bluuebunny/crossref_metadata_2025 huggingface dataset:
Uptake of potassium by Setaria anceps and Macroptilium atropurpureum from the same standard solution culture
Authors: Whelan BR , Edwards DG
Published: November 2004

The influence of potassium supply on growth and potassium uptake by Setavia anceps cv. Nandi and Macroptilium atropurpureum cv. Siratro grown in association in standard solution culture was studied. Different degrees of competition were induced by introducing Siratro plants of three different ages (6, 12, 18 days) to the experimental solutions at the commencement of the experiment. Setaria seedlings were 12 days old at this point. Competition between the two species was compared at a high and at a low level of potassium supply. Throughout the duration of the experiment, Setaria plants absorbed potassium at a much greater rate than did the Siratro plants grown in association. Although the potassium absorption rates of Setaria declined more rapidly as the solution supply was exhausted, they generally remained above those for Siratro. The higher potassium concentrations obtained in Setaria than in Siratro plants grown in association ensure a superior ability for the grass to continue growth following exhaustion of the potassium supply. Rapid early growth of Siratro plants in some situations may provide some advantage in competing for the available potassium supply simply through a greater root mass.
Flowering responses to vernalization and photoperiod in annual medics (Medicago spp.)
Authors: Clarkson NM , Russell JS
Published: November 2004

The three processes thought to control flowering times in annual medics (Medicago spp.) are a vernalization requirement, a long day requirement and a high temperature requirement. To examine the first two processes, seed of seven cultivars of six species was vernalized at 1�C for periods of up to 11 weeks, then grown to flowering under three photoperiods in a glasshouse. To study the third process, the time to flowering of selected treatments from this expcrirnent was compared with flowering data from plants grown in the field at a range of temperatures lower than in the glasshouse. Vernalization and photoperiod caused large shifts in flowering time but the effects varied widely among species. M. scutellata was almost insensitive to both factors but in M. rugosa acceleration of up to 91 days was caused by treatment. Vernalization and short dark periods were additive in accelerating flowering and largely able to substitute for each other. Species flowered almost simultaneously when given their most favourable conditions for flowering. High temperature accelerated flowering in all species studied. However, in species other than M. scutellata it was necessary for a vernalization requirement to be met before this effect was observed. A new finding was that the vernalization response in M. truncatula and M. littoralis was largely reversed after more than 7 weeks of vernalization. This suggests a previously undetected flowering mechanism in these species.
Accuracy of soil water budgets based on a range of relationships for the influence of soil water availability on actual water use
Authors: Johns GG , Smith RCG
Published: November 2004

The accuracy of six published functions for deriving dryland water use from evaporative demand and soil water status was assessed by incorporating them in water budgets which were used to estimate dryland soil water status from actual climatic records. Budget-derived estimates were compared with values actually measured under improved pastures in the field over an 842 day period. The root mean square (RMS) of the differences between computed and observed soil water values was used to evaluate the various functions. RMS values were found to vary from 8.1 to 29.5 mm for the various functions tested. Soil water estimations made by using a simple ratio function were generally as good as or better than those made by using more complex functions. The sensitivity of the various functions to changes in their input assumptions was tested. The results of these tests will facilitate the selection of the optimum functions for conditions other than those encountered in this study. Reduced accuracy of soil water prediction resulted from the use of functions to set water use equal to the potential rate, regardless of the overall dryness of the soil profile, whenever recent rainfall was calculated to have made water available in the surface zone.
Inheritance of the resistance of Krish sorghum to sugarcane mosaic virus
Authors: Conde BD , Moore RF , Fletcher DS , Teakle DS
Published: November 2004

When two plants of Krish sorghum resistant to sugarcane mosaic virus were selfed or used in crosses with susceptible inbred lines, the segregation patterns of the S1, F1, bc1F1, F2 and F3 populations indicated that resistance is controlled by a single gene, with resistance dominant. One of the parents of Krish, i.e. Q12117 introduced from Coimbatore, India, as 'Sorghum halepense 2n = 20', is probably the source of the gene for resistance; tests of Q12117 revealed that three out of 34 seedlings were resistant after being inoculated with the virus four times. The relationship of the Krish gene with the N gene, which controls the mosaic and necrotic reactions in sorghums infected with the Australian Johnson grass strain of sugarcane mosaic virus, has not been definitely established, but it could be either closely linked or an additional allele at the N locus. The Krish gene for resistance has been transferred by means of a backcrossing program into several commercial sorghum breeding lines without losing its effectiveness against Australian and some overseas strains of sugarcane mosaic virus.
Competition and population dynamics in legume-grass swards with Stylosanthes hamata (L.) Taub. (sens. lat.) and Stylosanthes humilis (H.B.K.)
Authors: Torssell BWR , Ive JR , Cunningham RB
Published: November 2004

