Multiple Shape Coexistence in ^{110,112}Cd

From detailed spectroscopy of ^{110}Cd and ^{112}Cd following the β^{+}/electron-capture decay of ^{110,112}In and the β^{-} decay of ^{112}Ag, very weak decay branches from nonyrast states are observed. The transition rates determined from the measured branching ratios and level lifetimes obtained with the Doppler-shift attenuation method following inelastic neutron scattering reveal collective enhancements that are suggestive of a series of rotational bands. In ^{110}Cd, a γ band built on the shape-coexisting intruder configuration is suggested. For ^{112}Cd, the 2^{+} and 3^{+} intruder γ-band members are suggested, the 0_{3}^{+} band is extended to spin 4^{+}, and the 0_{4}^{+} band is identified. The results are interpreted using beyond-mean-field calculations employing the symmetry conserving configuration mixing method with the Gogny D1S energy density functional and with the suggestion that the Cd isotopes exhibit multiple shape coexistence.

High-precision half-life measurement for the superallowed β+ emitter ²⁶Al(m)

A high-precision half-life measurement for the superallowed β+ emitter 26Al(m) was performed at the TRIUMF-ISAC radioactive ion beam facility yielding T 1/2 6346.54 ± 0.46(stat) ± 0.60 (syst) ms, consistent with, but 2.5 times more precise than, the previous world average. The 26Al(m) half-life and ft value, 3037.53(61) s, are now the most precisely determined for any superallowed β decay. Combined with recent theoretical corrections for isospin-symmetry-breaking and radiative effects, the corrected Ft value for (26)Al(m), 3073.0(12) s, sets a new benchmark for the high-precision superallowed Fermi β-decay studies used to test the conserved vector current hypothesis and determine the V(ud) element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

Internal gamma decay and the superallowed branching ratio for the beta(+) emitter (38)K(m)

The branching ratio for the superallowed beta(+) decay of (38)K(m) was measured at TRIUMF's ISAC radioactive ion beam facility. The M3 internal transition between the isomer and the ground state of (38)K(m) was observed with a branching ratio of 330(43) ppm. A search for the nonanalogue beta-decay branch to the first excited 0(+) state in (38)Ar was also performed and yielded an upper limit of < or =12 ppm at 90% C.L. These measurements lead to a revised superallowed branching ratio for (38)K(m) of 99.967(4)%, and increase the (38)K(m) ft value by its entire quoted uncertainty to ft=3052.1(10) s. Implications for tests of the nuclear-structure dependent corrections in superallowed beta decays and the extraction of the Cabibbo-Kobayashi-Maskawa matrix element V(ud) are discussed.

Precision branching ratio measurement for the superallowed beta+ emitter 62Ga and isospin-symmetry-breaking corrections in A>or=62 nuclei

A high-precision branching ratio measurement for the superallowed beta+ decay of 62Ga was performed at the Isotope Separator and Accelerator radioactive ion beam facility. Nineteen gamma rays emitted following beta+ decay of 62Ga were identified, establishing the dominant superallowed branching ratio to be (99.861+/-0.011)%. Combined with recent half-life and Q-value measurements, this branching ratio yields a superallowed ft value of 3075.6+/-1.4 s for 62Ga decay. These results demonstrate the feasibility of high-precision superallowed branching ratio measurements in the A>or=62 mass region and provide the first stringent tests of the large isospin-symmetry-breaking effects predicted for these decays.

An Australian temperate pastures database

A census of pasture types and their composition and attributes (e.g. purpose and carrying capacity) was carried out throughout southern Australia from June to October 1994. This paper describes the survey process and subsequent creation of an Australian temperate pastures database. Data were created for 562 local government areas (LGAs) from ‘desk estimates’ by trained agriculturists. They identified about 2500 pasture types, which were grouped into 120 standardised pasture categories. Some findings from the data are identified, namely the high relative importance on an area basis of unimproved native pastures, the importance of weedy species (e.g. Vulpia), and the marked decline with increasing rainfall in importance of annual medics compared with subterranean clover. This paper provides examples of the data and their use for assessment of the regional economic impact of increases in productivity of pasture species.

