The 65 spring and 14 winter cultivars of barley on the 1981 U.K. National List were examined electrophoretically for allozyme variants of phosphoglucoisomerase (PGI). Two different banding patterns were observed, a ‘fast’ and a ‘slow’ migrating type. With the exception of six spring cultivars in which the ‘slow’ type was found, all the cultivars were classified as ‘fast’. F2 progeny of crosses between ‘fast’ and ‘slow’ plants were used to interpret the banding patterns as resulting from the dimeric isozymes of two alleles (allozymes) each producing a triple band pattern, the faster two bands of which were considered to be ‘secondary’ or artefact bands. With the notable exception of Dragon and its sister line RPB 1115–75 all of the other ‘slow’ cultivars and breeders' selections were found to have the ‘slow’ cultivar Midas in their breeding history. Midas was bred using material from three ‘fast’ cultivars and a γ-ray mutant strain, the irradiation which produced this strain being regarded as the likely cause of the ‘slow’ isozyme. Unlike all the other cultivars tested, Midas was found to be a mixture of genotypes comprising 73% ‘slow’ and 27% ‘fast’ plants, a ratio which was most probably due to founder effects caused by the breeders' selection programme. In the light of the present investigation and other reports it is concluded that it is not an uncommon occurrence to find plants with different electrophoretic banding patterns within inbred cultivars.

This result has serious implications for cultivar registration as there is a possibility of selecting electrophoretically distinct plants from within existing registered cultivars. It is concluded therefore that the protection afforded to plant breeders under Plant Breeders' Rights schemes could be seriously threatened by the use of electrophoretic characters for cultivar registration except in some specific incidences where it may be possible to apply appropriate safeguards. The implications for plant breeders of the existence of isozymes of PGI, of possibly different efficiencies, within commercial cultivars of the genus Hordeum are also discussed.

Several nitrification inhibitors were compared with nitrapyrin, which was taken as the standard, when injected with aqueous urea into ryegrass leys at Rothamsted during 1977–81 and at Liscombe Experimental Husbandry Farm, Dulverton, Somerset, during 1977–9. Injection was done in either autumn or winter or spring.

All the inhibitors slowed down the rate of nitrate formation from the injected urea. Sodium trithioearbonate (STC) was less effective than nitrapyrin and potassium ethyl xanthate (KEtX) less effective than STC. A mixture of nitrapyrin and carbon disulphide was better than nitrapyrin alone, and a mixture of STO and KEtX was better than STC alone.

At Rothamsted, injecting inhibitors in autumn or winter improved yields and N uptakes, probably because they prevented loss of nitrate N by leaching and perhaps by denitrification. STC, STC-KEtX mixture and etridiazole were as good as, and nitrapyrin–CS2 mixture better than, nitrapyrin alone. Injecting inhibitors in spring frequently decreased yields, perhaps because NH4:NO3 ratios were too large, and increased them only when more than 150 mm of rain fell afterwards.

At Liscombe, where rainfall was higher, but soil temperatures were similar to those at Rothamsted, the benefits from using inhibitors in autumn were larger, but there were none from using them in spring.

Two sources of sulphur-coated urea (SCU) were compared with calcium ammonium nitrate (CAN) as sources of N for cotton and sorghum in the savannah zone of Nigeria. At the lowest rate of N application (30 kg/ha for cotton and 40 kg/ha for sorghum), SCU-11 with a dissolution rate of 11% in 7 days was found to be more effective than SCU-30 having a dissolution rate of 30% in 7 days and CAN. A single application of SCU-11 produced a higher sorghum yield than a divided application of CAN at the same rate. These results indicate that a slow-release nitrogen fertilizer might be useful for improved grain sorghum and cotton varieties.

Selections for erect-(E) and lax-leaf (L) posture in winter wheat were made from a cross between parents which contrasted in the character. By the F5 generation there were consistent, heritable differences between E and L lines. The lines were evaluated in three field experiments and a glasshouse experiment.

In an experiment in which plots were automatically sheltered from rain and in which there were three irrigation treatments, there was no treatment-posture interaction, and over all treatments E lines outyielded L lines by 0·26 t/ha. When fully irrigated the water use of both E and L lines between 1 May and maturity was approximately 280 mm. Withholding water caused a reduction in water use and a corresponding reduction in grain yield for both E and L lines.

When the four most erect- and the four most lax-leaved lines were considered over all three field experiments, E lines maintained a slight, though not significant, grain yield advantage of 0·17 t/ha over L lines. However, the E lines produced significantly more biomass, averaging 0·7 t/ha more than L lines, and this extra biomass was not produced at the expense of additional water requirement. However, results from the glasshouse experiment suggested that the E lines may be more susceptible to a substantial pre-anthesis drought.

