Experiments investigating effects of foliar disease control on wheat grain protein concentration (GPC) are reviewed. Fungicidal control of rusts (Puccinia spp.) and powdery mildew (Erysiphe graminis) increased or had no significant effect on GPC in almost all cases, whilst control of the Septoria spp. often resulted in reduced GPC, but with exceptions. Reasons for these differences are discussed with reference to host pathogen interactions. Irrespective of infection strategy (biotrophic or necrotrophic), controlling severe infection increased nitrogen yield and the proportion of above-ground crop nitrogen that was partitioned to the grain. Similar effects are recorded for above-ground biomass and dry matter harvest index. The relationships between fungicide effects on green flag leaf area duration (GFLAD) and GPC were examined and shown to be unaffected by mode of action of the fungicide. Interactions between fungicide use and cultivar, nitrogen and growing season are related to the amount and type of pathogen present, and environment. An economic analysis demonstrated that fungicide effects on GPC should not affect the choice of fungicide or application programme, but that applications of foliar urea at the start of grain filling can deliver a cost-effective method of eliminating GPC reductions that may occasionally result from fungicide use.

Leaflet movement in soyabean (Glycine max (L.) Merr.) is considered to be an important physiological adaptation for intercepting sunlight for photosynthesis. Solar tracking may serve to increase plant production by maximizing light interception. The objective of this study was to determine the response of A (leaflet net assimilation rate), τ (stomatal conductance) and Ci (internal leaf carbon dioxide concentration) when penultimate fully expanded leaflet angles were changed. Soyabean (cv. Enrei, Maturity group VI) was planted at Niigata University, Japan, at two densities (25 and 16 plants/m2) in mid-May of 1992 and 1993. PFD (photon flux density), A, τ, and Ci were measured with a portable leaf photosynthesis instrument. The more towards vertical the leaflets were moved, the lower the PFD and A were. A measured at R5 showed no light saturation, but did show this at V13 and R3. While A measured at 09.00 h showed no saturation point, there was saturation at 12.00 h and 15.00 h at or less than 1500 μmol/m2/s. At R3 a high correlation (r = 0.89, P < 0.01) was found between PFD and A for naturally oriented leaflets, but not for horizontal ones. These results suggest that leaflet movement is an adaptation to optimize A.

Perennial ryegrass (Lolium perenne L.) cultivars with increased water-soluble carbohydrate (WSC) concentrations were evaluated under controlled environment conditions. The growth and carbon partitioning of these cultivars was compared with standard cultivars during vegetative growth. The high WSC cultivars had shoot growth rates that were not significantly different from the standard cultivars, confirming that the extra WSC in these cultivars was not made available through reductions in yield potential. The extra WSC stored in these cultivars coincided with lower concentrations of neutral detergent fibre in the dry matter. When the cultivars were grown in hydroponic solution the high WSC cultivars Aurora and Ba10727 were found to also have less root mass and a lower root[ratio ]shoot ratio than the standard cultivars. However, this trait was not consistent across all high WSC cultivars with Cariad having the same root[ratio ]shoot ratio as the standard cultivars at the end of the experiment. The reduction in the root mass of the cultivars Aurora and Ba10727 was far greater than necessary to provide the extra carbon stored as WSC in these cultivars. The implications of these results for the breeding of cultivars of perennial ryegrass with increased WSC concentrations are discussed.

Mycorrhizal and non-mycorrhizal tomato plants (Lycopersicon esculentum Mill. cv ‘Amalia’) were subjected to water stress by withholding irrigation water for 72 hours and then reirrigated for 120 hours. Water stress reduced root mycorrhizal colonization, although the presence of the fungus Glomus clarum stimulated tomato plant growth. During the stress period the effect on the growth was more pronounced in aerial biomass than in the root biomass. The decrease in the soil water potential generated a decrease in leaf water potential (Ψl) and leaf turgor potential (Ψt), particularly in the non-mycorrhizal plants. Although the absence of osmotic adjustment provoked the loss of turgor in stressed plants, both Ψl and Ψt recovered after a short reirrigation period. Mycorrhizal infection improved photosynthetic activity (Pn) and stomatal conductance (gs) in non-stressed and stressed plants. These increases were accompanied by higher root hydraulic conductivity values, indicating enhanced water uptake in drought conditions. Neither Pn nor gs fully recovered after rewatering. The beneficial effect of the mycorrhizal symbiosis on the water status of tomato plants stimulated plant growth.

