bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ Immunofluorescent Labelling of Ribulose-1,5-Bisphosphate Carboxylase in Leaves of C3 and C4 Plants
Authors: Hattersley PW , Watson L , Osmond CB
Published: January 2006

Antibodies raised to wheat and spinach ribulose-1,5-bisphosphate carboxylase (RuP2Case) have been used to locate the enzyme in hand-cut leaf blade transections of 40 C3 and C4 species, and one crassulacean acid metabolism (CAM) plant by immunofluorescence (using the indirect technique). The sample includes species from seven plant families, both monocotyledons and dicotyledons. In C3 and CAM species, specific fluorescence is associated with chloroplasts of all leaf chlorenchymatous cells when labelled with anti-RuP2 Case, while in species with 'classical' C4 leaf anatomy RuP2 Case is located almost exclusively in 'bundle sheath' ['Kranz' or 'photosynthetic carbon reduction' (PCR)] cell chloroplasts. Ten C4 species exhibit various types of 'non-classical' C4 leaf anatomy (Alloteropsis, Aristida, Arundinella, Cyperus, Fimbristylis, Triodia and Salsola types) and, for all but one of these types, immunofluorescent labelling of RuP2 Case provides the first direct experimental evidence of a cellular compartmentation of photosynthetic carbon metabolism and of the location of PCR compartments. Leaves of two Atriplex C3/C4 hybrid individuals and of Panicum milioides, a putative C3/C4 intermediate, exhibited a C3 antibody labelling response.
Leucyl β -Naphthylamidase Activities in Developing Seeds and Seedlings of Pisum sativum L
Authors: Collier MD , Murray DR
Published: January 2006

The activities of two soluble enzymes which hydrolyse L-leucyl �-naphthylamide have been measured in extracts from tissues of seeds and seedlings of Pisum sativum L. by using the chelator 1,10-phenanthroline as a selective inhibitor. In all the tissues studied, the phenanthroline-insensitive enzyme contributed the major proportion of the total activity against this substrate. In developing seeds, most of the activity of both enzymes is found in the maturing cotyledons, which develop maximum phenanthroline-sensitive and -insensitive activities respectively of 0.51 and 1.26 �mol per min per cotyledon (cv. Melbourne Market, dwarf) or 0.84 and 1.32 �mol per min per cotyledon (cv. Telephone, tall). In the cotyledons of germinating seeds, both enzyme activities increase within 24 h to values which are substantially lower than the maximum values found during development. These activities are maintained between 1 and 6 days from imbibition then they decline rapidly during the period of maximum rate of removal of protein from the cotyledon.
The highest activities of both enzymes occur in tissues which are very active metabolically. This supports the view that they function as aminopeptidases in the general turnover of cellular proteins, rather than playing some additional specific role in the mobilization of storage proteins during germination.
Response of Radiata Pine to Salt Stress. I. Water Relations, Osmotic Adjustment and Salt Uptake
Authors: Sands R , Clarke ARP
Published: January 2006

Transpiration, total needle water potential and osmotic water potential, and proline concentration in needle sap were determined in radiata pine (Pinus radiata D. Don) seedlings subjected to a step- wise decrease in osmotic potential of their liquid rooting medium by addition of CaCl2 or NaCl (absorbable), or PEG 4000 (non-absorbable). Resultant concentrations of N, P, K, Mg, Ca, Na, and Cl were determined in needle, stem, and root tissue as well as in expressed needle sap.
Seedling damage resulting from salt treatment was not due to water stress. CaCl2 caused greater damage than iso-osmotic concentrations of NaCI, and the damage was associated with Cl excess and an induced P deficiency. Seedlings rapidly salinized with NaCl rapidly and continuously absorbed ions into their needle sap until death, whereas those more slowly salinized appeared able to keep absorption to a lower level and escape visible injury. Proline accumulated in needle sap under both water and salt stress. Proline accumulation under salt stress could not be explained in terms of water stress alone. Radiata pine seedlings appeared better adapted to avoid rather than tolerate high ion concentrations in their living tissues.
Supply of Sucrose and Its Metabolism in Developing Grains of Wheat
Authors: Jenner CF , Rathjen AJ
Published: January 2006