It is concluded that varieties of winter wheat with the erect-leaf habit may provide an opportunity of increasing biomass production. In an environment in which a preanthesis drought is unlikely to occur, such varieties may give the highest yields. However, on light soils prone to early drought or at sites which would not permit the maximum expression of leaf area index at anthesis, varieties with a lax-leaf posture may give greater yield.

The production of green beans was studied in sowings made from December to February, September to February, and from October to February in three seasons, and over six oonsecutive seasons for a mid-season sowing.

With September-October sowing the rate of emergence was slow, and establishment sometimes poor. Possible virus disease, and the lack of continuity of setting pods resulting from cool weather, were problems. Good yields were obtained from midseason sowings (31 October-18 December), up to 19·6 t/ha, with good yields for late sowings up to 13·9 t/ha in ^he first three seasons. In another three seasons mid-season sowings (late November-early December) resulted in poor yield due to periods of hot weather (> 35 °C max.) prior to and during flowering.

There was a relationship between quality and yield. The greatest yield and best quality green pods were obtained when conditions favoured rapid growth and rapid setting of pods, and when there was a high rate of pod maturation.

For yield of dry seed the early sowings were best, 3·6 and 2·8 t/ha in two seasons. A total of 460 mm of water was required for the first six sowings, but fell to 360 mm for the mid-February sowing (rainfall plus irrigation).

Although it was possible to grow beans over a 9-month period the January and early February sowings appeared to be the least risk prone with the present cultivars.

Studies were conducted in two consecutive years at Mead, Nebraska, to investigate the relationship between lodging, certain morphological characters and grain yield of sorghum.

Morphological characters correlated with lodging were plant height, length of prepeduncle internode and rind thickness. Lodging was negatively correlated with number of days from sowing to 50% bloom and grain yield but was not correlated with grain weight of the head.

Rhizobium strains adapted to high temperature, and genotypes of green gram, were used to study the symbiotic N2-fixation in a summer season at two moisture levels in calcareous soil. Different interactions between strains and genotypes were observedatthe two moisture levels. At both moisture levels, strain S4 with the green gram genotype S8 showed the greatest grain yield, nitrogenase activity, leghaemoglobin and ethanolsoluble carbohydrate of nodules.

The residual effects of sulphur-coated urea (SCU) fertilizers were evaluated by measuring the pH and mineral-N in the soil profile after 2 years of application of these fertilizers to soils in the various ecological zones of the savannah of Nigeria. Changes of 0·2–0·3 pH units relative to the control (without applied N) were detected on the sandier soils at Kadawa and Mokwa but not on the heavier Samaru soils. There was little or no difference among the sulphur-coated urea and calcium ammonium nitrate in their acidification effects. Also residual nitrogen levels were low in plots that received SCU but did not differ significantly from those of calcium ammonium nitrate.

A series of trials were conducted during 1979–82 under semi-arid conditions in a Mediterranean-type environment to study the edge effects in mechanized durum wheat and barley variety trials when uncropped pathways are left between plots. Varietal differences in edge effects on grain yield were in most trials not significant. Thus, edge effects do not distort significantly the relative ranking of varieties.

Edge effects were significant for all traits studied and higher in grain and straw yields. These effects were also higher in drier seasons. The overestimation of grain yield from whole plots was 13–18% in relatively high rainfall seasons and 29% in a dry season. In two seasons the scores on the two outer rows were higher than on the two central rows by 89 and 117 % for grain yield, by 72 and 73% for straw yield, by 44 and 48% for numbers of tillers, by 6% for 1000-grain weight and by 14 and 40% for number of grains per tiller. The edge effect was not confined to the outer rows, but it extended to the inner rows of the plot; the magnitude of this effect varied with season and trait.

Rows adjacent to the pathway and unprotected from wind had a lower value for all traits than the opposite rows of the pathway, which were protected by the inner rows.

In 68 spring barley crops grown in five experiments at Rothamsted and Woburn between 1980 and 1982, and given adequate K fertilizer, there was a positive correlation (r = 0·76; P < 0·001) between maximum % K in dry matter of young plants and the grain yield at final harvest. In all crops changes in % K in dry matter during the growing season were directly related to changes in fresh weight to dry weight ratio (FW: DW) suggesting that differences in % K in dry matter were the result of differences in tissue hydration. Potassium concentrations expressed on the basis of tissue water were not correlated with grain yield. All crops maintained K concentrations in their tissue water of about 200 mmol/kg tissue water, except at the end of the growing season when water loss during ripening caused a steep rise.

