bluuebunny/crossref_metadata_2025 huggingface dataset:
Net Carbon Exchange Rates of Field-Grown Crops in Relation to Irradiance and Dry Weight Accumulation
Authors: Sale PJM
Published: January 2006

A range of summer and winter vegetable crops has been grown under favourable conditions, and the relation between net carbon exchange and irradiance determined at several stages of growth, using large field assimilation chambers and semi-closed gas analysis systems. For all crops, leaf area index was an important determinant of net carbon exchange rate during early stages of growth, and rates increased markedly from day to day during the period of rapid vegetative development. Except for cauliflower and cucumber, for which leaf area ceased to be so important as the crops developed, maximum rates of CO2 uptake were achieved at maximum leaf areas, and were in excess of 90 mg CO2 dm-2 (ground area) h-1 for sweet corn, about 64 for rockmelon, 50 for broad bean, cauliflower and cabbage, and 45 mg dm-2 h-1 for cucumber. For both rockmelon and cucumber, net carbon exchange rates in the morning were often greater than those at the same irradiances in the afternoon, which suggests partial stomatal closure at about midday. In all crops, variations in temperature of up to 10°C either side of the ambient temperature, imposed at any time during the day, generally had little effect on negative CO2 flux (uptake), but positive CO2 flux at night was strongly influenced by temperature. In cucurbits uptake was reduced at temperatures above 35°C, but rapidly recovered when the temperature was again lowered. High growth rates were achieved by all crops for most months of the year, and the efficiency of utilization of incident energy was also high compared with other reported values. However, growth rates were not related to the maximum rates of CO2 uptake in the day, for net carbon exchange over each 24 h depended also on factors such as the ratio between day- and nightlength and night temperatures.
Altitudinal Variation in the Photosynthetic Characteristics of Snow Gum, Eucalyptus pauciflora Sieb. ex Spreng. IV. Temperature Response of Four Populations Grown at Different Temperatures
Authors: Slayter RO
Published: January 2006

Photosynthetic temperature response curves were measured at leaf temperatures from 10 to 40°C on seedlings of E. pauciflora grown from seed collected at tree-line (elevation 1905 m) in the Snowy Mountains area and at three lower elevations, 915, 1215 and 1645 m, which correspond to those used in an earlier field study (Slatyer and Morrow 1977). The material was grown in naturally lit, temperature-controlled greenhouses at day/night temperatures of 8/4, 15/10, 21/16, 27/22 and 33/28°C. Comprehensive measurements were made on the tree-line population, in which peak rates of net photosynthesis, Pamb, reached 75 ng cm-2 s-1 at a temperature of 20�°C, from material grown at 21/16°. Minimum levels of intracellular resistance, rt, were 2.8 s cm-1, and of leaf gas-phase resistance to CO2 transfer, r1, were 3.2 s cm-1. Changes in rt and r1, with measurement temperature, appeared to be of approximately equal importance in mediating the overall photosynthetic temperature response. Changes in the CO2 compensation point, Γ were of increasing importance at higher measurement temperatures. The photosynthetic temperature optimum was markedly affected by the growth temperature regime. In the tree-line population, it increased from about 16° when grown at 8/4° to 24° when grown at 33/28°. The relationship between the observed photosynthetic temperature optimum and the day temperature of the growth regime indicated a preferred temperature for photosynthesis of 20.0°, and a tendency for the temperature optimum to shift by 0.34° per degree shift in the day growth temperature. A similar effect of growth temperature on the photosynthetic temperature optimum was noted in the three lower-elevation populations, in which preferred temperatures of 21.5, 24.2 and 27.2° were calculated for the material collected at 1645, 1215 and 915 m respectively. These temperatures were several degrees higher than the field-observed temperature optima, although the gradient of preferred temperature with elevation was comparable to that noted in the field study.
Photosynthesis and Respiration of Developing Soybean Pods
Authors: Sambo EY , Moorby J , Milthorpe FL
Published: January 2006

Net CO2 uptake by soybean pods in the light was much less and output in darkness much greater than from equal areas of leaves. The net photosynthesis decreased, becoming negative, and dark respiration increased as seed filling progressed. The photochemical efficiency was the same but the diffusive resistance of pods was about twice and the internal resistance two to three times those of leaves. Fluxes into open deseeded pods were initially much greater than into intact pods but drying out of the tissue soon led to fluxes only about three times greater.
From these measurements and light- and CO2-response curves of intact pods, estimates of gross photosynthesis, photorespiration and dark respiration of seeds and hulls were made. These indicated that seed reassimilated slightly more CO2 than they respired when young and about two-thirds thereof at a later stage. Hulls fixed about similar amounts but these were insufficient to prevent net effluxes from pods during the later stages of their development, even at irradiances of 190 W m-2.
On a daily basis, direct uptake of CO2 made a negligible contribution to the total import of dry weight by the pod; nevertheless, photosynthesis in the seeds and hulls refixed some 50-70% of the CO2 respired by these tissues.
Factors Influencing the Rate and Duration of Grain Filling in Wheat
Authors: Sofield I , Evans LT , Cook MG , Wardlaw IF
Published: January 2006

