Clean water: Factors that influence Its availability,quality and its use: Summary of the International Water Conference

The International Water Conference held in La Jolla, California during 28–30 November 1995, had an objective to provide an opportunity for international information exchange on new research applications and timely policy issues effecting the availability, use and quality of water for power generation. This Conference included the topical areas, the use of water and the management of chemical quality in process wastewaters; physical and biological transformation due to discharges in open surface waters, watersheds and wetlands; the role of risk and cost-benefit assessments; and discussion of the Clean Water Act containments. This Conference Summary contains an overview of the present state of the knowledge regarding the use of water by the electric utility industry and potential future issues as discussed in papers presented at the Conference and a summary of the most important findings and conclusions.     

Ultrastructural and Cytochemical Aspects of the Biological Control of Botrytis cinerea by Candida saitoana in Apple Fruit

ABSTRACT Biocontrol activity of Candida saitoana and its interaction with Botrytis cinerea in apple wounds were investigated. When cultured together, yeast attached to Botrytis sp. hyphal walls. In wounded apple tissue, C. saitoana restricted the proliferation of B. cinerea, multiplied, and suppressed disease caused by either B. cinerea or Penicillium expansum. In inoculated apple tissue without the yeast, fungal colonization caused an extensive degradation of host walls and altered cellulose labeling patterns. Hyphae in close proximity to the antagonistic yeast exhibited severe cytological injury, such as cell wall swelling and protoplasm degeneration. Colonization of the wound site by C. saitoana did not cause degradation of host cell walls. Host cell walls in close contact with C. saitoana cells and B. cinerea hyphae were well preserved and displayed an intense and regular cellulose labeling pattern. In addition to restricting fungal colonization, C. saitoana induced the formation of structural defense responses in apple tissue. The ability of C. saitoana to prevent the necrotrophic growth of the pathogen and stimulate structural defense responses may be the basis of its biocontrol activity.     

Forest decline, nutrient supply and diagnostic fertilization in southwestern Germany and in southern California

Since the mid-1970's new types of forest damage (of unknown origin) were observed in West Germany. Nonspecific foliage losses and foliar discolorations are the most common symptoms. This resulted in a comprehensive research program being initiated in the fall of 1983 to investigate the nutritional status of Norway spruce (Picea abies (L.) Karst.) stands in southwest Germany, growing on a variety of sites. Forests at these sites revealed light to moderate damage or acute site-and species-specific nutritional disturbances involving Mg, K, Ca, Mn, and Zn. Historical comparisons of needle-analysis data showed a dramatic change of the nutrient supply at many sites over the last one or two decades.

As a working hypothesis, the adverse impacts of air pollutants (e.g. photo-oxidants) and/or acidic atmospheric precipitation are seen as inciting factors causing increased leaching of nutrient elements. The tree's potential to compensate for the nutrient losses by increased uptake are limited by the often poor nutrient supply for forest soils. Accelerated soil acidification increase nutrient leaching from the soil, probably enhancing decline. Over a short period, fertilization led to a decrease or to the disappearance of the symptoms, and to the improvement in the nutrient composition of the foliage.

Microscopy investigation of Norway-spruce needles indicated the regeneration potential on a histological level for moderate yellowed needles after fertilization. Furthermore, needles of nutrient-deficient-trees reveal typical tissue damages different to those caused by SO₂ or O₃.

Acid mist increased the leaching of K, Ca, Mg, Mn, and Zn from the foliage. Even when nutrients are being leached from the foliage, nutrient uptake canbe increased by improving the nutrient supply in the soil.

Preliminary studies on the effects of damages caused by ozone (O₃) on ponderosa pine suggest imbalance in micronutrient concentrations of foliage.     

Penicillium digitatum Suppresses Production of Hydrogen Peroxide in Host Tissue During Infection of Citrus Fruit

ABSTRACT During the infection of citrus fruit by Penicillium digitatum there is little evidence of a host defense response. This suggests that P. digitatum has the ability to suppress host defenses. The current study demonstrates that P. digitatum suppresses a defense-related hydrogen peroxide (H(2)O(2)) burst in host tissue. In contrast, the nonhost pathogen, Penicillium expansum, triggers production of a significant amount of H(2)O(2) in citrus fruit exocarp. Using laser scanning confocal microscopy, we demonstrated that P. digitatum suppressed an elevation in H(2)O(2) up to 42 h after inoculation. Nevertheless, H(2)O(2) levels around wounds inoculated with P. expansum increased by 63-fold above the control. P. digitatum continued to suppress H(2)O(2) production in citrus fruit exocarp up to 66 h postinoculation and H(2)O(2) levels were actually threefold below that of noninoculated controls. In contrast, the H(2)O(2) level was still about 11-fold above the control value in wound sites inoculated with P. expansum. Studies on the effect of organic acids (as pH modulators) on the response of citrus fruit to compatible and noncompatible pathogens indicated that pathogenicity was enhanced only when host-tissue acidification was accompanied by the suppression of H(2)O(2). Additionally, pathogenicity of both P. digitatum and P. expansum on citrus fruit was significantly enhanced by the H(2)O(2)-scavenging enzyme catalase. Based on our study and previous reports regarding the potential involvement of citric acid and catalase in green mold pathogenesis, we suggest that these compounds are strongly associated with the virulence of P. digitatum.     

Nutritional disturbances and histological changes in declining forests

“New type” forest damages have been observed in West Germany since the mid-1970's and discussed in North America since the early 1980's. Various types of damage are associated with typical foliar discoloration symptoms related to site characteristic nutritional disturbances. The macronutrients are generally Mg, Ca, and K. Based on foliar and soil analysis results diagnostic fertilization trials were established at a wide variety of sites and stands in West Germany as well as in North America. The appropriate application of fast soluble fertilizers proved that damage symptoms associated with nutritional disturbances can frequently be mitigated within a relatively short period. The observed visual revitalization corresponds well with foliar analysis data obtained continuously for the last 5 yr. Soil analyses also reflect the improved nutrient supply. Investigations of older fertilizer trials indicated that stands fertilized before the appearance of “new type” damage symptoms are considerably more vital when compared to the untreated control plots. Remarkable results were derived from histological research. Microscopic analysis of needles proved the regeneration potential on a histological level for moderately yellowed needles after fertilization. Furthermore, needles of nutrient deficient trees reveal typical differences of tissue damages when compared to SO₂ fumigated or O₃ impacted needles. Thus, histological investigations can be used as a diagnostic tool to differentiate between direct and indirect forest damages.     

Crystal structure of inhibitor-bound human 5-lipoxygenase-activating protein

Leukotrienes are proinflammatory products of arachidonic acid oxidation by 5-lipoxygenase that have been shown to be involved in respiratory and cardiovascular diseases. The integral membrane protein FLAP is essential for leukotriene biosynthesis. We describe the x-ray crystal structures of human FLAP in complex with two leukotriene biosynthesis inhibitors at 4.0 and 4.2 angstrom resolution, respectively. The structures show that inhibitors bind in membrane-embedded pockets of FLAP, which suggests how these inhibitors prevent arachidonic acid from binding to FLAP and subsequently being transferred to 5-lipoxygenase, thereby preventing leukotriene biosynthesis. This structural information provides a platform for the development of therapeutics for respiratory and cardiovascular diseases.