Competition between the annual legume Stylosanthes humilis and the annual grass weed Digitaria ciliaris, between the perennial legume Stylosanthes hamata and Digitaria ciliaris, and between Stylosanthes hamata and the perennial pasture grass Urochloa mosambicensis was studied at Katherine, N.T., by the replacement method. All species were mutually exclusive in mixtures. In pure stands S. hamata yielded significantly more than the three other species, and its competition with Digitaria was significantly stronger than that for S. humilis in competition with Digitaria (as measured by the relative crowding coefficient, k). Changes in species proportion in mixed swards were measured for two seasons in three phases of the annual life cycle: (1) germination–establishment, (2) main growth period, and (3) seed production, and were expressed by a 'phase parameter' analogous to the relative reproductive rate commonly used in competition experiments. When the legume constituted 75% of the viable seed sown in the first year, the legume proportion in terms of dry matter at the end of the second season was 0.02 for S. humilis–Digitaria, 0.35 for S. hamata–Urochloa and 0.80 for S. hamata–Digitaria. These results are discussed with reference to the phase parameters. Simulation, with variation of the phase parameters assumed log normal and independent within the observed ranges, indicated that under climatic conditions resulting in grass dominance in undefoliated S. humilis–Digitaria mixtures, legume dominance could be expected in undefoliated, high fertility S. hamata–Digitaria mixtures.
Seasonal pasture contamination and availability of nematodes for grazing sheep
Authors: Southcott WH , Major GW , Barger IA
Published: November 2004

In December 1970 and in January, February, March, April, May and September 1971 separate plots of sown pasture, each 0.1 ha, were contaminated by grazing sheep infected with gastrointestinal nematodes. In succeeding months each plot was grazed by worm-free tracer lambs for 2 weeks; the lambs were then withdrawn and held for 2 weeks in pens before slaughter for total differential worm counts. Observations on each plot continued for 12 months; the numbers of worms found in the tracer lambs indicated the seasonal occurrence of nematode larvae on pasture. For Haemonchus contortus, larval availability from deposition was rapid in summer and slow in autumn, maximum inhibition at the fourth larval stage occurring in larvae picked up in the winter months. Ostertagia spp. presented a marked contrast, with curtailed development in summer and contamination in autumn producing high levels of infection on pasture in late winter and early spring when inhibition was at maximum levels. Of the other species studied, intestinal Trichostrongylus spp, showed a similar pattern of development to H. contortus in summer, but as with Ostertagia spp. autumn contamination could produce infection peaks in late winter and spring. Inhibition at the fourth larval stage was not a characteristic of intestinal Trichostrongylus spp. For T. axei autumn and winter conditions favoured development, and peak infestations occurred in spring and coincided with maximum inhibition. Nematodirus spp. developed mainly in summer and most inhibition occurred at this time. Spring (September) contamination with Nematodirus spp. did not result in detectable levels of infection. For all other species spring contamination was rapidly translated to pasture and the infection was comparatively short-lived. All species were capable of overwintering on pasture and with the possible exception of T. axei a persistence of infection of at least 12 months was demonstrated. For Ostertagia spp. the importance of late summer and autumn contamination in its epizootiology and control in a summer rainfall region has been confirmed.
Simulating change in cattle liveweight during the transition period in a dry monsoonal climate
Authors: Ive JR
Published: November 2004

The change in liveweight of tropical crossbred steers grazing Townsville stylo or mixed Townsville stylo–sabi grass pastures was recorded for 3 years during the annual transition period between the dry and wet seasons, a period commonly associated with a loss of liveweight. The experiment was conducted at Katherine, Northern Territory (14.3°S., 132.3°E.). A non-linear regression model was developed relating weekly changes in liveweight to the quantity of living fodder on offer at the commencement of the week and to the rainfall for the week. The model was used to estimate the mean start and duration of the period during which the rate of gain in liveweight is below the dry season rate, on the basis of local meteorological data covering 25 years. Predictions from the model were compatible with previous findings. The root mean square error of the model increased when the yield of either nitrogen, phosphorus or total digestible nutrient was substituted for the yield of living dry matter. Therefore the difference in yield of living dry matter, rather than its botanical composition, accounted for the different rates of gain in liveweight recorded on the two pasture treatments. Consequently the inclusion of the perennial sabi grass allowed higher gains in liveweight (or less loss) because of the higher growth rate (and therefore greater living dry matter yield) of the perennial grass compared with the annual Townsville stylo. Furthermore it is suggested that predictions from the model could apply to other pasture species provided that the quality of juvenile growth during the transition period is relatively constant.
Variation of leaf characteristics with level of insertion on a grass tiller. II.* Anatomy
Authors: Wilson JR
Published: November 2004