Controlled-environment conditions were used to examine the effects of cultivar and of temperature and illuminance after anthesis on grain setting and on the duration and rate of grain growth. After an initial lag period, which did not differ greatly between cultivars, grain dry weight increased linearly under most conditions until final grain weight was approached.
Growth rate per grain depended on floret position within the ear, varied between cultivars (those with larger grains at maturity having a faster rate), and increased with rise in temperature. With cultivars in which grain number per ear was markedly affected by illuminance, light had relatively little effect on growth rate per grain. With those in which grain number was less affected by illuminance, growth rate per grain was highly responsive to it, especially in the more distal florets. In both cases there was a close relation between leaf photosynthetic rate as influenced by illuminance, the rate of grain growth per ear, and final grain yield per ear.
The duration of linear grain growth, on the other hand, was scarcely influenced by illuminance, but was greatly reduced as temperature rose, with pronounced effects on grain yield per ear. Cultivars differed to some extent in their duration of linear growth, but these differences accounted for less of the difference in final weight per grain than did those in rate of grain growth. Under most conditions the cessation of grain growth did not appear to be due to lack of assimilates.
Light-Enhanced Dark 14CO2 Fixation by Leaves in Relation to the C4 Dicarboxylic Acid Pathway of Photosynthesis
Authors: Raghavendra AS , Das VSR
Published: January 2006

The technique of light-enhanced dark carbon dioxide fixation has been employed to critically examine the primary route of CO2 incorporation in leaves of two C4 plants (Setaria italica and Amaranthus paniculatus) in comparison with that of a C3 plant (Rumex vesicarius). Prior illumination of detached leaves enhanced their dark 14CO2 fixation five- to tenfold over that of unilluminated leaves. No variation was observed among C3 and C4 plants, in the conditions required for their light-enhanced dark fixation. Fifty to sixty percent of initially incorporated radioactivity by the leaves of R. vesicarius was in 3-phosphoglycerate. The leaves of S. italica and A. paniculatus fixed most of the radioactivity into the C4 acids malate and aspartate. Sugar phosphates, including 3-phosphoglycerate, were not labelled at all. Our data confirm that, in C4 plants, CO2 is initially fixed through phosphoenolpyruvate carboxylation and thus disprove earlier claims that ribulose bisphosphate can be the primary acceptor of CO2 in a C4 plant. The observations further suggested that aspartate formation during carbon fixation might be favoured by illumination.
Acid Phosphatase Activities in Developing Seeds of Pisum sativum L
Authors: Murray DR , Collier MD
Published: January 2006

The seedcoats contain almost all of the acid phosphatase activity (EC 3.1.3.2) in the pea seed in the earliest stages of expansion. The seedcoat activity is maximal by the end of the period of rapid cell expansion and declines as the embryo matures. The developing cotyledons show a later rise in acid phosphatase activity to a maximum shortly before dehydration. The activity in the embryonic axis shows a marked increase only during dehydration.
The acid phosphatase activity in the seedcoats results almost entirely from an isoenzyme with high electrophoretic mobility in 5.5% polyacrylamide gels (RF 0.97). This isoenzyme has not been detected in other tissues from the plant. The phosphatase activity in the cotyledons is accounted for by one major isoenzyme at RF 0.75 and by four minor components. The partially purified enzyme from the seedcoats shows a broad pH optimum from pH 5.0 to pH 6.0. In contrast, the preparation from the cotyledons has an optimum close to pH 5.6 and is slightly more sensitive to inhibition by 0.2 mM PI.
Enhancement by Low Temperatures of the Anaerobic Induction of Cocklebur Seed Germination
Authors: Esashi Y , Ohhara Y
Published: January 2006

Non-dormant, upper cocklebur (Xanthium pensylvanicum Wallr.) seeds, incapable of germinating under ordinary conditions, can germinate when previously subjected to anaerobiosis; this has been termed the anaerobic induction of seed germination. Aerobic presoaking of the seeds was also required for successful anaerobic induction, and exerted two counter-acting effects on seed germination.
When the time period of aerobic presoaking was sufficiently prolonged, the increasing duration of an anaerobic treatment resulted in proportional increase of germination potential but, when it was short, the effect of the anaerobiosis was saturated in a few days. Prolonging the aerobic presoaking period caused less response of the seed to the anaerobic induction, suggesting the development of some germination-inhibiting system during the aerobic presoaking period. This system could not develop in the absence of O2 or at low temperature. Thus, low temperature during prolonged presoaking produced a maximal response to anaerobic induction. Various germination stimulants, CO2, ethylene, gibberellic acid and benzyl adenine, did not significantly alter the effects of the presoaking.
Contrasting Responses of Morphologically Similar Wheat Cultivars to Temperatures Appropriate to Warm Temperature Climates With Hot Summers: a Study in Controlled Environment
Authors: Bagga AK , Rawson HM
Published: January 2006

