Variability and genetic parameters of chlorophyll content in forage peanut genotypes using the SPAD index.

This study aimed to verify the existence of variability and to estimate genetic parameters for chlorophyll content in forage peanut genotypes.

Water stress induced alterations in ornithine aminotransferase of ragi (Eleusine coracana): Protection by proline against heat inactivation and denaturation by urea and guanidinium chloride

Water stress resulted in a specific response leading to a large and significant increase (80-fold) in free proline content of ragi (Eleusine coracana) leaves and seedlings. L-Proline protected ornithine aminotransferase, an enzyme in the pathway for proline biosynthesis, isolated from normal and stressed ragi leaves against heat inactivation and denaturation by urea and guanidinium chloride. The protection of the stressed enzyme by L-proline was much more complete than that of the enzyme isolated from normal leaves. While L-ornithine, one of the substrates, protected the stressed enzyme against inactivation, it enhanced the rate of inactivation of the normal enzyme. α-Ketoglutarate protected both the normal and stressed enzyme against inactivation and denaturation. These results support the suggestion that ornithine aminotransferase has undergone a structural alteration during water stress. In view of the causal relationship between elevated temperature and water stress of plants under natural conditions, the protection afforded by proline against inactivation and denaturation of the enzyme from stressed leaves assumes significance. These results provide an explanation for a possible functional importance of proline accumulation during water stress.

Analysis of growth physiology and phytochemical content of Eruca and Diplotaxis Cultivars under different light and temperature regimes

Rocket is a leafy brassicaceous salad crop that encompasses two major genera (Diplotaxis and Eruca) and many different cultivars. Rocket is a rich source of antioxidants and glucosinolates, many of which are produced as secondary products by the plant in response to stress. In this paper we examined the impact of temperature and light stress on several different cultivars of wild and salad rocket. Growth habit of the plants varied in response to stress and with different genotypes, reflecting the wide geographical distribution of the plant and the different environments to which the genera have naturally adapted. Preharvest environmental stress and genotype also had an impact on how well the cultivar was able to resist postharvest senescence, indicating that breeding or selection of senescence-resistant genotypes will be possible in the future. The abundance of key phytonutrients such as carotenoids and glucosinolates are also under genetic control. As genetic resources improve for rocket it will therefore be possible to develop a molecular breeding programme specifically targeted at improving stress resistance and nutritional levels of plant secondary products. Concomitantly, it has been shown in this paper that controlled levels of abiotic stress can potentially improve the levels of chlorophyll, carotenoids and antioxidant activity in this leafy vegetable.

Deleterious effect of TRIS buffer on growth rates and pigment content of Gracilaria birdiae Plastino & EC Oliveira (Gracilariales, Rhodophyta)

This work evaluated the effects of Tris (hydroxymethyl)-aminomethane (TRIS) buffer and its interaction with nutrient concentration on the development of Gracilaria birdie, a common species on the Brazilian coast that has been exploited for agar production. Responses to different conditions were assessed through growth rates and pigment content (chlorophyll a, phycoerythrin, phycocyanin and allophycocyanin). Provasoli`s nutrient solution with and without TRIS addition was tested at concentrations of 12.5, 25 and 50%. The pH was also monitored. G. birdiae grew better in the absence of TRIS and at low nutrient concentrations, 12.5 and 25% (growth rates of 10.8-11.3%.day(-1)). Higher contents of phycoerythrin and chlorophyll a were observed without TRIS at 12.5 and 25% (Phycoerythrin, 649.6-698.0 mu g g(-1) fresh biomass; Chlorophyll a, 156.0-168.6 mu g g(-1) fresh biomass). These findings highlight the deleterious effect of TRIS on growth and phycoerythrin and chlorophyll a content. They also demonstrate the importance of appropriate nutrient concentration for laboratory cultures, depending on the intrinsic characteristics of each species.

