Showing papers by "The Hertz Corporation published in 1990"

Activating mutations in p53 produce a common conformational effect. A monoclonal antibody specific for the mutant form.

Abstract: Point mutations in the p53 gene are the most frequently identified genetic change in human cancer. They convert murine p53 from a tumour suppressor gene into a dominant transforming oncogene able to immortalize primary cells and bring about full transformation in combination with an activated ras gene. In both the human and murine systems the mutations lie in regions of p53 conserved from man to Xenopus. We have developed a monoclonal antibody to p53 designated PAb240 which does not immunoprecipitate wild type p53. A series of different p53 mutants all react more strongly with PAb240 than with PAb246. The PAb240 reactive form of p53 cannot bind to SV40 large T antigen but does bind to HSP70. In contrast, the PAb246 form binds to T antigen but not to HSP70. PAb240 recognizes all forms of p53 when they are denatured. It reacts with all mammalian p53 and chicken p53 in immunoblots. We propose that immunoprecipitation of p53 by PAb240 is diagnostic of mutation in both murine and human systems and suggest that the different point mutations which convert p53 from a recessive to a dominant oncogene exert a common conformational effect on the protein. This conformational change abolishes T antigen binding and promotes self-oligomerization. These results are consistent with a dominant negative model where mutant p53 protein binds to and neutralizes the activity of p53 in the wild type conformation.

SK&F 96365, a novel inhibitor of receptor-mediated calcium entry

Abstract: A novel inhibitor of receptor-mediated calcium entry (RMCE) is described. SKF these concentrations of SKF however, the ATP-gated Ca2(+)-permeable channel of rabbit ear-artery smooth-muscle cells was unaffected by SK&F 96365. Thus SK&F 96365 (unlike the 'organic Ca2+ antagonists') shows no selectivity between voltage-gated Ca2+ entry and RMCE, although the lack of effect on ATP-gated channels indicates that it discriminates between different types of RMCE. The effects of SK&F 96365 on functional responses of cells thought to be dependent on Ca2+ entry via RMCE were also studied. Under conditions where platelet aggregation is dependent on stimulated Ca2+ entry via RMCE, the response was blocked by SK&F 96365 with an IC50 of 15.9 microM, which is similar to the IC50 of 8-12 microM observed for inhibition of RMCE. Adhesion and chemotaxis of neutrophils were also inhibited by SK&F 96365. SK&F 96365 is a useful tool to distinguish RMCE from internal Ca2+ release, and to probe the role of RMCE in mediating functional responses of cells. However, SK&F 96365 is not as potent (IC50 around 10 microM) or selective (also inhibits voltage-gated Ca2+ entry) as would be desirable, so caution must be exercised when using this compound.

Ninhydrin-reactive nitrogen measurements of microbial biomass in 0.5 m k2so4 soil extracts

Abstract: Amato and Ladd showed that the amount of ninhydrin-reactive nitrogen (ninhydrin-N) extracted from soil by 2 m KCl following chcl 3 fumigation is a reliable and sensitive indicator of the amount of soil microbial biomass. However, when we attempted the assay in 0.5 m k 2 so 4 soil extracts, serious analytical problems (e.g. precipitation of CaSO 4 and K 2 SO 4 ) occurred, which invalidated the ninhydrin-N determinations. As measurement of biomass C (and probably biomass N) in soils by fumigation-extraction is more reliable when K 2 SO 4 , rather than KCl, is used as the extractant, we modified the ninhydrin-N assay procedure to permit measurements in 0.5 m K 2 SO 4 . Our modified procedure is described. A strong relationship ( r = 0.99) between ninhydrin-N measured in KCl and K 2 SO 4 soil extracts was obtained (KCl-ninhydrin-N = 0.90 K 2 SO 4 -ninhydrin-N). There were also strong linear relationships ( r = 0.91−95) between biomass C, biomass N and biomass ninhydrin-N (all extracted with 0.5 M K 2 SO 4 ). We conclude that reliable ninhydrin-N measurements are obtained in 0.5 m K 2 SO 4 soil extracts by our modified procedure.