The influence of leaf insertion level on anatomical characteristics in transverse sections of blades and sheaths on primary tillers of a grass, Panicum maximum var. trichoglume, was examined in plants growing under controlled light, temperature and nutritional conditions. Leaves from insertion levels 3, 5, 7, 10 and 13 from the base of the tiller were harvested when fully expanded and 5, 10 and 20 days thereafter. The flag leaf (leaf 16) was harvested at full expansion only. Gradients in anatomical characteristics with insertion level were clearly evident in leaves compared at a similar stage of development. Leaf blades and sheaths of higher insertion level had a greater proportion of sclerenchyma and vascular tissue, thicker lignified cell walls and cuticle, and a smaller average size of mesophyll, bundle sheath and epidermal cells. Lignification and cuticle development was greater in sheaths than in blades. These anatomical changes would explain the previously reported increase in cell wall content, and decrease in digestibility, of leaves at increasing insertion level. The anatomy of the leaf blades from all insertion levels did not change as leaves aged. However, sheaths in general, and those from higher insertion levels in particular, exhibited a marked increase in lignification of sclerenchyma and thickening of cuticle in the 5 days following the emergence of the ligule. These changes in the leaf sheaths appeared to be closely associated with the large decrease in digestibility over the same period.

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*Part I, Aust. J. Agric. Res., 27: 343 (1976).
Importance of phosphorus and nitrogen in the nutrition of grass seedlings growing in mulga soil
Authors: Silcock RG , Noble A , Whalley RDB
Published: November 2004

A pot experiment was conducted to compare the Importance of nitrogen and phosphorus fertilizers to seedling growth of four grasses on mulga soil. Two native species, Monachather paradoxa (mulga oats) and Digitaria ammophila (silky umbrella grass), and two exotic ones, Anthephora pubescens (wool grass) and Cenchrus ciliaris cv. Biloela (buffel grass), were tested. Digitaria and the two exotic grasses reacted similarly to applied phosphorus while Cenchrus utilized soil nitrogen more readily than the others. Phosphorus produced marked growth responses, increased the nitrogen and phosphorus contents of the plants, reduced the time between emergence and tillering and reduced root/shoot ratios. Nitrogen fertilizer produced no significant responses and actually retarded very early seedling growth. There were no nitrogen x phosphorus interactions.
Factors affecting the nutritive value of the diet and the composition of rumen fluid of grazing sheep and cattle
Authors: Langlands JP , Sanson J
Published: November 2004

The digestibility and nitrogen content of the diet and of the green fraction of the diet, and concentrations of individual volatile fatty acids in the rumen were measured in sheep and cattle grazing together on five Phalaris tuberosa pastures varying in forage availability. The sheep and cattle were aged 5 and 6 months respectively. Measurements were made at monthly intervals for 5 consecutive months during which animals were rotated between pastures. Measurements of forage availability, structure and composition were subjected to a principal components analysis from which orthogonal variables describing pasture composition were calculated. These were related to the nutritive value of the diet and the composition of rumen fluid by regression analysis. Diets selected by sheep were of higher digestibility and nitrogen content than those selected by cattle, because they contained more green material and the green material selected by the sheep was of higher digestibility and nitrogen content. The nutritive value of the diet of sheep varied with the availability of green forage, and that of cattle with both the availability of green and the bulk of forage on offer. Cattle were the more sensitive to changes in the quantity of green material available, and differences between sheep and cattle in the nutritive value of diets were reduced as the quantity of green material and the bulk of forage increased. The rumen liquor of cattle contained proportionately more acetic acid, and the proportions of other volatile fatty acids were less than in sheep. These differences were generally associated with differences in selective grazing.
Transmission of prune dwarf virus by peach pollen and latent infection in peach trees
Authors: Smith PR , Stubbs LL
Published: November 2004

Pollen from peach trees infected with prune dwarf virus (PDV) was used to hand-pollinate emasculated flowers on Golden Queen peach trees in the nursery. Symptoms of rosetting developed 20–25 days later on five of the 10 trees used, and PDV could be detected only in these affected trees. Rosetting symptoms developed in the remaining five trees 6–12 months later. Peach trees with latent or incipient infection also occurred naturally in the orchard. 14% and 12% of symptomless Golden Queen and Pullar's Cling trees, respectively, growing next to trees affected with peach rosette and decline were infected with PDV.
Patterns of assimilate distribution in soybeans at maturity. I. The influence of reproductive development stage and leaf position
Authors: Stephenson RA , Wilson GL
Published: November 2004

Leaves at upper, middle and lower positions in the canopies of soybeans were allowed to assimilate 14CO2 at one of several stages of reproductive development from pod set to maturity (49, 35, 25, 7 and 0 days before maturity respectively), and the distribution of 14C activity in the plants was determined at maturity. Pods in the axils of the treated leaves were always the major location for final assimilate accumulation, and together with those at the two nodes above and two below, averaged over the three leaf positions, accounted for 60–70% of the activity from all treatment stages. More remote pods were much less important sinks. Higher leaves contributed relatively more of the total final activity to their adjacent pods than those lower in the canopy, except when treated towards pod maturity. Little activity was found in stems, except in the segment immediately adjacent to the treated leaf in mid canopy, and then only at the earliest stage before rapid seed growth was occurring, when the stem segment could act as a sink. The corresponding result for the lower leaf was a relatively large amount of activity in the root, an adjacent active sink; otherwise recovery in the roots was low for all occasions and leaf levels. Treated leaves accounted for some 10% of residual activity, although much more was retained by them when treated towards maturity.
The effect of withholding water during flowering on seed production in Trifolium subterraneum L
Authors: Andrews P , Collins WJ , Stern WR
Published: November 2004