Effects of temperature, irradiance and photoperiod on growth and pigment content in some freshwater red algae in culture

The responses of relative growth rate (% day-1) and pigment content (chlorophyll a, phycocyanin and phycoerythrin) to temperature, irradiance and photoperiod were analyzed in culture in seven freshwater red algae: Audouinella hermannii (Roth) Duby, Audouinella pygmaea (Kützing) Weber-van Bosse, Batrachospermum ambiguum Montagne, Batrachospermum delicatulum (Skuja) Necchi et Entwisle, 'Chantransia' stages of B. delicatulum and Batrachospermum macrosporum Montagne and Compsopogon coeruleus (C. Agardh) Montagne. Experimental conditions included temperatures of 10, 15, 20 and 25°C and low and high irradiances (65 and 300 μmol photons m-2 s-1, respectively). Long and short day lengths (16:8 and 8:16 LD cycles) were also applied at the two irradiances. Growth effects of temperature and irradiance were evident in most algae tested, and there were significant interactions among treatments. Most freshwater red algae had the best growth under low irradiance, confirming the preference of freshwater red algae for low light regimens. In general there was highest growth rate in long days and low irradiance. Growth optima in relation to temperature were species-specific and also varied between low and high irradiances for the same alga. The most significant differences in pigment content were related to temperature, whereas few significant differences could be attributed to variation in irradiance and photoperiod or interactions among the three parameters. The responses were species-specific and also differed for pigments in distinct temperatures, irradiances and photoperiods in the same alga. Phycocyanin was generally more concentrated than phycoerythrin and phycobiliproteins were more concentrated than chlorophyll a. The highest total pigment contents were found in two species typical of shaded habitats: A. hermannii and C. coeruleus. The expected inverse relationship of pigment with irradiance was observed only in C. coeruleus. In general, the most favorable conditions for growth were not coincident with those with highest pigment contents.

Photosynthetic responses and proline content of mature and young leaves of sunflower plants under water deficit

In mature and young leaves of sunflower (Helianthus annuus L. cv. Catissol-01) plants grown in the greenhouse, photosynthetic rate, stomatal conductance, and transpiration rate declined during water stress independently of leaf age and recovered after 24-h rehydration. The intercellular CO 2 concentration, chlorophyll (Chl) content, and photochemical activity were not affected by water stress. However, non-photochemical quenching increased in mature stressed leaves. Rehydration recovered the levels of non-photochemical quenching and increased the F v/F m in young leaves. Drought did not alter the total Chl content. However, the accumulation of proline under drought was dependent on leaf age: higher content of proline was found in young leaves. After 24 h of rehydration the content of proline returned to the same contents as in control plants.

Water chemistry, and biological traits and mercury content of Salvelinus alpinus and S. namaycush in Laflamme and Pingualuit lake

Pingualuk Lake fills a deep crater in the Parc National des Pingualuit on the Ungava Peninsula (Nunavik, Canada) and is isolated from nearby surface waters. The main objectives of this study were to determine and compare the concentrations of two atmospherically derived contaminants, mercury and perfluorinated chemicals (PFCs), in the lake water column and fish of Pingualuk Lake and to assess the physical and biological factors influencing contaminant concentrations. Mercury concentrations in arctic char muscle tissue were comparable to those of char in other Arctic lakes, while the total amount of PFCs was below reported levels for remote lakes in the Arctic and elsewhere. Stable isotope and stomach content analyses were made to investigate the feeding ecology of the Pingualuk Lake arctic char population and indicated the possibility of multiple feeding groups. Genetics characteristics (MH and mtDNA) of fish from Pingualuk Lake revealed that this population is likely distinct from that of nearby Laflamme Lake. However, both arctic char populations exhibit differential variation of their allele families. Physical characteristics determined for Lake Pingualuk revealed that the water column was inversely stratified beneath the ice and extremely transparent to visible and ultraviolet radiation. The highest mercury concentrations (3- 6 pg/mL THg) occurred just beneath the ice surface in each lake. Pingualuk Lake, given its near pristine state and exceptional limnological features, may serve as a most valuable reference ecosystem for monitoring environmental stressors, such as contaminants, in the Arctic.