A comparison of kriging, cubic splines and classification for predicting soil properties from sample information

Abstract: SUMMARY The clay content of the topsoil in two regions of contrasting physiography was predicted from sample data using four different procedures. The predictors were the means of mapped classes, the usual kriging estimator, a cubic spline interpolator and a kriging estimator within classes using a pooled within-class variogram. The performances of the procedures were evaluated and compared. In the first region, Sandford St Martin on Jurassic sediments where there were some abrupt changes in soil, the classification predicted best within those classes bounded by sharp change. Elsewhere the usual kriging performed somewhat better, and kriging within classes was still more precise. In the second region, Yenne on the alluvial plain of the Rhone where the soil varied gradually, kriging performed better than classification, though a small improvement resulted from combining kriging with classification. Both prediction by class means and kriging attempt to minimize the estimation variance, and their mean prediction variances were close to the theoretical values overall. Spline interpolation is more empirical, and though it followed the abrupt changes better than kriging, it fluctuated excessively elsewhere, and its overall performance was poorer than that of kriging.

An evaluation of methods for measuring the microbial biomass in soils following recent additions of wheat straw and the characterization of the biomass that develops

Abstract: Four methods for measuring soil microbial biomass in soils containing recently-added wheat straw were tested: fumigation-incubation (FI). substrate-induced respiration (SIR), fumigation-extraction (FE) and soil adenosine 5'-triphosphate (ATP). The measurements were made at 13 and 35 days after addition of wheat straw (2% w/w) to a sandy loam (10.4% clay) and a non-calcareous clay (39% clay) soil. FI was unsuitable for measuring soil biomass C and N in straw-amended soils—in some cases, negative biomasses were measured. Biomass C measured by SIR was closely correlated with ATP but the intercept of the regression equation was significantly different from zero because of soil type, not straw amendment. Biomass C, N and ninhydrin N (all measured by FE) and ATP were all closely linearly correlated, irrespective of whether the soils were amended and with intercepts not significantly different from zero. It was concluded that biomass could be reliably estimated by cither FE or ATP in soils which have recently received decomposable substrates (e.g. straw). Straw addition roughly doubled the amount of biomass in the sandy loam soil (from ca 160 to 300μCg−1 soil) and increased it by ca 50% in the clay soil (from ca 620 910μg Cg−1 soil). The new biomass that developed had the same ATP concentration, C/N ratio and biomass C/ninhydrin N ratio as the original biomass. Meancd over the two soils and two treatments, the biomass had an ATP concentration of 9.2μmol ATPg−1 biomass C, a C/N ratio of 6.8 and a biomass C/ninhydrin N ratio of 31, all values similar to those that have been reported for unamended soils. The biomass of the sandy soil, whether unamended or not, had a higher specific respiration rate (mg CO2-C evolved g−1 biomass C day−1) than that in the clay soil, despite the similarity in the ATP concentration of the biomass in the two soils. Most of the increase in biomass following straw addition was found in the soil and not in the straw, although the concentration of biomass (nmol ATP g−1) was higher in the straw.

Survival of the soil microbial biomass at elevated temperatures

Abstract: A grassland soil was incubated for 240 days at either 15. 25 or 35°C. Changes in soil microbial biomass were monitored throughout the incubations in three ways: from soil ATP content, by the fumigation-extraction method and by a new version of the fumigation-extraction method in which carbohydrate released by fumigation is measured, rather than total C. All three methods of measuring biomass concur in showing that the biomass drifted downwards very slowly at 15° (with a mean decline of 0.11% per day) and 25°C (0.21% per day), whereas it fell precipitously during the first 50 days of incubation at 35°C (1.72% per day over the 0–50 day period). Both CO 2 output and biomass C remained remarkably constant over the 150–240 day period in all the incubations. The specific death rates of the biomass over this period were 0.0072, 0.016 and 0.25 day −1 at 15. 25 and 35°C respectively. The corresponding biomass turnover-times were 139, 62 and 4 days. Raising the incubation temperature had two effects: the rate of release of substrate increased but the specific death rate increased even more. The activation energy of death was 130kJ mol −1 , similar to values for thermal death in bacteria, suggesting that thermal denaturation was the process responsible for the enhanced death rate at 35°C. Although some of the CO 2 liberated during these prolonged incubations must have come from the initial microbial biomass, through cryptic growth and consumption of intracellular C reserves, most can only have come from soil organic matter. Some chemical or biochemical process (or processes) must operate on soil organic mailer to release a steady flow of substrate to the waiting biomass. The measurement of carhohydrate released by fumigation may provide a convenient way of measuring soil microbial biomass and deserves further testing.