Cold damage and development of rice: a conceptual model

Loss of yield in rice owing to exposure to suboptimal (<20�C) temperatures is a widespread phenomenon; in Australia there is circumstantial evidence that cold damage is substantial and that it can occur at any time during the growing season. Damage may take the form of reduced potential yield, abnormal spikelet development, and reduced spikelet fertility. In extreme cases plants may be completely infertile. We are using a conceptual model based on the daily cycle of temperature to quantify a cooling index and the impact of cold. The daily impact of cold varies with the phenology of the crop (i.e. some stages of development are particularly cold-sensitive), and the total or cumulative impact depends on the summation of thermal time below a critical minimum temperature for cold damage. We are in the process of quantifying the variables of the model for 2 cultivars of rice. This aims at prediction of yield loss in response to seasonal variation in temperature, and identifying the likely benefit which will arise from using particular parent lines in later breeding for cold tolerance.

Thermal requirement for germination and seedling growth of wheat

Two cultivars of wheat, Hartog (a spring type) and Rosella (winter) were sown at 2, 5, 8, 10, 15, 20 and 25�C on porous sand medium held at constant soil matric potential. The thermal times required for germination, onset of coleoptile elongation and emergence were similar, 27, 35 and 130�C days respectively, for the two cultivars over the temperature range of 2-25�C. By extrapolation, the base temperature for germination and coleoptile elongation was 1�C and for emergence 0.4�C. The rate of seedling elongation and emergence of both cultivars increased linearly with temperature between 5 and 25�C. Final percentage germination, final coleoptile length and total emergence of both cultivars were independent of temperature between 8 and 25�C but were smaller at 2�C. Differences between the two cultivars were confined to response to low temperature (2OC) during germination and to high temperature (25�C) during coleoptile elongation.

Differences in flowering responses of wheat to temperature and photoperiod

Apex and ear development were studied in one spring wheat (Hartog) and five winter wheats (Rosella, Maris Templar, Maris Huntsman, Priboy and Krasnodar 39) subjected to vernalizing or non-vernalizing temperatures under either short or long photoperiods until ear initiation (double ridges), followed by either short or long photoperiods until ear emergence. Hartog produced ears in all treatments, and it initiated ears faster than winter varieties in all treatments. Four types of winter wheat were distinguished by their mandatory requirements for ear development. The only winter variety to reach ear emergence without vernalization was Maris Templar; short days were an effective substitute provided that long days were experienced after ear initiation. In Priboy, photoperiod was unimportant both before and after ear initiation. Maris Huntsman and Rosella required long photoperiods after initiation, whereas Krasnodar 39 required long days during vernalization. If these conditions were not met, either the shoot apexes died without producing a terminal spikelet or the ears died before emerging. Plants in all treatments which reached ear emergence proceeded normally to maturity. The suitability of the different types for particular regions is discussed. All varieties in all treatments initiated ears when the shoot apex reached a volume of about 0.13 mm3. Relative growth rates of the apex, related to thermal time, were constant during the vegetative phase; they determined the time to ear initiation and, through it, controlled the time of ear emergence. Differences between varieties in their basic vegetative period are attributed to differences in the relative growth rates of their vegetative apexes. These growth rates were much lower in winter wheats than in the spring variety, but increased sharply in them at or just before the first visible signs of initiation in those treatments which allowed normal development. Vernalization was not the cause of this accelerated growth. In winter wheats, vernalization promoted faster initiation of ears, and hence flowering, and the survival and normal development of initiated ears. It is suggested that vernalization acts by reducing the effectiveness of an inhibitor of cell division.

Variability in seedling elongation of wheat, and some factors associated with it

Coleoptile lengths of 22 cultivars of wheat (Triticum aestivum L.) were measured in darkness at 2 depths of sowing (2 and 6 cm) under minimal mechanical stress and at 4 cm depth under 0.76 kPa mechanical stress. The experiments were done to describe variability in elongation abilities and to develop a technique for genotypic screening for tolerance of high soil strength. Of the 8 cultivars with shortest coleoptiles, 6 had cv. Condor parentage. Lengths of coleoptiles of all cultivars were reduced by 18% on average, under 0.76 kPa mechanical stress. Lengths were correlated with time to median emergence (r = 0.72) and total emergence percentage by 20 days after sowing (r = 0.77). Some cultivars with shorter coleoptiles took an extra 2-3 days to reach median emergence and attained a poorer total emergence percentage than those with long coleoptiles. A doubling of seed weight resulted in an increase of only 9% in coleoptile lengths, with no effect on emergence. The results suggest that cultivars appropriate for emergence from particular soil types or under adverse conditions could be selected under minimum soil stress because their performance ranking was similar under mechanical stress.

