The chlorophyll a content was measured at 62 oceanographic stations. At each station samples were collected from eight standard depths between the water surface and 150 m. Integrated values (chlorophyll α mg/m2) are used in the presentation of the results and discussion. The recorded quantities of chlorophyll α were rather high, amounting to as much as 634 mg/m2. The areas with high chlorophyll a content (> 200 mg/m2) were located in the region of the Anvers Island and Brabant Island, on the shelf around Joinville Island and opposite the Antarctic Sound, close to Clarence Island and beyond the regions recommended in the BIOMASS-SIBEX programme to the east and south of the South Orkney Islands. In the acetonie extracts of photosynthetizing pigments large quantities of phytoxanthin were found using the TLC method, what precludes the use of the Lorenzen method for determination of chlorophyll α and its degradation products.
Coarse-scale studies on chlorophyll a distribution in a region covering the Scotia Front zone showed an increased chlorophyll content and its deeper distribution at stations situated in the frontal zone. The sources of chlorophyll α were probably both the phytoplankton released from melting ice as well as spring bloom.
According to the general classification of shallow eutrophic lakes, two alternative types are distinguished: phytoplankton-dominated and macrophyte-dominated lakes. The latter type is rare and currently endangered by human activity. In order to determine the effect of reduced inflow of surface water by an earth dyke on the lake trophic state, certain biological and physico-chemical parameters were evaluated. This work focuses on two lakes of similar morphometric characteristics situated in the agricultural landscape. The effect of the earth dyke on the trophic state was positively verified. The lake situated in the catchment basin, in which the inflow of surface water was reduced, was defined as meso-eutrophic, with a small amount of phytoplankton and high water transparency. The reference lake was highly eutrophic, with low water transparency and a large amount of phytoplankton. The water body surrounded by the earth dyke was macrophytes dominated (65% of the lake area), whereas the reference lake was a phytoplankton-macrophyte type (42% of the lake area). The trophic evaluation of a lake can be underestimated because of a significant amount of biogenic compounds accumulated in plant tissues. Thus, the values of Carlson’s indices in macrophyte-dominated lakes may not account for the total amount of nutrients in the water body.
In order to evaluate morphological and physiological traits related to drought tolerance and to determine the best criteria for screening and identification of drought-tolerant genotypes, we grew two tolerant genotypes (MCC392, MCC877) and two sensitive genotypes (MCC68, MCC448) of chickpea under drought stress (25% field capacity) and control (100% field capacity) conditions and assessed the effect of drought stress on growth, water relations, photosynthesis, chlorophyll fluorescence and chlorophyll content in the seedling, early flowering and podding stages. Drought stress significantly decreased shoot dry weight, CO2 assimilation rate (A), transpiration rate (E), and Psii photochemical efficiency (Fv/Fm) in all genotypes. In the seedling and podding stages, Psii photochemical efficiency was higher in tolerant genotypes than in sensitive genotypes under drought stress. Water use efficiency (WUE) and CO2 assimilation rate were also higher in tolerant than in sensitive genotypes in all investigated stages under drought stress. Our results indicated that water use efficiency, A and Fv/Fm can be useful markers in studies of tolerance to drought stress and in screening adapted cultivars of chickpea under drought stress.
At the northern border of pack ice the study on chlorophyll a content, density of cells, species composition and domination in samples from the drifting ice floes and from brash ice was carried out. 102 taxa of algae were found in the pack ice. In the study area algal taxa were rather uniformly distributed. In different ice layers the qualitative composition of diatom assemblages was similar and usually the diatom Nitzschia cylindrus was dominant and most frequent. Chlorophyll a content (from 0.12 to 334.5 mg m-3) and the density of cells (from 0.3 to 362 x l0 6 cm) varied strongly in various habitats. Ice floes near the northern pack ice border contained low values of chlorophyll a (mean value 0.50 ±0.28 mg m-3) . However, brash sea ice originating from ice floes, contained 142.4 ±117.5 mg m-3 of chlorophyll α in visibly discoloured and 30.1 ±24.3 mg m~3 of chlorophyll α in not visibly discoloured parts on average. The range of chlorophyll α content and the presence of characteristic species allow to distinguish brash sea ice infiltration assemblage of diatoms.
Chlorophyll a content and the density and species composition of algae were determined in drifting sea ice north of the Elephant Island (between 54-56°W and 60°30'—61°00'S) at the end of October 1986. In yellow-brownish pieces of brash ice the amount of chlorophyll α was on average 203.5 ± 149.9 mg m-3 at the density of algal cells of 255.7+137.8-103 in cm3. In not visibly discoloured ice the respective values were about 80 times lower, and in surface water about 700 times lower. 69 algal taxa were recorded in the samples, almost all of which were diatoms. Nitzschia cylindrus dominated in all the samples. A comparison of species composition in the investigated habitats revealed that the highest species similarities occurred between samples collected in discoloured ice, lower in the uncoloured ice and the lowest ones in water.
In this paper, we present results indicating ozone effect on visible plants response as well as on other parameters, such as dry weight, chlorophyll concentration, cell membrane stability and salicylic acid content in bioindicator plants. Ozone-resistant and -sensitive clones of white clover (Trifolium repens L. cv. "Regal") were used in the investigations. The experiment was carried out in ambient air conditions of the Wielkopolska province (Poland) in 2005 growing season. The exposure led to changes in the level of plant response parameters that might be used as potential biomarkers of oxidative stress triggered by tropospheric ozone in ambient air conditions.
Trinexapac-ethyl is one of the newest growth regulators used in agriculture and horticulture. As a most growth retardants it acts by inhibiting gibberellin (GA) biosynthesis. A field study was conducted to determine the effects of trinexapac-ethyl on growth of winter wheat. Trinexapac ethyl was used alone (75 g a.i./ha and 125 g a.i./ha) and in the mixture with chlorocholine chloride (50 g a.i./ha + 675 g a.i./ha) at the 2nd node stage. Trinexapac-ethyl and its mixture with CCC activity was weather dependent. Their influence on the crop was strictly related to the temperature and rainfall during an individual year of trials. Plant growth regulators much more influenced winter wheat plants in abundant rainfall and higher temperature conditions. Lodging was not observed during the experiment.
We measured the total chlorophyll (Chl a+b) content in seedling leaves of fifteen maize cultivars infested by two studied aphid species (oligophagous Rhopalosiphum padi L., monophagous Sitobion avenae F.) 7 and 14 days after the beginning of infestation, using a SPAD-502 chlorophyll meter. Chlorophyll loss was more severe in R. padi-infested than in S. avenae-infested plants. Chlorophyll depletion was greater after long-term (14 days) than after short-term aphid infestation in the investigated host systems. Seedlings of Złota Karłowa and Tasty Sweet were more damaged by aphid feeding; Ambrozja and Płomyk plants were less damaged by aphid feeding.