Sucrose and other soluble carbohydrates were measured in the grain and other parts of ears of wheat growing in the field. Amounts of sucrose in the cells of the endosperm fluctuated conspicuously from time to time, but there was no marked reduction in sucrose as the grain ripened, and in the final stages of ripening, as the grain lost water, the apparent concentration of sucrose increased. Amounts of sucrose and other soluble carbohydrate in the rachis were more or less steady throughout the grain's growth with, perhaps, an upward trend as the grain ripened. In the peduncle, sucrose remained steady throughout, but amounts of other soluble carbohydrate fell progressively with time.
At frequent intervals throughout development, isolated endosperm was cultured for 5 h in solutions of [14C]sucrose to evaluate changes in its capacity to absorb and metabolize the sugar. Amounts of [14C]sucrose absorbed increased progressively with the age of the grain. No marked changes associated with development were observed in the incorporation of radioactivity into the fraction (excluding sucrose) extracted from cultured endosperm with boiling ethanol, even after the grains had ceased growing. However, amounts of [14C]starch produced in the cultured endosperm rose to a maximum at about the mid-point of the grain's development, and then fell progressively to near zero in endosperm in which the deposition of starch had ceased. Although the trends for other insoluble radioactive material resembled trends for starch, radioactivity was incorporated into this fraction in endosperm no longer able to synthesize radioactive starch.
These results are taken as evidence that the normal developmental pattern of accumulation of dry matter in the endosperm is determined within the endosperm itself, rather than through the provision of precursors from the rest of the plant.
Water Relations of Mountain Ash (Eucalyptus regnans F. Muell.) Forests
Authors: Connor DJ , Legge NJ , Turner NC
Published: January 2006

Measurements of the vertical gradients of water potential and stomatal resistance were made in adjacent mature and regrowth forests of mountain ash to follow diurnal and seasonal behaviour. The vertical gradient of water potential at dawn in either forest was shown to be consistent with the theoretical static head of -0.1 bar m-1 but the daytime gradients in the regrowth forest were steeper (down to - 0.45 bar m-1) than in the mature forest which did not fall below -0.27 bar m-1. Stomatal resistance measurements could not be related to height but, consistent with the water potential data, the leaves of the mature forest had higher resistance to water loss than did those of the regrowth. The observations are discussed in relation to the problems of water supply to the leaves of tall trees and the possible contribution of stomatal control to the established water yield characteristics of mountain ash forests.
Thermal Adaptation of Pennisetum: Leaf Photosynthesis and Photosynthate Translocation
Authors: Pearson CJ , Derrick GA
Published: January 2006

Leaf photosynthetic rates, loss of photosynthate 14C, sucrose concentrations and invertase activities were measured in three genotypes of Pennisetum growing at daylnight temperatures that ranged from 18/13 to 33/28°C. Leaves at low temperature had low photosynthetic rates, exported 14C more slowly, retained a higher proportion of photosynthate 14C, had higher sucrose concentrations and aged (physiologically) more slowly than did leaves growing at higher temperatures. The genotype that retained most photosynthate in the source leaves was the most cold-intolerant whereas there was no correlation between photosynthetic rates and previously observed growth rates.
Assimilate Source-Sink Relationships in Capsicum annuum L. II. Effects of Fruiting and Defloration on the Photosynthetic Capacity and Senescence of the Leaves
Authors: Hall AJ , Brady CJ
Published: January 2006

The photosynthetic capacity of leaves of fruiting Capsicum plants that expanded during or shortly after anthesis remained steady throughout the growth of the fruit. The formation and growth of the fruit was associated with a reversal of the decline in photosynthetic capacity of some of the leaves that had expanded before anthesis. In deflorated plants, the photosynthetic capacity of leaves at all levels of insertion declined continuously.
The variations with age of the net CO2 exchange of the leaf inserted one internode above the fruit were attributable almost exclusively to changes in intracellular resistance, while in the corresponding leaf of deflorated plants both leaf and intracellular transfer resistances were important determinants of photosynthesis.
Fruiting reduced the age-related loss of soluble and fraction 1 protein and of ribulosebisphosphate carboxylase activity in the leaf immediately above the fruit. The ratio of fraction 1 protein synthesis to that of other soluble proteins in fully expanded leaves showed no tendency to decline with age in plants of either type. Intracellular resistance in fruiting plants did not appear to be linked to changes in either fraction 1 protein content or ribulosebisphosphate carboxylase activity.
Contribution of the Root System to Nitrate Assimilation in Whole Cotton Plants.
Authors: Radin JW
Published: January 2006

Cotton (Gossypium hirsutum L.) is a species in which most nitrate is assimilated in the green shoot. A physiological role for the small amount of nitrate reductase activity in the roots can be questioned on the basis of relative magnitude. In this investigation, cotton plants were grown on nutrient solutions containing either 1 or 5 mM nitrate, and balance sheets were developed for the transport and metabolism of nitrate and reduced nitrogen in the root and shoot during exponential growth. At either nitrate level, assimilation in the roots was adequate to supply all the nitrogen for root growth. However, some of the reduced nitrogen was exported in the xylem, leaving a net deficit of about 10% at 1 mM nitrate and 36% at 5 mM nitrate. This deficit was presumably satisfied by reduced nitrogen from the shoot. Thus, at these two nitrate concentrations, root growth apparently depended more upon nitrogen assimilated in the roots themselves than upon nitrogen from the shoot. The different fates of nitrogen assimilated in the root and in the shoot may be related to the demonstrated differential regulation of nitrate reductase activity in these two sites.
Varietal Differences in Light Requirements for Germination of Celery (Apium graveolens L.) Seeds and the Effects of Thermal and Solute Stress
Authors: Pressman E , Negbi M , Sachs M , Jacobsen JV
Published: January 2006

