Life Sciences Commons^™

Evalution Of The Efficacy Of The Photosystem Ii Inhibitor Dcmu In Periphyton And Its Effects On Nontarget Microorganisms And Extracellular Enzymatic Reactions, Steven N. Francoeur, Audrey C. Johnson, Kevin A. Kuehn, Robert K. Neely

Faculty Publications

We examined the efficacy of the photosystem II inhibitor 3-(3,4-diclorophenyl)-1,1-dimethyl urea (DCMU) for inhibition of algal photosynthesis in periphyton associated with submerged decomposing litter of Typha angustifolia. We also investigated the possible nontarget effects of DCMU exposure on heterotrophic microorganisms (i.e., bacteria and fungi) and extracellular enzyme activity associated with decaying litter. Standing-dead Typha leaf litter was submerged for 34 and 73 d, returned to the laboratory, and used for controlled laboratory experiments that examined the effect of DCMU on algal ([¹⁴C]bicarbonate, pulse-amplitude modulated fluorometry), bacterial ([³H]leucine), and fungal ([¹⁴C]acetate) production. Simultaneous assays …

Algal Regulation Of Extracellular Enzyme Activity In Stream Microbial Communities Associated With Inert Substrata And Detritus, Steven T. Rier, Kevin A. Kuehn, Steven N. Francoeur

Faculty Publications

We tested the hypothesis that algae influence the activities of extracellular enzymes involved in mineralization processes within microbial assemblages in streams. We tested the prediction that the factors that influence algal biomass and photosynthesis (i.e., diel fluctuations in photosynthetically active radiation [PAR], long-term variations in light regime, and community development stage) would have a corresponding effect on extracellular enzyme activities. We also tested the prediction that algae would influence enzyme activities on inorganic substrata and in detrital communities where they ultimately would influence plant litter decomposition rates. We allowed microbial communities to develop on inert substrata (glass-fiber filters) or on …

Genome Size Evolution In Relation To Leaf Strategy And Metabolic Rates Revisited, Jeremy M. Beaulieu, Ilia J. Leitch, Charles A. Knight

Biological Sciences

• Background and AimsIt has been proposed that having too much DNA may carry physiological consequences for plants. The strong correlation between DNA content, cell size and cell division rate could lead to predictable morphological variation in plants, including a negative relationship with leaf mass per unit area (LMA). In addition, the possible increased demand for resources in species with high DNA content may have downstream effects on maximal metabolic efficiency, including decreased metabolic rates.

• MethodsTests were made for genome size-dependent variation in LMA and metabolic rates (mass-based photosynthetic rate and dark respiration rate) using our own …

Physiological And Biochemical Responses Of Resistant And Susceptible Wheat To Injury By Russian Wheat Aphid, Lisa D. Franzen, Andrea R. Gutsche, Tiffany Heng-Moss, Leon G. Higley, Gautam Sarath, John D. Burd

Department of Entomology: Faculty Publications

We examined the physiological and biochemical responses of resistant (“Halt” and “Prairie Red”) and susceptible (“TAM 107”) wheat, Triticum aestivum L., to injury by the Russian wheat aphid, Diuraphis noxia (Mordvilko). Photosynthetic capacity was evaluated by measuring assimilation/ internal CO₂ (A/C_i) curves, chlorophyll fluorescence, chlorophyll, and nonstructural carbohydrate content. Total protein and peroxidase specific activity also were determined. No significant differences were detected in chlorophyll concentration between aphid-infested and control TAM107 plants. The aphid-infested resistant cultivars had similar or significantly higher chlorophyll concentrations compared with their respective control plants. Measurements over time showed that infested Halt plants …

Corticular Photosynthetic Dynamics For A Coastal Evergreen Shrub: Myrica Cerifera, Jaclyn K. Vick

