Quality,reputation and price in horticultural markets

This paper first examines the effects of quality and reputation for quality on prices of rockmelons, tomatoes and avocados on the Brisbane, Australia, wholesale produce market from November, 1982 to May, 1983. Price data were recorded for individual grower consignments and compared with overall market price averages and ranges. This examination leads to a hypothesis about quality-price relationships in which quality affects prices in three different ways. The buyer's assessment of quality relative to what is available on the market locates a product line relative to the average market price. A reputation for quality delays price changes after quality itself has changed, with price drops occurring more rapidly than price recovery. After a price drop due to quality problems, prices are erratic relative to market trends due to a reputation for unreliable quality.A detailed analysis of quality and price data for rockmelons consigned by a major grower to seven different agents on the Sydney, Australia, wholesale market in 1979, 1980 and 1981 is then used to test the hypothesis. It is concluded that these data do not refute the hypothesis and that the hypothesis provides a useful basis for quality-price investigations.     

The Effects of Enriching Live Foods With Highly Unsaturated Fatty Acids on the Growth and Fatty Acid Composition of Larval Red Drum Sciaenops ocellatus

Three experiments were carried out to test the effects of enrichment of live food (rotifers) with varying levels of n-3 highly unsaturated fatty acids (HUFA) on the growth rate and fatty acid composition of red drum larvae. Additionally, the fatty acid compositions of red drum eggs and day-1 larvae were compared. The enrichment techniques were successful in that the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were elevated in the rotifers fed the enrichment diet. Red drum larvae fed the control rotifers produced the highest growth rate of the three experiments. Larvae fed rotifers with no HUFA supplement (NHUFA) had a significantly lower growth rate than the controls for that experiment. The fatty acid compositions of the eggs and day-1 larvae did not vary significantly and contained high levels of 16:0, 16:1 n-7 and DHA (22:6 n-3). Based on these data, the lack of DHA in the diet significantly reduced the growth rates of larval red drum. The 10-day-old red drum larvae had similar fatty acid profiles at the end of the experiments regardless of the diet they were fed, indicating that dietary inputs have little effect on the fatty acid composition of larvae during the first ten days of growth. Red drum larvae appear to have the ability, though limited, to bioconvert EPA to DHA since there was a significant increase in the levels of DHA from day 1 to day 10 in the NHUFA larvae. However, the efficiency of this bioconversion is not sufficient for optimal growth and supplemental DHA at least to the level found in the control rotifers (0.3–0.4mg/100mg tissue) is necessary to maximize growth. The exact role of EPA could not be determined from this study due to the inability to produce an EPA-free rotifer.     

Initiation of Plant Disease Resistance by Physical Interaction of AvrPto and Pto Kinase

Resistance to bacterial speck disease in tomato occurs when the Pto kinase in the plant responds to expression of the avirulence gene avrPto in the Pseudomonas pathogen. Transient expression of an avrPto transgene in plant cells containing Pto elicited a defense response. In the yeast two-hybrid system, the Pto kinase physically interacted with AvrPto. Alterations of AvrPto or Pto that disrupted the interaction in yeast also abolished disease resistance in plants. The physical interaction of AvrPto and Pto provides an explanation of gene-for-gene specificity in bacterial speck disease resistance.     

Rapid actin transport during cell protrusion

Transformed rat fibroblasts expressing two variants of green fluorescent protein, each fused to beta-actin, were used to study actin dynamics during cell protrusion. The recently developed FLAP (fluorescence localization after photobleaching) method permits the tracking of one fluorophore after localized photobleaching by using the other as a colocalized reference. Here, by visualizing the ratio of bleached to total molecules, we found that actin was delivered to protruding zones of the leading edge of the cell at speeds that exceeded 5 micrometers per second. Monte Carlo modeling confirmed that this flow cannot be explained by diffusion and may involve active transport.     

Accumulation and erosion of Mars' south polar layered deposits

Mars' polar regions are covered with ice-rich layered deposits that potentially contain a record of climate variations. The sounding radar SHARAD on the Mars Reconnaissance Orbiter mapped detailed subsurface stratigraphy in the Promethei Lingula region of the south polar plateau, Planum Australe. Radar reflections interpreted as layers are correlated across adjacent orbits and are continuous for up to 150 kilometers along spacecraft orbital tracks. The reflectors are often separated into discrete reflector sequences, and strong echoes are seen as deep as 1 kilometer. In some cases, the sequences are dipping with respect to each other, suggesting an interdepositional period of erosion. In Australe Sulci, layers are exhumed, indicating recent erosion.