Synecological comparisons sustained by ecophysiological fingerprinting of intrinsic photosynthetic capacity of plants as assessed by measurements of light response curves

In some literature variations in photosynthetic rates are considered to be of little relevance for individual fitness. This depends among other things on how one defines fitness, i.e. if one takes strictly Darwinian fitness as seed production or if one needs to evaluate particular traits and consider plant establishment. It also matters if one takes the Darwinian "organism individual" as the central entity in evolution ("individual fitness") or the "species individual" in a modified "Structure of Evolutionary Theory" sensu Stephen Jay Gould. A phenotypically expressed trait like photosynthetic rate, even if intra- and interspecific differences may be small, can matter in habitat performance and niche acquisition. Light dependence curves (LCs) of photosynthetic rates are now readily measured under field conditions using miniaturized equipment of pulse amplitude modulated fluorometers. In contrast to actual momentary measurements of quantum yield of photosynthesis under actually prevailing ambient conditions, LC measurements reflect the expressed intrinsic capacity of photosynthesis. In this review we explore the power of LC measurements yielding cardinal points such as maximum apparent electron transport rate of photosystem II (ETRmax) and saturating photosynthetically active radiation (PARsat) in making intra- and interspecific comparisons of plant performance and synecological fingerprinting in ecophysiological studies across species, sites, habitats and ecosystems.

Tracheal instillation of urban PM2.5 suspension promotes acute cardiac polarization changes in rats

The mechanisms by which PM2.5 increases cardiovascular mortality are not fully identified. Autonomic alterations are the current main hypotheses. Our objective was to determine if PM2.5 induces acute cardiac polarization alterations in healthy Wistar rats. PM2.5 samples were collected on polycarbonate filters. Solutions containing 10, 20, and 50 µg PM2.5 were administered by tracheal instillation. P wave duration decreased significantly at 20 µg (0.99 ± 0.06, 0.95 ± 0.06, and 0.96 ± 0.07; P < 0.001), and 50 µg (0.98 ± 0.06, 0.98 ± 0.07, and 0.96 ± 0.08; 60, 90 and 120 min, respectively) compared to blank filter solution (P < 0.001). PR interval duration decreased significantly at 20 µg (0.99 ± 0.06, 0.98 ± 0.07, and 0.97 ± 0.08) and 50 µg (0.99 ± 0.05, 0.97 ± 0.0, and 0.95 ± 0.05; 60, 90, and 120 min, respectively) compared to blank filter and 10 µg (P < 0.001). QRS interval duration decreased at 20 and 50 µg in relation to blank filter solution and 10 µg (P < 0.001). QT interval duration decreased significantly (P < 0.001) with time in animals receiving 20 µg (0.94 ± 0.12, 0.88 ± 0.14, and 0.88 ± 0.11) and 50 µg (1.00 ± 0.13; 0.97 ± 0.11 and 0.98 ± 0.16; 60, 90 and 120 min, respectively) compared to blank filter solution and 10 µg (P < 0.001). PM2.5 induced reduced cardiac conduction time, within a short period, indicating that depolarization occurs more rapidly across ventricular tissue.