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An in-flight beam of $^{16}$N was produced via the single-neutron adding ($d$,$p$) reaction in inverse kinematics at the recently upgraded Argonne Tandem Linear Accelerator System (ATLAS) in-flight system. The amount of the $^{16}$N beam which resided in its excited 0.120-MeV $J^{\pi}=0^-$ isomeric state (T$_{1/2}\approx5$ $\mu$s) was determined to be 40(5)% at a reaction energy of 7.9(3) MeV/$u$, and 24(2)% at a reaction energy of 13.2(2) MeV/$u$. The isomer measurements took place at an experimental station $\approx30$ m downstream of the production target and utilized an Al beam-stopping foil and a HPGe Clover detector. Composite $^{16}$N beam rate determinations were made at the experimental station and the focal plane of the Argonne in-flight radioactive ion-beam separator (RAISOR) with Si $\Delta$E-E telescopes. A Distorted Wave Born Approximation (DWBA) approach was coupled with the known spectroscopic information on $^{16}$N in order to estimate the relative $^{16}$N isomer yields and composite $^{16}$N beam rates. In addition to the observed reaction-energy dependence of the isomer fraction, a large sensitivity to angular acceptance of the recoils was also observed., Comment: 21 pages, 7 figures

Beta-delayed one-neutron ( β n ) emission has been investigated by confining radioactive ions in an ion trap and detecting the β particles and recoiling nuclei that emerge following decay. In this approach, the β n energy spectrum and branching ratio can be deduced without needing to detect the neutrons, as the neutron emission is inferred from the observed time of flight of the recoiling ions. This paper details the dominant effects that influence the extraction of the neutron energy from the time-of-flight measurement and explores the impact they have on the energy calibration and resolution.

Spectroscopic data, such as precise γ-ray branching and E2/M1 multipole-mixing ratios, provide vital constraints when performing multi-dimensional Coulomb-excitation analyses. Consequently, as part of our new Coulomb-excitation campaign aimed at investigating the role of exotic non-axial (triaxial) deformations in the unstable refractory Ru-Mo isotopes, additional beta-decay data was obtained. These measurements make use of ANL’s CARIBU facility, which provides intense beams of radioactive refractory isotopes along with the excellent efficiency and angular resolution of the GRETINA γ-ray tracking array. In this article, we report on the analysis of the A = 110 decay chain, focussing on the identification of previously unreported states in 110Ru following the decay of 110Tc.

The capabilities of 7 Li-enriched Cs 2 7 LiYCl 6 (C 7 LYC) scintillation detectors for fast neutron spectroscopy are explored in benchmark experiments that exploit its excellent pulse-shape discrimination between neutrons and γ rays, and its unprecedented ≈ 10% energy resolution for fast neutrons in the few MeV range, obtained through the 35 Cl(n,p) reaction. Energy- and angle-resolved elastic and inelastic neutron scattering cross-section measurements of 56 Fe(n,n’) were performed at Los Alamos National Laboratory with a pulsed white neutron source and an array of 1 ″ × 1 ″ C 7 LYC crystals. The results convincingly establish the utility of this dual n/ γ scintillator for fast neutron spectroscopy. Intrinsic efficiency measurements of both 1 ″ × 1 ″ and the first ever 3 ″ × 3 ″ C 7 LYC crystal have been initiated, using mono-energetic fast neutron beams at UMass Lowell generated via the 7 Li(p,n) reaction. The spectroscopic capabilities and potential of C 7 LYC are discussed in the context of developing this emerging scintillator for targeted science applications.

A piecewise-linear model of the Kramers-Kronig (K-K) relations has been used to analyze electromagnetic dispersion data on RF polymers and composites. This K-K analysis revealed that concrete knowledge about the complex low-frequency material dispersion is critical to the analysis and understanding of the microwave dispersion. Furthermore, and more practically, the confidence in the material dispersion measurements may be, to some degree, ascertained through use of the K-K relations.