Seed germination in one wild and two cultivated varieties of celery (Apium graveolens L.) was found to be light-dependent and mediated through the phytochrome system. Seeds of cv. Florida at 20°C were very sensitive to light and germination could be promoted by green safe light as well as by short far-red irradiation of brief duration, while seeds of wild celery did not respond to far-red and were less responsive to green safe light. At the optimal temperature, continuous irradiation with white light caused maximal germination in all varieties. The need for light could be satisfied in cv. Florida by two daily short irradiations. In wild celery, more than six short irradiations were needed, while in cv. Alabaster short irradiations did not bring about the full light effect. Daily alternating temperatures also could replace the light requirement. Two varieties, cv. Florida and the wild, differ in their tolerance to high temperature. Seed germination of wild celery is more thermophilic than that of cv. Florida. Thermodormancy is induced by 35°C of shorter duration in seeds of cv. Florida than in those of wild celery. Light enhanced the induction of thermodormancy. Solute stress increased the number of short irradiations required for germination.
Effects of Routine Handling on Maize Growth
Authors: Beardsell MF
Published: January 2006

Maize (Zea mays L. cv. XL45) plants were grown from seed in controlled-environment rooms. Twice-daily weighings of the plants and containers for 7 days reduced height, and removing plants from the rooms for two 20-min periods daily for 7 days gave significant reductions in stem and leaf dry weights and total leaf area. Transpiration rates were not affected by either of these treatments. Short-term removal from the rooms (up to 10 min daily) produced no significant reductions in plant characteristics. Measuring leaf lengths daily for 10 days resulted in significant reductions in stem dry weight and plant height. It is suggested that control plants should always be subjected to the same degree of handling as treated plants.
Observations on the Aleurone Layer. II. Fluorescence Microscopy of the Aleurone-Sub-Aleurone Junction With Emphasis on Possible β-1,3-Glucan Deposits in Barley
Authors: Fulcher RG , Setterfield G , Mccully ME , Wood PJ
Published: January 2006

The structural organization of the cell walls at the aleurone-sub-aleurone junction has been examined by fluorescence microscopy in ungerminated seeds of two varieties of Hordeum vulgare L. (cultivars Himalaya and Vanier). The sub-aleurone cell walls that are immediately adjacent to the aleurone layer are considerably thicker than the remainder of endosperm walls and contain extensive deposits of aniline blue-positive material. The latter was not significantly affected by periodate oxidation and was removed from tissue sections only by β-1,3-glucanases or hot dimethyl sulphoxide. These deposits may represent the primary substrate for endo-β-1,3-glucanases secreted by the aleurone layer during germination.
Nitrate Reductase Activity in Relation to Dwarfism in Sorghum bicolor (L.) Moench
Authors: Vaishnav PP , Bhatt K , Singh YD , Chinoy JJ
Published: January 2006

Nitrate reductase (NADH) (NR) activity in pot culture experiments was studied in nine cultivars of S. bicolor (L.) Moench varying widely in height at maturity. The data were computed for curvilinear regression analysis and a best-fit polynomial curve was obtained. The NR activity showed an inverse correlation with plant height. We suggest that the physiology of dwarfism is governed by a number of complex metabolic processes. Further, the dwarf cultivars, by virtue of their high NR activity, may prove better for the selection of high-yielding, protein-rich cultivars for genetic manipulations.
Transpirational, Leaf Area, Stomatal and Photosynthetic Responses to Gradually Induced Water Stress in Four Temperate Herbage Species
Authors: Johns GG
Published: January 2006

A series of physiological parameters was monitored under glasshouse conditions on micro-swards of four temperate herbage species. The micro-swards were grown on large soil cores so that the slow onset of water stress usually encountered in the field was simulated when water was withheld.
Generally, water use per unit cover continued at a high rate even when water stress was causing considerable leaf death. Leaf diffusive conductance fell only gradually and did not reach minimum values until after much of herbage on the swards was dead. Stomatal closure in all species reduced water use per unit foliage cover by only 20-30%.
Under increasing water stress, gross photosynthesis resembled stomatal conductances in remaining substantial (>50% of controls) even when relative water contents had fallen to below 80%. Both water use and gross photosynthesis were reduced more as a result of the reduced leaf area available for gaseous exchange than by the influence of stomatal action.
Leaf moisture retention curves were similar for all species, there being a loss of c. 10% of relative water content per unit leaf water potential, down to drier than -5 MPa.
It was concluded that the generally inferior herbage yields of white clover under dryland field conditions could be due in part to its relatively high leaf diffusive conductances when under water stress, while the better than average tall fescue yields under similar conditions may be attributed in part to its ability to roll its leaves tightly when water stress prevails.
Agronomic and Physiological Responses of Soybean and Sorghum Crops to Water Deficits. IV. Photosynthesis, Transpiration and Water Use Efficiency in Leaves
Authors: Rawson HM , Turner NC , Begg JE
Published: January 2006

