Gas exchange and leaf water potential were investigated with regard to water stress in potted 6-month old plants of Copaifera langsdorffii. Leaf water potential (Ψ = -2.0 MPa) in stressed plants was near the osmotic potential (π = -2.2 MPa) at 0900 h during 22 d with water stress. Transpiration rates (if were in linear relation to stomatal conductance (gs) during stress, while water potential and net photosynthetic rate (PN) at 0900 h were in a curvilinear relation. More pronounced decrease of P N occurred only at gs between 0.01 to 0.08 mol nr2 s-1. Increase in water use efficiency (WUE) coincided with morning Ψ diminution from -2.0 MPa to -2.2 MPa. This 10 % decrease in Ψ corresponded to a 60 % decrease in gs (from 0.15 to 0.06 mol m*2 s*1). When pre-dawn Ψ (-3.4 MPa) was close to the Ψ measured at 0900 h (-3.5 MPa), both the and gs were around zero. Therefore, Ψ at 0900 h, π and values of gas exchange were closely related during the days of stress. Values of Ψ for zero and for stomatal closure (-3.5 MPa) were in the same range for sclerophyllous plants.
The influence of air humidity on leaf-air gas exchange and leaf water potential (4^) was investigated during daily courses in control and water stressed potted young plants of Copaifera langsdorffii. When leaf-air water vapour concentration difference (AW) increased during the day, stomatal conductance (g^) and net photosynthetic rate (P]vj) decreased under both soil moistures. Moderate AW induced lower values of g^ and Pn unwatered than control plants, High AW in atmosphere produced strong depression in g^ (from 0.22 to 0,01 mol m'^ s’’) and (from 6.5 to 0.7 pmol m'2 s'*) in control plants around midday, with recuperation of T'. Expected conductance tese) was calculated as fimction of AW, which was useful for discriminating soil to atmosphere water stress. In špite of momentary T or soil water stress, P^, g^, and water use efficiency decreased when AW increased during day course.
Influence of soil drought (40 d) on gas exchange of 10 cultivars of spring cereals (wheat, barley, triticaie and oats) grown in growth chamber was studied. When soil water content was decreased from 60 to 35 % of Ml water capacity, a new steady levels of net photosynthetic rate, transpiration rate and stomatal conductance (about twice, 3-4 and 2-3 fold lower, respectively) were observed after 3 d for both studied oat cultivars and after 5 d for others. These levels were maintained almost the same till the end of the experiment. Calculated water use efficiency (WUE) of water stressed plants increased 3-4 fold, the highest being for barley while the lowest for Oats. At die beginning of the night dark respiration of well watered plants was a little higher than that of water stressed plants but at the end of ihe night was the Sáme independently of water treatment, aithough 20-30 % lower than at the begitming of the night.
Carbon dioxide, a natural acidic gas, may be ušed for in vivo titration of the buffers in the compartments of cells that contain carbonic anhydíase in intact leaves. A gas systém for the measurement of the CO2 capacity (total inorganic carbon content) of leaves under different extemal CO2 concentrations has been developed. The systém consists of a leaf chamber and of two open (flow-through) channels, one for pre- loading the leaf with CO2 and the other for measurement of the desolubilized CO2. CO2 concentration in the loading channel may be adjusted from 0.03 to 20 %, while CO2 free air is flowing in the burst (desolubilization) channel. The leaf chamber (4.3 X 4.3 X 0.3 cm^) is switched either into the loading channel or into the burst channel. After loading the leaf with high CO2 in the dark the .chamber is switched into the burst channel and the desolubilized CO2 is measured. Preliminary measurements show that the CO2 capacity of a sunflower leaf decreases when the CO2 concentration is increased from 0.03 to 15 %, because of saturation of buffers. The systém can be ušed for direct, non-destructive measurements of pH and buffer capacity in leaf chloroplasts in order to investigate the influence of pH on photosynthesis, the operation of proton pumps and other pH-stabilising mechanisms.
The response of some photosynthetic parameters (CO2 assimilation, transpiration rate, stomatal conductance, intercellular CO2 concentration, water-use efficiency, and chlorophyll content), shoot development, and the morphological features of the root system to differentiated conditions of nitrogen supply was tested in festulolium (Festulolium braunii K. Richert A. Camus) varieties (Felopa and Sulino). Nitrogen fertilization with no nitrogen added
[0 g(N)], single dosage [0.23 g(N)], and double dosage [0.46 g(N)] per pot and per year was applied. Lack of nitrogen resulted in formation of longer and finer roots and lowered chlorophyll content, CO₂ assimilation, and water-use efficiency, resulting in lower dry matter accumulation. Application of both dosages of nitrogen resulted in improved aboveground features, while root features were enhanced without nitrogen fertilization. Dependence between physiological parameters and morphological traits was significant and positively correlated in the case of the aboveground parts of plants and negatively correlated to the belowground parts., G. Mastalerczuk, B. Borawska-Jarmułowicz, H. M. Kalaji, P. Dąbrowski, J. Paderewski., and Obsahuje bibliografii
We studied water relations and gas exchange in six almond genotypes grafted on GF677 in response to withholding irrigation for 14 days and a subsequent 10-day rehydration period. The responses to drought stress significantly differed in the almond genotypes; the tolerant plants were distinguished and monitored. Leaf relative water content (RWC) decreased by more than 23%, leaf water potential dropped to less than -4.3 MPa, and electrolyte leakage increased to 43% in dehydration-sensitive genotypes. Photosynthesis (PN) and stomatal conductance (gs) of drought-sensitive genotypes were significantly reduced by 70% and 97% in response to water deficiency. Water stress significantly enhanced wateruse efficiency up to 10 folds in drought-tolerant almonds. The difference between leaf temperature and its surrounding air temperature (ΔT) increased significantly to more than 187% under water stress in drought-tolerant genotypes. In addition, the reduction in the g s and further ability to preserve RWC were involved probably in drought-tolerance mechanism in almond. Negative significant correlations were found between ΔT, PN, and gs. Based on the correlations, we suggested that ΔT could be used as a simple measurement for monitoring water stress development in the irrigation management of almond orchards. In conclusion, ‘Supernova’ and the Iranian genotypes ‘6-8’ and ‘B-124’, were found to be more droughttolerant compared with other genotypes in this experiment., S. Karimi, A. Yadollahi, K. Arzani, A. Imani, M. Aghaalikhani., and Obsahuje bibliografii
Gastric or intestinal luminal tonometry is a method for monitoring critically ill patients. It offers an index of the adequacy of aerobic metabolism in a tissue that is particularly sensitive to alterations in its perfusion and oxygenation: the gut mucosa. It is based on the measuring the increase in tissue CO2 production that accompanies anaerobic metabolism. The method simply consists of a balloon in the stomach, which measures intramucosal pCO2. From this measurement and from the arterial bicarbonate concentration gastric intramucosal pH (pHi) can be calculated, assuming that bicarbonate concentration in the gastric mucosal tissue is in equilibrium with systemic arterial bicarbonate. Despite possible clinical benefit from the measurement and the therapy of low pHi values in critically ill patients, the theoretical, experimental and pathophysiological implications for the monitoring of intramucosal acidosis in the gut are not yet fully understood. There are still some open methodological questions crucial for further clinical interpretation., V. Černý, K. Cvachovec., and Obsahuje bibliografii