Responses to Water Stress in Adapted and Unadapted Carrot Cell Suspension Cultures

The responses of suspension-cultured cells of carrot to polyethyleneglycol (PEG)-induced water stress were studied after transferto culture medium containing PEG at concentrations between 0%and 25%. Growth characteristics, cellular osmotic potentialand organic solute concentration changes were followed in unadaptedcells and in cell lines adapted to growth in various PEG concentrations.A decline in fresh and dry weight increase occurred in unadaptedcells with decreasing water potential, while dry weight gainwas unaffected in adapted lines. Substantial osmotic adjustmentwas observed in adapted lines, due mainly to increased glucose,fructose and sucrose. Proline concentration increased up to40-fold in adapted and 12-fold in unadapted cells and otheramino acids including alanine, histidine and arginine showedsimilar, though smaller, responses. Polyamines and glycinebetainedid not increase significantly in either adapted or unadaptedcells. Changes leading to long-term adaptation to water stressare discussed in relation to short-term stress—shock responses. Key words: Water stress, cell culture, Daucus carota, osmotic adaptation, solute accumulation     

Genotype by environment interaction in the assessment of tolerance of partially resistant potato clones to potato cyst nematodes

Genotype by environment interactions in a number of field trials in different years are examined in relation to tolerance of potato cyst nematodes and the subsequent yield losses. A biplot technique is used to display the interaction effects graphically and facilitate identification of any patterns in the data. The results are assessed and discussed in relation to breeding strategies and the variation found between different nematode populations.     

THE EFFECT OF COMMERCIAL TRAPPING ON RABBIT POPULATIONS

The effect of commercial trapping on two rabbit populations in West Wales, was investigated during 1946 to 1949. On two farms rabbits were caught alive in snares, marked and released just before trapping; the total number of rabbits marked, divided by the fraction of marked rabbits recovered in the trapped sample gave an estimate of the population before trapping started. Trapping usually removed 30–40 % of the rabbits present, a proportion compatible with a careful cropping of the population. At one farm, studied for 3 years, the population increased steadily.
Breeding was intense from January to June inclusive, and from weight and age distributions it was apparent that in 1948 and 1949 considerable breeding also occurred in autumn. The sex ratio varied around a mean of about 50%.
Data are given on movements, obtained from recapture records of zog marked animals. They suggest that rabbits probably forage over an area of not more than 150 yards in diameter. The records from recaptured marked animals indicate that the mean expectation of life is about 6 months.     

Effects of Gibberellic Acid on the Activation, Synthesis, and Release of Acid Phosphatase in Barley Seed

Acid phosphatase activity was present in unimbibed barley seed,but rose during incubation of embryoless half-seeds and isolatedaleurone layers, and was further increased by 10^–6 M gibberellicacid (GA₃). Release of total acid phosphatase activity fromhalf-seeds and aleurone layers was markedly enhanced by GA₃.Inhibitor studies with cycloheximide and actinomycin D suggestedthat de novo synthesis of acid phosphatase occurred followingimbibition. Gel nitration, electrophoresis, and [¹⁴C]leucineincorporation studies revealed that a single molecular formof acid phosphatase was present in dry seed, whereas on incubationtwo further forms arose. A proportion of the three molecularforms of the enzyme was synthesized de novo. Gibberellic acidstimulated activation, but not de novo synthesis, of all threemolecular forms of acid phosphatase. Although a small amountof one of the molecular forms was secreted in the absence ofGA₃, the presence of gibberellin greatly increased secretionof the same form of acid phosphatase.     

Presence of Sarcoma Genome in a “Non-infectious” Mammalian Virus

Virus particles, antigenically related to mouse sarcoma virus, can be induced from hamster tumour cells. They are “defective” in their failure to replicate in or transform hamster, mouse or rat cells, although they contain viral-specific RNA and, with “helper” mouse leukaemia virus, show sarcomagenic activity.     

Trans‐equatorial migration,staging sites and wintering area of Sabine’s Gulls Larus sabini in the Atlantic Ocean

The migrations and winter distributions of most seabirds, particularly small pelagic species, remain poorly understood despite their potential as indicators of marine ecosystem health. Here we report the use of miniature archival light loggers (geolocators) to track the annual migration of Sabine’s Gull Larus sabini, a small (c. 200 g) Arctic‐breeding larid. We describe their migratory routes and identify previously unknown staging sites in the Atlantic Ocean, as well as their main Atlantic wintering area in the southern hemisphere. Sabine’s Gulls breeding in northeast Greenland displayed an average annual migration of almost 32 000 km (n = 6), with the longest return journey spanning close to 39 000 km (not including local movements at staging sites or within the wintering area). On their southern migration, they spent an average of 45 days in the Bay of Biscay and Iberian Sea, off the coasts of France, Spain and Portugal. They all wintered in close association with the cold waters of the Benguela Upwelling, spending an average of 152 days in that area. On their return north, Sabine’s Gulls staged off the west African coast (Morocco, Mauritania, Senegal), spending on average 19 days at this site. This leg of migration was particularly rapid, birds travelling an average of 813 km/day, assisted by the prevailing winds. Sabine’s Gulls generally followed a similar path on their outbound and return migrations, and did not exhibit the broad figure‐of‐eight pattern (anti clockwise in the southern hemisphere and clockwise in the northern hemisphere) seen in other trans‐equatorial seabirds in the Atlantic and Pacific oceans.