bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Properties and Ribulosebisphosphate Carboxylase and Oxygenase Activity of Fraction-1 Protein from the Marine Alga Halimeda cylindracea (Chlorophyta)
Authors: Akazawa T , Osmond CB
Published: January 2006

Ribulosebisphosphate carboxylase/oxygenase activity was detected in Halimeda cylindracea and Chaetomorpha crassa. In H. cylindracea carboxylase activity (72-250 micromoles CO2 fixed per hour per milligram chlorophyll) was sufficient to account for measured photosynthetic rates. The activity of the oxygenase was only 1 % that of the carboxylase but otherwise both enzymes showed properties similar to those of the same enzymes in higher green plants. Fraction-1 protein from H. cylindracea was purified to a homogeneous state as tested by poly- acrylamide gel electrophoresis at pH 8.9. The activity of the ribulose-1,5-bisphosphate carboxylase in the purified preparations was 0.1 micromoles CO2 fixed per minute per milligram protein (pH 7.0). The H. cylindracea fraction-1 protein was shown to comprise two subunits, A and B, with molecular weights 5.4 × 104, and 1.35 x 104, respectively, typical of the plant-type ribulose-1,5-bisphosphate carboxylase. The amino acid composition of the large subunit A was similar to that from spinach and Chlorella enzymes, whereas that of the subunit B was markedly distinguishable from the enzymes of other origins. The close resemblance of the H. cylindricea protein to the plant enzymes was further supported by the formation of a spur in the double immunodiffusion precipitation line, indicating probable existence of sequence-homology of the catalytic larger subunit A, typical of the plant-type enzyme molecules.
Effect of Sulphur Supply on the Seed Globulin Composition of Lupinus angustifolius
Authors: Blagrove RJ , Gillespie JM , Randall PJ
Published: January 2006

Seeds from L. angustifolius grown at three levels of applied sulphur contain similar amounts of protein whereas the ratio of total nitrogen to total sulphur in the whole seed and in the extracted protein is greatly increased under sulphur deficiency. This large change in nitrogen to sulphur ratio is accompanied by suppression of the synthesis of conglutins α and γ which usually contain most of the sulphur-containing amino acids found in these seeds. This is balanced by synthesis of an increased amount of conglutin β which normally contains no methionine and a lower proportion of cystine. Studies of the protein subunit composition show that the overall molecular weight distribution of the polypeptides is independent of the level of sulphur, but under sulphur deficiency the higher molecular weight subunits do not contain the disulphide linkages normally present. It is not known whether these higher-molecular-weight conglutin β subunits are normally absent or present only in trace amounts in the seeds.
Stress Metabolism. VII. Salinity and Proline Accumulation in Barley
Authors: Chu TM , Aspinall D , Paleg LG
Published: January 2006

Barley plants (cv. Prior) were grown in nutrient culture and subjected to a variety of salinity stress treatments when 10-12 days old. Salinity stress was either imposed abruptly by transferring plants to a solution containing NaCl of - 5.7 or - 10.7 bar osmotic potential, or gradually by transferring plants daily to solutions of successively lower osmotic potential (- 1 bar per day). Prolonged exposure to salinity stress was achieved by holding plants in a - 10.7 bar osmotic potential solution for 6 days.
Proline accumulated rapidly in plants subjected to a salinity stress greater than - 5.7 bar osmotic potential. Accumulation appeared to be controlled by tissue osmotic potential rather than by turgor, and continued for 24 h after the saline solution was removed from the root medium. Proline accumulation continued for at least 3 days in plants held at - 10.7 bar osmotic potential, during which time the plants continued to grow slowly. The accumulated proline made only a minor contribution to osmotic regulation in the plant,
Photosynthesis and Transpiration in Dicotyledonous Plants. II. Expanding and Senescing Leaves of Soybean
Authors: Woodward RG , Rawson HM
Published: January 2006

The history of net photosynthesis and transpiration per unit leaf area was determined for intact soybean leaves from their unfolding to senescence during flowering and pod filling on untreated (podded) and partially depodded plants growing in a glasshouse. Leaf diffusive resistances to CO2 were calculated and a water use efficiency parameter was derived (net mass of carbon dioxide fixed per unit mass of water transpired per millibar vapour pressure deficit).
Net photosynthesis and transpiration behaved similarly through all stages of leaf development. A number of peaks were evident in these parameters. The first was associated with leaf expansion and occurred when the leaf reached its maximum area. The second peak coincided with flowering of the plant and later peaks occurred during pod filling. Stomatal and mesophyll resistances also exhibited similar behaviour during the life of the leaf; the possible causes of this linkage are discussed. Water use efficiency increased rapidly up to the time of full lamina expansion. Thereafter, it rose slowly or remained stable until leaf senescence approached, when the efficiency declined.
Net photosynthesis and transpiration of leaves were very similar in both podded and partially depodded plants. It appears that to prevent a shortage of assimilate during flowering and pod filling, photosynthesis may be maintained or increased in some leaves and the response is not related to the number of pods available for filling. The increases in photosynthesis were correlated with both higher stomatal and mesophyll conductances. Mechanisms by which the plant may control leaf photosynthesis are discussed.
Thermodormancy in Seedlings of Eucalyptus obliqua L'herit
Authors: Blake TJ
Published: January 2006

