bluuebunny/crossref_metadata_2025 huggingface dataset:
Features of the growth and mineral nutrition of Noogoora burr (Xanthium occidentale Bertol.), a noxious weed in central New South Wales
Authors: Hocking PJ
Published: November 2004

Aspects of the growth and accumulation, partitioning and redistribution of selected minerals in the weed Xanthium occidentale (Noogoora burr) are described for a population from central New South Wales. Plants required 240 days from emergence to fruit maturity. Uptake of most elements occurred until midway through fruit development. Rates of nutrient intake by roots were similar to those of some crop species. Fruits made up of 46% of the dry matter of a mature plant and contained 58- 79 % of its P, N and S, 18-39 % of the Cl, Na, Mg and K, but < 19 % of the Ca and Mn. Dead leaves had the greatest proportion of the total plant Mg, Na, Cl, and especially Mn and Ca. The elements P, N and S were redistributed from above-ground parts to the fruits with efficiencies of 43-63 %, but there was negligible (< 10%) redistribution of Cl, Mn, Ca and Na. Redistribution from above-ground plant parts could have provided 43-55 % of the dry matter, N, P, K, S and Mg accumulated by fruits. The amount of free nitrate-N stored in stems and leaves decreased rapidly during fruit filling. Leaves were more important than stems as a source of nutrients for redistribution, but the stem was more important for redistribution of dry matter. Cotyledons of parent seeds redistributed dry matter and nutrients to seedlings with net efficiencies ranging from 16-97 %, but gained Cl and Ca. Redistribution from cotyledons provided 2-45 % of the amount of a nutrient accumulated by seedlings. Seeds made up 38 % of the fruit dry matter and had 60-93% of its S, P and N, but only small proportions of its Ca, Cl, Na and Mn. Seeds had 38% protein and 39% oil. It is concluded that the high capacity of Noogoora burr to accumulate reserves of nutrients for redistribution to fruits contributes to its success as a weed.
Estimation of daily flows of digesta in grazing sheep
Authors: Corbett JL , Pickering FS
Published: November 2004

Chromium-51 and ruthenium-103 markers were infused constantly into the rumen of grazing sheep. Abomasal digesta were sampled every 3 h for 24 h, and the marker concentrations indicated that flow rates of organic matter (OM) and nitrogen (N) in both liquid (filtrate) and particulate (filtrand) fractions varied with time of sampling, generally by �30% from the values calculated from 24-h mean marker concentrations. The apparent flows were always least around midday and greatest after nightfall, possibly reflecting rumination. The patterns of variation, described by Fourier equations, did not differ significantly between sheep within experiments nor between the several types of pasture used, but there were changes in phase with time of year that corresponded with changes in the time of evening civil twilight. General equations were calculated to allow determination of mean daily OM and N flows from analyses of digesta samples taken at fixed times of day. Variation about the 24-h mean OM flow through the ileum was less than for the abomasum, and indicated that digesta took c. 3 h to pass through the small intestine. Variation in estimates of faeces OM and N excretion was small and essentially random. In two experiments, concentrations of 51Cr-EDTA in ruminal fluid during constant infusion varied by up to 15 % from the 24-h mean, which implied some changes in ruminal fluid volume.
Cultivar cross environment interactions for kernel yield in Virginia type peanuts (Arachis hypogaea L.) in Queensland
Authors: Shorter R , Norman RJ
Published: November 2004

Twelve Virginia type peanut cultivars were evaluated for kernel yield at 10 sites in 1979 and nine sites in 1980 in southern and northern Queensland. Two trials, harvested 9-14 days apart, were grown at each site in 1979, resulting in a total of 29 test environments. In 1979 the cultivar x site (c x s) interaction was significant, although the cultivar x harvest date within-site interaction was not. Over all 29 environments the cultivar x environment (c x e) interaction was significant. In orthogonal sets of five sites and 2 years, cultivar x year x site interactions were significant, whereas cultivar x year and c x s interactions generally were not. Pattern analysis revealed that cultivars of dissimilar genetic origin had different productivity responses across environments. An environmental classification based on c x e interactions indicated that there were no temporal or closely related regional environment groups with similar c x e interactions. Lower critical percentage differences between new and established cultivars in a pre-release testing program would be obtained by adding environments rather than replicates, or by accepting a greater risk of misjudging a new cultivar's superiority (higher probability of type I error).
Effect of defoliation on reproductive development of the peanut
Authors: Santos RB , Sutton BG
Published: November 2004

The effect of defoliation at various growth stages on the pattern of reproduction of the peanut plant (cv. Virginia Bunch), grown in pots, was examined. In all treatments, only the small proportion of the flowers which formed early in the flowering phase contributed to pod yield at maturity. In those treatments where defoliation caused a reduction in pod yield (i.e. cutting after pod formation) final pod number was reduced by inhibition of further fruit formation and degeneration of pods already formed. The data indicate that a minimum leaf area of c. 50 cm2 is required to retain a pod on this variety. This places a lower bound on the relationship between plant size and pod number, which is qualitatively established in the literature.
Development of annual ryegrass toxicity
Authors: Stynes BA , Bird AF
Published: November 2004

