Phytoplankton and water quality long term trends are presented from a 20-year monitoring program of Chesapeake Bay and several of its major tributaries. Increasing phytoplankton biomass and abundance are ongoing within this estuarine complex, with diatoms the dominant component, along with chlorophytes and cyanobacteria as sub-dominant contributors in the tidal freshwater and oligohaline regions. Diatoms, dinoflagellates, and cryptomonads are among the major flora downstream in the tributaries and within the Chesapeake Bay. Water quality conditions within the three tributaries have remained rather stable over this time period; while there are long term trends of reduced nutrients, increasing bottom oxygen, and decreasing water clarity for the lower Chesapeake Bay. Of note is an increasing trend of cyanobacteria biomass at 12 of the 13 stations monitored at tributary and Chesapeake Bay stations, plus the presence of 37 potentially harmful taxa reported for these waters. However, the overall status of the phytoplankton populations is presently favorable, in that it is mainly represented and dominated by taxa suitable as a major food and oxygen source within this ecosystem. Although potentially harmful taxa are present, they have not at this time exerted profound impact to the region, or replaced the diatom populations in overall dominance.
Maximum growth of suspension cultures of Paul's Scarlet rose required a low pH (5.2 to 5.4) during the division phase (day 0 to 7) and a higher pH (5.8 to 6.0) during the expansion phase (day 7 to 14). The fresh weight increase was reduced by approximately 22%, but the dry weight was not influenced when cells were grown for 14 days in a CO2 deficient environment. Kinetic studies showed that the first five days of growth was the critical period of nonautotrophic CO2 fixation when cells were grown in medium buffered at pH 5.4. The phosphoenolpyruvate carboxylase activity was highest (0.50 × 106 cpm min−1· g−1 fresh weight) during the period when nonautotrophic CO2 fixation appeared to be critical for growth.
Maximum growth of suspension cultures of Paul's Scarlet rose has been demonstrated in a minimal organic medium possessing only 4 organic compounds: napthaleneacetic acid, kinetin, myo-inositol, and sucrose. Myo-inositol was not essential for growth, but sustained growth was reduced by 90% when it was omitted. Maximum growth required nitrate plus a supplemental amount of either NH 4 (+) or glutamine.
Electron micrographs of Pisum sativum L. hypocotyl tips treated to localize adenyl cyclase revealed discrete deposits on the internal membranes of cytoplasmic vacuoles which correspond to previously localized enzymes described as acid phosphatases. It remains to be determined whether the specificity of the substrate, adenylyl‐imidodiphosphate, used in the present study is such as to exclude all phosphatase activity other than adenyl cyclase. The acid phosphatase localized in earlier studies by other investigators may be an adenyl cyclase. In the differentiated cells of the root cap, lead precipitate was localized in distinct areas bound to the smooth endoplasmic reticulum.
Bicarbonate-'4C was provided to 5-and 11-day-old suspension cultures of Paul's Scarlet rose, and the incorporation of 4C into lipid, protein, amino acids, and organic acids was determined. The rate of bicarbonate uptake was approximately the same by 5-and 11-day-old cells, but the distribution of 4C among cell constituents was markedlv different. In 5-dav-old cells a larger proportion of the "4C entered protein, whereas in 11-day-old cells there was a greater tendency for "4C to accumulate in malate.The '4C in protein was distributed among 10 amino acids each having greater than 1 % of the total 14C recovered in protein. The distribution of "4C among tricarboxylic acid cycle intermediates indicated that the aspartate family of amino acids was synthesized directly from oxaloacetate produced as a result of nonautotrophic C02 fixation. However, this was not the sole source of oxaloacetate used for the synthesis of aspartate, for in a double labeling study with bicarbonate-14C and acetate-3H it was shown that oxaloacetate was drained simultaneously from the tricarboxvlic acid cycle for this purpose.Privation studies have shown that CO2 is required for the normal growth of microbial (22), animal (6, 15), and nonphotosynthetic plant cells (16,19). In explaining this requirement, some authors have emphasized the importance of nonautotrophic CO2 fixation for replenishment of carbon skeletons diverted from the TCA2 cycle into other metabolic pathways (2,16,17,23). Other authors have proposed that the product of CO2 fixation served as a direct source of carbon for amino acid synthesis (7,8,10), and was therefore necessary for growth. In previous work we showed that suspension cultures of Paul's Scarlet rose require CO2 for nonautotrophic growth (13). The present study compared the use of bicarbonate-'4C by 5-versus 11-day-old cells and looked specifically at the relationship of nonautotrophic CO2 fixation to the TCA cycle and the synthesis of amino acids incorporated into protein. growth conditions and composition of the medium were the same as used previously (5, 14), with two exceptions; the concentration of molybdic acid in the medium was 0.01 mg/l, and potassium iodide was 0.5 mg/l. One-gram samples of cells were harvested at selected times and incubated in 25-ml Erlenmeyer flasks containing 5 ml of the medium (pH 7.5). The medium contained 4 ,uCi of NaHW4CO3 (specific radioactivity 10 /Ci/ptmole). The depletion of bicarbonate-"C from the medium was determined by removing 10 ,l of the incubation medium at various time intervals and assaying for radioactivity. The uptake of bicarbonate-4C by cells was corrected for the direct loss of "4CO2 to the atmosphere by running controls which consisted of duplicate amounts of bicarbonate-'4C in a medium containing no cells. MATERIALS AND METHODSAt the end of the incubation period the medium was filtered through Miracloth. The recovered cells were washed thoroughly with deionized water, were placed into 15 ml of hot 80% ethanol, and homogenized for 3 min on a VirTis grind...
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