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Lips, S.H. 1996. The influence of enriched rtiizosphere CO2 on N uptake and metabolism in wild-type and NR-deficient barley plants, -Physiol. Plant, 97: 47-54, Positive influences of high concentrations of dissolved inorganic carbon (DIC) in the growth medium of salinity-stressed plants are associated with carbon assimilation through phosphoenolpyruvate carboxylase (PEPc) activity in roots: and also in salinity-stressed tomato plants, enriched CO, in the rhizosphere increases NOJuptake, In the present study, wild-type and nitrate reductase-deficient plants of barley (Hordeum vulgare L. cv. Steptoe) were used to determine whether the influence of enriched CO, on NOi uptake and metabolism is dependent on the activity of nitrate reductase (NR) in the plant. Plants grown in NHJ and aerated with ambient air. were transferred to either NO)Or NH; solutions and aerated with air containing between 0 and 6 500 jimol mor' CO2. Nitrogen uptake and tissue concentrations of NO3 and NH4 were measured as well as activities of NR and PEPc, The uptake of NO3 by the wild-type was increased by increasit^ CO2, This was associated with increased in vitro NR activity, but increased uptake of NO^ was found also in the NR-deficient genotype when exposed to high CO2 concentrations; so that the influence of CO2 on NOj uptake was independent of the reduction of NO3 and assimilation into amino acids. The increase in uptake of NO3 in wild-type plants with enriched CO2 was the same at pH 7 as at pH 5, indicating that the relative abundance of HCO3 or CO, in the medium did not influence NOj uptake. Uptake of NHJ was decreased by enriched CO, in a pH (5 or 7) independent fashion. Thus NOJ and NHI uptakes are influenced by the CO, component of DIC independently of anaplerotic carbon provision for amino acid synthesis, and CO, may directly affect the uptake of NO; and NHJ in ways unrelated to the NR activity in the tissue. Introduction ^^ j-p^ j ^^5^ Assitnilation of dissolved inorgatiic car-Research on the effect of elevated atmospheric CO2 on bon (DIC = CO2 -1-HCO3) irt the tiutrient solution by plant growth and physiology bas been focused on the ef-plant roots in the dark has been widely observed (Vapaafects of elevated attrtospberic CO2 on the production and vuori and Pelkonen 1985, Vuorinen et al, 1992, Cramer utilization of photosynthate (Taylor et al, 1994, Ele-and Lewis 1993, Cramer et al, 1993, but the signiftvated atmospheric CO2 itihibits shoot respiration (Bunce cance of this process is controversial. The influence of 1994, Thomas and Griffin 1994, WuUschleger et al, enriched CO2 on plant grovsfth was reviewed by Enoch 1994, Ziska and Bunce 1994), while high CO2 in the soil and Olesen (1993), As a consequence of the small coninhibits root respiration (Qi et al, 1994), The effect of el-tribution to the overall carbon btidget of the plant made evated CO2 on apparent respiration may, at least par-by CO2 uptake by roots, they concluded that CO2 prima-

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The review focuses on sulfated steroids that have been isolated from seaweeds, marine sponges, soft corals, ascidians, starfish, and other marine invertebrates. Sulfur-containing steroids and triterpenoids are sourced from sedentary marine coelenterates, plants, marine sediments, crude oil, and other geological deposits. The review presents the pharmacological profile of sulfated steroids, sulfur-containing steroids, and triterpenoids, which is based on data obtained using the PASS program. In addition, several semi-synthetic and synthetic epithio steroids, which represent a rare group of bioactive lipids that have not yet been found in nature, but possess a high level of antitumor activity, were included in this review for the comparative pharmacological characterization of this class of compounds. About 140 steroids and triterpenoids are presented in this review, which demonstrate a wide range of biological activities. Therefore, out of 71 sulfated steroids, thirteen show strong antitumor activity with a confidence level of more than 90%, out of 50 sulfur-containing steroids, only four show strong antitumor activity with a confidence level of more than 93%, and out of eighteen epithio steroids, thirteen steroids show strong antitumor activity with a confidence level of 91% to 97.4%.

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