An experiment was conducted in a glasshouse to study the effects of withholding water during flowering on seed production in subterranean clover. Two strains, Northam A (long duration of flowering) and Geraldton (shorter duration) were grown as swards in boxes, defoliated weekly until flowering, and subjected to the following watering regimes: T1, a control; T2, water withheld over the whole of the flowering period; T3 and T4, water withheld for short periods only, during flowering. Regular determinations were made of soil water, leaf water potential and inflorescence number. Seed yield and some of its components were measured in all treatments. The prolonged stress (T2) reduced seed yield by about 80% in both strains. Rates of inflorescence production, duration of flowering and individual seed weight were also reduced. The shorter stress treatments (T3, T4) had no effect on seed yield in the longer-flowering cultivar Northam A, but in cv. Geraldton, T4 caused a marked reduction in seed yield. The practical implications of this differential strain response are discussed.
Chemical and integrated control of the long-tailed mealybug, Pseudococcus longispinus (Targioni-Tozzetti) (Hemiptera: Coccidae) in the Riverland of South Australia
Authors: Furness GO
Published: November 2004

Chemical control of the mealybug Pseudococcus longispinus (Targioni-Tozzetti) was most effective if sprays were applied when the mealybugs were in the dispersive crawler stage and when the host plant afforded the least shelter. A two-spray program with sprays applied in August and late November effectively controlled a dense infestation of the mealybug on citrus. Red scale (Aonidiella aurantii (Maskell)), the major insect pest of citrus, was also effectively controlled. An overall pest management program has been developed for citrus in which all insect pests are controlled by combination of natural enemies and insecticides as required. Outbreaks of the mealybug, and other secondary pests, are controlled by sprays of aminocarb or methomyl. These two insecticides prevented the population resurgence of mealybugs in the subsequent generation which occurred when maldison was used. Bioassays showed that aminocarb and methomyl were toxic for less than a week to the mealybug and to parasites and predators, whereas maldison and methidathion were toxic to the parasites and predators for about a month. Parasite pupae inside the host mealybug survived sprays of maldison and aminocarb. It is suggested that natural enemies emerging after spraying, from resistant or protected stages, survive sprays of aminocarb and methomyl but not sprays of more persistent insecticides like maldison; and that these survivors continue to suppress populations of their hosts. Hence aminocarb and methomyl are probably specific in their action against the mealybug and the other secondary pests of citrus because of their short persistence.An insecticide check experiment failed to demonstrate that natural enemies significantly reduce populations of the mealybug. Possible reasons for the failure are discussed.
Characterization of three strains of organophosphorus-resistant cattle ticks (Boophilus microplus) from Bajool, Tully and Ingham
Authors: Roulston WJ , Schuntner CA , Schnitzerling HJ , Wilson JT , Wharton RH
Published: November 2004

Three new strains of organophosphorus-resistant cattle tick from central and northern Queensland named Bajool, Tully and Ingham are described. In dosage-mortality tests on larvae they all have relatively low levels of resistance but can be distinguished from one another and from other described strains. The levels of acetylcholinesterase activity in the three strains differ from those previously described, and all have enhanced ability to detoxify either coumaphos or chlorpyrifos or both. The Bajool strain came from a property reporting control difficulties with chlorpyrifos. Larvae were found to have a seven times increased resistance to chlorpyrifos, about 14% of the acetylcholinesterase activity present in the Yeerongpilly susceptible strain, and increased ability to detoxify chlorpyrifos. In spraying trials involving all parasitic stages, 0.025% chlorpyrifos produced mortalities of 92 and > 99% of the Bajool and Yeerongpilly strains respectively. The Tully strain came from a property using ethion, and the larvae had a six times increased reistance to ethion and coumaphos. The level of acetylcholinesterase activity was about 1.6 times that in the Yeerongpilly strain and the larvae had enhanced ability to detoxify coumaphos. Spraying trials with 0.075% ethion and 0.025% coumaphos produced mortalities of about 90 and > 99% in the Tully and Yeerongpilly strains respectively. The Ingham strain came from a property which had experienced control failures with coumaphos, clenpyrin and chlorpyrifos. The larvae had a four to five times increased resistance to coumaphos and chlorpyrifos, an acetylcholinesterase activity level 1.8 times as great as that of the Yeerongpilly strain, and enhanced detoxication of both chlorpyrifos and coumaphos. Spraying trials with the recommended concentrations of acaricides gave mortalities of 83% with chlorpyrifos, 78% with coumaphos and 93% with ethion compared with > 99% for the Yeerongpilly strain with each of these acaricides.
The effect of sowing date on the growth and yield of three sorghum cultivars in the Ord river valley. I. Agronomic aspects
Authors: Millington AJ , Whiting MIK , Williams WT , Boundy CAP
Published: November 2004