Ryegrass pasture, containing seed galls induced by Anguina agrostis and colonized by Corynebacterium rathayi, was harvested from experimental plots near Katanning in Western Australia. Plant growth stage, numbers of emerged inflorescences and numbers of galls present were estimated for 10 harvests collected at weekly intervals, commencing 22 September when the first inflorescences had emerged. The concentration of toxin (corynetoxins) at each harvest was estimated using a bacterial inhibition bioassay. Levels of toxin were up to 459 �g per m2 pasture prior to and during anthesis, but the concentration increased rapidly during the final four harvests (corresponding to ripening) and reached a maximum level of 6292 �g m-2. A possible relationship between toxicity and the presence of ultramicroscopic particles observed in the galls was investigated. Galls from each harvest were sectioned and examined under the electron microscope. Particles were not found in galls sampled prior to anthesis, but were found in galls from the last four harvests. From these results, the production of toxin appears to be related to physiological aging of the plant and may also be related to the accumulation of particles.
Water uptake in relation to pre-harvest sprouting damage in wheat: ear characteristics
Authors: King RW , Richards RA
Published: November 2004

Wetting of mature wheat ears during simulated and natural rainfall and sprouting in the ear were studied in a group of c. 50 cultivars and in lines near-isogenic for awns, pubescence, glaucousness and club head. Cultivars differed by up to two-fold in ear water uptake over the first hours of exposure to simulated rain (2.6 mm h-1 in a misting chamber). Some of these differences were still evident after 30 h. Awns and their associated structures accounted for some of the varietal differences in ear water uptake. Those cultivars and near-isogenic lines with awns absorbed up to 30% more water. As well, sprouting in the ear was enhanced by at least 40%, and water penetrated more rapidly to the grain in ears of awned lines. Loss of free water on drying was little influenced by the awned character. The club head character enhanced ear water uptake by 25%. Pubescence and glaucousness had no effect on ear wetting. Cultivars can vary widely in post-harvest dormancy and plant breeders have utilized such differences in their selection for control of pre-harvest sprouting. However, further reduction of sprouting should also result simply from selecting for awnless cultivars.
Mycotoxins and fungal damage in maize harvested during 1982 in Far North Queensland
Authors: Blaney BJ , Moore CJ , Tyler AL
Published: November 2004

A survey for mycotoxins and fungal damage in maize (Zea mays L.) grown during 1982 in Far North Queensland is reported. This season had a rainfall distribution which was typical for the region. The 293 samples examined came from 111 farms in eight maize-growing districts. The samples were first subjected to rapid screening tests for fungal damage. Aflatoxins B1, B2, G1, G2, ochratoxin A, T-2 toxin, and sterigmatocystin were not detected, but zearalenone was found in 85% of the samples. The concentrations of zearalenone were correlated with the extent of Gibberella zeae cob rot as indicated by the proportion (up to 2%) of kernels in each sample having a reddish-purple discoloration. In four samples the zearalenone concentration exceeded 1 mg kg-1, but the mean � s.d. (n = 293) concentration in all samples was 0.17 � 0.225 mg kg-1. Concentrations were highest in districts with the highest rainfall during the period of maize growth.
The influence of body weight at point-of-lay on the production responses of restricted-reared pullets
Authors: Balnave D
Published: November 2004

The food intake, age at sexual maturity, egg weight and daily egg mass output of pullets fed on a time restriction basis during growth were significantly influenced by body weight at 21 weeks of age. Egg production was not affected significantly when 21-week body weight varied between 1.3 and 1.8 kg. It is suggested that one of the major factors influencing the performance of a pullet flock during lay is the number of birds of abnormally low body weight present at the end of the growing period.
Effects of fertilizer and grazing sheep on pasture heterogeneity in a small-scale grazing experiment
Authors: Taylor JA , Hedges DA , Whalley RDB
Published: November 2004

The presence of plant species and the amount of sheep faeces were recorded systematically across the plots of a fertilizer x grazing randomized block experiment. Sampling sites were classified according to species presence, and the number of classificatory groups was taken as a measure of paddock heterogeneity. Unfertilized plots were more heterogeneous than fertilized plots. Irrespective of fertility level, pastures were generally more heterogeneous at the higher stocking rates. However, the floristic heterogeneity of a plot partly reflected the fertility and stocking level of the neighbouring plots. This suggests that the arrangement of plots within small-scale grazing experiments can influence the results by modifying the botanical consequences of the imposed treatments. The camping and grazing behaviour of sheep also influenced the homogeneity and composition of the pasture of the plots. On the unfertilized plots, these animal-induced differences were as large as those induced by the fertilizer treatments.
Temporal changes in carbon dioxide exchange rates, acetylene reduction and distribution of nitrogen in Barrel Medic (Medicago trunculata Gaertn.) grown in the field
Authors: Alston AM , Puckridge DW
Published: November 2004