Theses and Dissertations

I quantified seasonal variations in corticular photosynthesis in 1st through 5th order branches of Myrica cerifera L. (Myricaceae) in order to determine whether corticular photosynthesis contributes to whole plant carbon gain by reducing respirational CO2 loss. Maximum % refixation was 110 ± 39 % of CO2 efflux in the dark (Rd) in 1st order branches during winter, minimum was 18 ± 3 % in 5th order branches during summer. Variations in % refixation paralleled changes in photosynthetically active radiation (PAR). As light attenuated with increasing branch order % refixation decreased. Increased PAR in the winter due to a more sparse …

Influence Of Nutrient Concentrations And Nacl Salinity On The Growth, Photosynthesis, And Essential Oil Content Of Peppermint And Lemon Verbena, S. J. Tabatabaie, J. Nazari

Turkish Journal of Agriculture and Forestry

Growth and essential oil content of peppermint (Menhta piperita var. officinalis) and lemon verbena (Lipia citriodora var. Verbena) were evaluated in response to salinity and nutrient solution concentrations, measured as electrical conductivity (EC 0.7, 1.4, 2.8, 5.6, and 5.6_{Na} dS m^{-1}). In peppermint, the highest fresh weight and dry weight were observed in the 1.4 dS m^{-1} treatment. The increased EC with either NaCl or all nutrients at 5.6 dS m^{-1} reduced the fresh weight of lemon verbena. The maximum fresh weight and dry weight in lemon verbena were obtained in both 1.4 and 2.8 dS m^{-1} treatments. Increasing EC …

Simulations Of Phytoplankton Species And Carbon Production In The Equatorial Pacific Ocean 1. Model Configuration And Ecosystem Dynamics, Baris Salihoglu, Eileen E. Hofmann

OES Faculty Publications

The primary objective of this research is to investigate phytoplankton community response to variations in physical forcing and biological processes in the Cold Tongue region of the equatorial Pacific Ocean at 0N, 140W. This research objective was addressed using a one-dimensional multicomponent lower trophic level ecosystem model that includes detailed algal physiology, such as spectrally-dependent photosynthetic processes and iron limitation on algal growth. The ecosystem model is forced by a one-year (1992) time series of spectrally-dependent light, temperature, and water column mixing obtained from a Tropical Atmosphere-Ocean (TAO) Array mooring. Autotrophic growth is represented by five algal groups, which have …

Coupling Coherence Distinguishes Structure Sensitivity In Protein Electron Transfer, Tatiana Prytkova, Igor V. Kurnikov, David Beratan

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Quantum mechanical analysis of electron tunneling in nine thermally fluctuating cytochrome b562 derivatives reveals two distinct protein-mediated coupling limits. A structure-insensitive regime arises for redox partners coupled through dynamically averaged multiple-coupling pathways (in seven of the nine derivatives) where heme-edge coupling leads to the multiple-pathway regime. A structure-dependent limit governs redox partners coupled through a dominant pathway (in two of the nine derivatives) where axial-ligand coupling generates the single-pathway limit and slower rates. This two-regime paradigm provides a unified description of electron transfer rates in 26 ruthenium-modified heme and blue-copper proteins, as well as in numerous photosynthetic proteins.

Effect Of 28-Homobrassinolide On Salinity-Induced Changes In Brassica Juncea, Shamsul Hayat, Barket Ali, Syed Aiman Hasan, Aqil Ahmad

Turkish Journal of Biology

Seedlings of Brassica juncea Czern & Coss cv. Varuna generated from seeds soaked in 0, 50, 100, or 150 mM NaCl for 6 h were treated with 0, 10^{-10}, 10^{-8}, or 10^{-6} M 28-homobrassinolide (HBL) after 14 days of growth. Plants that received only NaCl treatment exhibited a decrease in nitrate reductase and carbonic anhydrase activity, chlorophyll content, and P_N 60 days after sowing (DAS), and decreased seed yield at harvest (140 DAS). Subsequent treatment with HBL significantly increased all of the above parameters. The 10^{-8} M concentration of HBL generated the best response and also overcame the detrimental effects …