Detailed diurnal measurements of photosynthesis, transpiration and water use efficiency of leaves of sorghum and soybean were made during the reproductive growth of field plants. Photosynthesis was measured mainly by infrared gas techniques. The indication in well watered plants was that diurnal net carbon fixation per unit area of sorghum leaves was some 2.3 times greater than that of comparably illuminated soybean leaves while concurrent transpiration losses were less. Simple carbon budgets for the two crops over 24 h suggested that the assimilation by a leaf area equivalent to that of the flag leaf was required solely to sustain respiration by the sorghum head during mid- grain filling, while approximately 5 cm� of leaf was required to sustain respiration of each soybean pod.
The comparisons made on a diurnal basis between plants of soybean exposed to different water deficits during grain filling demonstrated the increasing importance of early morning and late afternoon photosynthesis as water became less available. They also showed the rapidity with which plants can recover from stress once water is supplied. It is calculated that, for continuously clear conditions, as daily minimum leaf water potential fell from - 1 .5 to - 2.5 MPa, the integrated daily assimilation by leaves was reduced by about 9 % for every 0.1 MPa change; soybean leaves were not measured at leaf water potentials much below - 2.6 MPa. A ratio between gas phase and residual resistances remained relatively stable over the range of leaf water potential measured. However, the water use efficiency of single leaves was reduced with increasing soil water deficits because of changes in leaf temperature and leaf-to-air vapour pressure differences.
Effect of Ethylene on the Respiratory Response of Isolated Sweet Potato Mitochondria
Authors: Arron GP , Day DA , Grover SD , Laties GG
Published: January 2006

The plant hormone ethylene had no apparent effect on the redox state of the respiratory chain components of sweet potato mitochondria during oxidation of succinate. Low temperature e.p.r. spectra of sweet potato mitochondria, in various respiratory states, were not altered by the presence of ethylene. Oxygen uptake rates and ADP/O ratios of sweet potato mitochondria oxidising malate or succinate were also not affected by ethylene. The role of ethylene in the stimulation of respiration in plant tissues is discussed.
Physiological Basis of Genetic Differences in the Growth of Grains of Six Varieties of Wheat
Authors: Jenner CF , Rathjen AJ
Published: January 2006

The physiological basis of genetic variation in rate of accumulation of dry matter (growth) in wheat grain has been investigated by culturing ears of six different varieties on solutions of sucrose. Differences between varieties in accumulation of dry matter in the cultured ears were similar to those for grains growing in the field. Intracellular concentration of sucrose was positively correlated with increases in dry matter in treatments within varieties, but was not related to differences between varieties. In comparisons between varieties, high intracellular levels of sucrose were more often associated with low rates of accumulation of dry matter than with high rates. It is concluded that, within the varieties investigated here, genetic variation in the rate of deposition of dry matter in the endosperm is not attributable to variation in supply of assimilate to the grain.
No single or simple parameter of the growth of the grain at anthesis, or in the succeeding 2 weeks, was related to the grain's subsequent rate of growth. The weight of ethanol-insoluble material in the endosperm itself at day 19 was not indicative of the amounts of this fraction deposited in the endosperm in the week that followed day 19. Significant variation between the varieties was observed in the relationship (viz. the slope) between the intracellular amounts of sucrose and the rate of accumulation of ethanol-insoluble dry matter (mostly starch), a relationship which is presumed to reflect kinetic properties of the process(es) converting sucrose to starch. In the six varieties investigated, all the observed differences in grain growth rate could be attributed to variation in the slope defined above, and/or in day 19 endosperm dry matter. It is suggested that these two parameters reflect two independent physiological determinants, accounting for much of the genetic variation in the rate of growth of wheat grain.
Regulation of Movement of Assimilate Into Ovules of Pisum sativum Cv. Greenfeast: a 'remote' Effect of the Pod.
Authors: Williams AM , Williams RR
Published: January 2006

14CO2 was fed to the single leaf of pea plants (P. sativum cv. Greenfeast) pruned to leave one leaf and one pod. Localized heating of the pod, removal of ovules and determination of 14C activity in soluble sugars and starch fractions were used to investigate the enhanced movement of 14C from the leaf into the ovules at higher pod temperatures. The low levels of 14C detected in the starch fractions indicate that conversion of soluble sugars to starch is not involved in the response to temperature. The response was similar with only localized heating of the pod and with the ovules removed; therefore, it must be independent of the ovules. It is proposed that the pod tissue produces a stimulus which has a 'remote' effect on export of assimilates from the leaf.
Response of Barley Shoot Apices to Application of Gibberellic Acid: Initial Response Pattern.
Authors: Nicholls PB
Published: January 2006