Barrel medic (cv. Jemalong) was grown on a red-brown earth at Adelaide to examine dry matter production and nitrogenase activity in relation to environmental conditions and carbon dioxide exchange. At 4-10-day intervals, measurements were made of dry weight and nitrogen content in plant parts, and mineral nitrogen content of the soil. Rates of acetylene reduction and carbon dioxide exchange, and environmental variables were measured. Curves fitted to data for solar radiation and carbon exchange rate were used to calculate daily values for net carbon dioxide uptake. Estimates of dry weight production derived from these net uptakes of carbon dioxide gave a similar curve to measured dry weight, but overestimated maximum dry weight by almost 20%. The difference is presumed to be due to materials lost from the roots. At maturity, dry weight and plant nitrogen content had declined by 10 and 14% respectively from their maxima of 1.02 kg m-2 and 26.1 g m-2 in October. All fractions of the plant except the litter and seed lost nitrogen. Rates of acetylene reduction reached a maximum of 39 mmol m-2 day-1 104 days from sowing, when the medic began to flower, and declined to almost zero by 145 days. At this time carbon dioxide exchange rates were high, and the plants were still accumulating nitrogen; from approximately 14 g N m-2 at day 104 to 24 g N m-2 at day 145. These changes are discussed in relation to environmental conditions and soil nitrogen content.
A comparative analysis of the growth of sweet and forage sorghum crops. II. Accumulation of soluble carbohydrates and nitrogen
Authors: Ferraris R , Charles-Edwards DA
Published: November 2004

Well-watered crops of sweet sorghum (cv. Wray) and forage sorghum (cv. Silk) were grown in south-eastern Queensland. Treatments consisted of four sowing dates, two intra-row spacings and harvests taken at six physiological growth stages from the third ligule to 3 weeks after grain maturity. Plant density effects on the concentration of sugars and nitrogen were slight, and changes in yields of these components were a function of density effects on dry matter yields. At any growth stage, the concentration of sugars in both cultivars was decreased with delay in sowing date. The delay in sowing date led to an increased nitrogen concentration in cv. Wray, but in cv. Silk the nitrogen concentration was highest in early and late sowings. At maturity, the concentration of sugars in cv. Wray averaged 40'70, 10 times the level in cv. Silk. In both cultivars, accumulation was a near linear function of either time or radiation sum. The partitioning of carbohydrate differed little between cultivars but altered with their ontogeny. The efficiency of light use for sugars production was greater in cv. Wray and altered with ontogeny. In contrast, concentration of nitrogen was similar for both cultivars and decreased curvilinearly with time or degree days. The partitioning of nitrogen altered with ontogeny and the amount partitioned to leaf material was greater in cv. Silk pre-anthesis but was less post-anthesis. Yield of stem sugars in cv. Wray exceeded 10 t ha-1 when the crops were sown early in the season, but was only 3 t ha-1 with late-sown crops.
Corynetoxins are not detoxicated by in vitro fermentation in ovine rumen fluid
Authors: Vogel P , McGrath MG
Published: November 2004

Tunicamycin and seed galls of annual ryegrass (Lolium rigidum) containing corynetoxins, the causal agents of annual ryegrass toxicity, were incubated in ovine rumen fluid-buffer mixtures. A bacterial inhibition assay of extracted incubation mixtures revealed that no detoxication occurred under these in vitro conditions.
Genetic variability in sunflower cultivars under drought. II. Growth and water relations
Authors: Gimenez C , Fereres E
Published: November 2004

Experiments were conducted between 1981 and 1983 at Cordoba, Spain, to determine the morphophysiological basis for the differences in yield responses to drought of eight sunflower genotypes. There was genotypic variation in most characters examined, particularly in maximum leaf area and in leaf area duration, biomass accumulation and distribution, and in root water extraction. Long-season genotypes had greater leaf area and produced more biomass under drought conditions, exploring the subsoil down to 270 cm. Short-season genotypes restricted water extraction to the top 180 cm of the soil profile and had about half of the leaf area duration of a long-season cultivar. Evidence is presented of small differences in osmotic adjustment among genotypes. The relations between leaf area and grain yield as well as calculations of a carbon balance for the reproductive period suggest genotypic differences in photosynthetic efficiency under drought.
Effect of temporary flooding on cotton growth and nitrogen nutrition in soils with different organic matter levels
Authors: Soomro AW , Waring SA
Published: November 2004

A glasshouse experiment was conducted to study the effect of temporary flooding on the growth and development of cotton (Gossypium hirsutum L. cv. Deltapine 61) and the recovery of nitrogen applied as urea fertiliser in two black earths differing in organic matter content, with three water treatments. Two floodings were applied, at 15 days after planting and at 45 days.Plant dry weight and growth characteristics of the cotton plant such as height, number of leaves, leaf area and fruiting points were greatly reduced by the flooding treatments. The cotton plants were more affected by the first than the second flooding. A greater depression in the various growth characteristics was found in the high organic matter soil than the low organic matter soil. The soils behaved differently in their interaction with the water treatments. With the control water treatment, cotton grown on the high organic matter soil produced more dry matter and assimilated more nitrogen but had a lower nitrogen concentration and apparent recovery of urea nitrogen than did cotton grown on the low organic matter soil. For the flooding treatments the low organic matter soil produced more dry matter and assimilated more nitrogen, but had a lower nitrogen concentration and a higher apparent recovery of urea nitrogen than did cotton grown on the high organic matter soil.The lower apparent recovery of urea nitrogen in the high organic matter soil during temporary flooding appears due mainly to higher loss of nitrogen by denitrification, although other mechanisms may be significant. The wider implications of the results in terms of field practice with irrigated cotton are discussed.
Nutritional restraints on subterranean clover grown on acid soils used for crop-pasture rotation
Authors: Coventry DR , Hirth JR , Fung KKH
Published: November 2004

