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At least 1,369 records · Page 76Linked to original sources
PubMed2001

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

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 (DeltaW). 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 DeltaW the 'nominal value' of gas exchange demands a small aperture.

Atmosphere↗
PubMed1975

[A survey of work environment of upper-shoe factories. (author's transl)].

A research was carried out by the authors in order to asses the environmental, hygienic, microclimatic and risky features of the work environment of some upper-shoe factories, mainly in relation to the onset of polyneuropathy. The close connection between work environment and some noxious chemical compounds is underlined, and the opportunity to set up an organic regulation of the matter, stressed.

Air Pollutants↗
PubMed2001

[Water distribution and microclimatic effects of sprinkler irrigation on spring wheat field].

Measurements of sprinkler irrigation on spring wheat field indicated that spring wheat canopy could intercept water by 25-30%, and compared with that above canopy in first milking period, the uniformity coefficient below canopy could be increased by 7-9%. Floating and evaporation loss of sprinkler irrigation water could reach 20-25% of the total. In addition, sprinkler irrigation on spring wheat field could decrease air and soil temperature, and increase air actual vapor pressure and relative humidity, which played a definite role in restraining crop transpiration.

Microclimate↗
PubMed1975

[Efficacy of aerosol disinfection with lactic acid and its effect on the body of poultry].

Comparative studies were carried out to establish the efficacy of lactic acid as a disinfection means. The following pattern was observed in employing the agent: a 20 per cent conc. of the acid at the rate of 20 cu. cm per cubic meter is dispersed three times as an aerosol (at 8, 12, and 6 oclock) in the course of twenty minutes. It was found that the microbial contamination of the air drops three to four times. More pronounced is the bactericidal effect on the coliforms and moulds. The birds of the group treated with lactic acid gain 30 g more per day up to the end of the fattening period. Dependable is the higher serum level of protein as well as the higher protein content of the liver and heart musculature and of the essential amino acid tryptophane in the blood serum and liver of the test birds. Higher was also the glycogen content of the liver of the test group broilers.

Aerosols↗