A significant enhancement of water vapour uptake at low pressure by amine-functionalization of UiO-67

The functionalization of the metal–organic framework, UiO-67, with –NH2 groups is proven effective for increasing the water uptake capacity at low relative pressure at 298 K.

Ecological significance of net photosynthesis activation by water vapour uptake in Ramalina capitata from rain-protected habitats in central Spain

The reactivation of net photosynthesis and dark respiration from water vapour and from liquid water in the lichen Ramalina capitata var. protecta (H. Magn.) Nimis from sheltered habitats in Central Spain was investigated. CO2 gas-exchange response and thallus water content were measured in the laboratory as dry thalli were allowed to equilibrate by water vapour uptake under different relative humidities, and as saturated thalli dried. Water content of thalli from different habitats was also measured in the field during rainfall. The results show that the lichen is very efficient in using water vapour from the air for photosynthesis. Net photosynthetic rates were measured at very low water potentials (up to – 26-9 Megapascal) with water contents of the thalli below 30% dry weight. Maximum net photosynthetic rates measured after water vapour uptake were in some cases similar to those obtained after hydration by liquid water, while respiration rates were always lower after water vapour uptake, indicating a relatively larger activation of the photobiont. Moreover, photosynthetic rates at thallus water contents below 60% dry weight were higher when hydration was achieved through water vapour uptake than with liquid water. Field measurements had shown that this lichen reached water contents through water vapour absorption of 40% dry weight that would allow a positive balance of CO2 uptake. Possible ecological implications of differences in photosynthetic activation depending on the water source are discussed in terms of the carbon gain under natural conditions of this ombrophobous lichen.

Water vapour uptake and drought resistance in immobile instars of Parasitengona (Acari: Prostigmata)

Eggs and protonymphs of a number of terrestrial Parasitengona were tested for drought resistance and their ability to take up atmospheric moisture. Species of the Erythraeoidea display higher drought resistance in both instars than species of the Trombidioidea. This is achieved by evolutionary modifications of the ground plan of the Parasitengona, including reduction of body openings and additional sealing of others with lipids, resulting in reduced water loss. Water vapour uptake is not evident in erythraeoid eggs or protonymphs but has been observed in the Trombidioidea and probably constitutes a characteristic of at least the stem species of the terrestrial Parasitengona. The resulting increase in fresh mass is about 50% before the protonymph stage begins; its role is probably not related to drought resistance or osmotic regulation. Instead, it presumably serves to extend the cuticle and thus provides more space for the development of the subsequent instar.

On the mechanism of water vapour sorption from unsaturated atmospheres by ticks

The nascent salivary secretion of 41 partly dehydrated and unfed adult female Amblyomma variegatum, 5­8 months post-ecdysis, during water vapour uptake at 93.5 % relative humidity and 20 °C, had an osmolality of between 298.6 and 769.7 mosmol kg-1 (mean ± s.d. 470.3±85.8 mosmol kg-1). This range would allow water vapour uptake at relative humidities of approximately 98­99 %, but it would not suffice for lower relative humidities down to 80­85 %, the critical equilibrium humidity of A. variegatum. At this relative humidity (85 %), an osmolality of 9796 mosmol kg-1 is required for water vapour uptake. It is proposed that hydrophilic cuticle in the hypostome could play a role in water condensation and that the slightly hyperosmotic secretion of the agranular alveoli of the salivary glands might alter the water affinity at the adsorbing cuticle surface and release the adsorbed water. The water-enriched secretion would then be drawn into the mouth by the powerful suction of the pharynx. This hypothetical hydrophilic cuticle component of water vapour uptake in A. variegatum merits closer investigation. The sorption kinetics of A. variegatum support an additional 'osmotic' component of water vapour uptake at humidities near saturation. A nanolitre osmometer particularly suited to sample volumes smaller than 5 nl was developed. This device does not require the transfer of fluid after collection, and its measurement range is extended beyond the 5 osmol kg-1 that can be measured using commercial apparatus.