The Henry's law solubility and the decomposition reaction kinetics of nitrous acid (HN02) in aqueous solutions have been determined by measuring the material distribution between the gas and liquid phase of the pertinent species with the use of a bubbler-type gas-liquid reactor in conjunction with a high-sensitivity chemiluminescence NO* detector. The pH-dependent solubility of N(III) (=HN02 + N02") was measured for the pH range 2.13-3.33. The Henry's law coefficient and the acid dissociation constant of HN02 corresponding to 25 °C are determined to be 49 ± 3 M atm™1 and (5.3 ± 0.4) X 10™4 M, respectively. The temperature dependence of the solubility over the range 0-30 °C yielded A/7°sol = -9.7 ± 0.3 kcal mol™1 and AS°sol = -24.8 ± 0.7 cal mol™1 K™1. The rate constants of the aqueous-phase reactions 2HN02 NO + N02 + H20 (5) and 2N02 + H20 -H+ + N03™ + HN02 (6) determined at 22.0 ± 0.1 °C are k¡ = 13.4 ± 1.0, k_5 = (1.6 ± 0.1) X 108, and k6 = (8.4 ± 1.5) X 107, all in units of M'1 s™1. The values of AG°sol and A5°S0l for the dissolution of HN02 determined in this work are at variance with the latest values recommended by the National Bureau of Standards but are essentially identical with the previously selected set of values. The rather limited solubility of HN02, in combination with its low atmospheric concentrations, suggests that HN02 by itself contributes insignificantly to the acidification of atmospheric water, e.g., cloudwater. However, aqueous-phase reactions that produce HN02 followed by degassing remain a plausible route for the production of atmospheric HN02.

No abstract

No abstract

Ranunculus trichophyllus is an amphibious plant that produces thin and cylindrical leaves if grown under water but thick and broad leaves if grown on land. We found that such heterophylly is widely controlled by two plant hormones, abscisic acid (ABA) and ethylene, which control terrestrial and aquatic leaf development respectively. Aquatic leaves produced higher levels of ethylene but lower levels of ABA than terrestrial leaves. In aquatic leaves, their distinct traits with narrow shape, lack of stomata, and reduced vessel development were caused by EIN3-mediated overactivation of abaxial genes, RtKANADIs, and accompanying with reductions of STOMAGEN and VASCULAR-RELATED NAC-DOMAIN7 (VDN7). In contrast, in terrestrial leaves, ABI3-mediated activation of the adaxial genes, RtHD-ZIPIIIs, and STOMAGEN and VDN7 established leaf polarity, and stomata and vessel developments. Heterophylly of R.trichophyllus could be also induced by external cues such as cold and hypoxia, which is accompanied with the changes in the expression of leaf polarity genes similar to aquatic response. A closely-related land plant R. sceleratus did not show such heterophyllic responses, suggesting that the changes in the ABA/ethylene signaling and leaf polarity are one of key evolutionary steps for aquatic adaptation.

No abstract