Seedlings of barley (Hordeum vulgare L. cv. Clipper) were grown in either controlled-environment chambers or in a frost-free glasshouse in short days and were treated with aqueous gibberellic acid solutions at the 1½-leaf stage.
A single application of gibberellic acid resulted in enhanced rates of growth of the apex and subjacent leaf primordia for only a relatively short period in the life cycle of the plant. The first morphological response to the treatment was an increased dome length, which was followed by increased rates of growth and development of subjacent leaf primordia and basal spikelet primordia. After the period of enhancement, the growth rates of the apices of the treated plants fell to values comparable to those of the control plants.
Salinity Damage to Norfolk Island Pines Caused by Surfactants. I. The Nature of the Problem and Effect of Potassium, Sodium and Chloride Concentration on Uptake by Roots
Authors: Truman R , Lambert MJ
Published: January 2006

As part of an investigation into the deterioration of Norfolk Island pine, Araucaria heterophylla (Salisb.) Franco, on the coast of eastern Australia, seedlings were grown in nutrient solutions in which sodium was substituted for potassium over the range 0.1 - 2.1 mM to give six treatments, each with four ratios of sulfate to chloride. Potassium was freely taken up and translocated to the shoots, the levels in the shoots being higher than those in the roots. However, the levels of potassium in both shoots and roots were significantly reduced in solutions in which sulfate predominated over chloride. Uptake and translocation of sodium was restricted, the ratio of sodium (shoots) to sodium (roots) being less than unity. The concentration of chloride in the shoots and roots generally increased with increasing solution chloride concentration but was significantly reduced at the lowest potassium-to-sodium ratio.
In a second experiment the ratio of sodium to potassium was kept at 50:1, sodium and chloride in the solutions increasing from 2.5 to 460 mM and potassium from 0.05 to 9.2 mM. At the lower concentrations, uptake and translocation followed similar patterns to those found in the first experiment. However at solution concentrations of 20 mM sodium and above, levels of sodium in the shoots exceeded those of potassium and chloride. At sodium chloride concentrations of 260mM - 460mM, plants showed toxic symptoms with salt encrustations appearing on the stems.
Analysis of the saturation extracts of soils taken from beneath affected seaside trees showed that the concentrations of sodium and chloride were not sufficiently high to account for the high levels of these elements found in the shoots of affected trees.
Effects of Indoleacetic Acid on CO2 Fixation, Electron Transport and Phosphorylation in Isolated Chloroplasts
Authors: Robinson SP , Wiskich JT , Paleg LG
Published: January 2006

The effects of indoleactic acid (IAA) on CO2 fixation, electron transport and photophosphorylation were examined. The rate of CO2 fixation by preparations of intact chloroplasts was not significantly increased by the addition of IAA (0.2 - 5 �M). Electron transport and coupled phosphorylations were similarly unaffected when measured with ferricyanide or methyl viologen as the electron acceptor. Cyclic phosphorylntion mediated by phenazine methosulfate was also not increased by IAA. It is concluded that the hormone does not affect photosynthesis by isolated chloroplasts in short-term experiments and that the increased CO2 uptake observed with leaves following application of IAA may result from some effect of the hormone other than a direct interaction with the chloroplasts.
Radial Movement of Calcium and Magnesium to the Xylem in Roots of Zea mays
Authors: Ferguson IB
Published: January 2006

The appearance of calcium and magnesium in xylem exudate of excised roots of Z. mays seedlings has been used to compare movement of the two ions from the external solution to the xylem vessels. The ratio of calcium to magnesium in exudate was found to be higher than the ratio of the ions absorbed by the root, indicating a preference of root cells for magnesium over calcium. Whilst both ions follow a radial pathway predominantly in the apoplast, the capacity of plants for discriminatory absorption and transport of the two ions would appear to lie in differential absorption by the root cells of the ions moving in the apoplast.
Natural and Ethephon-Stimulated Ripening of F1 Hybrids of the Ripening Inhibitor (rin) and Non-Ripening (nor) Mutants of Tomato (Lycopersicon esculentum Mill.)
Authors: Tigchelaar EC , Mcglasson WB , Franklin MJ
Published: January 2006