Lime, N and molybdenum fertilizers were used to establish how soil acidity limits the growth of subterranean clover (Trifolium subterraneum), in pot culture, on acid soils taken from north-east Victoria. The results indicate that two nutritional factors associated with the growth of subterranean clover are affected by excess acidity. These are manganese toxicity and ineffective nodulation of the clover. The plants grown on one unlimed soil (Rutherglen) had manganese concentrations and symptoms consistent with manganese toxicity. Liming the second soil (Lilliput) overcame a N deficiency by way of increased nodule formation. A third nutritional factor commonly associated with excess acidity, and found on the Lilliput soil, molybdenum deficiency, was not alleviated by the application of lime. Instead, the application of molybdenum fertilizer gave increases in clover dry matter production at all lime rates. In the absence of molybdenum fertilizer, the molybdenum concentration of the herbage was extremely low, irrespective of liming. These results are discussed in relation to already established field responses of subterranean clover to lime, and the management of the clover-ley system on the strongly acid soils.
The pathogenicity of an Australian isolate of Acremonium zonatum to water hyacinth, and its relationship with the biological control agent, Neochetina eichhorniae
Authors: Galbraith JC
Published: November 2004

The first description of Acremonium zonatum on water hyacinth in Australia is made. Its pathogenicity was studied as part of the search for a microorganism already present in Australia which could be developed as a mychoherbicide to supplement the arthropod biological control programme in this country. Following inoculation with A. zonatum, extensive leaf infections developed, favoured by injury and free moisture, but new leaves continued to form. Feeding by the weevil, Neochetina eichhorniae, increased infection by A. zonatum in relatively dry conditions, but it is unlikely that this was due to feeding scars acting as ports of entry. A. zonatum spores were transported on the feet and in the digestive tract of the weevil. The growth of infected plants, estimated by standing crop, was reduced by 49% compared to the control. A further decrease occurred in infected plants infested by weevils, but the total reduction in growth was not equal to the sum of the individual effects of fungus and weevil. Infection did not develop in 15 other plant species inoculated with the Australian isolate of A. zonatum. Although not a virulent pathogen, A. zonatum has some favourable characteristics for consideration as a mycoherbicide and has not appeared antagonistic to N. eichhorniae in these studies. Its role probably lies in exerting a chronic stress on plants already under attack by arthropod biological control agents.
A comparative study of the quality status of Condor Wheat grown in Northern Victoria and Southern New South Wales
Authors: Archer MJ , O'Brien L
Published: November 2004

Australian Wheat Board quality advisers had formed the opinion that Condor wheat (Trificum aestivum L.) grown in north-west Victoria possessed weaker dough properties than that grown in southern New South Wales, even at similar grain protein contents. Samples of commercially grown Condor wheat from north-west Victoria and southern New South Wales were collected by Australian Wheat Board field officers to objectively investigate this observation. Testing of these samples indicated Condor grown in north-west Victoria to have significantly weaker dough properties than that grown in southern New South Wales. Doughs were less tolerant to mixing in the farinograph and had reduced extensograph maximum resistance, even when there was no difference in protein content between the samples from the two regions. The reduced dough strength in the Victorian samples was associated with lower nitrogen: sulfur ratios and residue protein content and fewer rheologically important disuifide groups per 50 g of flour. These differences were presumed to have resulted from some aspect of the environment during plant growth and development.
Rhizosheaths -a neglected phenomenon in Australian agriculture
Authors: Goodchild DJ , Myers LF
Published: November 2004

Rhizosheaths are formed as a result of a proliferation of root hairs that enmesh sand grains to form cylinders on non-branching roots, usually of xerophytic plant species. Their occurrence in eastern Australia on the roots of the mesophytic grasses, Secale montanum and Triticum aestivum, is reported and their probable importance discussed. A technique for separating soil particles from the root hairs is described which should facilitate the study of these structures in other plants.
Phenotypic variation for disease resistance and virulence within naturalized populations of Stylosanthes humilis and Colletotrichum gloeosporioides
Authors: Vinijsanun T , Cameron DF , Irwin JAG , Barnes A
Published: November 2004

The extent of variation for host disease reaction and pathogen virulence was studied in naturalized populations of Stylosanthes hurnilis and Colletotrichurn gloeosporioides, the causal fungus of an anthracnose disease of Stylosanthes spp. Diseased plants (S0) were collected from the field at three sites (Townsville, Wrotham Park and Niall) in North Queensland, and first generation selfed (S1) progenies (host-lines) and single spore fungal cultures were grown for each of the collections made. Within a site, all host-lines were inoculated with each fungal isolate from that site, and a fourth experiment was conducted with representative host-pathogen combinations from each site. Sufficient seed was obtained to allow testing of 12, 10 and 8 collections from Niall, Wrotham Park and Townsville respectively. Significant variation (P < 0.01) between disease severity values for host-line means, fungal isolate means and host-line/fungal isolate interactions was found in all four experiments. Differences between fungal isolate means were the main source of variation in three of the four experiments. Both the differences in virulence within the pathogen population and the differences in resistance of the hostlines appeared to be quantitatively inherited. One host-line from Wrotham Park was significantly more resistant than the susceptible check, cv. Paterson, in two replicated experiments indicating that selection for some improvement in resistance within the naturalized populations should be possible. However, none of the host-lines from the Townsville and Niall sites were significantly more resistant than Paterson, suggesting that little natural selection for resistance has occurred within the naturalized host populations over the 10 years following the first outbreak of the disease in northern Australia.
Competition between Trifolium subterraneum L. and established seedlings of Hypericum perforatum L. var. angustifolium DC
Authors: Moore RM , Williams JD , Nicholls AO
Published: November 2004