Honeydew as a contact kairomone for aphid parasitoids

Abstract: Aphidius rhopalosiphi De Stefani-Perez, four other primary parasitoids and three hyperparasitoids of cereal aphids responded to cereal aphid honeydew on filter paper discs by greatly increasing visit times. Both female and male parasitoids responded, females generally more strongly. A. rhopalosiphi females were shown to habituate to honeydew, and to dishabituate fully in 90 min. Their response increased with increasing concentrations of honeydew up to 0.25 mg/μl, but no further increase was detected at 0.5 mg/μl. The response did not occur when direct contact with the treated paper was prevented. A. rhopalosiphi responded to some honeydew from non-host aphids as strongly as to that from host aphids. A. rhopalosiphi responded to the honeydew produced by Metopolophium dirhodum (Walker) reared on artificial diet and to the diet itself as strongly as to honeydew from M. dirhodum reared on wheat. The response of A. rhopalosiphi to honeydew therefore appears not to be caused by specific plant chemicals in the honeydew, and is probably not caused by aphid-specific chemicals. The results are discussed in relation to host location by A. rhopalosiphi. Resume Le miellat, kairomone de contact pour des parasitoides de pucerons Les parasitoides primaires de pucerons des cereales: Aphidius rhopalosiphi, A. picipes, A. ervi, Praon volucre et Ephedrus plagiator, ainsi que leurs hyperparasitoides, Dendrocerus carpenteri, Phaenoglyphis villosa et Alloxysta victrix ont reagi a du miellat de Sitobion avenae imbibant des disques de papier filtre, en prolongeant beaucoup leur temps de visite. Les femelles et les mâles ont reagi, mais les femelles generalement plus fortement. L'augmentation du temps de visite etait probablement provoque par la diminution de leur vitesse dans les zones traitees, leur tendance a sejourner dans ces zones et a y retourner apres les avoir quittees. Les femelles de A. rhopalosiphi s'habituaient au miellat, mais s'en deshabituaient totalement en 90 minutes. Leurs reactions augmentaient avec la concentration en miellat jusqu'a 0,25 mg/μl, sans qu'il y ait eu une nouvelle augmentation a 0,5 mg/μl. La reaction etait supprimee en absence de contact direct avec le papier. A. rhopalosiphi a repondu a quelques miellats produits par des non-hotes aussi fortement qu'a celui de ses hotes. A. rhopalosiphi a reagi au miellat produit par Metopolophium dirhodum, eleve sur milieu artificiel, et au milieu nutritif lui-meme, aussi fortement qu'au miellat de M. dirhodum eleve sur du ble. Ainsi, la reponse d'A. rhopalosiphi a un miellat apparait comme n'etant pas due a la presence de substances chimiques specifiques de plantes, ni, probablement, a des substances produites par les pucerons. Les resultats sont discutes en relation avec la localisation de l'hote par A. rhopalosiphi.

Secondary-structure dependent chemical shifts in proteins.

Abstract: Chemical shift data have been collected on eight proteins that have the same conformation in solution as in their crystal structures. Ring-current shifts have been calculated and subtracted from the exerimentally measured shifts, to leave shifts that depend only on local conformation. Overall, the shifts show an approximately normal distribution with no appreciable skewness, thus confirming that ring-current shifts have the overall effect of skewing the distribution to high field. In helices, NH and C(alpha)H have a high significant tendency to resonate to high field, whereas they resonate to low field in beta-sheets. Side-chain protons resonate slightly to high field in beta-sheets. Chemical shift distributions are narrowest for side-chain protons, and widest for amide protons. When only slowly exchanging amide protons are considered, the high field shift for amide protons in helices is more pronounced, but there is only a small difference in sheets. C(alpha)H signals at the N-terminal end of helices tend to resonate to higher field than those at the C-terminal end, whereas for NH signals it is the C-terminal end that resonates to higher field. There is no significant effect of position within the helix on side-chain signals, implying that the helix dipole has little effect on shifts within the helix.

