Water loss after stomatal closure: quantifying leaf minimum conductance and minimal water use in nine temperate European tree species during a severe drought

Residual canopy transpiration (Emin_canop) is a key physiological trait that determines trees' survival time under drought after stomatal closure and after trees have limited access to soil water. Emin_canop mainly depends on leaf minimum conductance (gmin) and vapor pressure deficit. Here we determined the seasonal variation of gmin and how gmin is related to interspecies variation in leaf cuticular and stomatal traits for nine European tree species in a mature forest. In addition, we determined the species-specific temperature responses of gmin. With this newly obtained insight, we calculated Emin_canop for the nine species for one day at our research site during the 2022 central European hot drought. Our results show that at ambient temperatures gmin ranged from 0.8 to 4.8 mmol m-2 s-1 across the nine species and was stable in most species throughout the growing season. The interspecies variation of gmin was associated with leaf cuticular and stomatal traits. Additionally, gmin exhibited strong temperature responses and increased, depending on species, by a factor of two to four in the range of 25-50 °C. For the studied species at the site, during a single hot drought day, Emin_canop standardized by tree size (stem basal area) ranged from 2.0 to 36.7 L m-2, and non-standardized Emin_canop for adult trees ranged from 0.3 to 5.3 L. Emin_canop also exhibited species-specific rapid increases under hotter temperatures. Our results suggest that trees, depending on species, need reasonable amounts of water during a drought, even when stomates are fully closed. Species differences in gmin and ultimately Emin_canop can, together with other traits, affect the ability of a tree to keep its tissue hydrated during a drought and is likely to contribute to species-specific differences in drought vulnerability.

[Symptomatic isolated atrial septal defects (ostium secundum) in the infant]

Poorly tolerated solitary ASD in the baby is rare. The main criteria for diagnosis have been drawn from a series of 9 cases. The symptoms are often atypical, especially at first: usually a marked pansystolic murmur, a tricuspid flow murmur, late appearance of a doubling of B2, and a non-specific cardiac outline, except for the cardiac enlargement and the increased pulmonary vascularity. The ECG is rather more helpful, with constant RVH. At catheterisation, there is a major left-to-right shunt, the pressures in the right and left atria are equal, and pulmonary hypertension is rare. It is particularly common to find associated extra-cardiac abnormalities. Under medical treatment the prognosis is good, and early surgical closure is not normally required.

[Treatment of hyaline membrane disease with the plasminogen urokinase combination]

The authors present the results obtained using a therapeutic combinaison of plasminogen-urokinase in vivo in 14 premature infants suffering from respiratory distress. 86 % survived, a considerable improvement over classical survival rates. In addition it appeared that the duration of oxygen therapy was shorter, secondary to limitation of extension of the disease.

[Agenesia of the pulmonary valves manifested by ventilation disorders. In the newborn]

Agenesia of the pulmonary valves is often responsible for severe disorders of ventilation by bronchial compression in newborns. This may be involved in case of respiratory distress, with a double murmur, expressing the stenosis of an avalvulated pulmonary ring and the massive pulmonary regurgitation. The bad tolerance is due to the association with an interventricular dilatation of the pulmonary artery, which characterizes this malformative complex. The prognosis is severe and the treatment is disappointing since all surgical attempts failed at this age.