High (30°C) day and night temperatures reduced mainstem elongation in E. obliqua seedlings resulting in a temporary quiescence in height growth after 8 days of high temperature treatment; rapid stem elongation did not recommence when seedlings were returned to conditions usually favourable to growth. Associated with the onset of quiescence were: an increase in the respiratory quotient and a decrease in the respiration rate of upper terminal buds; an accumulation of inhibitory substances; and an increase in total polyphenols in the stem.
Membrane Phase Changes in Chilling-Sensitive Vigna radiata and Their Significance to Growth
Authors: Raison JK , Chapman EA
Published: January 2006

Changes in the growth response of mung bean hypocotyl were studied as a function of temperature and related to structural and functional changes in membranes. The temperature coefficient for growth increased abruptly below 28°C and again below 15°C. The Arrhenius activation energy of mitochondrial succinate oxidase also increased below these same temperatures. Changes in molecular ordering were detected in the membrane lipids of both mitochondria and chloroplasts at about 28 and 15°C by electron spin resonance spectroscopy. The results demonstrate a precise relationship between changes in the molecular ordering of membrane lipids and the physiological response of plants to changes in temperature.
Alcoholic Fermentation and Activity of Some Enzymes in Rice Roots Under Anaerobiosis
Authors: John CD , Greenway H
Published: January 2006

Rice was initially grown in aerated solutions. When tillering commenced, anaerobiosis was imposed by flushing nitrogen gas through nutrient solutions for up to 6 days ('adapted plants'); plants which remained in aerated solutions are referred to as 'non-adapted plants'.
Under anaerobiosis, CO2 evolution and ethanol production by excised apical root tissues were five times greater for adapted than for non-adapted plants. For excised tissues from adapted plants, carbon lost as CO2 and ethanol approximately equalled that of aerobic CO2 evolution, i.e. CO2(N2) / CO2(air) = 0.30. This ratio was only 0.06 for apical tissue from non-adapted plants. Ethanol was not produced under aerobic conditions, even by tissue from adapted plants.
Anaerobiosis of the root environment caused rapid increases in activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC). Cycloheximide largely inhibited the increases in activities of these enzymes under anaerobiosis.
Elevated activities of ADH and PDC persisted for several days after transfer of adapted plants to aerated solutions. Despite these high activities of PDC and ADH, ethanol was not produced in root tissue from adapted plants under aerobic conditions, which indicates that either PDC or ADH is under fine control. Experiments in vitro suggest that this control is afforded at least partly by activation of PDC by NADH and inhibition by NAD+. It is suggested that NADH can replace thiamin pyrophosphate in promoting PDC activity via effects on conformation of the enzyme.
Circadian Rhythm of Nitrate Reductase (NADH) Activity in Wheat Seedlings Grown in Continuous Light
Authors: Upcroft JA , Done J
Published: January 2006

A circadian rhythm of nitrate reductase (NADH) was observed when three cultivars of Triticum aestivum L. were grown in continuous light. The amplitude of the rhythm was greatest when the lamps used emitted both red and blue light. High rhythmic activity in roots occurred only when seedlings were germinated and grown in continuous light. Nitrite reductase was induced with no oscillation.
Ethylene as a Growth Hormone in Peach Fruit.
Authors: Jerie PH , Chalmers DJ
Published: January 2006

Ethylene production by whole fruit and mesocarp pieces of peach [Prunus persica (L.) Batsch. cv. Golden Queen] was measured throughout the growing season. Peach fruit have a double-sigmoid growth curve, in which a lag period of slow weight increase (stage II) is followed by a rapid stage of weight increase (stage III). Changes in ethylene production could not be related to stage I- stage II transitions, and ethylene remained low at the start of fresh weight stage III. Two weeks later, ethylene production rose sharply at the same time as the fruit started accumulating dry weight in dry weight stage III. Mesocarp pieces produced ethylene in a pattern similar to that of whole fruit. We conclude that, in peach, increasing ethylene production is one of the hormonal changes involved in dry matter accumulation during stage III of fruit growth.
Electrolyte Leakage Induced by Chilling in Passiflora Species Tolerant to Different Climates
Authors: Patterson BD , Murata T , Graham D
Published: January 2006

A method was devised to measure chilling sensitivity in a series of species and hybrids of Passiflora having a range of climatic requirements. Leaves from plants which had been grown under 25°C day/18°C night were chilled at 0°C in the dark. At the same time, leakage of electrolyte from thin strips of these leaves was measured at 0°C using conductivity. Two main stages of leakage were found: a relatively slow rate (stage 1) which was followed by a high rate (stage 2), during which most of the electrolyte was lost from the tissue. Potassium was the principal cation lost from the tissue, and its leakage was proportional to that of total electrolyte during the time course of leakage. Stage 2 occurred at about the same time as obvious lesions appeared on whole leaves, and apparently signified lethal chilling injury. When different species were compared, those which had originated from the tropical lowlands (P. maliformis L. and P. edulis Sims forma flavicarpa Degener) were killed in less than 10 days, but those tolerant of cooler climates (P. caerulea L. and P. edulis Sims) survived much longer. From the behaviour of a number of species and hybrids, the rate of leakage during stage 1 was related to the time taken to reach stage 2. Resistance to chilling in the species and hybrids examined was not an all-or-nothing property, but showed a gradual increase in the series: P. edulis forma flavicarpa < P. maliformis < P. cincinnata Masters < P. edulis < P. caerulea, with some hybrids occupying intermediate positions.
Stress Metabolism. VIII. Specific Ion Effects on Proline Accumulation in Barley
Authors: Chu TM , Aspinall D , Paleg LG
Published: January 2006

