Prevention of potato top-roll by aphicide and its effect on leaf area and photosynthesis

In a field of potatoes, top-roll, which is induced by the aphid Macrosiphum euphorbiae feeding on the leaves, was restricted to two rows of plants which accidentally received no phorate aphicide granules at planting. The photo-synthetic rate per unit leaf area and the ground cover of top-rolled leaves were respectively 50% and 20% less than those of normal plants which may account for the smaller yields of affected plants observed in previous experiments.     

Molecular Characterization of a Barley Gene Induced by Cold Treatment

A cDNA library was made from low positive temperature (6 ?C/2?C) grown barley shoot meristems. Several genes which are differentiallyexpressed, as measured by mRNA abundance, were selected fromthe library using a differential screen. This paper reportsan analysis of in vivo expression in several cultivars, theDNA sequence, copy number and chromosomal location of one gene(BLT14). In addition, genomic restriction fragment length polymorphismfor this gene in the 10 most widely UK-grown spring and 9 mostwidely UK-grown winter barley cultivars is analysed. Key words: Hordeum vulgare, low temperature, RFLP, differential expression, cDNA sequence     

Intermediary metabolism and shell growth in the brachiopod Terebratalia transversa

Juvenile Terebratalia transversa (Brachiopoda) metabolize carbohydrates in the anterior-most marginal mantle at a rate of 0.46 μM glucose/g/hr (in vitro incubation of mantle in C¹⁴-glucose in a carrying medium of 10^-3 M non-radioactive glucose). The rate declines to 0.18μM glucose/g/hr in full-grown specimens. Carbohydrate metabolism in the marginal (anterior-most) mantle averages approximately 3.7 times greater than metabolism in (a portion of the ‘posterior’) mantle situated between the coelomic canals and the marginal mantle. This ratio remains constant in specimens of all sizes (i.e. an ontogenetic trend in the ratio is absent at p≤ 0.05). Organic acids are not detectable within the mantle (HPLC techniques) even after simulated anoxia (N₂ bubbling during mantle incubation). Glucose metabolism in vitro declines in both the marginal and ‘posterior’ mantles during anoxia and the metabolic ratio between marginal/‘posterior’ mantles becomes 1/1. We found no difference (at p≤ 0.05) in mean metabolic activity or in sue-related metabolic trends among populations from depths ranging between mean sea level and 70 m. However, the activity within the ‘posterior’ mantle was more variable in specimens from 70 m than in those from shallower habitats (10 m - mean sea level). The size of the specimens analyzed was most variable in the groups obtained from the shallowest habitats and least variable at 70 m depth. Our results may help define the energetics of fossil as well as living brachiopod shell growth. Brachiopod shell growth is known to be very slow relative to that of bivalves and our results indicate that this is a result of the animals' slow metabolism. The inflation of the valves in T. transversa is, in part, a function of the high ratio of intermediary metabolism in the marginal vs‘posterior’ mantle (i.e. parallels the relative growth rates at the shell margin vs‘posterior’ areas). We found that the bivalve, Chlamys hastata, which is commonly associated with T. transversa, has a lower ratio of metabolic activities in the ventral/dorsal mantle areas than the brachiopod has in the anterior/posterior. The difference produces a flatter shell in the bivalve in accord with allometric principles. The higher metabolic rate in the marginal vs‘posterior’ brachiopod mantle and its more pronounced decline with anaerobiosis is reflected in the greater definition of growth increments in the outer shell layer. Our results do not support recent generalizations that correlate shell thickness of a wide variety of invertebrates inversely with metabolic rate. Growth rate as determined from width of shell growth increments is a better index of metabolic rate. Although the genetic basis of glucose metabolism is unknown, the observed metabolic variability is consistent with suggestions that populations of marine organisms living in stable offshore environments are genetically more variable but morphologically more uniform than populations from shallow water. Furthermore, our results support suggestions that bivalved molluscs and brachiopods are very different metabolically, but the data are neutral with respect to theories of competitive exclusion of the two taxa throughout geologic history.     

The use of protein A-sandwich ELISA as a means for quantifying serological relationships between members of the tobamovirus group

Indirect protein A sandwich ELISA (PAS-ELISA) was used to determine the serological relationship between eight tobamoviruses with antisera to 26 viruses and virus strains within the group. Very distant relationships were determined by trapping virus with heterologous antiserum and detecting it with homologous antiserum, while near and close relationships were differentiated by using heterologous antiserum each time. The results were esssentially consistent with previously recorded relationships determined by tube precipitin and other serological tests. Since PAS-ELISA requires much less antiserum than many conventional tests and does not require the purification of IgG or virus, it may offer many advantages in the detection of serological relationships.     