Variability in habit, flowering and seed production within the Kangaroo Valley cultivar of Lolium perenne when grown in a range of environments

Diversity of flowering and seed production characteristics were measured within and between seven populations of Kangaroo Valley perennial ryegrass. The hypothesis that these characteristics would not change when grown in diverse environments was tested. The average time from seedling emergence to spike emergence was similar for each of three biotypes that represented early, intermediate and late flowering populations. This occurred in spite of variation in this character of 54 to 72 days between plants within each of these biotypes. When data from all seven populations were combined, they formed a normal distribution with respect to time of flowering. Distinctive components of seed production were found for the different populations. Early flowering populations had higher seed yields and more but shorter spikes than late flowering populations. Wide variation in habit occurred within populations but there was a high correlation between erect habit and early flowering. Spikes of erect plants emerged 27 days earlier than prostrate plants. The seed formation characteristics of an early flowering population were unaltered when grown for three generations in diverse environments. The spike emergence and anthesis times for each of the seven populations were not changed when grown in new environments. We conclude that seed production of Kangaroo Valley ryegrass in environments similar to those described in these experiments will not significantly alter the population characteristic. For changes in the character of the population to occur, the new environment would have to be so severe to (a) restrict growth and select out a proportion of the progeny or (b) cause a change in the time of seed harvest.

Yield components and nitrogen partitioning of maize in response to nitrogen before and after anthesis

Zea mays hybrid XL66 was grown with irrigation in sand in the field and subjected to different rates of nitrogen supply from floral initiation to anthesis and again from anthesis to maturity. Nitrogen supply during spikelet differentiation affected grain number markedly. Nitrogen supply during grain filling had a small but significant effect on the rate of grain filling and an effect on the rate of nitrogen entry to the grain, causing a 1.3-fold change in percentage grain nitrogen. Increasing the nitrogen supply produced larger plants, but the distribution of nitrogen and dry weight among plant parts were similar and the harvest indices for dry weight (0.46) and nitrogen (0.66) were the same over all nitrogen treatments. We found no evidence that shoot size per se controlled grain number or rate of grain growth; rather, fertilizer management during spikelet differentiation had most effect on yield of XL66.

Root distribution in space and time in Trifolium subterraneum

Distribution of length and weight of roots of subterranean clover cultivars Northarn and Nungarin were measured in the field throughout a growing season. Plants were grown at seven populations from 2 to 1510 plants per m2 in coarse sand which had a bulk density of 1.4 g cm-3. Root growth was described by its vertical and horizontal distribution as functions of population and time after emergence. Differences in growth between cultivars were small. Root depth, which reached a maximum (plateau) at about 90 days, did not vary with plant population. Root density (length per volume of soil) increased faster at high population due to a higher density of' roots beneath the mainstream and an attenuation with distance away from the mainstem which did not appear to be affected by population. Root densities were 10 cm cm-3 in the uppermost core (0-10 cm depth) and 1.6 -3.5 cm cm-3 throughout the rooting zone (0-50 cm) at 119 days after emergence. Root death, estimated from dichlorotrianzinyl staining, was negligible. Leaf area per plant declined with population above 16 plants per m2; leaf area per unit root length (in cores beneath the mainstream) declined 90-fold with increase in population. Top weight and burr yield per plant at final harvest also declined with increasing population; burr yield per m2 also fell significantly at the highest population. It is concluded that the amount of root per unit area increases with population and that plants appear to adjust conservatively in some respects (to much lower leaf area per root length) while being unable to sustain dry matter partitioning (reducing burr/top yields) at the highest population studied.