When making RCS measurements on a ground-bounce range, EPS foam columns are frequently used as target supports for test bodies and air vehicles. Since background subtraction is rarely used to suppress foam-column scattering in large-scale RCS measurements, the columns must be structurally sound while maintaining a minimized RCS signature over the aspect angles, and radar frequency band, of interest. The goal is to devise a column that is unnoticeable in the measured data, yet strong enough to support a specified weight. The major factor that contributes to EPS foam-column scattering is shaping, and finding the optimal shape for a particular test is not trivial. Part 1 of this paper describes methods in the design and construction of EPS foam columns. Subjects include determination of EPS material properties, mathematical specification of column geometries, accurate and efficient computation of column mechanics and scattering, and effective optimization of column parameters. Part 2 of this paper shows comparisons of predicted column RCS to column measurements performed at NRTF. These comparisons give credibility to the concept of foam-column modeling and ground-bounce range scattering simulations, and give range engineers confidence in the foam-column design process.

β -decay spectroscopy of nuclei far from stability can provide powerful insight into a broad variety of topics in nuclear science, ranging from exotic nuclear structure phenomena, stellar nucleosynthesis processes, and applied topics such as quantifying “decay heat” discrepancies for advanced nuclear fuel cycles. Neutronrich nuclei approaching the drip-line are difficult to access experimentally, leaving many key examples largely under studied. The CARIBU radioactive beam facility at Argonne National Laboratory exploits spontaneous fission of 252 Cf in production of such beams. The X-Array and SATURN decay station have been commissioned to perform detailed decay spectroscopy of low-energy CARIBU beams. An extended science campaign was started during 2015; with projects investigating nuclear shape changes, collective octupole vibrations, β -delayed neutron emission, and decay-scheme properties which could explain the reactor antineutrino puzzle. In this article we review the current status of the setup, update on the first results and recent hardware upgrades, and look forward to future possibilities.

At the end of the second year of publication of Field Crops Research the Editor-in-Chief reviewd progress (Norman, 1980). Almost 14 years and more than 30 volumes later, when we have changed to a new format of the journal; when we have just about overcome the publication lag which arose from an increasing number of manuscripts accepted; when we are having to come to terms with new technologies developing around our interests; and when we have some concern that the geographical distribution of the journal and its sources of papers are not yet as wide as is in the best interests of an international journal and the research activity which it encourages, it is appropriate to undertake a review along similar lines to that of 1980. It is based on the publication of the last two years, 1991 and 1992, comprising Volumes 26-30 (inclusive). This excludes Volume 31 which was actually published in late 1992 but carries the 1993 date.

The 82Ge, 84Se, 132Sn, 130Sn, and 134Te (d,p) reactions have been measured with {approx}4-5-MeV-A rare isotope beams and CD2 targets at the HRIBF at ORNL. Energies and spectroscopic strengths have been measured for excitations in 83Ge and 85Se. Direct neutron capture calculations on 82Ge are presented. Preliminary results for single-neutron excitations in 131Sn, 133Sn, and 135Te are reported.

The development of high quality radioactive beams has made possible the measurement of transfer reactions in inverse kinematics on unstable nuclei. Measurement of (d,p) reactions on neutron-rich nuclei yield data on the evolution of nuclear structure away from stability, and are of astrophysical interest. Experimentally, (d,p) reactions on heavy (Z=50) fission fragments are complicated by the strongly inverse kinematics, and relatively low beam intensities. Consequently, ejectile detection with high resolution in position and energy, a high dynamic range and a high solid angular coverage is required. The Oak Ridge Rutgers University Barrel Array (ORRUBA) is a new silicon detector array optimized for the measurement of (d,p) reactions in inverse kinematics.

This paper presents a novel maximum a posteriori estimator for enhancing the spatial resolution of an image using co-registered high spatial-resolution imagery from an auxiliary sensor. Here, we focus on the use of high-resolution panchromatic data to enhance hyperspectral imagery. However, the estimation framework developed allows for any number of spectral bands in the primary and auxiliary image. The proposed technique is suitable for applications where some correlation, either localized or global, exists between the auxiliary image and the image being enhanced. To exploit localized correlations, a spatially varying statistical model, based on vector quantization, is used. Another important aspect of the proposed algorithm is that it allows for the use of an accurate observation model relating the "true" scene with the low-resolutions observations. Experimental results with hyperspectral data derived from the airborne visible-infrared imaging spectrometer are presented to demonstrate the efficacy of the proposed estimator.

This review of the work from our laboratory describes initial studies in which base excision repair in mtDNA was first seen. It considers the results of experiments in which the substrates for mtDNA repair were identified. The discussion then focuses on studies during which the sequence context for mtDNA damage and repair were explored. Next, it addresses factors that have been identified that influence mtDNA repair. Finally, it summarizes the results of studies that evaluated cell-specific differences in the repair of mtDNA and explored some of the biological consequences of these differences.