The ripening inhibitor (rin) and non-ripening (nor) mutants each contribute additively as heterozygotes to delay ripening as measured by time from anthesis to the respiratory peak. The rin mutant as a heterozygote has no effect on the magnitude of the respiratory rise, whereas nor reduces the respiratory peak to about 50% of normal. The respiratory rise is further reduced to about 25% of normal in the double mutant hybrid (+ rin, + nor). Peak ethylene and fruit carotene production is reduced about 50% in single mutant hybrids and to 25% of normal in the double mutant hybrid. Polygalacturonase activity 5 days after the respiratory peak in heterozygotes of rin and nor and the double mutant hybrid was 35, 25 and 10% of normal, respectively. Ethephon treatment hastened ripening in all genotypes, but the magnitude of specific ripening events was determined by genotype. The mode of action of these mutants is not directly through endogenous ethylene but probably via a slow change which precedes the ethylene rise and other concomitant ripening changes. It is proposed that polygalacturonase synthesis or activation may represent the primary genetic event which is inhibited in the mutants and attenuated in mutant hybrids.
Adaptive Importance of Mesocotyl and Coleoptile Growth in Rice Under Different Moisture Regimes.
Authors: Takahashi N
Published: January 2006

The lengths of mesocotyls (first internodes) and coleoptiles of rice varied greatly with the moisture content of the seed-bed. The optimum moisture content in most Indica cultivars was much higher for coleoptile than for mesocotyl growth, but not in some Japonica cultivars because the mesocotyl growth was not vigorous and did not vary with water content.
Under submerged conditions, coleoptile growth was markedly stimulated, particularly in Japonica cultivars but there was no mesocotyl elongation in either cultivar.
The plastic variability in the growth of coleoptile, leaves, mesocotyl and other internodes may be an adaptive response of rice to the water tension of the soil.
Endogenous ethylene formation and effects of ethylene and carbon dioxide were also studied.
A Model of Mass Flow in the Phloem
Authors: Lang A
Published: January 2006

An analysis is made of the flow of sieve tube sap in the path region of a translocating plant. A model is presented which describes such flow and its applicability to several hypotheses of translocation mechanism is discussed. The physical characteristics to be expected of sap flow are considered including the concept of an optimum concentration of sugar. The special role which may be played by sucrose is examined and the possibility that translocation flow may have the dynamic characteristics expected of a compressible fluid is introduced. It is concluded that a Fick's law relationship will describe mass flow translocation very satisfactorily regardless of the mechanism of drive involved.
Carbon Balance of the Sultana Vine (Vitis vinifera L.) And the Effects of Autumn Defoliation by Harvest-Pruning
Authors: Scholefield PB , Neales TF , May P
Published: January 2006

Components of the carbon balance in the Sultana vine (Vitis vinifera L.) were examined with emphasis on the autumn, post-harvest, period. The net photosynthetic rate (PN) of leaves decreased from 0.30 to 0.03 mg CO2 m-2 s-1 from January to May (late summer to autumn). Two-thirds of this decline cocurred in the month before leaf fall. This decline in PN as senescence progressed was mainly due to increases in the 'residual', non-gas-phase, resistance to CO2 transfer. 14C-labelled assimilates were shown to move from the leaves to the perennial portions of the vine in both early and late autumn, and this 14C label reappeared in the shoot growth of the following spring. However, the level of carbohydrate reserves in shoots, roots or trunk in the autumn to spring period was not significantly affected by a severe (c. 60%) defoliation in early autumn. This level of defoliation, which the vine is able to tolerate without cumulative effects, occurs where Sultana vines are 'harvest-pruned' as part of the harvesting method of trellis drying.
Osmotic Adjustment of Sorghum and Sunflower Crops in Response to Water Deficits and Its Influence on the Water Potential at Which Stomata Close
Authors: Turner NC , Begg JE , Tonnet ML
Published: January 2006

The soil and plant water status of irrigated and unirrigated sorghum [Sorghum bicolor (L.) Moench cv. TX610] and sunflower (Helianthus annuus L. cv. Hysun 30) crops were compared on several days from the late vegetative to the early grain-filling stages of development. Additionally, the stems of plants from the irrigated and unirrigated plots of both species were cut near their base; this caused the plants to quickly dry until the stomata closed. The leaf water potential and leaf osmotic potential were measured when the stomatal resistance reached 6 s cm-� to give the water potential for stomatal closure and to provide osmotic potentials at equal turgor. Carbohydrate and potassium levels of leaves were also monitored.
The mean daily minimum leaf water potentials in the irrigated sorghum and sunflower did not decrease below - 1 7 MPa and - 2.0 MPa, respectively, but decreased to - 2.1 MPa in the unirrigated sorghum and -2.6 MPa in the unirrigated sunflower. The osmotic potential at stomatal closure in the rapidly dried plants decreased with increasing leaf water deficit in both sunflower and sorghum: in both species the osmotic potential decreased approximately 0.6 MPa for each megapascal decrease in leaf water potential. The results indicate that both sorghum and sunflower adjusted osmotically in response to water deficits and that adjustment occurred at a rate of at least 0.1 MPa per day. The lowering of osmotic potential persisted less than 9 days after the relief of stress in both sunflower and sorghum. The soluble sugar concentration increased linearly in both sunflower and sorghum with osmotic adjustment: the rate of increase of soluble sugars was significantly greater in sunflower than sorghum. No changes in potassium concentration were observed during osmotic adjustment.
The water potential at which the stomata closed varied from - 1.5 to -2.6 MPa in sorghum and - 1.7 to -2.7 MPa in sunflower: the water potential that induced stomatal closure decreased as the osmotic potential decreased. Stomatal closure occurred at a mean turgor of -0-5 MPa in both species: systematic error in the measurement of osmotic potential on frozen and thawed leaf tissue is considered the reason for the low turgor potentials at stomatal closure. The adaxial stomatal closed before the abaxial stomata in the sorghum and unirrigated sunflower but, since the leaf water potential initially fell rapidly and then became stable before the adaxial stomata closed, both the adaxial and abaxial stomata closed at the same leaf water potential.
Characterization and Localization of β-Lectins in Lower and Higher Plants
Authors: Clarke AE , Gleeson PA , Jermyn MA , Knox RB
Published: January 2006