Deep-rooted crops used in rotation can improve the overall water and N use efficiencies of cropping systems and help minimize nitrate leaching to groundwater. Safflower (Carthamus tinctorius L.) is a deep-rooted annual crop grown in Mediterranean regions that might be useful for this purpose. Safflower's response to residual soil N measured to 2.7 m in the soil profile was evaluated in 1998 in field plots in the San Joaquin Valley, California, USA that were used previously for cotton over a 9-year period and had been fertilized with nine N rates from 0 to 230 kg N/ha. Residual soil NO3-N measured prior to safflower planting increased with prior cotton fertilization rates. Amounts present to a soil profile depth of 2.7 m varied from 760 to 2600 kg/ha. Safflower seed yield increased with increasing pre-plant residual NO3-N levels, from 1700 kg/ha in the control to 2200 kg/ha, and then declined to 1800 kg/ha at the largest residual N level. Oil per cent, and oil yield were affected by soil N only at the largest residual N level, while oil composition was not affected. Root growth and N uptake at depth increased in plots with larger amounts of residual N compared to those with less. Results suggest that N fertilization applied to safflower could be reduced or even eliminated following crops previously fertilized at economic levels. Residual N should be accounted in growers' management programmes.

Nitrogen balances from 283 conventional dairy farms situated in southern Sweden were investigated using the farm gate method. Nitrogen balances were determined for 1997 and 1998. Three N balances were calculated; for the whole farm, for crop production and for milk production. The aims of the investigation were to study if factors such as manure handling system, the amount of N obtained from mineral fertilizer per hectare and the proportion of sugar beet have an influence on the N balance. There was no significant effect of manure handling system on the N surplus per hectare or on N efficiency. The results showed that N efficiency was significantly improved by including sugar beet in the crop rotation and was negatively correlated with milk yield per hectare and fertilizer N per hectare. The N surplus per hectare was positively correlated with milk yield per hectare and fertilizer N per hectare. The comparison did not find a strong relationship between the amounts of N obtained from mineral fertilizer per hectare and supplied as manure. The latter was calculated theoretically. There was a weak, but significant, negative correlation between N from manure in 1997 and N from mineral fertilizer in 1998.

The paper seeks to compare the effectiveness of various functions as appropriate to express protein retention and lipid retention as a function of pig live weight. Linear descriptors were adequate for protein growth over the 20 to 120 kg live weight range, but not adequate when higher live weights were included. Linear descriptors were not adequate for lipid growth over any weight range. Quadratic and cubic polynomials, and the logistic function, were faulted on their failure to describe the known biology. Augmentation of the allometric function added nothing to the simple form. The Gompertz function was consistently effective for the description of daily protein retention rate. The Bridges and Richards functions are more flexible than the Gompertz with respect to the point of inflection, but when applied they resembled the Gompertz and therefore did not materially influence the descriptive outcome. The cubic polynomial, augmented allometric, Bridges and Richards functions, although favoured in other reports, were found to add nothing to the more simple functions. It is concluded that protein retention can be well expressed in relation to live weight by linear and Gompertz functions. Lipid retention could be well described by an allometric relationship with pig mass.

Previous approaches to the description of complex diets, based on n-alkanes and optimization techniques, have grouped the plant species to reduce the number of components. Diet estimates have been obtained with least-squares routines by minimizing the discrepancy between faecal alkane concentrations calculated from herbage concentrations and actual faecal alkane concentrations. The effect of diet selection within groups can only be assessed by using sensitivity tests or by giving subjective weights to the individual plants. In the current study, a new optimization algorithm was developed that selects weightings that lead to consistent estimates of group proportions. The diet of the wild rabbit in a southern Portuguese montado was used as a case study. Estimates of the diet composition obtained using the new algorithm were compared with those of a conventional routine. The new algorithm was shown to provide, on average, more accurate estimates of the proportions of the groups in the diet. The effect of grouping plant species according to criteria other than similarity in n-alkane pattern on the accuracy of estimates was shown to be non-significant.

