Chlorophyll fluorescence responses to CO availability reveal crassulacean acid metabolism in epiphytic orchids.

Crassulacean acid metabolism (CAM), a specialized mode of photosynthetic carbon assimilation characterized by nocturnal fixation of atmospheric CO and vacuolar malic acid storage, is found in a wide variety of vascular plant species, mainly those inhabiting water-limited environments. Identifying and characterizing diverse CAM species enhances our understanding of the physiological, ecological, and evolutionary significance of CAM photosynthesis. In this study, we examined the effect of CO elimination on chlorophyll fluorescence-based photosynthetic parameters in two constitutive CAM Kalanchoe species and six orchids.

Primary Sulfate Is the Dominant Source of Particulate Sulfate during Winter in Fairbanks, Alaska.

Within and surrounding high-latitude cities, poor air quality disturbs Arctic ecosystems, influences the climate, and harms human health. The Fairbanks North Star Borough has wintertime particulate matter (PM) concentrations that exceed the Environmental Protection Agency's (EPA) threshold for public health. Particulate sulfate (SO ) is the most abundant inorganic species and contributes approximately 20% of the total PM mass in Fairbanks, but air quality models underestimate observed sulfate concentrations.

Overview of the Alaskan Layered Pollution and Chemical Analysis (ALPACA) Field Experiment.

The Alaskan Layered Pollution And Chemical Analysis (ALPACA) field experiment was a collaborative study designed to improve understanding of pollution sources and chemical processes during winter (cold climate and low-photochemical activity), to investigate indoor pollution, and to study dispersion of pollution as affected by frequent temperature inversions. A number of the research goals were motivated by questions raised by residents of Fairbanks, Alaska, where the study was held. This paper describes the measurement strategies and the conditions encountered during the January and February 2022 field experiment, and reports early examples of how the measurements addressed research goals, particularly those of interest to the residents.

Geological evidence of extensive N-fixation by volcanic lightning during very large explosive eruptions.

Most of the nitrogen (N) accessible for life is trapped in dinitrogen (N), the most stable atmospheric molecule. In order to be metabolized by living organisms, N has to be converted into biologically assimilable forms, so-called fixed N. Nowadays, nearly all the N-fixation is achieved through biological and anthropogenic processes.

Stratospheric water vapor affecting atmospheric circulation.

Water vapor plays an important role in many aspects of the climate system, by affecting radiation, cloud formation, atmospheric chemistry and dynamics. Even the low stratospheric water vapor content provides an important climate feedback, but current climate models show a substantial moist bias in the lowermost stratosphere. Here we report crucial sensitivity of the atmospheric circulation in the stratosphere and troposphere to the abundance of water vapor in the lowermost stratosphere.