Intact 12-day-old barley (cv. Prior) plants or first-leaf sections were grown on iso-osmotic solutions of polyethylene glycol or a variety of inorganic salts for 24 h. All solutions caused a similar decline in leaf water potential with external osmotic potential in the intact plant, but the decline in internal osmotic potential was least on solutions of polyethylene glycol, causing a loss of turgor in plants growing on that osmoticurn. Plants growing on solutions of NaCl, KCl, Na2SO4 or CaCl, accumulated less proline than plants on iso-osmotic solutions of polyethylene glycol, but plants on MgCl2, solutions accumulated as much or more. With leaf sections, no proline accumulated on solutions containing the monovalent cations, whereas tissue floated on salt solutions containing Mg2+ or Ca2+ accumulated as much or more proline as that on iso-osmotic solutions of polyethylene glycol. NaCl was found to inhibit the proline accumulation caused by a reduction in external osmotic potential.
Relationship Between Changes in Abscisic Acid and Ethylene Production During Ripening of Avocado Fruits
Authors: Adato I , Gazit S , Blumenfeld A
Published: January 2006

Abscisic acid levels and the rates of ethylene production during successive stages of ripening in avocado fruits (Persea americana Mill.) were determined by gas chromatography. In fruits which were selected for abscisic acid determination according to their rate of ethylene production, a rise in free abscisic acid content was observed following an increase in the rate of ethylene production. Levels of bound abscisic acid were much lower and increased later than free abscisic acid.
Changes in Ultrastructure and Pigment Content During Development and Senescence of Fruits of Normal and rin and nor Mutant Tomatoes
Authors: Simpson DJ , Baqar MR , Mcglasson WB , Lee TH
Published: January 2006

Fruits of the normal Rutgers tomato cultivar and of the rin and nor mutants were examined at the following times: Rutgers at 17, 21, 32, 45, 47, 50 and 55 days after anthesis; rin and nor at 17, 21, 32, 50, 65, 78 and 95 days after anthesis. Ripening in Rutgers fruits began at about 47 days, and fruits were fully ripe by 55 days after anthesis. Full size was reached in both Rutgers and in the mutant fruits about 50 days after anthesis. Rin fruits subsequently turned yellow, and nor fruits developed some pink colour, but the fruits of both mutants remained sound and comparatively firm for up to 95 days after anthesis.
No unique differences in ultrastructure were noted between Rutgers and mutant fruits except that myelin figures were observed in 21- and 32-day nor fruits and spiral membrane tubules were found in the epidermis of 95-day rin fruits. In Rutgers fruits, the major change was the transformation of chloroplasts to chromoplasts during ripening; this transformation was completed within 5 days. A similar, but much slower and less complete, transformation was noted in the mutants. Some grana and chlorophyll were present even in 95-day fruits, although rin and nor fruits began to lose chlorophyll and to accumulate coloured carotenoids from the time the fruits reached full size. The slow changes in ultrastructural transformation of plastids, paralleled by the changes in colour, suggest either suppression of nuclear action or lack of capacity to produce cellular components essential for normal ripening. The latter suggestion was favoured by current information on the physiology of the mutants.
The Carbohydrate Moiety of Mung Bean Vicilin
Authors: Ericson MC , Chrispeels MJ
Published: January 2006

Mung bean (Phaseolus aureus Roxb.) vicilin, purified by DEAE-cellulose chromatography, is a glycoprotein (0.2% glucosamine and 1% mannose) which contains four different polypeptides with molecular weights of 63 500, 50000, 29 500 and 24 000 in the molar ratios 1 : 5 : 1 : 1. Two of these polypeptides (50 000 and 29 500) stain positively for carbohydrate. When vicilin is digested with pronase, the carbohydrate can be recovered as a glycopeptide containing mannose and glucosamine in the carbohydrate moiety and alanine, threonine and aspartic acid (or asparagine) in the peptide moiety. The total amount of carbohydrate (1.2 %) and the size of the carbohydrate unit (12 residues) suggest that each vicilin molecule contains only one carbohydrate side chain. Data indicate that this chain is attached via a glucosamine-asparagine link. The results raise the possibility that the presence of the two small polypeptides in vicilin preparations is the result of the breakdown of the major larger one. Indirect evidence suggests that vicilin may be a tetramer of four subunits, each with a molecular weight of 50 000, and that only one subunit has a carbohydrate side chain.
Effects of Microorganisms on Absorption and Distribution of Phosphate in Barley
Authors: Barber DA , Bowen GD , Rovira AD
Published: January 2006

Although it is well established that microorganisms can influence the absorption and translocation of phosphate by plants growing in solution culture, different investigations have recorded both stimulations and depressions. However, the experimental conditions differed in regard to the age, nutrition and species of plants, the origin of the microflora, the concentrations of phosphate supplied and the time over which absorption was measured. The effect of these variables on the nature of response to microorganisms was investigated. Microorganisms enhanced absorption and translocation in young seedlings during short periods of uptake while causing decreases over longer periods and in older plants. The possible mechanisms responsible for the effects of microorganisms are discussed.
Light-dependent Redistribution of Ions in Isolated Spinach Chloroplasts
Authors: Chow WS , Wagner AG , Hope AB
Published: January 2006