St John's Wort (Hypericurn perforatum) and Trifolium subterraneum were grown in mixtures and monocultures in 16 planting combinations. The experiment was biased to favour H. perforatum by establishing it 49 days prior to sowing T. subterraneum seed and by growing plants in a nutrient-rich medium.In monocultures maximum dry matter yields of H. perforatum after 188 days were half those of T. subterraneum at similar densities. Leaf areas of the two species were similar at all harvests. In mixtures, a single T. subterraneum plant completely suppressed H. perforaturn growth and caused extensive mortality, even at its highest density 16 plants per pot within 140 days, the period of the experiment. Increasing the numbers of H. perforaturn plants in mixtures had little effect on the growth of a single T. subterraneum plant. Final yields of T. subterraneum in such mixtures were similar to those of comparable densities in monocultures.The competitive superiority of T. subterraneurn in mixtures was attributed to its canopy height which overtopped most H. perforaturn leaves. The consequent reduction in photosynthesis and subsequent death of lower leaves of H. perforaturn contributed to its lower competitiveness and mortality in mixtures. The application of these findings to agronomic practices designed to prevent re-establishment by H. perforaturn is discussed.
Mode of action of mouse epidermal growth factor on the wool follicles of Merino sheep: an ultrastructural study
Authors: Hollis DE , Chapman RE
Published: November 2004

The follicular mechanisms involved in and associated with the depilatory action of infused mouse epidermal growth factor (mEGF) on wool follicles were investigated ultrastructurally in the course of research into biological wool harvesting as an alternative to conventional shearing. Ultrastructural alterations observed during mEGF-induced follicle involution indicated three separate follicular responses to mEGF. (i) Catagenic regression lasting 4 days occurred in all follicles. This process initially (at 1 day) involved decline in cellular proliferation in the follicle bulbs, decline in the formation of precursor structural proteins in inner root sheath (IRS) and fibre cells and a delay in their hardening, and deletion of cells by apoptosis. Synthesis of precursor proteins subsequently ceased in a proportion of the follicles at 2 days, culminating in the formation of tapered fibre ends at 4 days. Regeneration of these follicles commenced at 4-6 days. Fibre production continued in the remaining follicles, though on a much reduced scale, resulting in the formation of transiently thinned fibres. (ii) Disruptive lesions formed in IRS and fibre cells in the keratogenous zone of all follicles during infusion. Their formation involved initial dilatation and vesiculation of endoplasrnic reticulum and mitochondria1 swelling, evident as early as 1 h, and subsequent intercellular accumulation of flocculent material within 12 h, indicative of abnormal fluid transport. (iii) The sebaceous glands underwent transient hypcrplasia involving extensive deposition of glycogen at 2 days, before returning to normal by 4-6 days through apoptosis. These follicular responses demonstrate two diverse modes of action of mEGF infusion on the wool follicles: a quasi-physiological, catagenic, inhibitory action on fibre growth, resembling in part catagen of cyclic hair growth, thereby culminating in a fleece 'break' and/or fleece shedding, and an apparently unrelated pathological action on differentiating IRS and fibre cells and undifferentiated sebaceous cells.
Sequential sampling plans for nematodes affecting sugarcane in Queensland
Authors: Allsopp PG
Published: November 2004

The dispersion characteristics of root-lesion, root-knot, spiral, stubby-root, stunt and ring nematodes in soil, and root-lesion, root-knot and spiral nematodes in roots in sugarcane fields, were determined in studies in southern Queensland. The Poisson distribution, negative binomial distribution, Iwao's regression model and Taylor's power law analysis were used to determine the relationship between mean and variance of nematode counts. All methods showed that nematodes were aggregated (Iwao's G 1.12-1.65, Taylor's b 1.10-1.76). In general, Taylor's power law gave better fit compared with the other models (R2>0.61). Relationships to determine sample sizes for fixed levels of precision and fixed-precision-level stop lines for sequential sampling were developed for all species. There were functional relationships between variance and mean of untransformed population counts for all species, but suitable transformations eliminated significant correlations in most cases.
Studies of the severity and incidence of Paspalum leaf blight
Authors: Price TV , Williams BL
Published: November 2004