The pharmacokinetics, tissue distribution and excretion of 14C-labelled aflatoxin B1 (AFB1) were examined after oral administration (250 micrograms/kg body weight) in channel catfish (Ictalurus punctatus). Plasma concentrations of parent AFB1 were best described by a one-compartment pharmacokinetic model, in which peak plasma concentration (503 ppb) occurred at 4.1 hr after dosing. The absorption and elimination half-lives were 1.5 and 3.7 hr, respectively. AFB1 was highly bound (95%) to plasma proteins. Concentrations of 14C (in AFB1 equivalents) measured in the tissues were highest at 4 hr, ranging from 596 ppb in the plasma to 40 ppb in the muscle. AFB1 residues were rapidly depleted; at 24 hr the concentrations in the plasma and muscle were 32 and less than 5 ppb, respectively. Concentrations in the bile exceeded 2000 ppb (at 24 hr), whereas the highest concentration in the urine was 51 ppb (4-6-hr collection interval). Renal and biliary excretion accounted for less than 5% of the administered dose, indicating incomplete absorption. Pharmacokinetic modelling and tissue data demonstrate a very low potential for the accumulation of AFB1 and its metabolites in the edible flesh of channel catfish through the consumption of AFB1-contaminated feed.

Four cultivars of French beans ( Phaseolus vulgaris L.) were grown in the field at a range of plant spacings in two seasons. The distribution of pod sizes, particularly as it affected the uniformity of pod maturity, was examined. Individual plants were more variable in their contribution to yield as density increased. In a glasshouse experiment, a more detailed description of plant form and the distribution of flowering and pod sizes according to positions on the plants were recorded. The nodes which bore the majority of the early flowers became the main yielding nodes. This information allowed an interpretation of yield responses in the field to plant density in terms of patterns of flowering.

Response of cassava to row spacing and plant population density (0.62 plants m−2 in 180-cm rows; 1.23 plants m−2 in 90-, 180-, 270-, and 270- plus 90-cm (i.e. paired rows); and 2.46 plants m−2 in 90- and 180-cm rows), and to soybean intercrop at two row spacings of cassava (90 and 270 cm) was studied at a high latitude (27°S) in south-east Queensland, Australia, where low temperature limits a growing season to 9 months. Detailed observations were made in sole crops on leaf canopy structure and light penetration in the three row spacings at the medium density to allow an estimation of light availability for an intercrop between cassava rows. The low plant density or the 270-cm row plants produced the lowest total dry matter and tuber yield at harvest, while the two higher densities or the two narrower rows produced similar total and tuber dry weight. Intercropped cassava produced a similar tuber yield to the sole crop at the corresponding spatial arrangement, but total dry matter was lower in the former. Leaf area index was similar among the 90-, 180- and 270-cm row spacings in sole crops throughout the growth period. However, leaf area was unevenly distributed horizontally for a longer time as row spacing increased. This resulted in light penetrating the inter-row space for a longer period in wider rows in sole crops, more than 50% full sunlight reaching soil level for 90, 120 and 130 days after planting in the 90-, 180- and 270-cm rows, respectively. This light environment would be available for an intercrop if cassava growth is not affected by the intercrop. The results for cassava intercropped with soybean show that in fact cassava growth was reduced by the associated soybean, and hence light available for the soybean growth would have been more than that estimated above.

To determine if rheumatoid arthritis (RA) patients have an increased frequency of Epstein-Barr virus (EBV) shedding into saliva, throat washings were collected from 59 patients with RA and 64 healthy adult controls. EBV in filtered samples was detected by transformation of human umbilical cord lymphocytes. EBV was detected in 27% (16/59) of throat washings of RA patients compared to 11% (7/64) of control samples. This difference is significant (p less than 0.05). RA patients on steroids had a frequency of positivity of 43% (10/23) compared to 17% (6/36) in patients not on steroids. No correlation was demonstrated between steroid dose received by the patient and detection of EBV in throat washings. Parotid fluid samples were collected from 18 RA patients and 11 healthy controls and were tested for EBV by the transformation bioassay. EBV was detected in 18% (2/11) of samples from normal controls, but samples from RA patients were uniformly negative.