Seasonal changes of soil microbial biomass in an arable and a grassland soil which have been under uniform management for many years

Abstract: Annual changes in biomass C, N and P were followed in two soils from the Rothamsted Classical Experiments that have been under the same management for > 100 yr, one under continuous wheat and the other under grass. Sampling was at approximately monthly intervals, over a period of ca 1 yr. Annual changes were small in both soils and largely masked by experimental and sampling error. Over the year, the arable soil (0–23 cm) contained a mean of 689 ± 11.6 kg biomass C ha−1, 154 ± 2.9 kg biomass N ha−1 and 47 ± 3.3 kg biomass P ha−1, The corresponding means for the grassland soil were 1121 ± 24.6 kg biomass C ha−1, 255 ± 10.4 kg biomass N ha−1 and 129 ± 4.8 kg biomass P ha−1.

Transformation of Sugarbeet (Beta vulgaris) by Agrobacterium tumefaciens

Abstract: A method has been developed for the regeneration of transformed plants of the commercially important crop sugarbeet (Beta vulgaris L.), using Agrobacterium tumefaciens. Binary vectors were used, carrying both screenable and selectable genes. Plant regeneration from shoot-base tissues was found to be relatively rapid and frequent compared with petioles or leaf tissue. Inoculation of cultured shoot-base tissues resulted in the production of transformed plants, as determined by (1) introduced resistance to kanamycin, (2) introduced CAT or GUS activity, and (3) Southern blot analysis to show the integration of foreign DNA. The transformation frequency was found to be dependent upon expiant source, plant genotype and selection conditions used.

Mycorrhizal infection of clover is delayed in soils contaminated with heavy metals from past sewage sludge applications.

Abstract: Etude preliminaire des arriere-effets des metaux lourds dans un sol traite par des boues residuaires avant 1961 sur les mycorhizes aborigenes et sur une mycorhize introduite (Glomus mosseae) en essais en pots

Damage to oilseed rape seedlings by the field slug Deroceras reticulatum in relation to glucosinolate concentration

Abstract: SUMMARY Seedlings of nine commercial cultivars of oilseed rape were exposed to the field slug Deroceras reticulatum immediately after sowing in compost in trays. There was a small reduction in seedling numbers in the presence of slugs which was not related to glucosinolate concentration in seeds or seedlings. However, the number and leaf-area of seedlings with damage symptoms were strongly and inversely related to the total concentration of glucosinolates in seeds and one wk-old seedlings. The presence of barley seedlings as alternative food did not significantly affect this relationship. The glucosinolate concentration of seeds was closely correlated with that of wk-old seedlings. Analysis of individual glucosinolates in four cultivars spanning the range of concentrations found, showed that the concentration of most components declined as total glucosinolate concentration decreased. However, 2-phenyl ethyl-glucosinolate (gluconasturtiin) concentration tended to increase in seeds and 3-indolyl methyl-glucosinolate (glucobrassicin) increased in seedlings as total glucosinolate concentration decreased. Damage by slugs was inversely related to the concentration of those glucosinolates which decreased and was positively correlated with the two compounds which increased as total glucosinolate concentration decreased. The results support the hypothesis that glucosinolates in brassicas protect them from polyphagous herbivores, and, in particular, that an important function of glucosinolates in rape seeds is to protect seedlings from slugs. As glucosinolate concentrations of oilseed rape cultivars continue to decline, so the risk of slug damage to seedlings may well increase.

Effects of field beans, fallow, lupins, oats, oilseed rape, peas, ryegrass, sunflowers and wheat on nitrogen residues in the soil and on the growth of a subsequent wheat crop