The main aim of the experiment was to elucidate the causes of low sorghum grain yield in the Ord River valley. Three cultivars were studied: two dwarf, insensitive to day length (the hybrid RS610 and the inbred Meloland) and the day length-sensitive Q7844. The dwarf cultivars showed seasonal changes in time to maturity, but no seasonal changes in grain yield; sowing times need therefore depend only on mechanical difficulties of planting or harvesting in the wet season. Q7844 failed to initiate when the day length was longer than c. 12 hr 10 min, but the yield began to fall well before this day length was attained; a high stable yield was obtained only for sowings between about mid January and mid July. Overall mean yields were: RS610, 4694 kg/ha; Meloland, 4406 kg/ha; Q7844 (stable period only), 5074 kg/ha. Contrary to expectation, the yield of RS610 apparently increased with increase in maximum temperature. Meloland was less sensitive to temperature and to adverse environmental conditions. The causes of occasional yield failures are examined. It is suggested that Meloland deserves more attention than it has hitherto received, and that a dwarf photosensitive line might provide an acceptable 'wet season sorghum' for the Ord.
Diagnostic indices for sulphur status of subterranean clover
Authors: Spencer K , Jones MB , Freney JR
Published: November 2004

The variations in total sulphur, sulphate sulphur, and total nitrogen/total sulphur ratio, (N/S)t, in subterranean clover (Trifolium subterraneum L.) with age of plant, nutrient status, and plant part were studied in a glasshouse experiment on a sulphur-deficient soil. The concentrations of total sulphur and sulphate sulphur in the plant increased with increasing sulphur supply and decreased with plant age or with supplemental nitrogen. Overall, the laminae contained a higher concentration of total sulphur than the petioles; when the optimal concentration for growth was present, the concentration in the laminae was approximately twice that in the petioles. In sulphur-deficient plants there was little difference between the sulphate concentrations in laminae and petioles. In young sulphur-sufficient plants, higher concentrations were found in the petioles than in the laminae but this was reversed for the older plants. With increasing sulphur supply there were bigger relative increases in sulphate than in total sulphur and the magnitude of both these fractions changed more in petioles than in laminae. In general, the (N/S)t ratio increased with age of plant or supplemental nitrogen, and decreased with increasing sulphur supply. The changes with age were smaller in the laminae than in the petioles. Petioles had a higher ratio than laminae in sulphur-deficient clover, and a lower ratio where sulphur was adequate. Critical concentrations of total and sulphate sulphur in the tissue were lowered by extra nitrogen, fell markedly as the plant aged, but were not much affected by the maturity of the plant part. The (N/S)t ratio changes less with all factors than the other two indices, and thus promises fewer problems in interpretation.
The influence of calcium, phosphorus and vitamin D supplementation of a pea–barley ration for growing pigs
Authors: Stone BA , McIntosh GH
Published: November 2004

A diet based on field peas and barley can satisfy the mineral requirements of growing pigs provided that calcium is supplemented at least to the level of dietary phosphorus present, and that vitamin D3 supplementation is greater than Agricultural Research Council recommendations. Bone fragility and lameness observed in pigs on a low calcium-low vitamin D3 diet was overcome by increasing either of these components, and this was accompanied by increased metacarpal ash and femur breaking strength. A similar response could also be produced by increasing dietary phosphorus levels. Plasma calcium and phosphate concentrations were significantly influenced by changes in the dietary calcium/phosphorus ratio, whereas vitamin D3 changes had a minimal influence. Parathyroid activity appeared to reflect the plasma calcium concentration. There did not appear to be any relationship between plasma concentrations and bone fragility or lameness.In order to ensure adequate bone development in pigs offered a diet of plant origin, vitamin D3 supplementation and elevation of dietary calcium to the level of total phosphorus present is a minimum requirement.
Wheat frost injury — freezing stress and photosynthesis
Authors: Marcellos H
Published: November 2004

Although the lethal consequences of radiation frosts on wheat plants have been well described, effects of sublethal freezing have received little study. In this paper, studies of injury to leaves caused by freezing, and its influence on photosynthesis after thawing, are reported. Glasshouse-grown plants of three spring wheats were frozen at several temperatures in the range 0 to –4.5°C and their reaction to freezing stress measured. Injury to leaves caused by freezing stress was found to range from no damage to death over a temperature interval of 2°. Upper leaves were more resistant than lower, and the cultivar Z501 was found to be hardier by about l� than either Timgalen or Gamut. Net photosynthesis by whole plants in the period after thawing was reduced to levels as low as 30° of normal rates following mild stress, recovery to normal rates occurring by the following day. Severely stressed plants failed to recover over a 3 day period. Stomatal resistances were unaffected by low to mild freezing stress and could not explain the large reductions in photosynthesis rate following these stresses. The results have been discussed in relation to the underlying mechanisms, and to their implications for field crops.
The use of gibberellic acid to control alternate cropping of Late Valencia sweet orange
Authors: Moss GI , Bevington KB
Published: November 2004

