-old plants were measured according to the method of Lasce Á ve et al (1997). After 30 min in darkness, initial stomatal apertures were recorded.…”

“…Whole-plant and single-leaf gas exchange measurements Four-week-old plants were removed from the sand and inserted into an experimental chamber composed of independent shoot and root compartments (Lasce Á ve et al, 1997). The shoot compartment was inserted into an open-¯ow gas circuit.…”