The Mg2+, K+ and Cl- contents of chloroplast pellets collected after centrifugation in light and dark conditions have been determined in a specific reaction medium at pH 7.8 and 6.6. It was found that the light-induced proton uptake by chloroplasts was electrically balanced mainly by Mg2+ efflux and to a lesser extent by K+ efflux. Unlike results in other studies, Cl- influx was rather small.
A model for the ionic relations of envelope-free chloroplasts is considered. Light-induced changes in the ionic contents calculated from the model are in agreement with our observations. An attempt is made to apply similar considerations to another set of reported data.
Proline Accumulation in Tubers of Jerusalem Artichoke
Authors: Wright L , Wrench P , Hinde RW , Brady CJ
Published: January 2006

When separated whole tubers of Helianthus tuberosus L. were dried, and when tuber slices were plasmolysed in mannitol solutions, free proline accumulated in the tuber tissue. The amount of proline accumulated in tuber slices increased with the concentration of mannitol in the plasmolysing solution. A lag of approximately 24 h preceded proline accumulation in plasmolysed slices. During the lag period, the content of free arginine, a major component of the free amino acid pool, decreased by at least 50%. L-Indospicine, a competitive inhibitor of arginase (L-arginine amidinohydrolase EC 3.5.3.1) inhibited arginine catabolism in slices and also inhibited proline accumulation. On the other hand, cycloheximide, an inhibitor of protein synthesis, did not inhibit arginine loss or proline accumulation. An increase in the concentration of mannitol required for plasmolysis accompanied an increase in free proline in whole, dormant tubers stored at 4°C. These tubers are an example of a non-photosynthetic higher plant tissue in which free proline accumulates when the water potential decreases. The relationship between arginine catabolism and proline accumulation is discussed.
Stomatal Opening and Photosynthesis in Greening Leaves of Vicia faba L
Authors: Lurie S
Published: January 2006

The development of the ability of stomata to open in greening leaves of broad bean (V. faba L.), and the onset of photosynthetic activity in chloroplasts isolated from these leaves, were examined in parallel. The stomata showed biphasic kinetics of opening. They began to open after 4 h of illumination, which correlated with the beginning of cyclic phosphorylation. The extent of the stomatal aperture remained small (2 �m) until 8 h after the onset of illumination, at which time wider apertures were observed (6-8 �m). This wider opening was concurrent with the detection of carbon dioxide fixation seen in isolated whole chloroplasts from the greening leaves.
Changes in Diffusive Conductance and Water Potential of Wheat Plants Before and After Anthesis
Authors: Morgan JM
Published: January 2006

The relationships between stomatal conductance and leaf water potential, ΨL, of wheat plants during drying under controlled conditions showed three phases: (1) no apparent effect until ΨL reached about - 1.8 J g-1; (2) increasing closure as ΨL decreased to about - 3 J g-1; and (3) complete failure to open at lower ΨL values. At any given water potential in the first two phases, the stomata were always more open during the post-anthesis stage than during the pre-anthesis stage. Although the relationship between leaf water potential and relative water content differed with growth stage, this was not important in the overall plant response to a water deficit. Over a wide range of ΨL, the conductance of the adaxial surface was less variable and more sensitive than that of the abaxial surface. The ratio of these conductances was very variable and followed no discernible pattern. The water potential of spikelets was appreciably higher than that of flag leaves, especially at low values of the latter. Both organs died at about the same water potential (about
-4 J g-1); hence, spikelets survived longer periods of water deficit than leaves. These responses are discussed in respect of sensitivity of grain yield to the stage of growth at which a water deficit is experienced and to the phenomenon of spikelet death. Differences between three cultivars examined were small.
Photosynthesis in the Aquatic MacrophyteEgevia densa. I. 14CO2 Fixation at Natural CO2 Concentrations
Authors: Browse JA , Dromgoole FI , Brown JMA
Published: January 2006

In *14C time-course and pulse-chase experiments, the photosynthetic fixation rate for Egeria densa Planch. was about 19 �mol C (g dry wt)-1 min-1 (13.7 mg C (g dry wt)-1 h-1) at a total inorganic carbon concentration of 1.0 x 10-3 M, pH 6.8 and 75-80% light saturation. At this high rate, under conditions closely approximating those of plants in the field, 14C distribution into 3-phosphoglyceric acid, sugar phosphates and sucrose indicates that the Calvin cycle is the primary carboxylation mechanism and responsible for over 90% of the 14C initially incorporated. Malate accounts for only 5 % of the initial 14CO2 fixation and is not actively further metabolized. Additional label from Calvin cycle intermediates enters malate during the cold chase treatment.
It is suggested that the predominant 14C fixation into malic acid, noted in previous reports on Hydrocharitacean species, may be due to very low experimental CO2 concentrations and a consequent suppression of the Calvin cycle activity.
Compounds of the glycollate pathway were detected in sufficient quantities to give some support to the previous suggestion of photorespiratory activity in Egeria.
Photosynthesis in Salt-Stressed Grapevines
Authors: Downton WJS
Published: January 2006

