Spawning movements of humpback whitefish in interior Alaska rivers

This study was conducted to describe the spawning movements and identify spawning areas for humpback whitefish Coregonus pidschian in the Minto Flats–Chatanika River complex, Alaska, during 2008 and 2009. Radio transmitters were surgically implanted in humpback whitefish in 2008 (N = 60) and 2009 (N = 100), and fish positions were determined through a combination of boat and aerial surveys and fixed receiving stations. Two spawning areas were identified: one in the Chatanika River downstream of the Elliot Highway Bridge and the other in the Tanana River near Fairbanks. Humpback whitefish dispersed from the wetland complex of Minto Flats in June, moved upstream through late August, arrived at the spawning areas in early September and began moving downstream in early October. In 2009, spatially segregated movements were observed when approximately 40% of the radio‐tagged humpback whitefish moved to the Tanana River, suggesting that humpback whitefish in Minto Flats are comprised of mixed spawning stocks. These study results provide a complete account of humpback whitefish movements and their associated spawning habitats, which will allow for better‐informed management strategies.     

Storage protein changes during zygotic embryogenesis in interior spruce

The major storage proteins isolated from protein bodies of embryo tissues of interior spruce Picea glauca (Moench) Voss/Picea engelmanii Parry had apparent molecular weights of 41, 35, 33, 24 and 22 kD. Minor proteins of 30 and 27.5 kD were also observed. Based on their solubility characteristics, the 41 kD protein was identified as a water and buffer-soluble albumin, and the 35, 33, 24 and 22 kD proteins were characterized as buffer-insoluble, high salt-soluble globulins. Two-dimensional electrophoresis revealed each protein was composed of several isoelectric variants. Developmentally specific accumulation of storage proteins was observed during embryogenesis. The 41 kD protein only accumulated during the later stages of cotyledon maturation, whereas the other storage proteins began to accumulate during the early stages of embryo development. All storage proteins showed major accumulations during cotyledon maturation.     

Relationships between gas exchange adaptation of Sitka x interior spruce genotypes and ribosomal DNA markers

Adaptive physiological changes were investigated in seven populations of Sitka (Picea sitchensis (Bong.) Carr.) x interior spruce (P. glauca (Moench) Voss x P. engelmannii Parry ex Engelm.) spanning the Nass-Skeena transition zone in British Columbia, Canada. Each population was represented by an Si rDNA index that was calculated from the relative optical densities on a gel autoradiogram of five ribosomal DNA bands characteristic of Sitka spruce and interior spruce. This index estimates the proportion of the genome contributed by interior spruce. Physiological adaptations were assessed by gas exchange parameters measured under both well-watered and drought conditions. Under well-watered conditions, Sitka spruce populations had higher maximal photosynthesis at saturating light and ambient CO(2), higher quantum yield at the light compensation point, and higher dark respiration than interior spruce populations. Sitka spruce populations also reached maximal photosynthesis at lower photosynthetically active radiation and higher CO(2) concentrations, and had higher stomatal densities that resulted in lower stomatal limitations to photosynthesis than interior spruce populations. In contrast, interior spruce populations exhibited greater drought tolerance than Sitka spruce populations. Their gas exchange rates declined at a slower rate in response to drought. They maintained higher gas exchange rates in response to moderate to severe drought (predawn plant water potentials = -1.5 MPa), and their photosynthetic rates recovered faster when they were rewatered after exposure to drought. Comparison of the seven populations indicated that physiological parameters were significantly related to the Si rDNA index. An increase in Si rDNA index was associated with proportional changes in physiological measurements, suggesting that genetic interchange among species with contrasting ecological adaptations can enhance the environmental adaptation of natural populations.     

Relationship between nuclear DNA markers and physiological parameters in Sitka x interior spruce populations