The correlation between % K in dry matter and yield was the result of differences in FW: DW. Within each experiment there was a good correlation between FW: DW and grain yield, but because the relationship was different for each experiment the overall correlation for all crops was poor. The correlation between FW: DW and grain yield within experiments probably arises because crops with a higher FW: DW will have higher specific leaf areas and hence higher relative growth rates and yields.

Simulating the accumulation of dead leaf sheaths in perennial ryegrass by masking the tiller bases increased leaf and sheath length and tiller weight but decreased tiller production. Exposure of previously masked tiller bases or stripping back the subtending leaf and sheath to expose the tiller bud in its axil stimulated tiller production. A photomorphogenic effect is postulated which controls the partitioning of dry matter between the growth of new leaf and sheath tissue on existing tillers, and the development of new tillers from tiller buds.

The influence of various nitrogen and phosphorus sources, applied at the preseeding stage with two placement methods, on maize yield and fertilizer utilization, was studied in two field experiments and a pot experiment with a calcareous, heavy to medium heavy textured recent alluvial soil.

Phosphorus alone had no effect on crop yield. Nitrogen alone or nitrogen (various forms) and phosphorus had a clear positive effect on crop yield. As to the various sources the observed differences in the crop yield of the field experiments were not significant, while in the pot experiment ammonium sulphate gave the highest yields.

The data on the phosphate concentrations in the tops derived from phosphate fertilizer (Pf) indicate that the presence of nitrogen increased the utilization of phosphorus fertilizer. From the tested placement methods the incorporation method appears clearly superior in the pot experiment with a similar trend in the field experiment for all sources except ammonium phosphate-sulphate.

The utilization coefficients of the nitrogen fertilizer sources suggest that ammonium and urea were better utilized than nitrates, that the higher nitrogen utilization reflected higher yields and that phosphorus fertilizer exerted a beneficial effect on nitrogen fertilizer utilization. Finally they suggest that the addition of 120 kg N/ha enhanced the amount of soil nitrogen taken up in the maize grain by 53%.

Wool follicles and fibres of pre-ruminant lambs abomasally fed isoenergetic diets with daily amounts of lysine ranging from 0·12 to 1·94 g/(kg live weight)0·75 were examined by light and electron microscopy. In lambs which received ca. 0·9 g lysine/kg 0·76 daily, the follicles appeared normal, whereas in those which received less than 0·9 g lysine/kg0·75 daily several follicle abnormalities developed and the percentages of follicles affected increased as the amount of lysine was decreased. These abnormalities included the formation of autophagic vacuoles (or apoptotic bodies) in follicle bulb cells, and retarded and incomplete keratinization of the wool fibres, which led to the kinking of fibres at the mid-dermal level and gross distortion and partial degradation of fibres in the distal parts of follicles with thickened outer root sheaths. Following the introduction of a low-lysine diet, autophagic vacuoles developed in most follicle bulbs within 24 h. Impaired keratinization and kinking of fibres were evident in increasing proportions of follicles after 2 days, and gross distortion of fibres after 3–4 days. When the lambs were returned to a diet with adequate lysine recovery of normal follicle structure followed a similar time pattern, except that gross distortion of fibres persisted in the distal parts of some follicles for longer than 1 week. In some lambs given more than 0·9 g lysine/kg0·75 daily a small percentage of follicles had short keratogenous zones. Clumping of fibres, which occurred in the proximal parts of a small number of follicles, was unrelated to the amount of lysine in the diet.

A simple model of the mammary gland is described. In this model secretory cells are produced by cell division from undifferentiated cells, and the rate of division is determined by the level of a postulated hormone. The total activity of the milk secreting cells depends on the number of cells, substrate supply (assumed constant), and the amount of milk currently present in the animal. The secretory cells have a finite life, although their death may be expedited by milk remaining in the animal over a longer period of time. The model gives a good description of an experimental lactation curve; it is able to simulate the removal of milk by a suckling calf and machine milking with a variable number of milking periods a day.

The canopy of spring wheat grown with an ample supply of nitrogen was generally cooler than the canopy of a nitrogen-deficient crop. The warmer canopy matured 3–5 days earlier. The accumulated temperature difference was sufficient to account for the different times taken to reach maturity.