Rooted cuttings of grapevine (Vitis vinifera L. cv. Sultana syn. Thompson Seedless) were grown in sand culture irrigated with nutrient solution containing 1-125 mM NaCl. The effect of salinity on vine growth and photosynthesis is described. Salinity led to reduced growth where foliar symptoms of salt toxicity were absent. Rates of CO2 fixation decreased with increasing levels of chloride in leaves. This decrease in photosynthesis could be largely attributed to increased residual (mesophyll) resistance to CO2 fixation. Radiotracer studies showed that salt stress led to the accumulation of label in intermediates of the glycollate pathway. Salt-stressed leaves contained decreased amounts of sucrose and starch, but increased levels of reducing sugars.
Circadian Electrochemical Changes in the Pulvinules of Trifolium repens L
Authors: Scott BIH , Gulline HF , Robinson GR
Published: January 2006

In pulvinules of T. repens, circadian changes were observed in the content and influx of potassium. No corresponding changes were observed for calcium or sodium, although the influx of calcium has a light-dependent component. For both adaxial and abaxial cells, potassium influx becomes high prior to cellular swelling and remains high until shortly before shrinkage, when it falls and remains low for the remainder of the cycle. Circadian changes in transmembrane potential are also observed. Swollen cells are initially hyperpolarized (H ≈ 90 mV), but depolarize (to H ≈ 70 mV) about 9 h before shrinking. The potential reverts to the more negative value about 9 h before the cells again swell. The phasing of the potassium influx, water volume and membrane potential cycles of pulvinule cells may indicate sequential steps in an oscillating feedback system which could form the basis for the circadian behaviour.
Abscisic Acid and Xanthoxin Contents in the Long-Day Plant Lolium temulentum L. In Relation to Daylength
Authors: King RW , Evans LT , Firn RD
Published: January 2006

In L. temulentum L., flowering can be inhibited by application of abscisic acid (ABA) close to the shoot apex towards the end of an exposure to a single inductive long day. However, analysis by gas-liquid chromatography showed that the contents of endogenous ABA and xanthoxin in L. temulentum leaves are not consistently changed after an inductive photoperiod. Apex extractions carried out when (�)-ABA application near the apex is most inhibitory to flowering also showed no consistent effect of daylength on the content of ABA which was, however, much higher than in leaves. Thus it is unlikely that induction of flowering in L. temulentum by exposure to long days is due to changes in the endogenous levels of ABA and xanthoxin in the leaves or of ABA in the shoot apex.
Responses of Subterranean Clover Communities to Temperature. III. Effects of Temperature on Canopy Photosynthesis
Authors: Fukai S , Silsbury JH
Published: January 2006

Subterranean clover communities were grown at 12, 16, 20 and 24°C in naturally lit temperature- controlled glasshouses. Rates of net CO2 exchange of communities varying in leaf area index (LAI) from 1 to 8 were determined at several levels of irradiance at the temperature at which the plants were grown and at other measurement temperatures.
When measured at each of the four growth temperatures and at an irradiance of 250 W m-2, the net CO2 exchange rate increased with increase in LAI up to 3. Higher values of LAI affected the rate only slightly. At each growth temperature and an irradiance of only 50 W m-3, net CO2 exchange decreased with increase in LA1 over the range 2-8.
Net CO2 exchange rate followed a hyperbolic curve with increase in irradiance at all LAI values, the asymptote being largely independent of temperature and of LAI within the range 3-8.
The net CO2 exchange rates of a community, determined at different measurement temperatures, were also directly related to measurement temperature at high irradiance but, owing to increased respiration rate at high temperature, inversely related to temperature at low irradiance. Differences in net CO2 exchange rates of a community at high irradiance due to different measurement temperatures were greater than the differences due to different growth temperatures.
Regulation of the Movement of Assimilate Into Ovules of Pisum sativum Cv. Greenfeast: Effect of Pod Temperature
Authors: Williams AM , Marinos NG
Published: January 2006

Studies of 14C distribution in P. sativum cv. Greenfeast over 24 h indicate that 60-80% of 14C incorporated by the single leaf, on a plant pruned to leave one leaf and one pod, moves to the growing ovules at all developmental stages. Approximately 40% of the total activity was found in the ovules within 5 h after exposure of the leaf to 14CO2.
As the pod temperature increases there is an increase in 14C uptake by the ovules, from 2% of the total 14C assimilated by the leaf at 10°C to 28% at 30°C, within 2.5 h of 14C application. These results are discussed in relation to possible mechanisms of nutrient uptake by the pod. However, it is impossible at this stage to decide whether the transport of photosynthate into the developing fruit and its seeds is controlled simply by the metabolic sink status of the developing system or if, in addition, there is a 'remote' effect on the transport system itself.
Assimilate Source-Sink Relationships in Capsicum annuum L. I. The Dynamics of Growth in Fruiting and Deflorated Plants
Authors: Hall AJ
Published: January 2006

