Gases were extracted from the internal atmosphere of Elodea canadensis and Ceratophyllunz demersum in a closed system under reduced pressure. The volume of extractable gases varied throughout the daily period. Gases separated and quantitatively measured by gas chromatography included CO2, 02, N2, and CH4. Results from diurnal studies showed a lag between peak values for dissolved oxygen in the surrounding water and oxygen in the internal atmosphere. Lags were also observed in the CO2 values. As a result photosynthetic activity by these plants is not immediately reflected by changes in dissolved oxygen content of the surrounding water. The lacunal system apparently functions as a reservoir for metabolic gases. Experiments in which light intensity was controlled by floating screens indicated that at low intensities evidence of oxygen production in E. canadensis may be obtained only by observing the changes which occur within the internal atmosphere. At these intensities no increase in dissolved oxygen can be detected in the surrounding water although internal oxygen concentrations may increase slightly. Confirmation that carbon was being fixed by the plants under these conditions has been obtained by carbon-14 uptake studies using gas phase counting procedures. The observations cast further doubt on the reliability of using changes in dissolved oxygen as a sole measure of photosynthetic activity in aquatic ecosystems where submersed vascular plants are dominant.
A method was developed for determining uptake and translocation of mineral elements by intact submersed aquatic vascular plants in laboratory and field studies. Autoradiographs and radioactivity measurements provided direct evidence that 32P, 59Fe, and 45Ca were absorbed by the roots of Myriophyllum exalbescens and translocated to the shoot tissues. Similar evidence was obtained for absorption of 32P by the shoots and translocation to the roots. Data from experiments designed to compare the effect of substrate type (sand or muck) and the presence or absence of light showed no significant difference in the amounts of 32P absorbed by roots. Translocation of 59Fe from root to shoot tissues occurred mainly when plants were rooted in muck. 45Ca translocation from roots to shoots was greatest for plants rooted in sand and maintained in the light. 32P was generally distributed throughout Myriophyllum as revealed by autoradiography, with some accumulation occurring at the nodal and building regions. 59Fe and 45Ca were not translocated as readily but some accumulation of each occurred in the stem. 32P absorbed by the roots of Myriophyllum was translocated to the shoot system and released to the surrounding water. Experimental evidence showed that injury to submersed hydrophytes can result in additional release of phosphate to the water. The rate of release is increased as a result of physical damage to the shoot. This provides an additional pathway for the cycling of phosphorus in freshwater environments.
Social media platforms have become part of many people’s lives. Users are spending more and more time on these platforms, creating an active and passive digital footprint through their interaction. This footprint has high research potential in many research areas because understanding people’s communication on social media is essential in understanding their values, attitudes, experiences and behaviors. Researchers found that the use of social networking sites impacts adolescents’ eating behavior. If we define adolescents as individuals between ages 10 and 24 (WHO’s definition), 76% of USA young people at age 18–24 use Instagram, so the Instagram social network analysis is important for understanding young people’s expressions in the context of healthy food. This study aims to identify the main topic associated with healthy food on the Instagram social network via hashtag and community analysis based on 2,045,653 messages created by 427,936 individual users. The results show that users most associate Healthy food with healthy lifestyle, fitness, weight loss and diet. In terms of food, these are foods that are Vegan, Homemade, Clean and Plant-based. Given that young people change their behavior in relation to people’s behavior on social networks, it is possible to use this data to predict their future association with healthy food characteristics.
The summer stratification phosphorus budget for eutrophic Edinboro Lake in northwestern Pennsylvania was determined. Phosphorus loading from internal sources contributed 141 kg, (79%) and 55 kg, (68%) of the mass phosphorus increase in the lake in 198 1 and 1982, respectively. Calculated anaerobic sediment release rates of total phosphorus were 9.9 and 3.7 mg -m-2 . d a y ' for these two years. The observed summer maximum chlorophyll a concentration was 1.5-3 times greater than that predicted by existing models.Year-to-year variability in the internal phosphorus load for this lake and others is discussed. Without a data base that will permit the comparison of lakes and with and without a significant supply of internal phosphorus, prediction of the relative importance of internal loading in a particular lake will be difficult.
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