Fitness consequences of seed size in the valley oak <Emphasis Type="Italic">Quercus lobata</Emphasis> Née (Fagaceae)

Introduction   

We examined the functional relationship between seed size and seedling performance in the valley oak (Quercus lobata Née) by means of a 13-year common garden experiment.     

Release of catecholamines and specific protein from adrenal glands

Rabbit antiserums directed against a purified protein obtained from the catecholamine storage vesicles of the adrenal medulla of the cow were used to study the mechanism of secretion from the adrenal medulla. During secretion evoked by acetylcholine in isolated perfused adrenal glands, catecholamines and the specific intravesicular protein were released in relative amounts comparable to those present in the intact gland. Thus catecholamines are apparently released from the storage vesicles by a process resembling reverse pinocytosis.     

Proliferation of functional hair cells in vivo in the absence of the retinoblastoma protein

In mammals, hair cell loss causes irreversible hearing and balance impairment because hair cells are terminally differentiated and do not regenerate spontaneously. By profiling gene expression in developing mouse vestibular organs, we identified the retinoblastoma protein (pRb) as a candidate regulator of cell cycle exit in hair cells. Differentiated and functional mouse hair cells with a targeted deletion of Rb1 undergo mitosis, divide, and cycle, yet continue to become highly differentiated and functional. Moreover, acute loss of Rb1 in postnatal hair cells caused cell cycle reentry. Manipulation of the pRb pathway may ultimately lead to mammalian hair cell regeneration.     

Simultaneous selection of segregating two-row winter barley material in England and Italy

Summary Independent but simultaneous selection by two breeding teams of the same segregating two-row winter barley material at Cambridge, England and Fiorenzuola, Italy was carried out over the years 1978–1982 with the objective of comparing the individual selection of the two breeding teams and assessing the adaptation of the surviving selections. Visual selection in the generations F₃ to F₅ did not result in any clear cut compartmentalisation of the material and both teams were as likely to select from families previously selected only by the other team as from families they had themselves previously selected. Lines with specific adaptation to each site as well as lines well adapted to both sites were identified from yield trials carried out in F₅ and F₆. The former showed only a very small yield advantage over lines with general adaptation to both sites.     

Proximate Composition, Lipid Oxidation, and Sensory Characteristics of Fillets from Rainbow Trout Oncorhynchus mykiss Fed Diets Containing 10% to 30% Lipid

This study was conducted to determine the effects of increasing dietary lipid concentrations on fillet characteristics of post-juvenile rainbow trout. A feeding trial was conducted with fish meal based diets containing 10, 15, 20, 25, or 30% lipid for 24 wk. Menhaden oil was the lipid ingredient. Weight gain was significantly greater in fish fed the 30% lipid diet than in fish fed either 10%, 15% or 20% lipid diets. There were no significant differences in visceral somatic index. Fillet lipid concentration of fish fed the 30% lipid diet (9.2-g lipid/ 100-g fillet) was significantly higher (P < 0.05) than fish fed either the 10% or 15% lipid diets (5.8- and 6.9-g lipid/100-g fillet, respectively). In samples stored for 3 d at 5 C or S wk at -20 C, sensory panelists reported that the cooked fillets from fish fed the 30% lipid diet were "more fishy" than fish fed the 15% lipid diet, and preferred the cooked fillets from the 15% lipid treatment over the 30% lipid treatment. Triangle tests and fillet colorimetry showed no significant differences between fillets from fish fed the 15% and 30% lipid diets at any sampling time point. No significant differences in fillet concentrations of thiobarbituric reactive substances were observed among dietary treatments stored at either 5 C or -20 C. These results suggest that two main effects of feeding a 30% lipid diet (with fish oil as the lipid source) are a higher lipid concentration in the fillet and a "fishier" aroma compared to fillets from fish fed a 15% lipid diet.     

The effect of carbon and nutrient loading during nursery culture on the growth of black spruce seedlings: a six-year field study

We tested the effects of exponential nutrient loading and springtime carbon loading during nursery culture on the field performance of black spruce (Picea mariana (Mill.) B.S.P.). Seedlings were grown from seed with a conventional, fixed dose fertilizer (10 mg N seedling⁻¹) or an exponential nutrient loading regime (75 mg N seedling⁻¹). The following spring, seedlings were exposed for two weeks to either ambient (370 ppm) or elevated levels of CO₂ (800 ppm) and then planted in the field; seedling growth was followed for the next six years. Exponential nutrient loading increased seedling height, stem diameter and leader growth, with the largest increases in height and leader length occurring in the first three years after outplanting. Carbon loading increased seedling height and leader length, but only in seedlings that had been exponentially nutrient loaded. A combination of carbon and nutrient loading increased shoot height 26%, stem diameter 37% and leader length 40% over trees that received neither treatment. These results demonstrate that the growth enhancement seen under exponential nutrient loading is maintained under field conditions for at least six years. Carbon loading just before outplanting was a useful supplement to nutrient loading, but was ineffective in the absence of nutrient loading.     

The possible use of mitochondrial complementation as an indicator of yield heterosis in breeding hybrid wheat

Summary Nine hybrid wheats and their six parental lines were grown in a field trial at two seed densities. The ADP:0 ratios for mitochondria extracted from the six parental lines and for the appropriate 1:1 mixtures of mitochondria from these parental lines were measured. The percentage additional mitochondrial efficiency of the mixtures over their more efficient parental line was found to be significantly correlated with the percentage yield heterosis of fully restored relatively disease-free hybrids grown at the lower seed density. These results indicate that measurements of mitochondrial complementation may have some value as a first screening of potential parental lines and may thus facilitate the rational choice of suitable material for producing hybrid wheat.