This study examined the effect of early sowing of sugar beet on plant establishment, bolting and yield and whether or not the standard of establishment and degree of bolting determined the most appropriate harvesting sequence. At Arthur Rickwood Experimental Husbandry Farm four experiments were made between 1974 and 1978 testing four sowing dates of four varieties each harvested on three occasions during the autumn. At Broom's Barn three dates of sowing of two varieties were tested in three experiments between 1976 and 1978. Sowing dates throughout the experiments covered a range from late February to late April. Also, at Broom's Barn in 1977 there were many bolters (plants which have a tall, flower-bearing stem) where the crop was sown on 4 March. The effects of bolter-control treatments, either cutting down the inflorescence or removing the plant, on sugar yield were compared. Sowing before mid-March often resulted in very gappy crops and many bolters; in consequence yields were seriously reduced. Late-March sowings were almost free from plant establishment problems and, where the bolting-resistant variety ‘Nomo’ was used, bolters were few; yields of Nomo were greater than where sown in early April. Progressively more yield was lost by delaying sowing throughout April. Variation in the extent of bolting between sites, seasons and sowing-date treatments was accounted for by variation in the number of cool days (with a maximum temperature of less than 12 °C) after sowing. Yield was lost at a rate of 0·7% for every 1% of bolters over the range 5–40% bolting. During the autumn, crops at Arthur Rickwood which had more than 5% bolters and/or less than 60000 plants/ha gained 0·45 t/ha less sugar than did those with full, bolterfree plant stands. In 1977 many of the early-sown plants bolted; pulling the bolters or cutting the inflorescences improved yield, but not sufficiently to raise yields to the level produced by later-sown, bolter-free crops.

The results of experiments conducted for 2 years in north-western India under irrigated conditions are described here. Wheat following legume intercrops gave increases in growth, yield attributes, yield and N uptake. Various legume intercrops such as groundnut, cow peas (both for fodder and grain) and greengram reduced the need of fertilizer nitrogen for wheat in the succeeding season by 30–84 kg/ha compared with sorghum.

Opium poppy (Papaver somniferum Linn.) was sown at three sowing dates (10, 25 November, 10 December), row spacings (15, 30, 45 cm) and population densities (6 × 105, 3 × 105, 1·5 × 105 plants/ha) in a split-plot design at Lucknow. Sowing on 10 November resulted in higher yields of opium, seed, total dry matter and morphine content. Delayed sowing, higher plant density and narrow spacing produced low yields with less morphine content. Decline in opium yield was associated with decrease in plant height, leaf area index, capsule size and number of capsules per plant. The crop sown on 10 November removed most N. N concentration and uptake also increased when the number of plants per unit area was decreased. The study suggests that to achieve maximum yields poppy should be sown in rows 30 cm apart on 10 November with 3 × 105 plants/ha.

Six dryland crops (mungbean, cow pea, soya bean, groundnut, maize and sorghum) and two rice cultivars (C·171·136 and IR 36) were grown under rainfed and irrigated conditions on a dryland site with a clay loam soil at the International Rice Research Institute, Philippines. After the first 30 days of growth there was no effective rain, and the rainfed crops encountered different water deficits. Crop productivity, leaf area, plant water status, root distribution, and soil water use were measured.

Neither rice cultivar yielded seed under rainfed conditions, but all other crops did. With mungbean and cow pea there was little difference between the yields under rainfed and irrigated conditions, but groundnut, soya bean, sorghum and maize gave higher yields under irrigation.

The rainfed crops extracted different amounts of stored soil water, ranging from 100 mm for IR 36 to 250 mm for groundnut. The different amounts were associated with different growth durations, rooting depths and rates of soil water depletion from within the root zone. Biological productivity of the six rainfed crops with the C 3 photosynthetic pathway was linearly related to transpiration, which was estimated from soil water extraction and soil evaporation. Biological productivity per unit of transpiration for the two crops with the C 4 pathway was 2·2 times higher than for those with the C 3 pathway. The different seed yields of the rainfed crops were due to differences in harvest index and the chemical composition of seeds, as well as to biological productivity.

The results are discussed in relation to the potential for growing dryland crops after rice in rice-based cropping systems.

In the application of the Scholander pressure chamber technique to cassava water relations studies, the leaf water potential measured on central lobules was initially compared with that measured on entire leaves (including petiole). Measurements made using both a Campbell-Brewster hydraulic press and a pressure chamber of the leaf water potential in six different cassava clones were also compared. Although the central lobules showed a greater sensitivity to moisture loss after sampling than entire leaves, their leaf water potential was in close agreement with those measured on the entire leaves (r3 = 0·96). Therefore, for routine and field estimates in cassava, measurements made on the central lobules may be used to avoid the large reduction in total leaf area. The Campbell-Brewster hydraulic press satisfactorily estimated leaf water potential in M.Col. 1684 clone, which had the longest and narrowest lobules, but in other clones the leaf water potential was overestimated at high leaf potential (> -12·5) and underestimated at low water potentials (< -12·5). Over a wide range of leaf water potentials, a poor relationship between leaf water potentials estimated with hydraulic press and with the pressure chamber was observed for cassava because press estimates are influenced by lobule length and lobule width.