Abstract: The effects on a winter wheat test crop of a preliminary year of winter or spring field beans (Vicia faba), winter oats, winter oilseed rape, winter or spring peas (Pisum sativum), winter wheat, spring lupins (Lupinus albus), spring sunflowers (Helianthus annuus) or a cultivated fallow were compared in three 2-year experiments on clay-with-flints soil at Rothamsted from 1986 to 1989. In one experiment, autumn-sown ryegrass (Lolium perenne) and an uncultivated fallow, given weedkiller, were also included in the first year. Plots of test-crop wheat were divided to compare no N fertilizer with an optimal amount estimated from a predictive model.Amounts of take-all (Gaeumannomyces graminis) in the test crop of wheat following wheat were very slight in the first experiment, but large in the second and third. All the break crops reduced takeall to none or very slight amounts.Amounts of NO3-N in the soil in autumn after the first-year crops ranged from 7 to 95 kg N/ha. On average, they were least after oats, and most after cultivated fallow. In autumn 1988they were least after autumn-sown ryegrass. In early spring, amounts of NO3-N were generally less, ranging from 7 to 55 kg N/ha, depending on preceding crops, sowing date of the wheat and the weather. Amounts of NH4-N in soil were little affected by preceding crops or weather and were generally smaller in spring.The estimated average N fertilizer requirement of test-crop wheat following winter wheat was 230kg N/ha. This was increased by 10 kg N/ha following winter oats, decreased by 40 kg N/ha after spring peas and by 30 kg N/ha after winter rape, winter peas, spring beans and cultivated fallow. Other preliminary crops not represented every year had effects within this range.Grain yields of test-crop wheat given optimal N averaged 7·2 t/ha after winter wheat, c.1·5 t/ha less than the average after most of the break crops. The yield after oats was limited by self-sown ‘volunteers’ and that after ryegrass by limited soil N after ploughing.Of the break crops tested, winter and spring beans, winter oats, winter rape and spring peas all gave satisfactory yields. A farmer should choose between these on the basis of local farm circumstances and current economics of the break crops. Differences between effects on take-all and savings on fertilizer N were too small to influence this decision.

The action of diazoxide and minoxidil sulphate on rat blood vessels: a comparison with cromakalim.

Abstract: 1. The actions of diazoxide and minoxidil sulphate have been compared with those of cromakalim in rat aorta and portal vein. 2. Diazoxide and minoxidil sulphate hyperpolarized the rat portal vein in a similar manner to cromakalim. 3. Cromakalim, diazoxide and minoxidil sulphate increased 42K and 86Rb efflux from rat portal vein, although minoxidil sulphate had only a small effect on 86Rb efflux. 4. Cromakalim, diazoxide and minoxidil sulphate increased 42K efflux from rat aorta but only cromakalim and diazoxide increased 86Rb efflux from this tissue. 5. Glibenclamide inhibited the relaxant actions of cromakalim, diazoxide and minoxidil sulphate on rat aorta and the increase in 42K efflux produced by these agents in this tissue. 6. Diazoxide relaxed an 80 mM KCl-induced contraction of rat aorta, whilst cromakalim and minoxidil sulphate were without effect. 7. Cromakalim, diazoxide and minoxidil sulphate had no effect on cyclic AMP or cyclic GMP concentrations in rat aorta. 8. It is concluded that diazoxide and minoxidil sulphate like cromakalim exhibit K+ channel opening properties in vascular smooth muscle. Diazoxide exerts an additional inhibitory action not related to the production of cyclic AMP or cyclic GMP. The action of minoxidil sulphate may be primarily located at a K+ channel which is relatively impermeable to 86Rb.

THE JURASSIC SYSTEM IN NORTHERN EGYPT: I. Regional stratigraphy and implications for hydrocarbon prospectivity

Abstract: A systemotic lithostratigraphical description is presented of those Jurassic rocks encountered in Egypt north of 29°N at surface and in the subsurface. Based upon the scheme first proposed by Al-Far (1966), five formations (Masajid, Khatatba, Bir Maghara, Shusha and Rajabiah) are shown to make up a continuous succession from late Pliensbachian probably up to early Tithonian: the Gebel el Maghara Group. The compositions of stratigraphically -useful and diverse biotas are outlined, and used to erect a chronostratigraphical framework. From this, reliable comparisons are made with the Jurassic sequences of Palestine and Saudi Arabia. Furthermore, this more refined means of correlation enables a fuller understanding of the distribution of potential Jurassic source and reservoir rocks in northern Egypt.

Nitrogen deposition to land from the atmosphere

Abstract: . One direct measurement and two indirect estimates suggest that 35–40 kg nitrogen per hectare are deposited on arable land from the atmosphere each year in the south and east of England. This could contribute markedly to nitrate leaching and soil acidification. It may also change the flora and fauna of ‘natural’ ecosystems, as such amounts are likely to exceed the critical load.

Evaluation of methods for enumerating microorganisms in filter samples from highly contaminated occupational environments.