The effect of spraying commercial gibberellic acid (GA) on alternate cropping and yield of Late Valencia orange trees was studied in detail at three sites over three seasons. Two applications of GA were applied at a minimum concentration of 25 ppm (in two experiments 0.75% emulsifiable oil was used as an adjuvant) 3 weeks apart during April and May for Dareton (on the River Murray) or June and early July for Yanco (Murrumbidgee Irrigation Areas) prior to the heavy-crop blossom. These sprays partly inhibited flowering and the subsequent heavy crop was reduced by up to 22% (by fruit number). In the next season there were more flowers and the light crop was increased by up to 57% at Dareton and 228% at Yanco. Some treatments practically eliminated alternate cropping while all reduced considerably the heavyllight crop ratio. Mean weight yields over 2 years were increased by up to 17% at Yanco and 16% at Dareton with mean increases for all successful GA treatments of 12.6% and 7.2% respectively. This represented an increase of 34 and 24 kg fruitltree. No long-term adverse effects on yield were found.Apart from re-greening of the fruit present at the time of spraying, fruit quality was not affected. There were fewer non-saleable small fruit at Yanco in the heavy crop as a result of the GA treatments, and a better range of fruit sizes in both the heavy and light crops. Trees on Rough Lemon rootstock responded well to GA treatments, especially in terms of increased yield in the light crop. Poncirus trifoliata rootstock was less responsive than Sweet Orange. This method might be used for the commercial control of alternate cropping of Late Valencia orange trees.
Inheritance of the resistance to compression property of Australian Merino wool and its genetic correlation with follicle curvature and various wool and body characters
Authors: Watson N , Jackson N , Whiteley KJ
Published: November 2004

Resistance to compression is primarily a measure of the crimp structure of individual fibres. Fibre crimp, as distinct from staple crimp, has been shown to be an important aspect of wool quality with requirements depending on end use and processing conditions. A precise definition of its importance under various conditions must await further evidence.The consequences of these findings for Merino breeders depend upon the heritability of resistance to compression and its genetic and phenotypic correlation with other important wool characters. Estimates of such parameters are presented and used to formulate breeding plans for the Australian Merino. Follicle curvature was included among the characters studied because it was hypothesized that it would be as good a measure of fibre crimp as is resistance to compression. The results support this hypothesis. The most important conclusion is that, if textile requirements dictate that resistance to compression as well as fibre diameter must be controlled during Merino breeding, progress in clean wool weight will be severely restricted.
Effect of defoliation on root growth of some arid zone perennial plants
Authors: Hodgkinson KC , Becking HGB
Published: November 2004

The effect of defoliation on the extension, longevity and branching of roots was studied with use of root observation boxes. Three perennial species commonly found in the southern portion of the Australian arid zone—wallaby grass (Danthonia caespitosa), old man saltbush (Atriplex nummularia) and bladder saltbush (A. vesicaria)&,dash;were investigated and compared with lucerne (Medicago sativa). The rate of root extension of theAtriplex spp. was about double that of M. sativa and D. caespitosa and for all species was proportionately reduced with the severity of defoliation. Root mortality increased and branching of roots decreased with increasing severity of defoliation. Time-lapse photography showed that extension of the roots of D. caespitosa began to slow down about an hour after complete defoliation whereas extension of the roots of A. nummularia and M. sativa did not begin to slow down until 12–24 hr after defoliation.
Germination and dormancy breaking by ethephon in mature and immature seeds of Medicago truncatula (medic) and Trifolium subterraneum (clover)
Authors: Globerson D
Published: November 2004

The effects of ethephon (2-chloroethylphosphoric acid) and temperature on seed germination were studied in two cultivars of Medicago truncatula (medic) and one cultivar of Trifolium subterraneum (clover) grown under different controlled conditions. Ethephon promoted germination of immature and fresh mature seeds and increased the germination rate of old mature seeds. Ethephon thiourea and carbon dioxide had different effects on the germination of seeds of the medic cultivars. At 30°C, untreated seeds germinated poorly while the presence of 10 ppm ethephon increased germination significantly.
A growth model for Trifolium subterraneum L. Swards
Authors: Fukai S , Silsbury JH
Published: November 2004

