Composition and Distribution of Free Amino Acids in Flatpea (Lathyrus sylvestris L.) as Influenced by Water Deficit and Plant Age

Drought-stressed flatpea (Lathyrus sylvestris L.) plants from8 to 22 weeks old were analysed for nitrogen, soluble proteinand free amino acids. An increase in nitrogen and free aminoacid concentrations and a decrease in soluble protein levelwere observed in roots of plants up to 16 weeks old. The cumulativeconcentration of free amino acids increased with drought stress.Tissue concentrations of 2, 4-diaminobutyric acid (1.6–2.6%of the dry weight) were highest in leaves. Levels increasedsteadily, nearly doubling, in leaves and stems between weeks10 and 16. Levels in drought-stressed leaves were, on average,11.9% higher than those of controls. Estimated concentrationsof a mixture of 4-aminobutyric acid and an unknown amino acidwere highest in stems, increased in this tissue with age andtended to increase in stems and leaves and decrease in rootsin response to water deficit. Levels of the mixture of homoserineand another unidentified amino acid were not influenced by ageor water status of the plants. Root concentrations of asparagine,arginine, glutamine, aspartate, and another prominent, unidentifiedamino acid increased with plant age and reached a peak at thetime of flowering (14 to 18 weeks). Only the concentration ofthe unknown compound was elevated following drought stress.Concentrations of valine, isoleucine, leucine, phenylalanine,and methionine also increased during this period and were elevatedin drought-stressed plants. Proline levels increased with plantage and drought stress, but proline accounted for only about10% of the total free amino acids in the drought-stressed plants. Key words: 2, 4-Diaminobutyric acid, drought, flatpea     

Responses of Vegetable Seeds to Controlled Hydration

Leek, onion and carrot seeds were imbibed in water and in solutionsof polyethylene glycol (PEG) 6000 over the range –0.5to –4.0 MPa osmotic potential, for periods up to 28 dat 15 C. Seeds started to germinate after 7 and 14 d at –0.5MPa and –1.0 MPa PEG, respectively, but in the lattercase, germination did not exceed 5%. No germination occurredin solutions of lower (more negative) osmotic potential. Seedmoisture content increased with osmotic potential in all threespecies and the relationships were unaffected by the durationof imbibition in solutions of –1.0 to –4.0 MPa,though leek seeds had higher moisture contents than the otherspecies for any given osmotic potential. Linear relationships between response to priming (differencebetween mean germination times of primed and untreated seeds)and seed moisture content were obtained for each species, positiveresponses being obtained above 30–35% seed moisture contentwith optima at 46, 44.5 and 44% seed moisture contents in leek,onion and carrot, respectively. Priming had no effect on embryovolume or cell number per embryo in leek and onion. Carrot embryovolume increased by 43% and cell number per embryo doubled inprimed compared with untreated seeds, whereas seeds imbibedin water showed only a slight increase in cell number per embryoat the stage when radicles were beginning to penetrate the seedcoat. Allium cepa L. cv. Rijnsburger Robusta, onion, Allium porrum L. cv. Winterreuzen, leek, Daucus carota L. cv. Nantaise, carrot, germination, priming, polyethylene glycol, seed moisture, cell number, embryo volume     

Effect of Interferon on Some Aspects of Transformation by Polyoma Virus

WHEN BHK 21 hamster cells are infected with polyoma virus¹, there is no vegetative growth of virus, but stably transformed cells appear. These transformed cells are more easily transplanted than BHK 21 cells; they initiate their growth cycle in otherwise restrictive cultural conditions such as the absence of serum, high density and suspension; they grow with random orientation and have exposed on their surfaces receptor sites for certain glycoprotein agglutinins^2–5. The proportion of stably transformed cells is low, even after high doses of virus. But a much higher proportion (sometimes all cells) shows abortive transformation—changes characteristic of transformation, but which last only a few days. In suspension cultures, for example, most of the infected cells grow into small colonies of four to thirty-two cells⁶. In surface cultures deprived of serum DNA synthesis is initiated and the cells may then divide at least once⁷: they also temporarily lose the normal parallel orientation and develop the typical random appearance of transformed cells. Moreover, the polyoma nuclear T-antigen and also a surface antigen detected by immunofluorescence, appear temporarily in most polyoma infected BHK 21 cells⁸, while 3T3 cells exposed to SV40 virus show transient exposure of cell surface sites reacting with conconavalin A (ref. 9).     