Germination and seedling growth of prairie grass, tall fescue and Italian ryegrass at different temperatures

We measured the effects of temperature on the germination, emergence and growth during early tillering of Italian ryegrass (Lolium multiflorum), prairie grass (Bromus catharticus) and tall fescue (Festuca arundinacea). Radicle emergence (the percentage of seeds with emerged radicles) and 'field' emergence (the percentage of seeds with shoots > 1 cm long) were reduced at 35�C (constant, all lines), or 30/25�C (12/12 h, prairie grass and Tama Italian ryegrass only). All lines took longer to germinate at 15 and 10�C (constant) than at higher temperatures, and final percentage germination of tall fescue lines was lower at 10�C (constant) than at other temperatures. Italian ryegrass had the fastest shoot extension, and consequently the fastest 'field' emergence. Seed respiration rates were higher in fescue than in the other lines at 4 days from imbibition, and rates rose in all lines at 8 days. Over the first 20 days after sowing, growth rates were closely related (r = 0.87-0.99) to weights of seed and caryopses, when account was taken of perenniality (which was associated with relatively slow growth) and polyploidy (which was associated with growth faster than might be expected from seed size alone), and a multivariate relationship including temperature was developed (R2 = 0.88). Growth rates of shoots at 20 days after sowing were ranked Tama Italian ryegrass > prairie grass > Ucivex Italian ryegrass > tall fescue, and 24/19 > 21/16 > 18/13 > 30/25 > 15/10�C. Growth during tillering, up to 42 days after emergence, was ranked Italian ryegrass > prairie > tall fescue and 21/16 = 18/13 > 24/19 = 15/1O�C. Relative growth rates and relative rates of tillering were independent of temperature in Italian ryegrass, but were lower at 15/10 and 24/19 than at 21/16 and 18/13�C in prairie grass and tall fescue. Prairie grass had higher yield per tiller but lower tiller numbers than Italian ryegrass; tall fescue had both lower yield per tiller and lower tiller number. Italian ryegrass was therefore the species best adapted to variations in environment and competition at sowing.

Responsiveness to seasonal temperature and nitrogen among genotypes of kikuyu, paspalum and bermuda grass pastures of coastal New South Wales

Three experiments were carried out to test the hypotheses that (a) there are quantitative differences in growth rate and quality between newly registered cultivars and older cultivars in response to changes in temperature and fertility, and (b) responsiveness to temperature varies between sites because cultivars acclimatize to their current environment. Performance in simulated swards indicated that potential productivity was highest from bermuda grass (Cynodon x Burton Pearson). This was, however, a poor indicator of performance in the field, where yield of bermuda grass was depressed by weeds whereas that of kikuyu (Pennisetum clandestinum) was unaffected. In the field, a newly registered kikuyu, cv. Crofts, outyielded bermuda grass and paspalum (Paspalum dilatatum) either alone or when combined with lucerne. A further experiment compared cvv. Crofts, Whittet and common kikuyu at three levels of nitrogen at three sites. Peak growth rates were the same at all locations but Crofts outyielded the other genotypes by 60, 13 and 18% at Bega (37�S.), Camden (34�S.) and Taree (32�S.) respectively. Average growth rates varied seasonally and were correlated with temperature (r > 0.9). Analysis of temperature responsiveness (kg/ha.�C) indicated that responsiveness varied consistently between genotypes at any location. Furthermore, the base temperature (the temperature below which there was negligible growth) was the same for all genotypes at any location but it increased with increasing latitude. That is, there was a tendency to greater dormancy with increasing coldness of location. Nitrogen responsiveness was the same for all genotypes and sites. Seasonal variations in digestibility and mineral concentrations in kikuyu, bermuda grass and paspalum were similar in the field and in simulated swards; quality was the same in all kikuyu genotypes. Calcium, magnesium and nitrogen concentrations of plant tops (but not phosphorus and potassium concentrations) increased with increasing rates of application of nitrogen fertilizer.