Uptake, translocation and metabolism of fluazifop-butyl in Setaria viridis

The uptake and translocation of fluazifop-butyl was investigated in Setaria viridis. Young plants (three to four leaves) with a portion of the second, third or fourth leaf covered, were sprayed with a dose equivalent to 0.25 kg a.i. ha-¹. ¹⁴C-fluazifop-butyl was subsequently applied to the unsprayed area and the treatment resulted in plant death within 2 wk. Uptake by leaf 3 was rapid, with less than 5% of the applied dose remaining on the leaf surface after 24 h. The highest proportion of ^14C-activity was retained in the treated portion of the leaf. Only 2% of the applied dose was translocated from leaf 3 and 0. 76% accumulated in the apical meristem. Uptake by the younger leaf 4 was more rapid and the pattern of translocation differed in that more ¹⁴-^-activity accumulated in apical meristematic tissue. 6–30% of the applied dose was undetected and this was greatest when foliar uptake was slow. Artificial leaf surface experiments indicated that this undetected activity may have been due to volatility of fluazifop-butyl or degradation to volatile products. ^14C-activity extracted from treated leaves was identified as fluazifop-butyl, fluazifop acid and polar conjugates. The major ¹⁴C-activity extracted from the apical meristem was fluazifop acid and no fluazifop-butyl was detected in this extract.     

Identification of soybean mosaic, southern bean mosaic and tobacco ringspot viruses from soybean in the People's Republic of China

Samples of soybean plants with virus-like symptoms were collected from several locations in the People's Republic of China in 1981. These samples were used to prepare inocula for mechanical inoculation to soybean. Twenty-one virus cultures were obtained, the identities of which were determined by serology, symptomatology and host range. Sixteen cultures contained only soybean mosaic virus, four of which were more pathogenic than any previously studied; one culture contained only tobacco ringspot virus, another only southern bean mosaic virus, and three other cultures mixed infections of soybean mosaic and southern bean mosaic viruses. This is the first report of the occurrence of tobacco ringspot virus and southern bean mosaic virus in soybean in the People's Republic of China.     

Transformation-defective Strains of <Emphasis Type="Italic">Haemophilus influenzae</Emphasis>

THE mechanism of genetic transformation and recombination can be studied with mutants deficient in various stages of transformation and recombination, but their isolation has often proved to be difficult and time-consuming. We have developed a method for selectively removing cells which transform normally from cultures of Haemophilus influenzae. Mutants isolated from such cultures have been tested for DNA uptake, integration, ultraviolet and X-ray sensitivities and ultraviolet induced DNA synthesis delay.     

Effects of Inhibitory Concentrations of 3-Indolylacetic Acid and 3-Indolylacetonitrile on Cell Division and Tissue 2

Inhibitory concentrations of 3-indolylacetonitrile (IAN) cause,in cultured excised tomato roots, a marked decrease in the rateof cell division at the apical meristem but only a slight reductionin the lengths of mature exodermal and cortical cells. The reducedrate of cell division is associated with a decrease in the.number of meristematic cells at the root apex. By contrast,3-indolylacetic acid (IAA) causes marked reduction in the lengthsof mature cortical cells but does not markedly reduce cell-divisionrate at the apical meristem. Various lines of evidence indicate that both IAA and IAN causea relative increase in the number of longitudinal and a decreasein the number of transverse division walls in the meristematiczone of the root apex. Partial inhibition of the linear growth of excised tomato rootsby IAA and IAN is accompanied by increases in root and stelardiameters. These increases result from radial enlargement ofthe cortical cells and increase in the number of stelar cellsin the transverse section. The enlarged steles contain an increasednumber of lignified xylem elements, but only with the most inhibitoryconcentration of IAN (10^–4g./ml.) is there evidence ofthe development of secondary xylem. Both auxins increase significantlythe xylem vessel unit length.     

NEMATOCYSTS OF THE SEA ANEMONE METRIDIUM

Six types of nematocysts and their nematocytes in tentaclesand acontia of the sea anemone Metridium senile fimbriatum werestudied by electron microscopy. Microbasic b-mastigophores, microbasic amastigophores, and basitrichshave one fundamental feature in common: a straight, complexly-foldedshaft with dense spines pointing apically. An additional resemblancebetween a b-mastigophore and a basitrich is the possession ofa long, narrow, coiled thread bearing spines. An amastigophoreis characterized by a short, looped, unspined thread and a cup-shapedgranular matrix. Atrich and holotrich nematocysts have a coiled, spined tubeof uniform diameter which lies in an evenly granular matrixfilling the entire capsule. The above five nematocysts have three flaps at the apex of thecapsule which open upon discharge, and each nematocyte possessesa flagellum with which is associated one or two centrioles anda striated rootlet. The long rootlet of the b-mastigophorebearingnematocyte passes through a circular band of fibrils surroundingthe neck region of the capsule, and the short rootlet of theatrich lies in a dense fibrous sheath surrounding all but theapex of the capsule. The spirocyst differs from the other nematocysts in having athin, ridged, singlewalled capsule; an inverted tube containingbundles of tubules; an apical disk covered only by a thin layerof granular material and the nematocyst membrane; and the absenceof a flagellum in its nematocyte. Theories of excitation and mechanism of discharge of nematocystsand the function of spirocysts are discussed in the light ofthis and other recent studies of the fine structure of nematocysts.Special attention is drawn to the probable role of the foldsin the walls of shaft and thread in increasing the length ofthe tube upon discharge.