Nonbreeding and nests without eggs in the Lesser Black-backed Gull Larus fuscus

Estimates of the number of breeding Lesser Black-backed Gulls Larus fuscus at the Tarnbrook Fell gullery, Lancashire, have been made from annual counts of nests since 1981. During all of these surveys, the mean percentage of nests which did not contain eggs has been remarkably constant from year to year (54%± 1.9%). A study of specific nests at the colony in 1992 showed that the great majority of these "empty" nests did not subsequently receive eggs. in 1993, a study of a sample of territory-holding gulls was made on a 0.41-ha study plot to investigate and to quantify the occurrence of empty nests. Of the 62 pairs that defended a territory and constructed a complete nest, 27% subsequently failed to produce eggs. These birds attended their territory as a pair significantly less frequently than pairs that produced clutches and achieved significantly fewer apparently successful mountings. Sixty percent of pairs constructed more than one nest, and 58% of all nests built received no eggs. The construction of empty nests was not found to be related to the density of nesting gulls. Since 1981, estimates of the number of gulls in the colony have been based on the assumption that one nest represents one pair of gulls. This has been shown not to be the case, and a correction multiplier of 0.61 must be applied to counts of nests at the colony to obtain an estimate of the number of breeding gulls.     

The effects of ripening and drying of carrot seed (Daucus carota) crops on germination

Carrot seeds taken from the parent plant were capable of germinating before the stage when maximum seed dry weight was reached but even after this stage, when the seed moisture content had fallen below 20%, improvement in seed germination characteristics continued. In the latter stages of seed growth losses by shedding were 12–20 kg/ha/day. For low density crops (10 plants/m²) the yield of viable seed was at a maximum in crops whose seed was harvested with a moisture content of between 20 and 40% but no consistent relationship could be established for high density crops (80 plants/m²). There were no effects of umbel order or plant density on mean germination time or spread of germination. At any early harvest, percentage germination was highest for primary-umbel-seeds and seeds from low density crops but the differences between the seed origins diminished with later harvests. Drying the seeds on the umbels improved the percentage germination, reduced the mean germination time and the spread of germination particularly at the early harvests compared with seeds removed from the umbels and germinated immediately without drying.     

Loss of decreased-rubisco phenotype between generations of wheat transformed with antisense and sense rbcS

The elite UK winter wheat cv. Riband was transformed with constructs containing rbcS in sense and antisense orientations driven by the maize ubiquitin promoter with a transformation efficiency of 1.2%. Of 77 primary transformants 31% of the sense-rbcS transformed lines and 78% of the antisense-rbcS transformed lines had decreased rubisco content compared to wild-type and marker-only controls, with decreases of up to 60%. However, in the T1 progeny which inherited the transgene, only 5% showed significantly decreased rubisco content and these effects were on the margins of significance. Five potential T2 homozygous lines from T1 parents which had transgene segregation consistent with a single locus were identified. There was no significant decrease in rubisco content relative to wild-type in any of these lines (LSD of 8% for P= 0.05). Expression of antisense rbcS transgenes in two of these T2 lines was low but was increased following exposure of the plants to 37°C for 48 h. However this did not induce a significant decrease in rubisco protein content relative to controls. Southern analysis of two antisense lines showed that they had low copy number and 1–2 insertion events. In one of the two lines there was increased methylation of the ubiquitin intron in T2 samples compared to the TO primary transformant. Further work is required to establish whether methylation occurred in all the lines which lost the phenotype, and therefore the likelihood of this being the cause. The disappearance of the decreased rubisco-content phenotype between generations may therefore be attributable to (1) greater activity of the ubiquitin promoter due to greater stress in the T0 generation plants and/or (2) increased methylation of the transgene promoter region between generations.     