The development of yield in cassava, either as a sole crop or intercropped with quick-maturing soybean sown 1, 5 or 9 weeks after cassava planting, or a succession of two soybean sowings 1 and 14 weeks after planting, was followed at a high latitude (27°S) where the cassava growing season is limited to 9 months by winter temperatures. Competition, at least largely for nitrogen, restricted the growth of cassava, but after soybean harvest, leaf-area index increased such that there was little difference in interception of radiation among crops, and consequently growth rates and thus amounts of assimilate potentially available for tuber growth were similar. Competition from earlier-sown soybean greatly reduced branching by cassava. The reduced number of branches were sufficient to provide adequate leaf-area index, but were a reduced sink for assimilates during the main period of tuber growth. The slightly reduced assimilate supply available in early intercropped cassava was offset by the increased partitioning to tubers. As a result, soybean intercropping did not reduce tuber yield, except slightly in the case of double-intercropped cassava, but provided an additional yield of grain. Land equivalent ratio was particularly high at about 1.6 when soybean was sown within 5 weeks of cassava planting. When soybean was sown 9 weeks after cassava planting, land equivalent ratio was reduced to about 1.3 as a result of lower soybean yield.

The responses in the growth of peanuts (Arachis hypogaea L. cv. Florunner) to plant density and to spatial ratio (ratio of inter-row: intra-row spacing) in a tropical monsoonal environment were investigated. Biological yield (above-ground biomass plus pods) was unresponsive to spatial ratio over the range 1:1-1:7:19, but it increased markedly (12 600-16 900 kg ha−1), with increasing density up to the maximum density of 588 000 plants ha−1. In contrast, economic yield (commercially recoverable pods and kernels) was relatively unresponsive to plant density in the range of 88 000–394 000 plants ha−1, after which a marked decline was recorded (6 500 kg ha−1 pods or 4 900 kg ha−1 kernels, falling to 5 700 kg ha−1 pods or 4 300 kg ha−1 kernels). Economic yields were maximized at square plant-arrangements (6 900 kg ha−1 pods or 5 200 kg ha−1 kernels), but were relatively uneffected by increasing plant rectangularity from spatial ratios of 1:2.15-1:7.19 (6 100 kg ha−1 pods or 4 600 kg ha−1 kernels). The increase in biological yield with increasing plant was primarily attributed to differences in the amount of photosynthetically active radiation (PAR) intercepted (I), which was evident during both vegetative growth and kernel development. In contrast, I was unresponsive to spatial ratio. Neither density nor spatial ratio affected the average efficiency of conversion (Ec) of I to biological yield during vegetative growth (2.6-3.0 g MJ−1) nor during the entire life-cycle (2.1–2.3 g MJ−1). Average Ecm during kernel development was 55–60% of that during vegetative growth. Thus the higher economic yield of the square plant-arrangement was not associated with changes in I and Ec. Rather it was associated with greater partitioning of dry matter to reproductive yield and a greater proportion of total pods recovered at harvest.

Earlier experiments on cassava/soybean intercropping showed that early-maturing soybean reduced the growth of cassava, but that after soybean maturity partitioning of assimilates favoured tuber growth so that tuber yield was not reduced below that of sole cassava. An experiment was conducted to test the hypothesis that this favourable partitioning was due mainly to limited N availability to the intercropped cassava, and also to examine if performance of cassava/soybean intercropping was affected by the level of N application. There were three N treatments in both sole and intercropped cassava; no application, and application of 80 kg N ha-1 either at planting or at day 85 when soybean was harvested in intercropping. The experimental area was irrigated frequently to minimize the development of plant water stress. In sole-cropping, application of N at planting enhanced leaf area and dry-matter production during early stages of growth, but the effects did not persist until the final harvest. Dry-matter partitioning to tubers was reduced, and in consequence tuber yield tended to be less in this treatment than in the no-N control, although not significantly. Application at day 85 had negligible effects on dry-matter production and partitioning. The adverse effect of soybean on the growth and morphology of intercropped cassava was similar to, but more severe than, that of the no-N application in sole crop. Total dry-matter of intercropped cassava was always less than that of sole cassava in any N treatment. Lateral-branch production and leaf turnover were reduced by the presence of soybean, and the consequent reduction in shoot demand for assimilates resulted in an increased proportion of assimilates partitioned to tubers. When N was applied at planting, harvest index was higher in intercropped than in sole cassava, and tuber yield was similar in the two crops. Intercropping under no N application made only a slight further improvement in harvest index over the corresponding sole cassava, while severely reducing total dry-matter production. It appears, therefore, that the tuber-yield advantage of cassava/soybean intercropping is likely to be small under low availability of soil N.