The shaded fruit of the pepper plant was the main sink for assimilates during much of the growth period of this organ. Up to 90 % of the plant daily dry weight increase was deposited in the fruit, and growth of all non-fruit organs was correlatively reduced. No net transfer of dry matter from other organs to the fruit could be detected. In continuously deflorated plants, the partitioning of dry matter among organs was more evenly balanced. Net assimilation rates of fruiting plants exceeded those of deflorated plants, and these differences appeared to be associated with alterations in assimilate demand. Net assimilation rates of fruiting plants remained constant for up to 40 days under conditions of very little leaf surface turnover, indicating that leaves of these plants retain their photosynthetic capacity long after full expansion. Foliar senescence and abscission in deflorated plants was marked, but these processes were inhibited during the growth of the fruit. Some possible causes of this differential response are considered.
Proton Translocation, Electron Transport and Phosphorylation in Isolated Chloroplasts
Authors: Chow WS , Hope AB
Published: January 2006

The steady-state rates of proton translocation (ΦH) associated with rates of light-induced electron transport (Φe) have been studied under a variety of conditions, with and without phosphorylation, in both spinach and pea chloroplasts, and using the absorbance changes of phenol red as a pH indicator. The method is discussed critically and compared with others. Using values of ΦH estimated from the initial efflux of H+ after continuous illumination for 17 s, it has been found that ΦH/Φe increased to a maximum value of 2 under conditions which enhanced the permeability of membranes to H+ and a second ion. The maximum value of about 2 was observed over the whole pH range for which phenol red can be used as a pH indicator, namely pH 7.0 - 8.7. The stimulation of electron transport by phosphorylation was also studied with a view to enquiring into the ratio ΦHH/RATP, where ΦH is the proton flux via an ATPase giving rise to a phosphorylation rate RATP.
A scheme of the pathways of protons in the thylakoid membrane is proposed to account for the evariation of ΦH/Φe under a large range of conditions. This scheme is in line with the 'bobbing up and down' hypothesis for the mechanism of active proton transport in energy-transducing membranes.
Variation of Leaf Characteristics With Level of Insertion on a Grass Tiller. III. Tissue Water Relations
Authors: Wilson JR
Published: January 2006

Plants of a grass, green panic (Panicum maximum var. trichoglume) were grown under controlled environmental and nutritional regimes. Throughout the growth of the plants, leaves from varying levels of insertion on the main stem were sampled at comparable physiological age (viz, when just fully expanded) and their water relations characteristics measured over a range from full turgidity to a moderately stressed condition to determine whether there were inherent differences between leaves on the shoot.
Leaf water potential, osmotic potential, and pressure potential fell in a similar manner for the leaves from each insertion level as leaf relative water content declined. A small increase in the average water and osmotic potential, and also in the average matric potential component, estimated for a common reIative water content, was evident with increasingly higher level of leaf insertion. Despite marked increases in the proportion of cell wall material and a trend towards increasing lignification in leaves of higher insertion, the bulk coefficient of elasticity of the tissues showed no gradient of change, and the overall change in the matric potential component was small. Various other chemical and morphological characteristics showed definite gradients with insertion level: for example, stomatal frequency increased from 91 to 287 mm-2 from leaf 5 to the flag leaf.
There was no evidence of a progressive variation with insertion level in the water status of leaves sampled fresh from the plants, and thus no support for the theory that upper leaves on a tiller develop under inherently higher water stress, which could account for their xeromorphic chemical, anatomical and morphological features.
It appears that in green panic at least, the water relations characteristics measured, with the exception of stomatal frequency, exhibit no strong inherent gradients with insertion level of leaves which could seriously confound comparisons of water status between plants in different treatments.
Response of Radiata Pine to Salt Stress. II. Localization of Chloride
Authors: Foster RC , Sands R
Published: January 2006

Seedlings of Pinus radiata D. Don (radiata pine) were subjected to a stepwise decrease in the osmotic potential of their rooting medium by the addition of CaCl2, NaCl or polyethylene glycol 4000. The location of chloride within the root, stem and needle tissue was determined at the ultrastructural level using a silver precipitation technique.
Three main sites of chloride deposition were detected. In the roots, large amounts of precipitated chloride were observed in the hyphae of the mycorrhizas as well as between the cell wall and the plasmalemma of the outer cortical cells, suggesting that chloride was in part prevented from entering the root at these sites. In the stem, chloride was precipitated in the ray cells and in the tracheids where it occurred both in the cell lumen and in the inner layer of the secondary wall (the S2). Since tracheids constitute the largest proportion of a pine tree, this site could constitute a considerable sink into which excess chloride could be deposited, thus removing it from cellular metabolism. In the needles, chloride was precipitated in the epidermal and sub-epidermal cells, and in the mesophyll it was mainly located in the cell walls. In all living cells in the seedlings, chloride was precipitated mainly in the vacuoles. It was restricted to small discrete deposits in the cytoplasm and was absent from the ground plasm and organelles.
These observations support the hypothesis that, although radiata pine cannot tolerate high concentrations of chloride in vital tissues, it is adapted to avoid or delay its accumulation in such sites.
Effect of Temperature, Vapour-Pressure Deficit and Irradiance on Transpiration Rates of Maize, Paspalum, Westerwolds and Perennial Ryegrasses, Peas, White Clover and Lucerne
Authors: Forde BJ , Mitchell KJ , Edge EA
Published: January 2006