The presence of a class of arabinogalactan proteins, known as β-lectins, as detected by their interaction with the Yariv antigen, has been extended from earlier work (Jermyn and Yeow 1975) to include a number of lower plants. A comparison is made of the amino acid and carbohydrate composition of β-lectins isolated from green leaves and seeds from a number of species. The protein content of the isolated β-lectins from leaves has a range of 3-8%, while those examined from seeds have a more variable protein content. The amino acid compositions of the β-lectins from both leaves and seeds are generally similar, usually with high levels of serine, glycine, alanine and hydroxyproline. The monosaccharide compositions are also similar with an overall range of galactose/arabinose values between 1.3 and 2.8. Trace amounts of fucose, rhamnose, mannose and xylose are often detected.
The β-lectins were localized in various tissues using the Yariv antigen as a histochemical reagent. Intense staining was observed within the secretory canals of both the stem and leaves of Hedera helix. However, the staining of the leaves and petioles of Zantedeschia and Alocasia species was mainly associated with the plasma membrane and the cell wall of the aerenchyma. Specific staining is also reported in the reproductive tissues of Gladiolus and the possible function of the β-lectins is these highly specialised tissues is discussed.
Effects of Shade on Gas Exchange and Growth in Seedlings of Eucalyptus grandis Hill ex Maiden
Authors: Doley D
Published: January 2006

E. grandis seedlings grown under conditions of high (12.6) and low (2.8 Em-2 day-) daily integrals of photon flux density exhibited the same light response of photosynthesis when the rates were expressed on a unit leaf volume basis. The conversion of photosynthetic substrate to dry matter was more efficient in larger than in smaller plants.
Allocation of dry matter between leaves, stem and roots was influenced relatively little by the shading treatments, but the utilization of dry matter by the leaves and stem was affected. Plants raised under low light exhibited significantly greater areas per unit weight of leaf, and significantly greater lengths per unit weight of stem than did plants raised in the high-light treatment. Adaptation to shading in E. grandis seedlings was judged to be limited. A model was constructed which described adequately the growth of these seedlings after the age of about 14 days.
Feedforward Responses of Stomata to Humidity
Authors: Farquhar GD
Published: January 2006

Models for the responses of stomatal conductance to changes in humidity difference between leaf and air are developed. Feedforward of the stomatal response to humidity difference is present when stomata respond to a portion of the rate of transpiration of the leaf that is unaffected by changes in stomatal aperture (cuticular transpiration). A simple linear model of the responses of conductance is sufficient to predict many phenomena reported in the literature. These include the presence, under specified conditions, of a peak rate of transpiration, and an increase in the conductance and humidity difference at which this peak occurs, with increased general levels of stomatal opening.
Salt Stress and Comparative Physiology in the Gramineae. I. Ion Relations of Two Salt- and Water-Stressed Barley Cultivars, California Mariout and Arimar
Authors: Storey R , Wyn Jones RG
Published: January 2006

Two barley cultivars, California Mariout and the somewhat more salt-sensitive Arimar, were grown under different salinity regimes and in isosmotic polyethylene glycol (PEG) solutions. Shoot growth of both cultivars was inhibited more by NaCl than by PEG. The effects of various salt and osmotic stress regimes on the K+, Na+ and Cl- status, the fresh weight : dry weight ratio and osmotic potential of the tissue were determined. The changes in these parameters were dependent on the rate at which the stress was applied. A gradual increase in stress led to K+/Na+ exchange in the shoot so as to maintain an almost constant (K+ + Na+) content on a dry weight basis. Tissue dehydration largely accounted for the increase in osmotic pressure. In contrast, salt shock resulted in a rapid nonselective accumulation of salt. Both osmotic stress and shock similarly brought about a dehydration of shoot tissue. A gradual osmotic stress slightly enhanced K+ accumulation in the roots. The greater salt sensitivity of the Arimar cultivar appeared to be related to a poorer ability to regulate Na+ plus Cl- accumulation in shoots.
Structural Aspects of Protein Accumulation in Developing Pea Cotyledons. I. Qualitative and Quantitative Changes in Parenchyma Cell Vacuoles
Authors: Craig S , Goodchild DJ , Hardham AR
Published: January 2006