Levels of paspalum leaf blight (Ascochyta paspali) severity (%LAD), diseased dry matter (%DDM) and incidence on tillers and leaves on dairy pastures in northern Victoria assessed during the summer months (November-March) of 1983-84, 1984-85, 1985-86 and 1986-87 fluctuated between samplings and farms. Infected tissues accounted for 19-22% of the total dry matter in 1983-84 and 1984-85. Disease severity (%LAD) was significantly (P<0.001) linearly related to incidence of infected tillers (IT) or leaves (IL) and highest correlations were obtained following natural logarithmic transformations of severity and incidence data. Incidence of infected tillers on a 1 ha site in Northern Victoria ranged over 7- 19% in 1985-86 when samples were taken along a M-transect and 1.75-30% in 1986-87 when stratified random samples were taken using a microcomputer-based program 'Field Runner'. The latter reduced sampling bias, indicated that the distribution of disease was aggregated and a minimum sample size of 450 tillers was required. The fluctuating incidence levels with time were correlated with sampling intervals following grazing. Incidence of infected tillers on 11 farms in northern Victoria and Finley, N.S.W., in January 1987, ranged from 11.8 to 56.4%. The significance of the severity-incidence relationships, the aggregated distribution of paspalum leaf blight, variation in levels between farms, the effects of grazing on epidemics of paspalum leaf blight and crop loss and the use of 'Field Runner' in disease surveys is discussed.
Self-select feeding of commercial pullets using a complete layer diet and a separate protein concentrate at cool and hot temperatures
Authors: Balnave D , Abdoellah TM
Published: November 2004

Three experiments were conducted to examine the effects of self-select feeding to 40 weeks of age on food, protein and metabolizable energy (ME) intakes and egg mass output of pullets previously trained to this feeding system between 15 and 19 weeks of age and kept at cool (10�-20�C) and hot (25�-35�C) temperatures. In two experiments different lighting patterns were also compared without noticeable effect. Except for ME intake on the low-ME diet in Experiment 2, protein and ME intakes were significantly improved when pullets fed a low-ME (10.2 MJ/kg) or high-ME (12.0 MJ/kg) complete layer diet at both temperatures were offered a separate protein concentrate on a self-select basis. Increases in egg mass output were most pronounced when the high-ME complete diet was fed with the protein concentrate at the hot temperatures. The resulting egg mass output was similar to that obtained when the low-ME complete diet was fed with the protein concentrate or when a highly concentrated, complete diet, based on the intakes of the high-ME diet and the separate protein concentrate selected by pullets of similar age in an earlier study, was fed. Providing a separate granular source of calcium had no significant effect on the responses to self-select feeding.
Factors which affect the growth of grain legumes on a solonized brown soil. II. Genotypic responses to soil chemical factors
Authors: Atwell BJ
Published: November 2004

Lupins (Lupinus angustifolius cvv. Yandee, 75A-258 and P22872, and L. pilosus cv. P20957) and field peas ( cv. Dundale) were grown in the glasshouse in a sieved solonized brown soil. The soil was taken from sequentially deeper zones in the B horizon of the natural profile (8-83 cm below the surface). The pH (in CaCl2) increased from c. 6.3 to c. 8.2 with depth while sodium and chloride concentrations reached 83 and 62 mol m-3 (soil solution) respectively in the deepest unfertilized subsoil. Sodium concentrations reached 159 mol m-3 when the subsoil was fertilized. When plants were grown in the deepest subsoil, the growth of shoots and roots was inhibited by up to 75% in L. angustifolius but less severely in L. pilosus and pea. Roots of pea were affected least by the deep subsoil. Shoots of L. angustifolius, but not L. pilosus or pea, had severe chlorosis in the expanding tissue and necrosis of the oldest leaflets when grown on the deepest soil. Expanded leaflets of L. angustifolius had sodium and chloride concentrations up to 200 mol m-3 while iron concentrations were less than 208g g-1 dry weight in expanding tissues. Concentrations of manganese and zinc exceeded requirements for maximum growth but copper concentrations were sufficiently low to suggest deficiency in growing tissue of Yandee and 75A-258. No symptoms of deficiency were apparent. It is concluded that adverse chemical factors in the subsoil restrict root growth of L. angustifolius in the field. L. pilosus and field peas, on the other hand, appear to be significantly better adapted to these sodic, alkaline subsoils.
The role of vesicular-arbuscular mycorrhizas (VAM) in the phosphorus nutrition of cowpea (Vigna unguiculata (L.) Walp)
Authors: Ikombo BM , Edwards DG , Asher CJ
Published: November 2004

An experiment was conducted to establish the role of VAM in the phosphorus nutrition and early growth of cowpea (Vigna unguiculata (L.) Walp.) cv. Vita 4 in a podzolic soil (Haplustult). The experiment involved four treatments: (1) plants grown in unsterilized soil adequately supplied with phosphorus (240 kg P ha-1), (2) plants grown in unsterilized soil with low phosphorus (10 kg P ha-1), (3) and (4) plants grown in methyl bromide sterilized soil with low phosphorus (10 kg P ha-1). Plants in treatments (1), (2) and (3) were inoculated with Bradyrhizobium. A series of harvests was taken from 14 to 42 days after sowing; 15 harvests at two-day intervals from treatment (2) and 5 harvests at 7-day intervals from the other treatments. Root infection by VAM did not occur in plants grown in the sterilized soil treatments (3) and (4); growth of these plants was poor, and they showed symptoms of severe phosphorus deficiency. Phosphorus concentrations in the youngest fully expanded leaf (YFEL) of plants grown in treatments (3) and (4) were in the range 0.10 to 0.16% at all harvests. Plants which were grown in the unsterilized soil with 240 kg P ha-l (treatment (1)) grew very well; they had a high concentration of phosphorus (0.3 1 to 0.75%) in the YFEL at all harvests and exhibited a delayed and reduced level of infection by VAM. Plants grown in the unsterilized soil with 10 kg P ha-l (treatment (2)) were strongly colonized by VAM; infection was apparent at 14 days after sowing and reached a maximum (85% of root segments colonized) at 36 days after sowing. A strong increase in phosphorus concentration in the YFEL of plants grown in treatment (2) commenced at 22 days after sowing, while an increase in dry matter yield and phosphorus content of the whole tops above that of non-mycorrhizal plants grown in the sterilized soil was observed at 30 days after sowing. The sequence of events leads us to conclude that the recovery of cowpea plants from early phosphorus deficiency stress resulted from increased phosphorus absorption following the development of a mycorrhizal association with the roots.
A sensitive semi-quantitative biotin-streptavidin ELISA for the detection of potyviruses infecting cucurbits
Authors: Dietzgen RG , Herrington ME
Published: November 2004