Rates of water use [g H2O (g dry wt leaf)-1 h-1] of young plants of maize, paspalum, perennial ryegrass, Westerwolds ryegrass, peas, white clover and lucerne were measured during the day under controlled climate conditions with ample water available to the plant. Plants were grown and observations made with day/night temperatures of 32.5/27.5°C, 27.5/22.5°, 22.5/17.5°, and 17.5/12.5°C with a day/night vapour pressure deficit (VPD) of the air of 10/2mbar. Water use measurements were also made at 27.5/22.5° and 17.5/12.5°C under day/night VPD regimes of 5/2 and 15/2 mbar. Irradiance during the 12-h day was 170 W m-2 (400-700 nm). Further water use determinations were made at the four temperature regimes under 10/2 mbar VPD and an irradiance of 60 W m-2 (400-700 nm).
For a given species, transpiration rates increased with temperature at constant VPD under both irradiance environments, by factors ranging from 1.4 to 2.3. Transpiration rates of maize and paspalum (C4) were lower at a given temperature than were the rates of the C3 species, while lucerne and clover had the highest rates. Water use by lucerne was 2.5 to 3.5 times that of maize. Transpiration rates of maize and paspalum were lower under 60 W m-2 than under 170 W m-2 but irradiance had little effect on transpiration rate of the C3 species.
Though transpiration rate generally increased with increasing VPD, the difference in rates between plants at 5 mbar and 10 mbar VPD was much greater than between 10 mbar and 15 mbar.
The physiological adaption of different species to their growth environment is discussed, and the implications of the results with reference to water loss by young, single-spaced plants in the field is outlined.
Altitudinal Variation in the Photosynthetic Characteristics of Snow Gum, Eucalyptus pauciflora Sieb. ex Spreng. VI. Comparison of Field and Phytotron Responses to Growth Temperature
Authors: Slayter RO
Published: January 2006

A procedure for estimating field photosynthetic temperature optima from phytotron temperature response data, for elevational populations of E. pauciflora, is developed. It utilizes the principle that each population has a preferred temperature, Tpref, and an acclimation coefficient, α, which can be determined from phytotron-derived temperature response curves, and which enable the photosynthetic temperature optimum observed in a particular field temperature regime (Test) to be estimated from the expression
Test = Tpref - α(Tpref - Tequiv),

where Tequiv is a field temperature equivalent, in terms of its effect on the photosynthetic temperature optimum, to a known phytotron growth temperature.
Application of the procedure to sets of field and greenhouse data suggests that when Tpref and α are based on phytotron day growth temperatures, and when Tequiv is based on the proposition that a square-wave conversion of the field day-time temperature curve is equivalent to the phytotron day growth temperature, estimates of field and greenhouse temperature optima can be made which give good agreement with observed values. The agreement is best when active, current-year tissue is used as a basis of the field observations and when single leaves rather than shoots are used for field measurements.
The procedure is also used to compare actual rates of net photosynthesis, Pamb, obtained from field and phytotron studies, when both are plotted against equivalent temperature. Using this procedure, the large apparent differences between rates of net photosynthesis observed in the field and in the phytotron can be considerably reduced. This suggests that the notion of equivalent temperature may provide a useful means of minimizing the effects of physical, temperature-related differences in comparing field and phytotron responses, thereby widening the range of practical applications of phytotron experiments.
Alcoholic Fermentation and Malate Metabolism in Rice Germinating at Low Oxygen Concentrations
Authors: Avadhani PN , Greenway H , Lefroy R , Prior L
Published: January 2006

Germinating rice was exposed, in the dark, to low or zero O2 concentrations for 4-5 days by: (1) submergence under 4-5 cm of stagnant solution (3 ppm O2); (2) exposure to a N2 atmosphere; or (3) submergence under solutions flushed with N2.
These treatments completely inhibited root growth. Elongation of coleoptiles was stimulated in the stagnant solutions, but not in the N2 treatments.
In most experiments, low O2 concentrations resulted in twofold to eightfold increases of malate concentrations in the shoots. Absence of O2 during exposure to H14CO3-, for 30-60 min, inhibited CO2 dark fixation. This inhibition was considerably smaller when seedlings had been raised in N2 rather than in air. Under aerobic conditions during fixation, excised shoots from seedlings raised in N2 fixed more CO2 than shoots from seedlings raised in air.
Malate always contained 70% or more of the total fixed 14C, irrespective of the O2 regime during germination and during 14CO2 fixation.
Ethanol in stagnant solutions was shown to be formed by the rice seedlings, rather than by bacteria. Ethanol formation during one single day was 20-30-fold greater than the highest recorded amounts of malate in the seedlings. Alcoholic fermentation also responded quickly to changes in aeration regimes, indicating it was an important adaptive factor.
Another likely adaptive feature was the high K+ concentration in shoots, even of seedlings grown in the complete absence of O2. It is suggested that these high K+ concentrations have a function in maintaining turgor required for the rapid extension growth of the coleoptiles under low O2 concentrations.
Growth Responses on Young Wheat Plants to a Range of Ambient CO2 Levels
Authors: Neales TF , Nicholls AO
Published: January 2006