Our previous work has shown that early-maturing soybean is suitable for intercropping with vassava at a high latitude (27°S) in south-east Queensland, Australia, as it does not effect the tuber yield. The present study examines whether later-maturing cultivars of soybean with higher yield potential might be more productive. Plant arrangement for cassava was the same in sole crop and in intercrop, while two soybean rows in every six rows were replaced by a row of cassava in intercropping. All soybean cultivars dominated intercropped cassava, and their dry-matter growth and seed yield were not affected by competition with cassava. Growth of cassava was, on the other hand, severely restricted by intercropped soybean, particularly by late-maturing types. After removal of early-maturing soybean, cassava recovered quickly to produce high leaf-area and effectively intercepted solar radiation. Consequential high total dry-matter production, combined with high assimilate allocation to tubers, resulted in tuber yield at the final harvest similar to that in sole cassava. After the removal of late-maturing soybean, however, recovery was poor, and with a short growing season remaining, tuber yields were only 50–60% of that of sole cassava. In addition to their adverse effect on cassave growth, late-maturing cultivars were not suitable as an intercrop because of low harvest indices and low light-conversion efficiency (dry matter produced per unit intercepted radiation), although total light interception during the whole growth of cassava/soybean intercrop was similar to that of sole cassava. The low overall light-conversion efficiency in intercropping with late-maturing cultivars was due to very low dry-matter production of soybean during pod-filling when light interception was still high.

Soybean ( Glycine max (L.) Merr.) has been shown to acclimate to, and produce high seed yield in, continuously saturated soil. In trials conducted to clarify the physiological mechanisms underlying this potentially valuable trait, soybean cv. Fitzroy was grown on beds in two years at Lawes, S.E. Queensland, and irrigated either continuously (saturated soil culture, SSC) or after 60 mm cumulative open-pan evaporation (conventional irrigation, CI). Shoot growth was initially lower in SSC but subsequently greater than that in CI, particularly during seed growth. Root and nodule growth, nitrogenase activity, and leaf conductance to water vapour were all greater in SSC. Seed yields were 24% and 52% higher in SSC in the two years, and these responses were associated with greater numbers of pods through reduced pod abortion, and higher individual seed weights, in SSC. Nitrogen assimilation by shoots in SSC during seed growth was approximately double that in CI, and during senescence the loss of leaf area and nodule function, and the withdrawal of nitrogen from the leaves, was delayed. It is suggested that enhanced leaf water-status in SSC resulted in greater photosynthesis and sustained nodule during pod growth, which in turn enabled continued nitrogen supply to the seeds and thus delayed the impairment of leaf function which follows nitrogen depletion.

The nature, size, extent, and growth rate of modern electric power systems are discussed along with examples to illustrate the large number of concepts and techniques used and to indicate the variety of technological challenges faced by electric power systems engineers. The discussion then turns to the need for a variety of educational programs to cover the breadth required, to the qualifications for faculty members who staff these programs, and to the ways in which these programs should interact with the power industry. Finally, the electric power systems engineering education program at MIT is discussed in terms of faculity, students, course offerings, and research projects.

The secretion of mouse placental gonadotrophin was studied in vitro . Placental explants from 7–18 days p.c. were co-cultured with 17-day-old mouse fetal testes. The amount of testosterone secreted by these testes served as an indicator for the presence of gonadotrophins. The contralateral testes, cultured without placental tissue, served as controls. The culture medium was collected after one day; the amount of testosterone was determined by RIA. Testes co-cultured with placental explants from early pregnancies (7–8 days) and from late pregnancies (17–18 days) yielded a much higher amount of testosterone than their contralateral controls. Placental explants taken at 10–11 days p.c. had only a slight effect on testosterone secretion; from 13–14 days on a definite gonadotrophin stimulation was found. This biphasic pattern of testicular testosterone secretion by the mouse placenta suggests an early period of placental gonadotrophic activity at a time just before the onset of testis differentiation, and a later period, after day 13, just before the beginning of sex duct differentiation. The latter period coincides with the time at which maternal hypophysectomy is possible without termination of gestation and may thus provide an explanation for this phenomenon. The gonadotrophic stimulation by placental explants from 17 days p.c. could not be blocked by a Visking membrane. This might indicate the presence of a placental gonadotrophin at 17 days p.c. with a molecular weight below 15,000 daltons.