Chytridiomycosis Widespread in Anurans of Northeastern United States

ABSTRACT An emerging disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis has been associated with morbidity, mortality, and extinction of species. Typically, researchers have detected B. dendrobatidis only when examining amphibians for causes of mortalities; few data exist on infection rates where mortalities are lacking. During May-September 2000–2002 we obtained amphibian specimens killed by vehicles and others collected at remote off-road sites throughout Maine, USA, and from federal lands in 5 states in the Northeast. We detected infected specimens, mostly green frogs (Rana clamitans), at 5 of 7 national wildlife refuges, a federal waterfowl production area, and Acadia National Park. Seven of 9 species, including all Ranidae species, were infected throughout Maine; rates ranged from 14.6% in American toads (Bufo americanus) to 25.7% in northern leopard frogs (Rana pipiens). We did not detect any infections in 50 eastern gray tree frogs (Hyla versicolor) or 21 spring peepers (Pseudacris crucifer). Species that hibernate in terrestrial habitats seem to have lower rates of infection than species that hibernate in aquatic habitats. Infections peaked in spring and autumn and were associated with air temperatures optimal for B. dendrobatidis growth. The relatively high infection rates among species without documented die-offs suggest that either losses have occurred undetected, that the fungus is endemic and species have attained a level of resistance to infections becoming lethal, or that climatic conditions of the Northeast have a role in preventing infections from being lethal. Data on prevalence and distribution of this chytrid fungus in the Northeast may be useful in modeling its origins and predicting long-term ecosystem effects involving anurans.     

Viral Properties of Scrapie

ALTHOUGH scrapie agent has many unusual features^1–4, some aspects of its behaviour are analogous to viral properties⁵. The manner in which the agent invades the nervous system after peripheral inoculation immediately recalls such typically neurotropic viruses as poliomyelitis or rabies. After inoculation into the fore-limb changes occur first in the cervical cord; following injection into the leg they appear first in the lumbar cord⁶. We now report another way in which scrapie behaves as a classical virus.     

The potential of lentil (Lens culinaris) as a grain legume crop in the UK: an assessment based on a crop growth model

A crop growth model developed in Canterbury, New Zealand was used to assess the potential of lentil (Lens culinaris) as a grain legume crop in the UK. The model was validated using five sowing dates at Durham (54.77°N, 1.58°W) in 1999. Predicted time to flowering was within 7 days of actual time to flowering and predicted seed yields were within 9% of actual yields. Actual yields ranged from 1.40 to 1.65 t ha‐¹. Seed was of high quality. The model was used to predict rate of development and yields of spring and autumn sown lentils at eight sites along a transect from NW Scotland (Stornoway, 58.22°N, 6.32°W) to SE England (East Mailing, 51.28°N, 0.45°E) chosen to encompass important environmental gradients in the UK. In general, for a 1 May sowing with 150 or 250 mm plant available water (PAW) and a 1 October sowing with 150 mm PAW, predicted mean values over the period 1987–95 for maximum crop growth rate, maximum leaf area index, radiation intercepted, total dry matter produced and seed yield were closely positively related to monthly mean values for mean daily air temperature and increased along the transect from NW to SE UK. Time to flowering generally decreased along the transect from NW to SE UK ranging from 28 June to 9 July and from 20 May to 14 June with the May and October sowings respectively. For the 1 May sowing with 250 mm PAW, predicted mean seed yield ranged from 1.00 to 1.90 t ha‐1. For all sites, yield was very stable over the 9 yr period. For the 1 May sowing with 150 mm PAW, predicted mean seed yield ranged from 0.97–1.23 t ha‐1. Yields for the four more southerly sites were more variable at the lower PAW and, in exceptionally dry years, were substantially lower than average. For these sites, autumn sowing increased seed yields in exceptionally dry years and gave similar or greater mean seed yields to spring sowing with 250 mm PAW. For East Mailing, predicted yields for autumn sowing were on average 2.78 t ha‐1. Also, for Stornoway, because of its relatively high overwinter temperatures, the model predicted substantial increases in yield with autumn sowing. It is concluded that lentil has considerable potential as a grain legume crop in the UK.