Nutritional imbalance in wheat (Triticum aestivum L.) genotypes grown at soil water stress

An experiment was conducted to determine the effect of water stress on nutritional changes in tolerant (DS-4 and Chakwal-86) and susceptible (DS-17 and Pavon) genotypes in lysimeters. The stress was imposed at different growth stages (pre-anthesis, post-anthesis, terminal drought). The biomass (dry weight) and Ca, Mg and P concentration decreased with water stress in all the wheat genotypes. However, the tolerant genotypes had less reduction than susceptible at all the treatments. Potassium increased in all wheat genotypes due to water stress and was higher in tolerant than susceptible genotypes. Sodium content was not affected by water stress.     

ESTIMATION OF TOTAL BODY WATER IN HARBOR SEALS: HOW USEFUL IS BIOELECTRICAL IMPEDANCE ANALYSIS?

We evaluated bioelectrical impedance analysis (BIA) as a means of rapidly and inexpensively estimating total body water (TBW) of harbor seals ( Phoca vitulina ). Deuterium oxide dilution was used to estimate TBW in 17 adult females and 16 of their pups between birth and late lactation. Isotope dilution was also used to determine TBW in 12 adult males early and 10 of these males late in the breeding season. At the same time, resistance ( Rs ) and reactance ( Xc ) measurements were taken using a tetrapolar, impedance plethysmograph (Model 101 A, RJL Systems). Seals were sedated with diazepam prior to taking BIA measurements. Within-day duplicate Rs measurements on pups and adults, taken 2-240 min apart, differed by an average of 3.0%± 1.4% ( n = 42, CV = 102%). Movement of the seal during BIA measurements caused variability in both Rs and Xc values. BIA measurements were generally poor predictors of TBW. Rs was significantly correlated with TBW in pups only ( Rs = 0.93, P = 0.001, n = 11). Bioelectrical conductor volume (length2/ Rs ) was significantly correlated with TBW only in adult females ( Rs = 0.63, P = 0.02, n = 14). We conclude that BIA is not a reliable method of estimating TBW in wild harbor seals.     

Long-term response of the biotic community to fluctuating water levels and changes in water quality in Cootes Paradise Marsh,a degraded coastal wetland of Lake Ontario

During the early 1900s, more than 90% of the surface area of Cootes Paradise Marsh was covered with emergent vegetation; currently, less than 15% of the surface is covered with aquatic vegetation and the remainder is wind-swept, turbid, open water. The loss of emergent cover is significantly correlated with mean annual water levels that increased more than 1.5 m over the past 60 years. Species diversity and the percent cover of the submerged macrophtye community also declined dramatically after the 1940s, coincident with decreased water clarity and increased nutrients from pollution by sewage and stormwater effluent. Phosphorus levels in the marsh dropped ten-fold after the sewage plant was upgraded to a tertiary-treatment facility in 1978; however, there was no measurable improvement in water clarity, in spite of a decrease in chlorophyll concentrations. Long-term changes in the composition of the planktonic, benthic and fish communities accompanied changes in water clarity, nutrient status and macrophyte cover. Phytoplankton changed from a community dominated by diverse taxa of green algae and diatoms during the 1940s, to a less diverse community dominated by a few taxa of green and blue-green algae in the 1970s, then to a much more diverse community recently, including many taxa of green algae, diatoms and chrysophytes; however, because water turbidity continues to be high, and algae tolerant of low light levels are now very abundant. Daphnia, which were prominent during the 1940s (especially in the vegetated sites) were replaced in the 1970s by smaller zooplankton such as the cladoceran, Bosmina, and several rotifer species including Brachionus, Asplanchna and Keratella. In the recent survey conducted in 1993 and 1994, small-bodied forms still dominate the turbid open-water areas, while medium-sized cladocerans such as Moina were common near macrophyte beds. Generally, total herbivorous zooplankton biomass tended to be highest next to Typha beds and declined with increasing distance from the plants. Conversely, biomass of edible algae at these sites increased with distance from the macrophytes. Species diversity of aquatic insects declined dramatically over the past 40 years, from 57 genera (23 families and 6 orders) in 1948, to 9 genera (6 families and 3 orders) in 1978, to only 5 genera (3 families and 2 orders) in 1995. The diverse benthic community present 5 decades ago has now been replaced by a community consisting primarily of chironomid larvae, oligochaetes and other worms associated with low-oxygen environments. These successional changes illustrate the impact of natural (fluctuating water levels) and anthropogenic (deterioration in water quality) stressors on the character of the biotic communities, and reveal the complex interactions among the various trophic levels and the abiotic environment as degradation and remediation proceeded.     