Effects of photoperiod on growth and development of cassava were studied in controlled environments. Plants of cultivars M Aus 7 and M Aus 10 were grown under short (10-h) and long (16-h) photoperiods and harvested at approximately weekly intervals for a period of 13 weeks. Long photoperiods resulted in large increases in leaf area through increases in both number (both cultivars) and size of leaves (M Aus 7 only). The timing, extent and anatomical characteristics of storage root initiation were similar for both cultivars under 10-h and 16-h photoperiods but the subsequent balance between shoot and storage root growth strongly favoured shoot growth in long days. Dry matter partitioning followed a simple allometric pattern with the proportionality between the relative growth rate of shoots and the relative growth rate of storage roots remaining constant with time but being altered by photoperiod. Distribution to storage roots was quantitatively reduced in another experiment using M Aus 10 with each additional 1-h increment from 10-h to 16-h photoperiods. A treatment consisting of a short day (10 h) plus a 1-h night break in the middle of the dark period produced growth similar to long day treatment. Differences in cultivar response (Ceiba, CMC 84 and M Aus 7) to a range of photoperiods (11, 12, 13 and 14 h) were detected in a third experiment. The possible mechanisms and significance of these responses are discussed.

Sorghum plants (cv. RS610) grown in field stands at two population densities were manipulated to increase the supply of assimilates (by removing neighbouring plants) at one of three developmental stages—10-15 days after floral initiation, 1 week prior to three-quarters anthesis, and 1 week after three-quarters anthesis. Post-initiation exposure increased the number of grains per inflorescence 1.8-fold and 3.5-fold in medium and high density populations respectively, but had relatively less effect on grain size. Higher grain number resulted largely from more grains per secondary branch in the lower part of the inflorescence. Neither of the post-heading exposure treatments influenced grain number, but the higher supply of assimilates resulted in larger grains at both densities. Differences at one density only between yield characteristics of plants exposed at the two times provide evidence of inter-plant competition for assimilates to the extent that the potential size of the grain may be affected. Shading (10% light transmission) of plants grown in a glasshouse, whether for 1 week at anthesis or during grain filling, reduced grain yield at maturity by the same amount as the immediate reduction at the end of the shading period. The experiment was unable to demonstrate changes in the potential size of grains resulting from the loss of assimilates at anthesis. There was substantial compensation for the loss by translocation from other plant parts. *Part III, Aust. J. Agric. Res., 26: 11 (1975).

Cassava is a potential tuber crop for northern Australia where water stress is likely to occur during some stages of growth. Field and glasshouse experiments were conducted to examine the response of cassava to soil water deficits which developed at various stages. The field experiments, covering 10-month growth durations from planting in spring to harvesting in winter, showed that water stress occurring in summer or winter had small effects, but in autumn severely reduced the final yield. Autumn was the time of maximum bulking of underground storage organs in well-watered plants, and water stress which reduced assimilate production also reduced bulking. Temperature at this time was suboptimal for canopy development, and leaf area which was reduced during the stress did not increase after its relief, affecting further the growth of storage organs. Similarly, in the glasshouse experiment, plants recovered rapidly during early stages of growth, but when stress occurred later leaf area was reduced greatly, and recovery after its termination was poor. In all experiments, water deficits affected yield of storage organs but not the pattern of assimilate distribution, resulting in similar harvest indices among the plants of different watering treatments. It is concluded that the reduction in cassava yield (cv. M Aus 7) is caused by the reduction in total biomass production, and that stress occurring later in the season is most detrimental to yield because of the additional effect of reduced ability of old plants to recover leaf area after the stress is relieved.

In field and glasshouse experiments with grain sorghum (cv. RS610), the assimilate supply was varied by increasing or decreasing radiation and carbon dioxide supply; the potential grain storage capacity was altered by spikelet removal; and the transport system was reduced by incision of the culm. Plants grown at four population densities in the field were manipulated to increase (by removing neighbouring plants) or decrease (by shading) the supply of photosynthates during grain filling. These treatments affected grain size and thus yield. Removal of some of the spikelets at three-quarter anthesis resulted in a significant increase in the size of those grains remaining at maturity. From anthesis onward, a reduction in the capacity of the transport system in the culm had no significant effect on grain yield. These results are interpreted as evidence that grain yield is not limited by the storage capacity of the grain, or by the transport system involved in moving material from the stem to the grain. Treatments which altered the demand for assimilates by the grain, relative to the supply, did not affect net photosynthesis. Dry matter produced in excess of grain requirements accumulated in other plant parts, including the root. Potential grain size was influenced by interspikelet competition operating within 1 week after three-quarter anthesis. *Part II, Aust. J. Agric. Res., 22: 39-47 (1971).