This study attempted to determine if and why there are differences among three cultivars of wheat in their responses to temperature. The three semidwarf cultivars examined, Kalyansona, Condor and Janak, are currently used commercially. Temperature regimes chosen matched the range to which plants in warm temperate climates with hot summers would be exposed at different stages of development. Plants were grown in a phytotron in sunlit cabinets.
Responses to temperature were different among the cultivars. Kalyansona was relatively un- responsive to temperatures during the floret phase, being little affected in the sizes of upper leaves, in floret production and grain set, in overall plant growth or in grain yield. The sole character to respond to temperature in this cultivar was kernel weight, which declined with increasing grain phase temperature. In contrast, Condor demonstrated marked plasticity during the floret phase in all plant characters measured. Its plasticity was such that, at the lower temperatures, it outyielded Kalyansona by a substantial margin while at the higher temperatures its yield was relatively poor. On a plant basis, Janak performed similarly to Condor. Rates of photosynthesis were relatively unaffected by temperature in any cultivar.
This wide range of response among three superficially similar cultivars has promising implications for the tailoring of cultivars for different temperature zones. The importance of different plant characters to temperature stability is considered in the discussion.
Assimilate Source-Sink Relationships in Capsicum annuum L. III. The Effects of Fruit Excision on Photosynthesis and Leaf and Stem Carbohydrates.
Authors: Hall AJ , Milthorpe FL
Published: January 2006

Removal of the rapidly growing fruit from a Capsicum plant reduced the rate of net CO2 uptake by its leaves by up to 30% during the time period explored (0.5 - 7 days). This reduction was associated with increases in both the leaf (to about 200%) and intracellular (to about 30%) resistances, these changes having about equal effects on reducing the rate of CO2 uptake. Changes in photorespiration, dark respiration and CO2 compensation point were very small. The rate of CO2 uptake and the associated resistances were also changed by modifying the light regime and other factors affecting the source-sink balance.
Changes in the leaf resistance were not attributable to variations in the internal CO2 concentration or in the water economy of the leaf; its control mechanism remains unexplained.
The concentration of soluble sugars in the source leaf was completely unaffected but that of polysaccharides was changed by defruiting and by 50% defoliation. However, variations in the intracellular resistance were not closely related to these changes and there is yet no evidence of the nature of its control mechanism. Changes in both soluble sugars and polysaccharides in the stem were more pronounced than in the leaves.
Relation Between Salt Tolerance and Long-Distance Transport of Sodium and Chloride in Various Crop Species
Authors: Lessani H , Marschner H
Published: January 2006

The effect of NaCl concentrations up to 100 mM in the nutrient solution upon dry matter production and mineral composition of seven plant species was studied in a pot culture experiment.
The plants could be arranged into three groups according to the depression in dry matter production at 100 mM NaCl: tolerant (sugar beet; maize, cv. Velox); moderately tolerant (cress; sunflower; safflower; maize, cv. DC 790); and sensitive (pepper; bean, cv. Saxa and Contender). In all plant species, the chloride content increased more than the sodium content in the shoots with an increasing supply of NaCl. Differences between plant species were much higher in sodium content than in chloride content. In most plant species, a supply of NaCl decreased the potassium content much less than the calcium content.
Application of labelled sodium (22Na) and chloride (36Cl) to the leaves of plants without supplying NaCl to the roots revealed great differences between the species with regards to sodium and chloride retranslocation. No correlation could be found, however, between the retranslocation rates of chloride and sodium respectively within a particular plant species.
Part of the retranslocated 22Na and 36Cl had been lost through efflux from the roots. The efflux of 36Cl was low in all plant species. The efflux of 22Na was generally higher and differed considerably between the plant species, ranging from zero in sugar beet to 14% in bean. A significant positive correlation exists between this efflux of 22Na in the various plant species and the corresponding growth depression caused by an increasing supply of NaCl.
The Weights of Individual Grains of the Wheat Ear in Relation to Their Growth Potential, the Supply of Assimilate and Interaction Between Grains
Authors: Bremner PM , Rawson HM
Published: January 2006

The work reported here was done to explore the extent to which the mature weight of a grain is determined by (i) its potential for growth, defined as its intrinsic capacity to accumulate dry matter, and (ii) the resistance to assimilate transport imposed by the vascular system of the ear. Estimation of growth potential was attempted by observing the effects of systematic patterns of grain removal on the mature weights of grains remaining, these being compared with weights of matched grains from intact ears. Resistance to transport of assimilate was inferred from the apparent order of priority between grains for the supply of assimilate, as revealed by comparing their weights when assimilate supply was either normal, or reduced by plant shading.
When neighbouring grains were removed, those remaining usually grew larger to an extent that indicated growth potential appreciably in excess of that utilized in intact ears under the most favourable conditions. Although grains within a spikelet of an intact ear attain quite different weights, the experiments suggested that their differing potentials for growth seemed to play only a minor role in this, and that the major influence was the relative ease with which assimilate could reach the grains; this depended largely on the distance of the grains from the spike rachis. Comparing between spikelets, the difference found in intact ears between grains in the same spikelet location tended to persist when some grains were removed from each spikelet, indicating a possible role of growth potential as a controlling influence. This may be partly due to the sequence of morphogenesis, established as early as the double ridge stage.
Although the removal of competing grains within a spikelet usually enhanced the growth of the one remaining, this was not always so; there was evidence from one experiment that removal of competing grains towards the spikelet apex represented the removal of some beneficial influence.
The bearing of the results on possible limitations to grain yield are discussed.
Effect of Sodium Chloride on Expansion Rates and Invertase Activity of Leaves
Authors: Hawker JS , Walker RR
Published: January 2006