The vasopressin (VP) and aldosterone responses of swamp buffaloes and Friesian cattle were compared during 3 days of ad libitum water availability and 3 days of water deprivation. During the period of hydration, buffaloes showed significantly higher VP concentrations (2.31±0.09 v. 1.23±0.07 pg/ml), in spite of larger water excretion rate through urine, relative to cattle. During the period of dehydration, although VP increased progressively in both species, the concentration in the buffaloes (66.7±18.6 pg/ml) was five times higher than that of the cattle (12.5±3.2 pg/ml) on Day 3. Even though the rate of urine excretion in the buffaloes decreased markedly during water deprivation, the total volume of urine excretion was still greater than that of the cattle. Haematocrit, serum osmotic pressure and total protein in both species increased significantly during water deprivation, but the rate of the increase was greater in buffaloes than in cattle. There was no correlation between sodium or potassium excretion and aldosterone concentration in either species. These results demonstrated that the VP elevation in buffaloes was largely attributable to the greater decrease of plasma volume caused by the greater water excretion. The lower retentivity of plasma volume probably means that buffaloes have a greater dependence on external water rather than to conserve internal water, because of the evolutionary adaptation of buffaloes to wet environments.

A model is presented which will predict mean age at first egg (AFE) for pullets of laying strains reared under non-limiting environmental conditions but exposed to a single change in photoperiod during the rearing stage. An initial analysis of 12 previously reported trials involving a wide range of genotypes showed that the response to an increase in photoperiod is not simply the inverse of the response to an equal decrease in photoperiod applied at the same age. Maximum sensitivity to a reduction in photoperiod was found shortly before onset of lay, whereas maximum sensitivity to an increment in photoperiod was observed at around 10 weeks of age. Two experiments were conducted to provide further data. The first compared the effect of 3-h increases in photoperiod from 8 h to 11 h or from 11 h to 14 h with the double increment from 8 h to 14 h and also tested a reduction from 11 h to 8 h, all imposed at 17 weeks of age. AFE was advanced to a similar extent by the changes from 8 to 11 h and from 11 to 14 h (9.8 and 10.9 days respectively). Response to the double increment was not additive: AFE on this treatment was 13.3 days earlier than for constant 8 h controls. Reduction in photoperiod from 11 to 8 h at 17 weeks delayed AFE by 18.7 days compared with constant 11-h controls. In the second experiment, pullets of two strains were transferred from 8 to 16-h photoperiods and from 16 to 8 h at 5, 7, 9, 15, 17 and 19 weeks of age. Controls were kept on constant 8 and constant 16-h days. Transfer from 8 to 16-h photoperiods at 5 weeks of age had no effect on AFE. At 7 weeks there was a bimodal response with some pullets subsequently showing advanced maturity and others not. Maximum stimulation of early maturity (31 days on average for the two genotypes) was obtained at 9 weeks of age and response to stimulation declined linearly with age thereafter. The delay in AFE resulting from a reduction in photoperiod (16 to 8 h) increased linearly between 0 and 15 weeks. At 17 and 19 weeks, the response was bimodal, with some pullets maturing at the same age as long-day controls and others showing delayed maturity. Using all this evidence and some other unpublished data, a model is developed to predict AFE as a function of mean photoperiod and change in photoperiod during the rearing phase. Elements are incorporated to allow for the insensitivity of pullets younger than 50 days to an increase in photoperiod and the effect observed late in rearing when a change in photoperiod comes too late to alter AFE for the most precocious individuals in a flock. Two coefficients are required to adjust for genotype. One describes mean AFE for the genotype when reared on constant daylength and the other defines the rate at which age effects the response to a single change in photoperiod.