The biotin-streptavidin (BA)-ELISA system was optimized for the detection of three potyviruses infecting cucurbits, the watermelon strain of papaya ringspot virus (PRSV-W), zucchini yellow mosaic virus (ZYMV) and watermelon mosaic virus 2. BA-ELISA was four to eight times more sensitive than double antibody sandwich ELISA and detected all three viruses in the nanogram range. BA-ELSA was virus-specific but did not differentiate between different pathotypes of ZYMV. The use of egg-white avidin-enzyme conjugate or the simultaneous incubation of biotinylated antibody and streptavidin-enzyme conjugate decreased the sensitivity of BA-ELISA. The concentrations of PRSV-W and ZYMV in field-infected cucurbit specimens or in resistant breeding lines were estimated from calibration curves derived from a dilution series of purified virus in extracts of uninfected plants on each test plate. Thus it was possible to determine semi-quantitatively the degree and uniformity of resistance in plants from these lines and to differentiate resistant from tolerant selections.
Convergence and synchrony-a review of the coordination of development in wheat
Authors: Hay RKM , Kirby EJM
Published: November 2004

Although the ears, spikelets and florets of a wheat crop are initiate consecutively, all of the resulting grains of the crop ripen synchronously. Similarly, crops of winter wheat sown at widely different dates tend to ripen during the same period of a few days in the following summer. This review, which draws evidence from winter, spring and day-neutral varieties, and from a range of temperate and mediterranean environments, explores the mechanisms leading to this convergence of organ, plant and crop development. Central to these mechanisms are the roles of the environment (temperature, including vernalisation, and photoperiod) in determining the time of initiation of reproductive development (initiation of the collar) and the rates and durations of organ initiation (leaves, tillers, spikelets, florets); however, the mortality of organs, notably tillers and florets, caused by intra- and inter-plant competition also plays a major part in determining the duration of developmental processes and the number of initiated organs which survive. The observed synchrony of crop development cannot be achieved without the coordinated responses of a number of developmental processes (e.g. leaf and ear development) to the environment; how this coordination is achieved by the plant is largely unknown, and in spite of the widespread use of plant growth regulators, molecular aspects of the control of plant development are poorly characterised. In practice, the convergence of development rarely fails, and the few examples of failure of synchrony (e.g. in crops which have lodged or where an inappropriate variety has been used) are reviewed.
A comparative investigation of the volumes of plasma and extracellular fluids and the renal clearances of urea and creatinine in Merino sheep from flocks with different genetic capacities for wool growth
Authors: Williams AJ , Thornberry KJ , Nicol H
Published: November 2004

Adult castrate male Merino sheep (n = 24; average liveweight 47 kg), from two flocks, differing in their genetic capacity for wool growth as a result of selective breeding for clean fleece weight, consumed one of two diets, differing in both quality (i.e. digestibility and nitrogen content) and quantity, termed L and H. The L (low) and H (high) diets supplied 0.42 and 0.81 kg digestible dry matter day-' and 9.5 and 26.0 g nitrogen day-I respectively. We compared the volumes of plasma and extracellular fluids, as well as the concentration of urea in plasma and the rate of clearance of urea by the kidneys of sheep from these two genetic groups, consuming the different diets. The average plasma volume of these sheep, estimated from the dilution of Evan's Blue in plasma, was 2.24 L (s.e. 0.08). The average volume of extracellular fluid, estimated from the dilution of 35S-sulfate, was 10.3 L (s.e. 0.4). These distributional volumes were similar in sheep from the two genetic groups and were not influenced by the dietary treatments. The sheep consuming the H diet maintained significantly greater concentrations of urea-nitrogen in their plasma (7.2 v. 2.8 mmol L-1: s.e. 0.3) and cleared both urea (37.1 v. 16.1 mL min-I : s.e. 5.3) and creatinine (87 v. 49 mL min-1 : s.e. 11) at significantly greater rates from the plasma. The sheep from the two genetic groups had similar average values for these three traits.
The effect of chlorsulfuron and diclofop-methyl on the uptake and utilization of zinc by wheat
Authors: McLay LD , Robson AD
Published: November 2004