Growth, mineral composition and digestibility of maize, sorghum and barnyard millets at different temperatures

Barnyard millets (Echinochloa utilis and E. frumentacea), maize (Zea mays) and a sorghum hybrid (Sorghum bicolor x S. sudanense) were grown as spaced plants at temperature regimens from 15/10 to 33/28�C (dayhight). Leaf and stem dry weight, leaf area and leaf number were recorded every 2 weeks and the dry matter analysed for nitrogen, sulfur, sodium and in vitro digestibility. Tolerance to low temperatures was in the order maize > E. utilis >sorghum >E. frumentacea. At mean temperatures above 25�C, relative growth rates were similar for all species. Differences in leaf area, for which individual leaf size was mainly responsible, accounted for most of the dry weight responses to temperature, although net assimilation rate responses were also apparent. The dry weight response to temperature became negligible after adjusting for differences in stage of development. Dry matter digestibility decreased with temperature; it also decreased with time because of deteriorating stems, except in sorghum. Maize leaves were of low digestibility, similar to stems. The nitrogen : sulfur ratio of all species remained steady with age; in sorghum at low temperature it exceeded the 15: 1 maximum considered desirable for animals. Sodium was highest in E. utilis stems and increased with temperature, in contrast to sorghum. Maize had a marginal nitrogen: sulfur ratio and unacceptably low sodium concentration. It was concluded that more attention should be given to E. utilis as a forage for cool climates.

Daily changes in nitrate influx, efflux and metabolism in maize and pearl millet

Maize (Zea mays L.) and pearl millet (Pennisetum americanum (L.) Leeke) seedlings were exposed to [(15)N]nitrate for 1-h periods at eight times during a 24-h period (16-8 h light-dark for maize; 14-10 h for millet). Influx of [(15)N]nitrate as well as its reduction and translocation were determined during each period. The efflux of previously absorbed [(14)N]nitrate to the uptake solution was also estimated. No marked diurnal changes in [(14)N]nitrate efflux or [(15)N]nitrate influx were evident in maize. In contrast, [(14)N]nitrate efflux from millet increased and eventually exceeded [(15)N]nitrate influx during the late dark and early light periods, resulting in net nitrate efflux from the roots. The dissimilarity of their diurnal patterns indicates that influx and efflux are independently regulated. In both species, [(15)N]nitrate reduction and (15)N translocation to shoots were curtailed more by darkness than was [(15)N]nitrate influx. In the light, maize reduced 15% and millet 24% of the incoming [(15)N]nitrate. In darkness, reduction dropped to 11 and 17%, respectively. Since the accumulation of reduced-(15)N in shoots declined abruptly in darkness, whereas that in roots was little affected, it is suggested that in darkness [(15)N]nitrate reduction occurred primarily in roots. The decrease in nitrate uptake and reduction in darkness was not related to efflux, which remained constant in maize and did not respond immediately to darkness in pearl millet.

The 'Wits' appraisal of a sample of the South Wales population

The ‘Wits’ appraisal of a sample of a South Wales population was undertaken. The material was 25 headplates of 15-year-old males and a similar number of X-rays from 15-year-old females. The results were very similar to those first reported by Jacobson.

Daily changes in nitrate uptake and metabolism in Capsicum annuum

The diurnal pattern of nitrate uptake by Capsicum annuum L. cv. California Wonder in a constant environment is described by a Fourier harmonic, with the maximum uptake in the middle of the photoperiod and the minimum in the middle of the dark period. Comparison of the uptake pattern with that of nitrate reductase (EC 1.6.6.1.) activity suggests against a direct control of one process by the other. This was confirmed by the observation that the pattern of nitrate reductase activity was not altered by restricting nitrate uptake to one hour per day. Translocation of (15)N from the roots is much greater in the lightperiod than in the dark period. Reduction of (15)N in the leaves occurs in the lightperiod but very little is reduced in the dark period. Amino acid levels showed marked daily fluctuations but in the roots neither amino acids, sucrose, fructose, glucose nor malate showed fluctuations. The amino acid composition of roots and leaves differed: glutamine+glutamate were relatively more important in leaves than in roots whereas alanine was a more important constituent of roots than of leaves.

Photosynthate translocation in Capsicum annuum

The leaves of Capsicum annuum L. cv. California Wonder function as efficient carbon exporting organs for a large part of their life span. Young and old leaves export the same percentage of fixed carbon (74% within 24 hours) although fixation rates per unit area of young leaves may be three times that of old leaves. A constant feature of translocate distribution is a supply to the roots and to the terminal fruit of the main axis from both the main axis leaves and branch leaves. Carbon supply to branch fruit is flexible in that main axis leaves supply carbon to the very small fruit, but the subtending branch leaves supply more as the fruit grows and the branch node becomes more self-sufficient. Fruit are capable of carbon fixation but translocation to terminal fruit from main axis leaves supplies about 7.5 times as much carbon as direct fixation.