The effect of water deficit on floral initiation, leaf development and yield of commercial leaf of tobacco planted in the winter was studied in northern Queensland. The deficits were induced by different watering treatments at transplanting in combination with a range of times during which irrigation was withheld after transplanting. In addition, the effect of two periods of water deficits on flower and leaf development was investigated in a pot experiment under controlled environment conditions. Water deficits after transplanting delayed floral initiation and allowed more leaves to be produced. Moreover, the size of most leaves of commercial value was increased by water deficit; for example, withholding water for 28 days after transplanting increased the area and dry weight of commercial yield per plant by 33%. Results from the pot experiment demonstrated that the larger leaf area resulted from an extended period of linear growth and a greater rate of expansion after water deficits were relieved.

Growth analysis was applied to grain sorghum (cv. RS610) grown at low, medium and high population densities, i.e. 14,352, 143,520 and 645,836 plants ha-1 respectively. The medium densities had two arrangements of plants, square (S) and rectangular (R). Crop growth rates, inflorescence growth rates, leaf area indices, net assimilation rates and leaf growth rates were calculated from growth functions of plant dry matter and leaf area over time. Differences in crop growth rate between populations in the early stages were attributed to leaf area development—specifically to the initial leaf area (dependent on seedling number) and not to differences in leaf growth rates. Peak crop growth rates were 15.0, 27.5, 26.0 and 45.8 g m-2 day-1 for the low, medium (S), medium (R) and high populations respectively.The large difference between the growth rates of the medium (S) and the high populations was not explained by differences in the amount of radiation intercepted. Although leaf area indices were 4.6 and 10.2 respectively for the two populations, both canopies intercepted almost all of the noon radiation. Light extinction coefficients were 0.45 and 0.29 respectively. The relationship between net assimilation rate and leaf area index was such that for comparable leaf area indices above 2, plants at higher densities showed greater improvement in yield per unit increment in leaf area index. A maximum grain yield of 14,250 kg ha-1 was obtained at the high population density as a result of higher dry matter production, but a similar harvest index to that of the crops grown at the other densities. Inflorescence growth rate (g m-2 day-l) slightly exceeded crop growth rate in the latter part of grain filling, which indicated that there was some retranslocation to the grain of previously assimilated material. The maximum grain yield represents an efficiency of utilization of short-wave solar radiation during crop life of 2.5 x 10-6g cal-1. *Part IV, Aust. J. Agric. Res., 26: 25 (1975).

The relative contributions of different photosynthetic sites to the filling of the grain in grain sorghum (Sorghum vulgare cv. Brolga) were estimated by measuring the 14C in the grain after exposing various leaves and the head to radioactive carbon dioxide. Methods for preventing photosynthesis were also used. Of the grain yield, 93% was due to assimilation by the head and upper four leaves. The head contribution of 18 % was due equally to direct assimilation of atmospheric carbon dioxide and to reassimilation of carbon dioxide released within the grain by respiration of material translocated from the leaves. The remaining 75 % was equally assimilated by the upper four leaves, the flag leaf being the most efficient contributor per unit area and the third uppermost leaf the least efficient. The percentage contributions to the grain by the flag leaf and fourth leaf, estimated from the decrease in grain yield when they were shaded, agreed closely with the estimates obtained by using 14CO2.

Sorghum plants were allowed to assimilate known relative amounts of 14C in the two periods: (i) from full expansion of the third uppermost leaf to anthesis; and (ii) from anthesis to grain maturity. By comparing relative 14C activity in the mature grain, the relative partitioning of photosynthate between grain production and other uses in the two periods was calculated. Plant and grain dry weight data from another experiment showed the amounts of net photosynthesis in the two periods. It was then possible to calculate the maximum amount of the material assimilated in the pre-anthesis period that could have gone to grain production, and thus the percentage of grain material derived from this earlier period. The estimate was 12%.