The rate of expansion and the invertase (�-fructofuranosidase, EC 3.2.1.26) activity of leaves of two relatively salt-sensitive plants, Phaseolus vulgaris and Zea mays, decreased with increasing concentrations of NaCl from 0 to 50 mM in nutrient solutions supplied regularly in a porous growth medium. Sucrose concentrations in the leaves were higher and reducing sugar concentrations were lower at the higher concentrations of NaCl. Growth of leaves, invertase activity, and concentrations of reducing sugar and sucrose changed much less, if at all, with NaCl treatment of Hordeum vulgare, a reasonably salt-tolerant plant. Cellulase activities were not different in bean leaves from plants grown on different NaCl concentrations. The Km values for sucrose for invertase from bean leaves were 5.8, 8.1 and 10.4 mM for plants grown on 0, 20 and 50 mM NaCl respectively. NaCl at concentrations up to 200 mM did not affect the in vitro activity of invertase from barley, bean or maize leaves.
Effect of Nitrogen Source on Grain Development in Detached Wheat Heads in Liquid Culture
Authors: Donovan GR , Lee JW
Published: January 2006

Detached wheat heads (8 days post anthesis) were grown in liquid culture using media containing various nitrogen sources at different concentrations. Grain development in terms of dry weight, nitrogen, starch and protein were equivalent whether the nitrogen was supplied as either a complete spectrum of amino acids or as glutamine, asparagine or ammonium nitrate.
Where the concentration of nitrogen in the culture medium was varied while maintaining the sucrose concentration constant, no variations were observed in the rate of grain dry weight or starch accumulation. Nitrogen per grain and percentage grain nitrogen increased with increasing concentrations of nitrogen in the culture medium. Percentage grain nitrogen was higher in the 'high protein' cultivar Timgalen than in the 'low protein' cultivar WW 15 at equivalent nitrogen concentrations in the culture medium, but differences in percentage proteins were only small.
Effect of Temperature on Growth of Five Subtropical Grasses. I. Effect of Day and Night Temperature on Growth and Morphological Development
Authors: Ivory DA , Whiteman PC
Published: January 2006

Cenchrus ciliaris, Chloris gayana, Panicum maximum var, trichoglume, Panicum coloratum var. makarikariense and Pennisetum clandestinum were grown in two experiments in controlled environments, each experiment having all possible day/night temperature combinations of (1) 10, 20, 30, and 40°C and (2) 15,25, 30 and 35°C.
Both day and night temperatures significantly affected growth in all species. Growth was greatly restricted by constant temperatures of 10 and 15°, while maximum growth rates occurred at 29-35°C day temperatures with 26-30°C night temperatures. At optimum or supra-optimum temperatures a diurnal variation in temperature gave higher growth rates than a constant temperature for the same daily mean. By contrast, at suboptimum temperatures a constant temperature gave the highest growth rates and growth rate was decreased as the diurnal variation about a given daily mean temperature was increased.
Mathematical functions relating the growth of each species to day and night temperature and maximum growth rate at optimum temperatures were developed.
The effect of temperature on relative growth rate (Rw) was mediated through its effect on net assimilation rate (EA). Night temperature was found to affect Rw and EA independently of day temperature and therefore a prehistory effect of night temperature on photosynthesis in the subsequent day was indicated.
Temperature had significant effects on tillering in P. maximum and P. clandestinum but had little effect in C. gayana, C. ciliaris and P. coloratum. The optimum temperatures for leaf growth and leaf area development in C. ciliaris and C. gayana were higher than the optimum temperatures for growth of the whole plant, while optimum temperatures for stem growth were lower. In P. maximum, P. coloratum and P. clandestinum, optimum temperatures for all growth components were similar.
Differences between temperate and tropical grasses in morphological reaction to temperature are discussed.
Agronomic and Physiological Responses of Soybean and Sorghum Crops to Water Deficits. III. Components of Leaf Water Potential, Leaf Conductance, 14co2 Photosynthesis and Adaptation to Water Deficits.
Authors: Turner NC , Begg JE , Rawson HM , English SD , Hearn AB
Published: January 2006

Concurrent measurements of leaf water potential, leaf osmotic potential, leaf relative water content, quantum flux density, leaf conductance, 14CO2 photosynthesis, soluble and insoluble sugars, starch and potassium concentrations were made diurnally on six occasions between flowering and maturity on upper leaves of irrigated and rainfed crops of soybean (cvv. Ruse and Bragg) and a rainfed crop of sorghum (cv. TX 610). With adequate soil water, sorghum had lower values of leaf conductance than did soybeans at high light and yet had higher rates of photosynthesis. Stage of plant development had no effect on either leaf conductance or photosynthesis of the youngest fully expanded leaves of both sorghum and soybean, but starch accumulation in the leaf over the day was less at grain-filling than at flowering in the soybean. Starch and sugar levels in the leaf had no apparent effect on photosynthesis.
The daily minimum leaf water potential decreased in Ruse soybean from - 1.5 to -2.7 MPa as soil water was depleted. Late in the drying cycle, the daily minimum leaf water potential was higher in Bragg than in Ruse. In both cultivars, stomatal closure and decrease in 14CO2 photosynthesis commenced at leaf water potentials below - 1.5 MPa. Thus, the effect of water deficits on leaf conductance and photosynthesis occurred later in the drying cycle in Bragg than Ruse. As photosynthesis decreased with the depletion of soil water, starch accumulation in leaves of both cultivars of soybean decreased; changes in soluble and insoluble sugars and in potassium were small.
The relationships among leaf water potential, osmotic potential, turgor potential, and leaf relative water content did not change with season or soil water depletion. Bragg and Ruse soybeans showed a similar response and both approached zero turgor at the same relative water content (82-83 %) and the same leaf water potential (- 1.5 to - 1.7 MPa). No evidence ofr osmotic adjustment was found in either soybean cultivar.
Potassium Chloride in the Motor Tissue of Stylidium
Authors: Findlay GP , Pallaghy CK
Published: January 2006

