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Photosynthetic Properties (photosynthetic + property)
Selected AbstractsGrowth, photosynthetic properties and Rubisco activities and amounts of marine macroalgae grown under current and elevated seawater CO2 concentrationsGLOBAL CHANGE BIOLOGY, Issue 9 2002Alvaro Israel Abstract Growth rates, photosynthetic responses and the activity, amount and CO2 affinity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) were determined for common marine macroalgae grown in seawater (containing 14.5 ± 2.1 µM CO2) or CO2 -enriched seawater (averaging 52.8 ± 19.2 µM CO2). The algae were grown in 40 L fiberglass tanks (outdoor) for 4,15 weeks and in a field experimental setup for 5 days. Growth rates of the species studied (representing the three major divisions, i.e. Chlorophyta, Rhodophyta and Phaeophyta) were generally not significantly affected by the increased CO2 concentrations in the seawater medium. Rubisco characteristics of algae cultivated in CO2 -enriched seawater were similar to those of algae grown in nonenriched seawater. The lack of response of photosynthetic traits in these aquatic plants is likely to be because of the presence of CO2 concentrating mechanisms (CCMs) which rely on HCO3, utilization, the inorganic carbon (Ci) form that dominates the total Ci pool available in seawater. Significant changes on the productivity of these particular marine algae species would not be anticipated when facing future increasing atmospheric CO2 levels. [source] What is the best way to represent surface conductance for a range of vegetated sites?HYDROLOGICAL PROCESSES, Issue 9 2007Hikaru Komatsu Abstract Surface conductance Gs is a significant parameter for indicating the evaporative and photosynthetic properties of a vegetated surface. When comparing Gs values between different observation sites, some studies have used Gsmax and others have used ,smax (where Gsmax is the maximum Gs value measured during the measurement period, and ,smax is the maximum Gs value obtained with a vapour pressure deficit (VPD) of , 1·0 kPa during the measurement period). In this study, we demonstrate a clear justification for using ,smax instead of Gsmax when comparing Gs values between different sites. We examined whether both ,smax and Gsmax lead to the same conclusions in classifying vegetated sites. Komatsu (2003b) [Hydrological Processes 17: 2503,2512] reported a clear relationship between canopy height h and ,smax for coniferous forests with a projected leaf area index (LAI) of , 3·0. We examined not only the relationship between h and ,smax but also the relationship between h and Gsmax for coniferous forests with a projected LAI of , 3·0. Both ,smax and Gsmax decreased with increasing h. However, the relationship between h and Gsmax was less well defined than the relationship between h and ,smax because of biased Gsmax data. Consequently, we conclude that ,smax is a more appropriate index than Gsmax to represent Gs for sites with different vegetation. Copyright © 2007 John Wiley & Sons, Ltd. [source] PHOTOSYNTHETIC UTILIZATION OF INORGANIC CARBON IN THE ECONOMIC BROWN ALGA, HIZIKIA FUSIFORME (SARGASSACEAE) FROM THE SOUTH CHINA SEA,JOURNAL OF PHYCOLOGY, Issue 6 2003Dinghui Zou The mechanism of inorganic carbon (Ci) acquisition by the economic brown macroalga, Hizikia fusiforme (Harv.) Okamura (Sargassaceae), was investigated to characterize its photosynthetic physiology. Both intracellular and extracellular carbonic anhydrase (CA) were detected, with the external CA activity accounting for about 5% of the total. Hizikia fusiforme showed higher rates of photosynthetic oxygen evolution at alkaline pH than those theoretically derived from the rates of uncatalyzed CO2 production from bicarbonate and exhibited a high pH compensation point (pH 9.66). The external CA inhibitor, acetazolamide, significantly depressed the photosynthetic oxygen evolution, whereas the anion-exchanger inhibitor 4,4,-diisothiocyano-stilbene-2,2,-disulfonate had no inhibitory effect on it, implying the alga was capable of using HCO3, as a source of Ci for its photosynthesis via the mediation of the external CA. CO2 concentrations in the culture media affected its photosynthetic properties. A high level of CO2 (10,000 ppmv) resulted in a decrease in the external CA activity; however, a low CO2 level (20 ppmv) led to no changes in the external CA activity but raised the intracellular CA activity. Parallel to the reduction in the external CA activity at the high CO2 was a reduction in the photosynthetic CO2 affinity. Decreased activity of the external CA in the high CO2 grown samples led to reduced sensitiveness of photosynthesis to the addition of acetazolamide at alkaline pH. It was clearly indicated that H. fusiforme, which showed CO2 -limited photosynthesis with the half-saturating concentration of Ci exceeding that of seawater, did not operate active HCO3, uptake but used it via the extracellular CA for its photosynthetic carbon fixation. [source] Ecophysiology of Antarctic vascular plantsPHYSIOLOGIA PLANTARUM, Issue 4 2002Miren Alberdi Most of the ice and snow-free land in the Antarctic summer is found along the Antarctic Peninsula and adjacent islands and coastal areas of the continent. This is the area where most of the Antarctic vegetation is found. Mean air temperature tends to be above zero during the summer in parts of the Maritime Antarctic. The most commonly found photosynthetic organisms in the Maritime Antarctic and continental edge are lichens (around 380 species) and bryophytes (130 species). Only two vascular plants, Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl., have been able to colonize some of the coastal areas. This low species diversity, compared with the Arctic, may be due to permanent low temperature and isolation from continental sources of propagules. The existence of these plants in such a permanent harsh environment makes them of particular interest for the study of adaptations to cold environments and mechanisms of cold resistance in plants. Among these adaptations are high freezing resistance, high resistance to light stress and high photosynthetic capacity at low temperature. In this paper, the ecophysiology of the two vascular plants is reviewed, including habitat characteristics, photosynthetic properties, cold resistance, and biochemical adaptations to cold. [source] RATP: a model for simulating the spatial distribution of radiation absorption, transpiration and photosynthesis within canopies: application to an isolated tree crownPLANT CELL & ENVIRONMENT, Issue 4 2001H. Sinoquet ABSTRACT The model RATP (radiation absorption, transpiration and photosynthesis) is presented. The model was designed to simulate the spatial distribution of radiation and leaf-gas exchanges within vegetation canopies as a function of canopy structure, canopy microclimate within the canopy and physical and physiological leaf properties. The model uses a three-dimensional (3D) representation of the canopy (i.e. an array of 3D cells, each characterized by a leaf area density). Radiation transfer is computed by a turbid medium analogy, transpiration by the leaf energy budget approach, and photosynthesis by the Farquhar model, each applied for sunlit and shaded leaves at the individual 3D cell-scale. The model typically operates at a 20,30 min time step. The RATP model was applied to an isolated, 20-year-old walnut tree grown in the field. The spatial distribution of wind speed, stomatal response to environmental variables, and light acclimation of leaf photosynthetic properties were taken into account. Model outputs were compared with data acquired in the field. The model was shown to simulate satisfactorily the intracrown distribution of radiation regime, transpiration and photosynthetic rates, at shoot or branch scales. [source] | ||||||||||