The effects of the herbicides Hoegrass and Glean on the uptake of zinc by wheat were examined in two glasshouse experiments. Application of the active ingredients chlorsulfuron and diclofop-methyl decreased shoot weight, root weight and zinc uptake similarly to the herbicides Glean and Hoegrass. It can therefore be concluded that the effects of Hoegrass and Glean on zinc uptake in wheat can be attributed to these active ingredients and not to other constituents of the commercial herbicide preparations. Effects of chlorsulfuron on zinc uptake in soil were different from those obtained in solution. In soil, chlorsulfuron decreased both zinc concentrations in the youngest emerged blade and zinc content of shoots, while in solution where uptake is not likely to be limited by the rate of zinc diffusion to sites of absorption, there were no significant effects on zinc uptake. However, in both soil and solution, shoot and root weights were decreased by herbicide, particularly at low rates of zinc supply. Roots were shorter and thicker when herbicide concentrations in solution were increased.
Nitrogen fixation during vegetative and reproductive growth of irrigated soybeans in the field: application of δ 15N methods
Authors: Bergersen FJ , Turner GL , Peoples MB , Gault RR , Morthorpe LJ , Brockwell J
Published: November 2004

The dry mass, total nitrogen and the natural abundance of 15N were measured in stems plus leaves, pods and seeds during all stages of growth of a crop of irrigated Forrest soybeans. The sources of nitrogen accumulated in the seed and the magnitude of N2 fixation were calculated. During early growth, the proportion (PN2) of plant nitrogen arising from N2 fixation reflected residual effects of different rates of inoculation imposed two years previously and increased from 26-42% at 58 days to 49-57% at 71 days. Growth and accumulation of nitrogen in stems plus leaves ceased at about 108 days; growth of and nitrogen accumulation by seeds continued from 100 days to 142 days. During the most rapid phase of seed growth (100-125 days), 75-85% of seed nitrogen arose from N2 fixation. After net accumulation of plant nitrogen ceased (125 days), continued accumulation of seed nitrogen was derived mainly by relocation from pods and leaves but some N2 fixation continued. During ripening (142-167 days), there was loss of seed mass and nitrogen. The amounts of N2 fixed during seed development were substantial. After attainment of the maximum levels of nitrogen in the supporting shoots, N2 fixation totalling almost twice that achieved in the first 108 days of growth was directed exclusively to developing seeds during a period of only 34 days.
Plant and soil diagnostic tests for assessing the phosphorus status of seedling Macadamia integrifolia
Authors: Aitken RL , Moody PW , Compton BL , Gallagher EC
Published: November 2004

Seedling macadamia (Macadamia integrifolia cv. Hinde) were grown in pots in two glasshouse experiments for 23 weeks. Experiment 1 comprised ten soils at two P levels (nil and a rate calculated to be non-limiting to growth) with six replications. Experiment 2 consisted of another two soils with eight rates of added P (0-2560 mg P per 4 L pot) and six replications. Whole plant tops were harvested, dried and weighed, and leaves analysed for P. In addition, leaves from Experiment 2 were analysed for Cu, Zn, Mn and Fe. Roots were recovered from the soils, separated into proteoid and non-proteoid root material, dried and weighed. Control (nil added P) soils were analysed for soil solution P and Colwell, Olsen, Bray 1 and 0.005 M CaCl2 extractable P. At 90% of maximum whole plant top growth, P concentration in the leaf was 0.08%. When the leaf Fe/P ratio < 0.07 in Experiment 2, there was a significant yield depression associated with symptoms of severe iron chlorosis. Critical soil P levels at 90% of maximum whole plant top growth were 50, 23 and 29 mg kg-1 for Colwell, Olsen and Bray 1 extractable P, respectively. It was not possible to define a critical CaCl2 extractable P or soil solution P concentration because of the large increase in relative growth with a small increase in these parameters. Proteoid root growth (as a percentage of total root weight) decreased with increasing level of soil phosphorus, and there were very few proteoid roots at >100 mg kg-1 Colwell extractable P. Applying P to maintain high soil test levels (>100 mg kg-1 Colwell extractable P) would have detrimental effects on proteoid root development.
Effects of shade use on grazing, drinking, ruminating and postural patterns of Merino sheep
Authors: Johnson KG , Strack R
Published: November 2004

Eight animals in a flock of 20 Merino sheep were observed during four 24-h periods in summer (Tamax 31-37�C) to see whether their voluntary use of shade was related to patterns of foraging and posture. Observations were made at 15-min intervals on the 4 animals that used shade most (31% of the day) and the 4 animals that used shade least (12%). A related experiment revealed no significant differences in body core or skin temperatures or in respiratory rates between the groups. Feeding times, ruminating times and drinks per day were no different in groups making most and least use of shade; day-night patterns of these variables were also indistinguishable. Sheep in the shade stood for 2 h longer per day than sheep in the sun, though they behaved similarly at night. Thus shade use by sheep was not apparently related to patterns of feeding or watering, but was associated with postural modifications that probably have thermoregulatory consequences.
Application of the double-marker method for measuring digesta kinetics to rumen sampling in sheep following a dose of the markers or the end of their continuous infusion
Authors: Faichney GJ
Published: November 2004

Methods are described by which the double-marker method for measuring digesta kinetics may be applied to rumen samples taken from sheep maintained in steady-state conditions, while marker concentrations are declining after a single dose of the two markers, or cessation of their continuous infusion, or increasing in the pre-equilibrium phase of their unprimed continuous infusion. Also described are procedures for checking the consistency of analyses applied to digesta, fluid-phase and particle-phase samples and for physically reconstituting true digesta samples. Errors due to deviations of the markers from ideal behaviour are examined.