Identification of growth phenotypes in Aspergillus niger pectinase over-producing mutants using image analysis procedures

Relative growth rates of four strains of Aspergillus niger were estimated by image analysis of colonies grown with mineral salts and 10 g pectin/l. Water activity (aw) levels were 0.96 and 0.99 and 2-deoxy-D-glucose (2DG) was added up to 0.1 g/l. These techniques proved useful to select mould strains for pectinase production in culture media with different water activities. © Rapid Science Ltd. 1998     

有机相酶促酯化反应中水分调控技术的研究

在有机相酶促反应中,水含量是影响酶活力的关键因素.对异辛烷/正辛醇体系中柱状假丝酵母脂肪酶催化萘普森酯化反应中的水分调控技术进行了研究. 结果表明：水合盐对——Na₂SO₄·10H₂O/Na₂SO₄对系统水分的变化具有有效的缓冲作用;非极性硅藻土吸附固定酶,使之对水分的敏感性得到缓解;另外,加入分子筛去除副产物——“水”可促进酯化过程的进行.     

土壤大气湿度组合对玉米生长和WUE效应研究

采用人工气候生长箱盆栽试验,模拟土壤和大气湿度不同组合处理,发现土壤干旱和大气干旱显著抑制玉米生长。大气湿度提高,在一定程度能改善作物的水分状况,降低蒸腾,解除土壤干旱危害,产生生长和生理补偿效应,明显提高水分利用效率。     

A Description of Occurrence and Morphology of a New Species of Red-Water Forming Strombidium (Spirotrichea, Oligotrichia)

We describe a red-water ciliate, Strombidium lingulum n. sp., collected from a marine fjord in British Columbia (BC), Canada. In August, 1995, red-brown streaks were observed in the waters of Kyuquot Sound. BC. These streaks were composed of a ciliate population with an abundance in the surface of ˜ 1.5 × 10³ cells ml^-1. Density was reduced to < 50 cells ml^-1 below the surface. The bloom persisted for only a few hours; cells were observed for 3-4 days and were only occasionally observed in the weeks after the bloom. The red waters were speculated to be formed by a combination of downwelling events and an observed phototactic migration of the ciliate. As the ciliate was positively phototactic and pigmented, it may be mixotrophic; it was certainly heteroirophic, as it contained dinoflagellates and small ciliates in food vacuoles. Ciliates were preserved in Lugol's iodine and then both protargol stained and prepared for scanning electron microscopy.     

Development of a cost-effective glucose-corn steep medium for production of butanol by Clostridium beijerinckii

Corn steep water (CSW) medium (1.6% solids plus 6% glucose) was evaluated for growth and butanol production by Clostridium beijerinckii NCIMB 8052 wild-type and hyper-amylolytic, hyper-butanol-producing mutant strain BA101. CSW alone was not a suitable substrate, whereas addition of glucose supported growth and butanol production by both strains. In a batch-scale fermentation using an optimized 6% glucose-1.6% solids CSW medium, C. beijerinckii NCIMB 8052 and strain BA101 produced 10.7 g L⁻¹ and 14.5 g L⁻¹ of butanol, respectively. The total solvents (acetone, butanol, and ethanol) produced by C. beijerinckii NCIMB 8052 and strain BA101 were 14 g L⁻¹ and 20 g L⁻¹, respectively. Initial fermentation in small-scale flasks containing 6% maltodextrin-1.6% solids concentration CSW medium resulted in 6 g L⁻¹ and 12.6 g L⁻¹ of butanol production by C. beijerinckii NCIMB 8052 and strain BA101, respectively. CSW can serve as an economic source of nitrogen, vitamins, amino acids, minerals, and other nutrients. Thus, it is feasible to use 6% glucose-1.6% solids CSW medium in place of semi-defined P2 medium. Received 9 February 1998/ Accepted in revised form 1 September 1998     

Evidence for the Uptake of Large Anions through Stomatal Pores

Experiments were conducted with leek (Allium porrum L.) leaves to investigate whether aqueous solutions are able to penetrate stomata. Epidermal strips were used for the determination of transport rates. Stomata were opened by fusicoccin or closed by darkness or abscisic acid. A droplet containing the anionic fluorescent dye, uranine, was placed on the physiologically outer side of the epidermis and allowed to dry. With open stomata 30 times more uranine penetrated through the epidermal strips than with closed stomata (comparison of medians). In another experiment droplets of uranine solution were placed on leaf segments and epidermal strips were removed after drying of the droplets. Penetration of uranine through stomata was detectable under the microscope both with epidermal strips from the transport experiments and with strips obtained after application on leaf segments. As maximum uptake rates occurred during the drying process, it is concluded that penetration took place via water films. These results show that the physical restrictions preventing stomatal penetration of static droplets are not decisive for drying droplets and that stomatal uptake of dissolved ionic substances occurs under natural conditions, i.e. without surfactants or applied pressure.