Tag: Kerstiens G.

Na+, stomata and salt tolerance

 

Sodium-related partial stomatal closure and salt tolerance of Aster tripolium 

by Kerstiens G., Tych W., Robinson M. F., Mansfield T. A. (2002) 

in New Phytologist, 2002, 153, 3, 509 – DOI: 10.1046/j.0028-646X.2001.00330.x

Wiley Online Library – http://onlinelibrary.wiley.com/doi/10.1046/j.0028-646X.2001.00330.x/full

Summary

  • • When Aster tripolium is grown at high salinity, stomatal closure is induced by the presence of sodium ions in the apoplast surrounding the guard cells. The occurrence of this system in Aster tripolium and not in the closely related glycophyte Aster amellus suggests that it could be an important factor in the network of physiological attributes required for salt tolerance.
  • • Gas exchange and growth parameters were measured in Aster tripolium plants grown at different levels of salinity. A simple mechanistic model was constructed to test whether the Na-sensing feature of the guard cells was a realistic component of salinity tolerance.
  • • The model captured very well the behaviour of plants in terms of salt uptake and reduction of growth with increasing salinity. There was moderate variance between measured and modelled rates of decrease of conductance with increasing levels of salinity.
  • • No evidence was found to refute our hypothesis that stomatal closure in response to sodium plays an important role in salt tolerance of Aster tripolium.

Stomatal turgor mechanism

Photo credit: JXB

Fig. 5.

Images of stoma 1 from the experiment shown in Fig. 4 during a peak of the oscillation (a) and in the closed state 6 min later (b). The time of observation is also marked by arrows in Fig. 4. The arrow in (a) points to the slightly open pore.

Stomatal oscillations at small apertures: indications for a fundamental insufficiency of stomatal feedback‐control inherent in the stomatal turgor mechanism

by Kaiser H., Kappen L. (2001)

in J. Exp. Bot. (2001) 52 (359):1303-1313. – doi:10.1093/jexbot/52.359.1303. 

Abstract

Continuous measurements of stomatal aperture simultaneously with gas exchange during periods of stomatal oscillations are reported for the first time. Measurements were performed in the field on attached leaves of undisturbed Sambucus nigra L. plants which were subjected to step‐wise increases of PPFD. Oscillations only occurred when stomatal apertures were small under high water vapour mole fraction difference between leaf and atmosphere (ΔW). They consisted of periodically repeated opening movements transiently leading to very small apertures. Measurements of the area of the stomatal complex in parallel to the determination of aperture were used to record volume changes of guard cells even if stomata were closed. Stomatal opening upon a light stimulus required an antecedent guard cell swelling before a slit occurred. After opening of the slit the guard cells again began to shrink which, with some delay, led to complete closure. Opening and closing were rhythmically repeated. The time‐lag until initial opening was different for each individual stoma. This led to counteracting movements of closely adjacent stomata. The tendency to oscillate at small apertures is interpreted as being a failure of smoothly damped feedback regulation at the point of stomatal opening: Volume changes are ineffective for transpiration if stomata are still closed; however, at the point of initial opening transpiration rate rises steeply. This discontinuity together with the rather long time constants inherent in the stomatal turgor mechanism makes oscillatory overshooting responses likely if at high ΔW the ‘nominal value’ of gas exchange demands a small aperture.

Read the full article: JXB