A simple deterministic model to simulate the time course of potential dry matter growth by subterranean clover swards in the field is described. Relationships used in the model were obtained mainly from experiments in temperature-controlled glasshouses and from measurements of rate of carbon dioxide exchange in an assimilation chamber. Canopy carbon dioxide exchange rates in the light and in the dark are calculated in the model from leaf area index, total dry matter, air temperature, irradiance and the crop growth rate of the sward. Photosynthates are distributed among different parts of plants according to empirical relationships. The model can estimate the potential dry matter growth of swards grown at different levels of irradiance and at different temperatures. Dry matter yield of a crop growing in the field without limitation of water and mineral nutrients can be predicted to within 20% for 100 days of growth. Potential dry matter yield of pure subterranean clover swards at Adelaide is predicted by the model to be strongly influenced by the time of cessation of growth. If the growth is terminated in the middle of October, an early start to growth as well as a high plant density will be advantageous for a high final yield. On the one hand, if the growing season extends until late November, there will be only a small effect of time of commencement of growth on final yield. The model suggests that leaf area index is an important determinant of dry matter production up to about 200 g m-2, and that increased maintenance respiration at a dry matter yield above about 600 g m-2 results in a decreased growth rate. The effects of variation in irradiance and temperature on dry matter production at different growth stages are assessed. It is concluded from use of the model that the effects of temperature on crop growth rate depend on the amount of dry matter present and on the level of solar radiation.
Plasma coumestrol levels and cervical mucus responses in ewes ingesting coumestan-rich feeds
Authors: Kelly RW , Lindsay DR
Published: November 2004

The concentrations of free and conjugated coumestrol in plasma drawn from the jugular vein of ovariectomized ewes were measured during 17 days of feeding on two coumestan-rich diets. Average daily intakes (± SE) of coumestans for ewes fed on diets A and B were 952 ± 30 mg and 514 ± 1 mg respectively. There was no change in the concentration of free coumestrol in the plasma during the period of feeding of the two diets, except for the last day when the diets were interchanged. The concentration of free coumestrol appeared to be related to the amount of coumestans ingested—81 v. 37 ng/l0 ml plasma (P < 0.01) for ewes fed on diets A and B respectively. The effects of length of feeding and diet on the concentration of conjugated coumestrol were less well defined but showed similar trends.Despite the significant amounts of coumestrol in the plasma after 16 days of feeding on the two diets, the production of cervical mucus remained at basal levels. It was concluded that for the cervical mucus bioassay, ewes become refractory to coumestrol over prolonged periods of exposure.
Studies of the environmental physiology of tropical merinos
Authors: Hopkins PS , Knights GI , Feuvre AS Le
Published: November 2004

Rectal temperature measurements of tropical Merino sheep taken in the sun during summer indicated that there were high and low temperature groups. Animals of low temperature status (e.g. 39.4°C) also exhibited a low respiration rate (e.g. 110/min) in comparison with their less adapted counterparts (40.0° and 190/min). These differences were greatest when ambient temperatures were high. The repeatability of temperature status was 0.46 (P < 0.01). Animals of folds (+) phenotype had significantly higher rectal temperatures than folds (–) animals (P < 0.05). Shearing caused a marked but transient increase in rectal temperature. Compensatory mechanisms apparently involved an increase in cutaneous heat dissipation and/or a decrease in exogenous heat load. Evaporative water loss (80–115 ml/kg/day) greatly exceeded the non-evaporative water loss (40–65 ml/kg/day) of sheep in metabolism cages. Respiratory water loss could account for only 8–10% of the total daily evaporative water loss. Non-respiratory evaporative water loss (as measured by difference) was c. 75–100 ml/kg/day. There were no striking differences between high and low temperature status sheep in this regard. Measurements of respiratory (2 ml/kg/hr) and non-respiratory (5.5 ml/kg/hr) evaporative water loss made in hygrometric tents suggested that the greater non-respiratory water loss was partly due to a higher rate of loss and partly to a longer period of loss per day. This suggestion was supported by the diurnal patterns of rectal temperatures and respiration rates reported here, though no firm conclusions could be made as to the thermotaxic effect of non-respiratory water loss and thermoregulation of tropical Merinos with varying amounts of wool cover.
The influence of level of feed intake on sperm-producing capacity of testicular tissue in the ram
Authors: Oldham CM , Adams NR , Gherardi PB , Lindsay DR , Mackintosh JB
Published: November 2004

The experiment examined the effect of supplementing a roughage diet with lupin grain on the capacity of testicular tissue to produce spermatozoa. Changes in testicle size were estimated by comparative palpation. At the end of the experiment the rams were castrated and the morphology of the testes and their capacity to produce sperm were studied. At the highest level of feed intake, liveweight increased by 32% and testicle volume by 67% during the feeding period of 9 weeks. Rams on a diet that reduced testicle size produced 18 x l06 sperm/g testis per day, and those on a diet that increased testicle size produced 26 x l06 sperm/g testis per day. Those rams whose testes were increasing in size at castration had significantly larger seminiferous tubules, which occupied a significantly greater proportion of the testicle volume, than rams fed on diets that reduced the size of their testes. The variation in rates of sperm production, together with the large differences in testicle weight, resulted in wide differences in total sperm production among rams fed on different diets.
Availability to grazing sheep of gastrointestinal nematode infection arising from summer contamination of pastures
Authors: Donald AD , Morley FHW , Waller PJ , Axelsen A , Donnelly JR
Published: November 2004