Abstract: Scanning electron microscopy (SEM), light microscopy (LM), epifluorescence microscopy (FM), and culture were used to asses catches of microorganisms in parallel air samples on membrane filters from heavily contaminated working environments that differed in the relative abundance of bacteria, actinomycetes, and fungal spores. Except in pig houses, estimates by SEM and LM were similar, but those by FM and culture were smaller. However, in pig houses, the fluorescent stain enabled bacteria on skin scales, not seen by SEM or LM, to be counted. Although counts obtained by culturing were always smaller than those obtained by SEM or LM, they sometimes exceeded those obtained by FM. Counts suggested that 0.1–68% of bacteria + actinomycetes and 3–98% of fungal spores were viable. However, samples for culturing may have contained larger aggregates than parallel samples collected with a sampling apparatus. All spore types recognized by LM included aggregates—those of bacteria + actinomycetes sometimes exceeding 200 ...

Immediate contact reactions to chemicals in the fragrance mix and a study of the quenching action of eugenol

Abstract: In this study, the nature of non-immune immediate contact reactions (NIICR) produced by cinnamic aldehyde, benzoic acid and sorbic acid were investigated, with particular interest in the 'quenching' ability of eugenol. Three groups of human subjects were studied, and the guinea-pig ear was also used as a model of NIICR. Cinnamic aldehyde, benzoic acid and sorbic acid were all able to produce NIICR in the majority of subjects studied. There was a strong correlation between the susceptibility of each subject to each urticant, but no correlation between the susceptibility to NIICR and age, atopic status or tanning ability. Eugenol caused a reduction in NIICR induced by all three urticants. This 'quenching' effect was apparent even when the eugenol was applied up to 60 min prior to application of cinnamic aldehyde, and its effect was not eliminated by washing. In the guinea-pig-ear model, ear thickening was induced by all three urticants, and this response was inhibited by eugenol.

Inhibition of insulin secretion from rat islets of Langerhans by interleukin-6. An effect distinct from that of interleukin-1.

Abstract: Glucose-induced insulin secretion from islets cultured in the presence of interleukin-6 (IL-6) for 12-24 h was inhibited to a similar extent as when islets were treated with interleukin-1 beta (IL-1 beta). However, unlike IL-1 beta, IL-6 did not potentiate insulin secretion during an acute (30 min) exposure of islets to the cytokine, nor did it inhibit DNA synthesis during a 24 h culture period. A 12 h pretreatment of islets with tumour necrosis factor-alpha (TNF-alpha) combined with IL-1 beta potentiated the inhibitory effect of IL-1 beta on secretion, such that 20 mM-glucose-induced insulin secretion was abolished. No synergistic inhibition of secretion was observed with TNF-alpha and IL-6. However, IL-1 beta and IL-6 were found to inhibit insulin secretion in an additive manner. These results suggest that IL-6 inhibits insulin secretion in a manner distinct from that of IL-1 beta, and that IL-6 is unlikely to mediate the inhibitory effects of IL-1 beta or TNF-alpha on rat islets of Langerhans.

The Effect of Temperature on Photosynthesis and Carbon Fluxes in Sunflower and Rape

Abstract: Sunflower (Helianthus annuus L.) and oilseed rape (Brassica napus L.) were grown at constant temperatures of 30 °C (warm) and 13 °C (cold). Maximal rates of photosynthesis between 5 °C and 35 °C were at higher temperatures in sunflower than rape. Photosynthetic rate over 4 h at the growth temperature declined in warm-and cold-grown rape and cold-grown sunflower, but remained constant in warm-grown sunflower. The stimulation of photosynthesis by 2 0 kPa O2 compared to 21 kPa 02 declined with decreasing temperature. At 10 °C in warm-grown rape photosynthesis was insensitive to 2-0 kPa 02. However, sensitivity to low O2 continued at 10 °C in warm-grown sunflower. Carbohydrates accumulated in the cold, particularly fructose, glucose and sucrose in warm-grown sunflower transferred to 13 °C. By monitoring changes of 14C in leaves after the assimilation of 14C02, the rates of carbon export from leaves, pool sizes and carbon fluxes between them were estimated. The transfer of warm- and cold-grown rape to 13 °C and 30 °C, respectively, had little effect on these parameters over 22 h. However, export of carbon from sunflower leaves at 13 °C was markedly less than at 30 °C, irrespective of the growth temperature, due to slower export from the transport pool. The rapid suppression of carbon export at 13 °C in warm-grown sunflower may be due to inhibited translocation rather than reduced sink demand in the cold. It is concluded that assimilate utilisation is more depressed in the cold than is photosynthesis; this imposes a greater restriction on biomass production in sunflower than in rape.