Eight populations of Sitka spruce (Picea sitchensis (Bong.) Carr.) and interior spruce (Picea glauca (Moench) Voss x Picea engelmannii Parry ex. Engelm.) seedlings were sampled from a zone of Sitka-interior spruce introgression in British Columbia, Canada. Restriction fragment length polymorphisms of the nuclear ribosomal RNA genes (rDNA) were used to define species-specific hybridization patterns for the Sitka spruce and interior spruce populations. Hybridization was estimated from an index based on the relative abundance of polymorphic rDNA combining bands for each population. Sitka x interior hybrid seedlings had an index value for the relative abundance of interior spruce rDNA (Si-rDNA) ranging from 0.07 (Lower Nass; the most westerly collected source) to 0.95 (Bulkley Valley low-elevation seed orchard). During shoot elongation, osmotic potential at saturation (Psi(sat)) and turgor loss point (Psi(tlp)) increased, whereas total turgor (Psi(PTotal)) decreased. After bud set in the summer and throughout the fall, Psi(sat) and Psi(tlp) decreased, whereas Psi(PTotal) increased. At all times of year, populations with a higher Si-rDNA index had lower Psi(tlp) and Psi(sat) and higher Psi(PTotal) than populations with a lower Si-rDNA index. During the fall, Sitka x interior hybrid seedlings exhibited a seasonal decline in the temperature causing 50% needle electrolyte leakage (LT(50)) and in the critical temperature indicating the initial point of freezing injury. Seedlings with a higher Si-rDNA index had lower LT(50) and critical temperature values indicating greater freezing tolerance in the fall. Throughout most of the year, seedling population Si-rDNA index was related to the degree of drought and freezing tolerance.     

Water Deficit Reduced Fertility of Young Microspores Resulting in a Decline of Viable Mature Pollen and Grain Set in Rice

Pollen formation in rice ( Oryza sativa L.) is highly vulnerable to environmental stresses such as heat, chilling and drought. In rice plants exposed to drought during male reproductive development, the most obvious damage often observed is a decline in the number of engorged pollen and grain set. This has been well characterized in rice under chilling and to a lesser extent under drought stress. Moreover, detailed literature on the immediate effects of drought on developing young microspores in rice is still limited. Here, we report findings from experiments on rice plants exposed to water deficit for three consecutive days during early stages of anther development. When the osmotic potential of the growing medium was equal to or less than −0.5 MPa, as induced by polyethylene glycol, the leaf water potential was significantly lowered and grain set was reduced. A strong correlation between grain set and viable young microspores (P < 0.001, r² = 0.8223) indicates that water deficit immediately reduced fertility of rice plants at the time of exposure. This result suggests a new underlying mechanism of water deficit-induced pollen abortion in rice.     

Heparanase and Syndecan-4 Are Involved in Low Molecular Weight Fucoidan-Induced Angiogenesis

Induction of angiogenesis is a potential treatment for chronic ischemia. Low molecular weight fucoidan (LMWF), the sulfated polysaccharide from brown seaweeds, has been shown to promote revascularization in a rat limb ischemia, increasing angiogenesis in vivo. We investigated the potential role of two heparan sulfate (HS) metabolism enzymes, exostosin-2 (EXT2) and heparanase (HPSE), and of two HS-membrane proteoglycans, syndecan-1 and -4 (SDC-1 and SDC-4), in LMWF induced angiogenesis. Our results showed that LMWF increases human vascular endothelial cell (HUVEC) migration and angiogenesis in vitro. We report that the expression and activity of the HS-degrading HPSE was increased after LMWF treatment. The phenotypic tests of LMWF-treated and EXT2- or HPSE-siRNA-transfected cells indicated that EXT2 or HPSE expression significantly affect the proangiogenic potential of LMWF. In addition, LMWF increased SDC-1, but decreased SDC-4 expressions. The effect of LMWF depends on SDC-4 expression. Silencing EXT2 or HPSE leads to an increased expression of SDC-4, providing the evidence that EXT2 and HPSE regulate the SDC-4 expression. Altogether, these data indicate that EXT2, HPSE, and SDC-4 are involved in the proangiogenic effects of LMWF, suggesting that the HS metabolism changes linked to LMWF-induced angiogenesis offer the opportunity for new therapeutic strategies of ischemic diseases.     

Engaging Great Barrier Reef Stakeholders: Mediation Analyses of Barriers Among the Antecedents of Pro-Environmental Behavior

Resource managers continually attempt to influence stakeholder behavior to protect ecosystems. To aid managers and further our understanding of the human dimensions of natural resource management researchers have developed theories of pro-environmental behavior and to identify barriers to such behavior. However, there is a paucity of research integrating the two. There is a need to understand how perceived barriers influence the adoption of pro-environmental behaviors directly and how these barriers interact with the antecedents to pro-environmental behavior. Using the value-belief-norm theory as a guiding framework, we sought to fill this gap by investigating the effect of two barriers (lack of knowledge and low self-efficacy) among the antecedents to climate change–related behavior of anglers and other stakeholders (n = 324) living adjacent to Australia’s Great Barrier Reef. Results suggested that modeling/theorizing about how barriers fit into this process is complex because of differing contexts and levels of inclusion of barriers in existing theories.