Primary production and chlorophyll a in waters of the Kara Sea in September 2007

These studies were performed from September 10 to 29, 2007 in the Kara Sea in transects westward of the Yamal Peninsula, near the St. Anna Trough, in the Ob River estuary (Obskay Guba), and on the adjacent shelf. Concentration of chlorophyll a in the euphotic layer varied from 0.02 to 4.37 µg/l, aver. 0.76 µg/l. Primary production in the water column varied from 10.9 to 148.0 mg C/m**2/day (aver. 56.9 mg C/m**2/day). It was shown that frontal zones divided the Kara Sea into distinct areas with different productivities. Maximum levels of primary production were measured in the deep part of the Yamal transect (132.4 mg C/m**2/day) and the shallow Kara Sea shelf near the Ob River estuary (74.9 mg C/m**2/day). Characteristics of these regions were low salinity of the surface water layer (19-25 psu) and elevated silicon concentration (12.8-28.1 µg-atom/l). It is explainable by river runoff. Frontal zones of the Yamal current within the Yamal and Ob transects showed high assimilation numbers reached to 2.32 and 1.49 mg C/mg Chl/hr, respectively; they were maximal for studied areas.

Pigment, carbohydrate and protein content of microbial mats from northern Victoria Land lake sediments

The composition of algal pigments and extracellular polymeric substances (EPS) was determined in microbial mats from two lakes in Victoria Land (Continental Antarctica) with different lithology and environmental features. The aim was to expand knowledge of benthic autotrophic communities in Antarctic lacustrine ecosystems, providing reference data for future assessment of possible changes in environmental conditions and freshwater communities. The results of chemical analyses were supported by microscopy observations. Pigment profiles showed that filamentous cyanobacteria are dominant in both lakes. Samples from the water body at Edmonson Point had greater biodiversity, fewer pigments and lower EPS ratios than those from the lake at Kar Plateau. Differences in mat composition and in pigment and EPS profile between the two lakes are discussed in terms of local environmental conditions such as lithology, ice-cover and UV radiation. The present study suggests that a chemical approach could be useful in the study of benthic communities in Antarctic lakes and their variations in space and time.

(Table 1) Composition of stomach and gut content of the amphipod Onisimus litoralis, and algal availability near Barrow, Alaska

Sea ice algae have been widely discussed as a potential food source for pelagic and benthic animals in ice-covered waters, specifically in the light of current substantial changes in the Arctic ice regime. Stomach and gut contents of the Arctic nearshore lysianassid amphipod Onisimus litoralis sampled from February to May 2003 indicate that Arctic ice algae were dominant food no earlier than the onset of ice melt. Crustaceans, common prey in a previous study, were absent in stomachs and guts during the survey period. Our data support the concept that sea ice-derived organic carbon is of specific relevance for Arctic plankton and benthos during the period of ice melt.

Isotopic signatures and mercury content of arctic char and their prey, and water chemistry of 18 arctic Canadian lakes

Concentrations of mercury (Hg) have increased slowly in landlocked Arctic char over a 10- to 15-year period in the Arctic. Fluxes of Hg to sediments also show increases in most Arctic lakes. Correlation of Hg with trophic level (TL) was used to investigate and compare biomagnification of Hg in food webs from lakes in the Canadian Arctic sampled from 2002 to 2007. Concentrations of Hg (total Hg and methylmercury [MeHg]) in food webs were compared across longitudinal and latitudinal gradients in relation to d13C and d15N in periphyton, zooplankton, benthic invertebrates, and Arctic char of varying size-classes. Trophic magnification factors (TMFs) were calculated for the food web in each lake and related to available physical and chemical characteristics of the lakes. The relative content of MeHg increased with trophic level from 4.3 to 12.2% in periphyton, 41 to 79% in zooplankton, 59 to 72% in insects, and 74 to 100% in juvenile and adult char. The d13C signatures of adult char indicated coupling with benthic invertebrates. Cannibalism among char lengthened the food chain. Biomagnification was confirmed in all 18 lakes, with TMFs ranging from 3.5 ± 1.1 to 64.3 ± 0.8. Results indicate that TMFs and food chain length (FCL) are key factors in explaining interlake variability in biomagnification of [Hg] among different lakes.

Seasonal variations of contribution of large and fine fractions of phytoplankton to primary production and chlorophyll a in the Sevastopol Bay from April 1985 till March 1986

It has been shown that in the Sevastopol Bay during the year primary production and chlorophyll "a" created by picoplankton (0.45-2.5 µm) consisted on the average 20-44% of total production. It was approximately a half of the level for oligotrophic waters of the ocean. Picoplankton of waters studied is represented by eucaryotes, cell diameter of which is, as a rule, about 2-3 µm. Contribution of the finest fraction of phytoplankton (0.43-0.85 µm) to primary production and con¬tent of chlorophyll "a" was insignificant (0-4%).