Electron probe micro-analysis of the motor tissue in the column of S. graminifolium shows a relatively high concentration of potassium and chloride (about 600 mM) in the anterior cells of the tissue compared with other regions, prior to and immediately after the rapid movement of the column. The distribution of KCl is more widespread during the slower resetting movement of the column. It is suggested that the fast movement (a cross-fertilization mechanism) and the subsequent slow resetting movement are brought about by changes in turgor pressure in the anterior cells, with the principal osmoticum being KCl. The fast movement could be produced by a sudden loss of KCl and water from the anterior cells to the extra-cellular space, after which the KCl would diffuse into other regions of the column, while at the same time being reaccumulated into the anterior cells during the slower time of resetting of the column. When the column is fully reset, most of the KCl would again be in the anterior cells.
Cotyledonary Storage Proteins in Pisum sativum. I. Molecular Heterogeneity
Authors: Thomson JA , Schroeder HE , Dudman WF
Published: January 2006

The two storage-protein fractions of pea seeds, legumin and vicilin, have each been resolved electrophoretically on a cellulose acetate gel matrix into multiple molecular species distinguished by electrophoretic mobility and by quantitative or qualitative differences in subunit composition or both. Electrophoretograms of these apparent holoproteins from a range of lines and cultivars were found to be genotype-specific, generally showing three strong bands, together with up to three additional minor bands, assignable to a vicilin series of components. A further three or four bands could be assigned to a legumin series, although the slowest of these showed apparent admixture of certain polypeptides typical of the vicilin fractions. Each putative holoprotein band in both the legumin and vicilin series behaved additively in the electrophoretograms of F1 offspring from reciprocal crosses between lines showing distinct patterns.
For comparison with the proteins distinguished electrophoretically on cellulose acetate gels, storage proteins from lyophilized protein bodies were fractionated on the basis of differential solubility at various ionic strengths and pH values. The single legumin and three vicilin fractions obtained by this method showed sedimentation velocities typical of the respective holoproteins. No overlap in the polypeptide composition of legumin with that of vicilin fractions was observed. The components represented in the four fractions accounted for all the major polypeptides in total storage-protein extracts and in the bands eluted from cellulose acetate gels. The distinctive polypeptide pattern and electrophoretic mobility of vicilin fraction 4 identified this protein as a contaminant of slow legumin bands in cellulose acetate gels, and as an additional vicilin species not recognized directly from the electrophoretic analysis.
Water Uptake by Mycorrhizal Roots of Radiata Pine Seedlings.
Authors: Sands R , Theodorou C
Published: January 2006

Seedlings of radiata pine (Pinus radiata D. Don) grown in a sandy soil inoculated with Rhizopogon luteolus had 72% of their short roots mycorrhizal at age 5 months whereas the uninoculated controls had only 6.0 %.
When water was withheld from the soil and soil water matric potential became more negative, the leaf water potential of both inoculated and uninoculated plants became more negative, transpiration rate was reduced, and the derived resistance of the plant plus soil to the flow of water increased. There was no significant difference between inoculated and uninoculated plants in transpiration rate, but leaf water potential was more negative and consequently the derived resistance of plant plus soil was greater in the inoculated plants. The resistance of plant plus soil was partitioned using a simple whole-plant model. Resistance within the soil was considered more significant than that in the plant, and the greater soil resistance associated with the inoculated plants was considered to be due to differences in root geometry.
Functioning of Conducting Elements of Phloem and Xylem in the Stalk of the Developing Fruit of Lupinus albus L
Authors: Pate JS , Kuo J , Hocking PJ
Published: January 2006

The economy of water and dry matter in fruits of white lupin (L. albus L.) was studied by measuring transpiration, CO2 exchange and weight changes over an 8-week growth period. These data were combined with analyses of upper stem tracheal (xylem) sap and fruit tip phloem sap to estimate rates of import of dry matter and water through xylem and phloem. Assuming unidirectional mass flow to operate, phloem carried 97 % of the dry matter and 27 % of the water entering the fruit, and xylem supplied the remainder of the water, 30 % of the minerals and 10 % of the amino compounds.
The structure of fruit stalks of various age was examined by light microscopy. Cross-sectional areas occupied by different tissues were measured, and numbers and mean transverse areas of conducting elements estimated. Sieve tubes comprised 0.66-1.13% of the stalk's cross-sectional area, vessels plus tracheids 0.27 - 0.50%. Secondary xylem consisted mainly of fibres. Sieve tubes occupied 18 - 27% of the phloem cross-sectional area. The fully grown stalk showed approximately three times as many sieve tubes in transverse section as vessels plus tracheids.
Transfer of dry matter and water through the fruit stalk was highest during the exponential phase of fruit growth. Peak specific mass transfer in sieve tubes was 3.95 g dry matter per square centimetre of sieve tube per hour, in tracheids plus vessels 0.28 g cm2 h-1. Maximum flow velocity in sieve tubes was 22 cm h-1, in tracheids plus vessels, 147 cm h-1. Values for specific mass transfer and flow velocities were several times less in stalks of very young or near-mature fruits.
Isolation and Composition of the Seed Globulins of Winged Bean, Psophocarpus tetragonolobus (L.) DC
Authors: Gillespie JM , Blagrove RJ
Published: January 2006