Daily changes in carbon-dioxide exchange and photosynthate translocation of leaves of Vicia faba

Net carbon-dioxide exchange and loss of photosynthate-(14)C from leaves of Vicia faba L. were estimated throughout a day (16/8 h light/dark periods) by infrared gas analysis and Geiger-Müller-tube monitoring, respectively. Net photosynthesis reached 95% of the mean maximum rate within 1 h of the start of the photoperiod, and thereafter remained relatively constant before declining during the last 2-4 h of the photoperiod. Respiration was highest at the start of the dark period. The loss of photosynthate-(14)C from leaves exhibited two phases: a rapid phase which was fastest but shortest following (14)C incorporation in the middle of the photoperiod, and a slower phase of much longer duration. Absolute rates of (14)C loss exhibited diurnal trends reaching 95% of the maximum 6 h after the start of the photoperiod and remaining high until darkness, and then declined markedly. Of the total carbon fixed in one 24 h period, about 50% was lost during the current photoperiod, 14% during the dark period and 5% during the next photoperiod. The estimated amount of carbohydrate remaining within the leaf followed a diurnal pattern of accumulation and depletion. The daily course of translocation was not closely related to that of net photosynthesis or carbohydrate concentration.

Daily Changes in Stomatal Aperture and in Carbohydrates and Malate Within Epidermis and Mesophyll of leaves of Commelina Cyanea and Vicia Faba

Stomatal apertures and methanol-, water-, and hydrochloric acid-soluble carbohydrates and malate were measured in the epidermis, mesophyll, and midvein of leaves of C. cyanea R. Br. and V. [aba L. over a period of 26 hr in one experiment and over 9 hr during the photoperiod in a second experiment.

Effects of pretreatment temperature on carbon dioxide exchange in alfalfa

The temperature response curves for net carbon dioxide exchange are described for plants of cultivars (cvs.) Vernal and Moapa alfalfa (Medicago sativa L.) grown at day/night temperatures of 30/25C and 20/15C, an irradiance of 25 nE cm−2 s−1 (400–700 nm), and a day length of 15.5 h. Net carbon dioxide intake (NCI) of the tops decreased with increasing temperature from 20 mg dm−2 h−1 at 10C to 5 mg dm−2 h−1 at 40C. The nature of the NCI-temperature response curve was affected by pretreatment temperature, with NCI being lower at all temperatures except 10C after growth at 20/15C. Photorespiration, which reached its maximum value at a higher temperature (20–30C) than that required for maximum NCI, accounted for 22% of the gross carbon dioxide intake (net carbon dioxide exchange in an oxygen-free atmosphere) at 10C and 55% at 40C. Pretreatment affected the relationship between net carbon dioxide output (NCO) and temperature, with NCO being higher at 10C but lower at 30C after growth at 20/15C as compared to 30/25C.

Studies on the daily course of carbon exchange in alfalfa plants

The diurnal pattern of carbon dioxide exchange is described for plants of cultivars Vernal and Moapa alfalfa (Medicago sativa L.) grown at day/night temperatures of 30/25C and 20/15C, an irradiance of 25 nanoEinsteins cm−2 s−1 (400–700 nm), and a day length of 15.5 h. The net carbon dioxide intake (NCI) of the tops reached 90% of its maximum value after 4–5 h of illumination at 20/15C, but after only 1–2 h at 30/25C; by contrast, NCI of the tops declined after 11–14 h from the start of the photoperiod at 20/15C and after 8.5–10.5 h at 30/25C. Net carbon dioxide output (NCO) of the tops increased throughout the dark period at 20/15C, but remained constant at 30/25C. NCO of the roots remained constant throughout the photoperiod at 20/15C, and increased linearly for 4–8 h at 30/25C. Similarly, NCO of the roots remained constant throughout the dark period at 20/15C, but changed with time (decreased) at 30/25C.