In two successive years, separate phalaris-subterranean clover pasture plots near Canberra were contaminated with nematode eggs by grazing with naturally infected sheep in each of the summer months (December, January, February) and the first month of autumn (March). At intervals until mid- to late winter, the availability of infection on pasture was estimated by grazing with worm-free 'tracer' lambs which were subsequently slaughtered for worm counts. Summer rainfall in both years was above average. Tracer counts of Haemonchus contortus and Ostertagia, Trichostrongylus and Nematodirus spp. per l08 eggs per hectare remained high during summer, with evidence that migration of larvae to the herbage could continue for at least 2 months after contamination. Rates of decline in tracer worm counts over the autumn and winter did not differ between years, and from an assumed maximum 2 months after contamination in each of the summer months, were fastest from December and slowest from February contamination. These rates were similar for all genera on December-contaminated plots, but on January and February plots, Ostertagia spp. declined more slowly. H. contortus numbers fell sharply in early autumn to be low by the end of May. By mid July there would be few larvae of all genera available on pastures contaminated in December and January, but this is less certain on February-contaminated pastures, especially for Ostertagia spp. Implications for the control of nematode infections in sheep by anthelmintic treatment and grazing management are considered.
Host resistance to cattle tick (Boophilus microplus) in Brahman (Bos indicus) cattle. III.* Growth on previously unexposed animals
Authors: Wagland BM
Published: November 2004

Length measurements were used to compare the growth of the parasitic stages of Boophilus microplus on previously unexposed Brahman (Bos indicus) and Shorthorn (B. taurus) cattle. Growth curves based on the length measurements were constructed. Growth was slower on Brahmans than on Shorthorns during the first 24 hr of larval and nymphal instars. After the first 24 hr, the growth rates of larvae, and of nymphs, during feeding to engorgement were the same on the rump and belly regions of both species of cattle. Larvae and nymphs engorged more slowly on the brisket than they did on the rump and belly regions of the Brahmans. The surface skin temperature was lower on the brisket of the Brahmans. On the basis of change in the length of the tick during development on Brahmans, 16 age categories were established, so that the length of the tick may be used to estimate the ages of ticks in populations on Brahman cattle. Age categories were also defined for ticks which had been processed in formalin and hot alkali.

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*Part II, Aust. J. Agric. Res., 29: 395 (1978).
Breeding Australian Illawarra Shorthorn cattle for resistance to Boophilus microplus. I. Factors affecting resistance
Authors: Utech KBW , Seifert GW , Wharton RH
Published: November 2004

Selection and breeding for tick resistance in an Australian Illawarra Shorthorn (AIS) herd was undertaken from 1966 to 1971. Mating of half the AIS herd with a Brahman bull in 1968–69 provided a comparison of tick resistance in selected Bos taurus and crossbred B. taurus x B. indicus cattle. Parent cows and their progeny were ranked for resistance to ticks, infestations of which were acquired as a result of grazing infested pastures, and from periodical artificial infestation with cohorts of c. 20,000 larvae of Boophilus microplus. Ranking and assessment of resistance levels were based on counts of semi-engorged female ticks on the right side. Parent cows selected for high resistance consistently carried fewer ticks than cows selected for low resistance. Mating of cattle selected for high resistance produced progeny that were significantly more resistant than the progeny of cattle selected for low resistance. However, the Brahman bull, which had slightly lower resistance than the AIS bull, produced progeny with higher resistance, even when mated with AIS COWS selected for low resistance. Pregnant cows were significantly less resistant than non-pregnant cows, and lactating cows were very much less resistant than non-lactating cows. Young cows were more resistant than older cows. Calves at foot carried fewer ticks than their dams when grazing infested pastures, but after weaning they were less resistant than their parents when resistance was determined from artificial infestations. Female calves carried fewer ticks than males on almost all occasions, but differences were not significant in winter. Significant seasonal changes in resistance were demonstrated in AIS and Brahman x AIS weaner and yearling cattle. All cattle were less resistant in winter. Changes were greatest in Brahman x AN females, on which the average numbers of female ticks that matured following artificial infestations in January 1970 (summer), July 1970 (winter) and January 1971 (summer) were 151, 1046 and 95 respectively.
A study of grain number in two contrasting wheat cultivars
Authors: Bremner PJ , Davidson JL
Published: November 2004

The origin of the grain number difference between two contrasting wheat cultivars (WW 15, Mexican semidwarf; Timgalen, Australian) was studied in terms of (i) the production and distribution of dry matter during the pre-anthesis development of the ear; (ii) the number of florets initiated; and (iii) interaction between grains during grain set. Grain yield was much more closely related to harvest index than to total dry weight, and harvest index appeared to be largely a function of the number of grains produced per unit area. The difference in grain number between the cultivars bore no relation to the number of florets initiated by them. Nor was the inhibition of grain set in the distal florets of spikelets by rapid growth of grains in basal florets involved. Large differences in grain number occurred between the cultivars where there was no detectable difference between them in the production and distribution of dry matter during pre-anthesis ear development, i.e. the semidwarf cultivar was superior in setting grains for some reason other than the pattern of distribution of dry matter between grain and straw.