The growth of wheat seedlings in a closed environment was measured from day 10 to day 24 after germination, in 12 separate and sequential experiments, in which the imposed variable was the ambient CO2 concentration. CO2 levels between 200 and 800 volumes per million (vpm) and a daily irradiance of 6.5 MJ m-2 were used.
The effects of CO2 concentration on various growth parameters strongly interacted with plant age. For instance, in the 10-day-old plants, relative growth rate and net assimilation rate were increased (by 35 and 55% respectively) by an increase in CO2 levels from 200 to 800 vpm, whereas these two growth parameters were reduced (by 44 and 16%) in 24-day-old plants over the same interval of CO2 concentration. Also, increasing CO2 levels reduced the leafiness (leaf area ratio) of the plant, and increased the dry matter in the leaves (specific leaf weight).
It is suggested that the observed large interactions on plant growth of plant age and CO2 concentration account for the relatively small enhancement by CO2 enrichment of total plant biomass and economic yield that are reported in the literature.
Effect of Temperature on Growth of Five Subtropical Grasses. II. Effect of Low Night Temperature
Authors: Ivory DA , Whiteman PC
Published: January 2006

The relationship between level of night temperature and cessation of growth and the effect of cumulative cold nights on the continuation of growth in Cenchrus ciliaris, Chloris gayana, Panicum maximum var. trichoglume, P. coloratum var. makarikariense and Pennisetum clandestinum was examined in two experiments. Estimated critical mean daily temperatures causing cessation of growth of buffel, green panic and Makarikari grasses were about 12°C and for Rhodes and Kikuyu were about 8°C. However, with a day temperature of 20°C, 'critical' night temperatures of all species were below 4°C.
Where the night temperature was decreased from 14 to 4°C, significant decreases in net assimilation rate (EA), but not leaf area ratio (FA), occurred after 5 days in C. ciliaris and P. maximum. Over a period of 10 consecutive exposures to a night temperature of 4°C there was a significant decrease in relative growth rate (Rw) but no apparent adaptive change in either Rw or EA. Leaf stomatal resistance (rs) in these same species, however, was decreased in successive photoperiods (at 23°C) following continued exposure to 4°C at night. After 10 days, the mean rs values were significantly higher following 4°C than 14°C nights in C. ciliaris, P. maximum, C. gayana and P. coloratum, but not in P. clandestinum.
Agronomic and Physiological Responses of Soybean and Sorghum Crops to Water Deficits I. Growth, Development and Yield
Authors: Constable GA , Hearn AB
Published: January 2006

The aim of the work reported in this series of four papers was a better understanding of crop response to water deficits in an area where water available for irrigation is limited. In part I, data on the effect of frequency of irrigation, applied post-flowering, on the growth, leaf area development and yield of soybean, cvv. Bragg and Ruse, and sorghum, cv. TX610, are evaluated.
Sorghum outyielded both irrigated and rainfed soybeans (5400 versus 2800 and 1800 kg ha-1, respectively). Soil water deficits during pod filling in soybeans caused early leaf death and cessation of pod filling, thus decreasing yield. Irrigation at approximately 90 mm and 135 mm soil water deficit resulted in similar yields.
In sorghum and in Ruse soybeans, there was a significant (17-25%) loss in stem dry weight during grain filling, which may have been caused by the relocation of stored assimilates. In Bragg soybeans, only the rainfed plants had a loss in stem dry weight during grain filling.
Differences in crop dry weight occurred later than predicted by photosynthesis measurements. Several factors could have contributed to this discrepancy, and we highlight the need for a greater understanding of the contribution from lower leaves and also of the factors affecting the storage and remobilization of reserve assimilates during grain filling.
Differences in the Behaviour of Adaxial and Abaxial Stomata of Amphistomatous Sunflower Leaves: Inherent or Environmental?
Authors: Aston MJ
Published: January 2006

Experiments were carried out on sunflower, Helianthus annuus L., to determine whether the differences in behaviour between the abaxial and adaxial stomata of amphistomatous plants are inherent or due to leaf orientation. A single leaf enclosed in a cuvette was observed in normal and reverse orientation and the conductance of each surface was followed as Iight and humidity changed and the stem was severed. The differences in behaviour were found to be the result of leaf orientation rather than the result of inherent differences between adaxial and abaxial stomata.
Stomatal and Mesophyll Resistances in Two Clones of Pinus radiata D.don Known to Differ in Transpiration and Survival Rate
Authors: Bennett KJ , Rook DA
Published: January 2006

The gaseous exchange characteristics of two clones of P. radiata were compared. Clone 457, which had a low survival rate in the field, showed a transpiration rate up to twice that of clone 456, which had a high survival rate. Transpiration in both clones was not markedly affected by leaf-air vapour pressure differences varying between 0.4 and 1.4 kPa.
The stomatal resistance of clone 457 was almost half that measured for clone 456 under all experimental conditions; however, increasing the leaf-air vapour pressure difference resulted in increased stomatal resistances in both clones.
The photosynthetic response to CO2 concentration was also determined. The measured rates for clone 457 were twice those of clone 456 and both clones gave maximum rates of apparent photosynthesis above about 700 ng cm-3 internal CO2 concentration (corresponding to about 1400 ng cm-3 external concentration). The differences in photosynthetic rate could be accounted for by the greater than twofold difference in mesophyll resistance between the clones. Mesophyll resistance was not affected by altering the leaf-air vapour pressure difference.
It is suggested that a factor in determining the relative survival rate of the two clones is the greater ability of clone 456 to limit transpiration water loss and that this more than compensates for the reduced rate of photosynthesis of this clone compared with clone 457.