The amino acid composition of winged bean seed meal is similar to that of soybean but their storage globulins are quite different. Winged bean proteins are soluble to the extent of 60% at the pH of a meal-water slurry (pH 6.6), 80% at pH 11 but only 12% at pH 5. However, the proteins are soluble to the extent of 80% from pH 5 to 9 in 10% NaCl rising to 90% at pH 11. There are no satisfactory ways of recovering all the proteins from solution by simple changes in pH or ionic strength.
Winged bean seed contains major proteins with sedimentation coefficients of 2 S and 6 S. Electrophoresis on cellulose acetate resolves three globulin fractions which we have named psophocarpins A, B, and C. The proteins from these electrophoretic regions have been isolated and partially purified. Psophocarpin A is essentially a single protein comparatively rich in sulfur-containing amino acids while the other fractions are composed of a number of related components which have not been separated.
When examined by SDS-polyacrylamide gel electrophoresis, the globulin fractions differed in the kind of subunit proteins they contain and in the extent of disulfide bonding. The 40 000 mol. wt subunit of psophocarpin A contains disulfide bonded chains of mol. wt 16 000 and 24 000. The proteins corresponding to the other electrophoretic regions are more complex.
Variability of the Seed Globulins of Winged Bean, Psophocarpus tetragonolobus (L.) DC
Authors: Blagrove RJ , Gillespie JM
Published: January 2006

Extracts from the seeds of 80 pure lines of P. tetragonolobus found in Papua New Guinea have been examined by polyacrylamide gel electrophoresis, There was little difference between the electrophoretic patterns except for variation in the proportion of one polypeptide. In its unreduced form, this polypeptide is the single subunit of psophocarpin A. A number of these genotypes have been studied more closely to obtain information regarding their protein content and the influence of extraction conditions on the protein pattern observed.
Salinity Damage to Norfolk Island Pines Caused by Surfactants. III. Evidence for Stomatal Penetration as the Pathway of Salt Entry to Leaves
Authors: Grieve AM , Pitman MG
Published: January 2006

The paper describes the effect of varied surfactant concentrations on penetration of NaCl into leaves of Norfolk Island Pine, Araucaria heterophylla (Salisb.) Franco. It confirms that the damage observed along the sea-coast in Sydney is similar to that produced by high NaCl levels in the foliage. The effect of surfactant in increasing NaCl uptake from sea-water spray is related to the reduction in surface tension and to the advancing contact angle of the spray on the leaf surface. It is suggested that sea-spray enters A. heterophylla needles through the stomata, and that the cuticle is particularly resistant to NaCI, compared with other plant species. Similar penetration and damage was found with sprays of CaCl2, MgCl2 and KCl showing that the damage was not due specifically to NaCI.
Effect of Temperature on Photoreductive Activity of Chloroplasts From Passionfruit Species of Different Chilling Sensitivity
Authors: Critchley C , Smillie RM , Patterson BD
Published: January 2006

The Hill reaction activity of chloroplast membranes isolated from five Passiflora species of different chilling sensitivity was determined as a function of temperature over the range 0 - 40°C. Activity was measured by the photoreduction of ferricyanide in the presence of gramicidin D. In two lowland tropical and chilling-sensitive species, P. quadrangularis and P. edulis forma flavicarpa, the apparent Arrhenius activation energy (Ea) for ferricyanide photoreduction was more than doubled at temperatures below 16 and 10°C, respectively. This increase in Ea was also characteristic of more chilling- resistant species. P. cincinnata, which is intermediate in chilling sensitivity between the two lowland tropical and the other two species studied, showed an increase in Ea below 15°C. A hybrid of this species with P. edulis forma flavicarpa behaved similarly. In chloroplasts from P. edulis, a species relatively resistant to chilling temperatures, there was an increase in Ea below 16°C, like that shown by P. quadrangularis, as well as another increase below 4°C. P. caerulea, the most chilling-resistant of the species studied, showed changes in Ea at 7 and 19°C. Thus, there was no clear correlation between the chilling sensitivity or resistance of a species and the presence or absence of a change in the temperature dependence of the Hill activity at low temperatures.
The heat stability of the photoreductive activity of chloroplasts isolated from the various Passiflora species also did not correlate with their chilling sensitivity. The heat stability of photoreductive activity in the most cold-tolerant species, P. caerulea, was comparable with that found for the tropical species, while chloroplasts from P. cincinnata were more heat-labile than chloroplasts from the other species.
Movement of the Column of Stylidium crassifolium as a Function of Temperature
Authors: Findlay GP
Published: January 2006

The column of the flower of S. crassifolium when mechanically stimulated moves through an angle of about 4 rad in 15 ms and then resets more slowly in several hundred seconds. The rates of the firing and resetting as a function of temperature have been investigated. Arrhenius plots of these rates are approximately straight lines yielding energies of activation of ~ 8 kJ mol-1 for firing and ~72 kJ mol-1 for resetting. These results suggest that resetting is the 'active' part of the movement, and is closely linked to the metabolic energy supply. The rate of firing is more likely limited by friction within the cell walls of the motor tissue, or possibly by the viscosity of extracellular water.
Effect of Thermal History on Photosynthate Translocation and Photosynthesis
Authors: Fussell LK , Pearson CJ
Published: January 2006

Plants of Pennisetum americanum, previously grown at a lower temperature, exhibited relatively low 14C translocation and photosynthetic rates when moved to a warmer environment. The source leaves retained the same amount of photosynthate as did leaves of plants that were grown continuously at high temperature. We hypothesize that the lack of adaptation is due to leaf structure, determined during pretreatment, limiting the above processes.
Enzymes of Nitrogen Metabolism in Legume Nodules: a Comparative Study
Authors: Boland MJ , Fordyce HM , Greenwood RM
Published: January 2006

Levels of activity of glutamine synthetase, glutamate dehydrogenase and NADH-dependent glutamate synthase in nodule cytoplasm extracts of twelve herbaceous legume species have been measured. Nodules of all species contained substantial quantities of glutamine synthetase. Levels of glutamate synthase were found to be between 7 and 100% of those of glutamine synthetase, while levels of glutamate dehydrogenase varied widely between 0.2 and 150% of those of glutamine synthetase. The estimated Km for hydroxylamine of glutamine synthetase was found to vary between 0.02 and 0.5 mM in nine species tested, while that of glutamate dehydrogenase for ammonia varied between 0.03 M and 0.1 M in the four species containing significant levels of that enzyme. It is proposed that the pathway of ammonia assimilation via glutamine synthetase and NADH-dependent glutamate synthase-catalysed reactions is universal in legume nodule metabolism.
Activation and Inactivation of Phosphoenolpyruvate Carboxylase in Leaf Extracts From C4 Species
Authors: Hatch MD , Oliver IR
Published: January 2006

The stability of phosphoenolpyruvate carboxylase (EC 4.1.1.31) was examined following extraction of the enzyme from leaves of several C4 plants. Extracts were rapidly processed on small Sephadex G-25 columns to free protein of small-molecular-weight compounds. With most of the species examined, activity was rapidly lost at both 0 and 25°C when the pH was about 7.8 or higher. Addition of bovine serum albumin to extracts incubated at 25°C and pH 8.2 not only prevented inactivation with several species, but resulted in a substantial increase in activity. The addition of dithiothreitol plus Mg2+ to extracts from some of these species reduced or prevented inactivation. With extracts maintained at 0°C, addition of either bovine serum albumin or dithiothreitol was effective only in reducing the rate of inactivation in extracts. Phosphoenolpyruvate carboxylase activity remained stable, or increased substantially, when extracts buffered between pH 7.4 and 6.9 were incubated at either 0 or 25°C. Activation was usually complete within an hour and was often significantly greater at 25°C or when bovine serum albumin was added. The activity of partially purified phosphoenolpyruvate carboxylase from Zea mays was similarly affected by pH, temperature, and bovine serum albumin.
The present studies raise doubts about the accuracy of phosphoenolpyruvate carboxylase determinations made during the course of some previous studies on C4 species. Reliable procedures for the determination of phosphoenolpyruvate carboxylase activity in C4 plant extracts are described. Possible physiological implications of the results are considered.
Response of Barley Shoot Apices to Application of Gibberellic Acid and Abscisic Acid: Dependence on Tissue Sensitivity
Authors: Nicholls PB
Published: January 2006

Stimulation by gibberellic acid of rachis internode elongation in barley grown in short days was dependent on either the timing of application or on the amount applied in a dose at day 10. There was no immediate rachis internode elongation in response to gibberellic acid treatment until floret initials appeared and then only if sufficient gibberellic acid was present in the shoot apices of the barley plants grown in short days.
Applications of gibberellic acid promoted the growth of the double-ridge meristem (upper ridge only) and this resulted in a group of abnormal spikelets being formed on the lower six nodes of the inflorescence, all of which were characterized by enhanced growth of the rachilla apical meristem.
In a 2 × 2 factorial experiment with gibberellic acid, abscisic acid was found to slightly reduce the growth rate of the vegetative barley apex between days 10 and 14. Abrupt cessation of primordium formation, coincident with the appearance of stamen initials, was observed following continued application of both gibberellic acid and abscisic acid whereas neither hormone alone had this effect. Enhanced growth of the rachilla apical meristem of the basal six spikelets following application of gibberellic acid resulted in the formation of branched inflorescences, and this result was not altered by the addition of abscisic acid to the treatment.
Growth of Peach [Prunus persica (L.) Batsch] Fruits After Treatment With Ethephon During Successive Periods of Fruit Development
Authors: Dann IR , Chalmers DJ
Published: January 2006

During the first stage of dry weight increase (DW I) of peach fruit, ethephon inhibited growth but stimulated the short-term uptake of 14C-labelled assimilate as well as the natural abscission of the fruitlets. Abscission appeared to be the primary effect, while inhibited growth was a secondary effect of ethephon. This stage of growth DW I) includes the first half of the lag phase of fresh weight increase (FW 11). During the remainder of FW I1 (after the start of DW 11), ethephon did not affect growth except at the highest concentration, which inhibited growth. After commencement of FW 111, which is the final stage of rapid fresh weight increase, ethephon stimulated fruit growth.
The data indicated that growth could be stimulated with ethephon during periods when the rate of fresh weight growth was rising but not when it was falling. Thus, endogenous ethylene appears to limit growth of peach fruit during the stages of rapid increase in fresh weight.
Chilling Resistance in Lycopersicon hirsutum Humb. & Bonpl., A Wild Tomato With a Wild Altitudinal Distribution
Authors: Patterson BD , Paull R , Smillie RM
Published: January 2006

Chilling resistance and other adaptations to low temperature were investigated in the wild tomato, Lycopersicon hirsutum, and the domestic tomato L. esculentum. Chilling resistance was assessed by the ability of seedlings to survive and grow after being exposed to 0°C for several days. For geogra- phical populations of L. hirsutum, chilling resistance was greatest in those derived from the higher altitudes. Other characteristics that correlated with the altitude of origin of the different populations were the rate at which the seeds germinated at low temperatures and chlorophyll development at low temperatures. L. esculentum cv. Rutgers did not tolerate chilling well and, in this respect, resembled low-altitude populations of L. hirsutum.
L. hirsutum is a suitable species for physiological studies of chilling resistance, and its altitudinal variants are potential sources of genes 'tailored' to different temperature environments. Methods based on the above-mentioned responses to chilling may enable selection of chilling-resistant seedlings from hybrids of L. esculentum and L. hirsutum.
Inhibition of the Capacity and Efficiency of Photosynthesis in Bean Leaflets Illuminated in a CO2-Free Atmosphere at Low Oxygen: A Possible Role for Photorespiration
Authors: Powles SB , Osmond CB
Published: January 2006

Mature, intact, attached leaflets of Phaseolus vulgaris illuminated at 2000 μE m-2 s-1 in CO2-free N2 containing 1% O2 for a 3-h treatment period showed an 80% reduction in the light-saturated CO2 assimilation rate. Young bean leaflets showed photoinhibition but exhibited a partial recovery of CO2 assimilation rate within 2 h of treatment whereas mature leaflets did not. Photoinhibition by illumination under conditions which prevent photorespiration was markedly dependent upon the exposure time. Photoinhibition was not observed following illumination in the presence of CO2-free N2 containing above 7% O2 or in N2 containing 1% O2 and an intercellular CO2 partial pressure equivalent to the CO2 compensation point in 21% O2 (62 μbar, 6.2 Pa). Photoinhibition involved concomitant reduction in the light-saturated and the light-limited rate of CO2 assimilation; apparent quantum yield was reduced following treatment. These experiments show that internal generation of CO2 by the photorespiratory carbon oxidation cycle is sufficient to prevent the photoinhibition observed when photorespiration is prevented. Possible mechanisms and implications of these data are discussed.
Comparative Studies on the Proteins From Seeds of Lupinus angustifolius L.
Authors: Blagrove RJ , Gillespie JM
Published: January 2006

The seeds of 99 genotypes of L. angustifolius were examined by electrophoresis on cellulose acetate and found to contain two major salt-extracted globulins, conglutins α and β, and a third minor globulin, conglutin γ. Dissociation with sodium dodecyl sulfate and electrophoresis on polyacrylamide gel showed variation in the number, proportion and molecular size of the subunits which constitute these proteins. This was confirmed by electrophoresis in polyacrylamide gel containing urea at acid pH. The globulins in the salt extracts of some of the seeds were subject to partial enzymic degradation unless conditions which inactivate proteolytic enzymes were used during extraction.
Crude protein level of the seed meal, determined for many of the genotypes from their nitrogen content, varied from about 30 to 50%. Only 5-10% of this total protein was water-extracted albumins. Amino acid analysis showed that the albumin fraction contains higher levels of many of the essential amino acids including cystine and particularly methionine.
Isolation From the Flowers of Dryandra praemorsa of a Flavonol Glycoside That Reacts With β-Lectins
Authors: Jermyn MA
Published: January 2006

A flavonol glycoside has been isolated from aqueous extracts of the flowers of Dryandra praemorsa (Proteaceae) that inhibits the reaction between β-lectins and the Yariv 'artificial antigens'. The flavonol is myricetin; the sugars are galactose (~ 90 %) and glucose (~ 10 %). The material analyses as a myricetin hexoside monohydrate, thus appearing to be a mixture of two components that have not been separated. The optical rotation is consistent with a β-configuration; experiments with compounds of known structure show that inhibitory activity is characteristic of flavonols glycosylated in the 3-position. Hyperin (the 3-β-D-galactopyranoside of the pentahydroxyflavone, quercetin) and the related quercitrin and rutin are somewhat less inhibitory but can be used to demonstrate the general characteristics of the inhibition with compounds of known structure. The inhibitory material can be attached to agarose to give a column packing that shows some capacity to bind β-lectins.