Structural changes in pea cotyledons during development were studied using light and electron microscopy. Changes in the vacuolar system and cytoplasm of cotyledon parenchyma cells, during the period of storage protein deposition, are reported. Eight days after flowering, the parenchyma cells each contain one or two large vacuoles that are replaced by progressively smaller vacuoles during the next 10 days of development. Stainable material that can be histochemically identified as protein appears on the inner surface of the vacuole tonoplast 8 days after flowering. These vacuoles become smaller and more frequent during development and the amount of proteinaceous material within each vacuole increases until, at days 16-20 after flowering, they become densely packed with protein and are described as protein bodies. At day 8, the vacuole(s) have an average diameter of 39 �m, an average volume of 41 000 �m� , representing 75 % of the cell volume, and a surface area of 5500 �m�. By day 20, the average protein body diameter has fallen to 1 �m. There are, however, approx. 175 000 such protein bodies per cell, occupying 91 500 �m� or approx. 20 % of the cell volume, and whose total surface area is 550 000 �m�. The surface to volume ratlo of the vacuole/protein bodies Increases 55 times between days 8 and 20. Apart from this increase in surface area available for possible entry of protein, no mechanism for such entry can be suggested from our nlicrographs.
Wheat Grain Growth: Anthesis to Maturity
Authors: Thornley JHM
Published: January 2006

A model of the wheat plant is described which consists of two components, the grain and storage material. Photosynthesis supplies further substrate to the store, from which material is used for grain growth at a rate that depends on the substrate level. The model allows predictions of grain dry weight at maturity and its dependence on total post-anthesis dry matter production, and leads to an interpretation of the source-sink interactions in this situation.
Distribution of Autofluorescence and Esterase and Peroxidase Activities in the Epidermis of Wheat Roots
Authors: Smith MM , O'brien TP
Published: January 2006

In the wheat root, peroxidases and esterases specific for a-naphthyl esters of acetate, propionate and butyrate are concentrated in cell walls, particularly the outer wall of epidermal cells undergoing extension. In contrast esterases specific for β-naphthyl esters of propionate and butyrate were intra- cellular and concentrated in epidermal and outer root-cap cells of the wheat root. Both α-naphthyl and β-naphthyl esters of longer-chain fatty acids proved to be poor substrates. The esterases and peroxidases associated with the outer epidermal wall may well be involved in turnover of phenolic acids cross-linked to polysaccharides. In this regard, ferulic acid and diferulate were shown to be constituents of wheat-root cell walls. The distribution of these substances can also be inferred from autofluorescence. Treatment with a commercial pig-liver esterase was without effect on the auto- fluorescence of the root cell-walls. Culture filtrates from Gaeumannomyces graminis did remove significant amounts of autofluorescent wall material. These preparations contained α-naphthyl acetate esterase as well as many polysaccharide hydrolase activities.
Effect of Calcium and Other Minerals on Ripening of Tomatoes
Authors: Wills RBH , Tirmazi SIH
Published: January 2006

Ripening of green tomatoes (Lycopersicon esculentum) cv. Daydream, as expressed by change of colour, increased ethylene evolution and respiration, was inhibited when the calcium content of the fruit was raised to greater than 40 mg/100 g fresh weight (1 mmol Ca/100 g). The inhibition of ripening was long-lasting as such fruit showed no signs of ripening even after 6 weeks storage at 20°C, and the application of 1000 �l/l ethylene for 3 weeks had no effect. Application of calcium also inhibited the ripening process in tomatoes that had commenced ripening. Further change in colour was halted and a reduction in respiration and ethylene evolution was observed when calcium was applied at any stage of ripening including fully ripe. Inhibition of ripening was not specific to calcium as other divalent metal ions-manganese, cobalt and magnesium-were as effective as calcium, while the monovalent metal ions sodium and potassium were less effective than calcium but did give some retardation of ripening. Silver was as effective as the divalent metals in inhibiting colour change but its effect on ethylene production was similar to that obtained with sodium and potassium.
Antitranspirants and the Regulation of Abscisic Acid Content
Authors: Milborrow BV
Published: January 2006

The antitranspirants farnesol and phenylmercuric acetate increased abscisic acid (ABA) contents of spinach leaves by the same amount as wilting, and so this can account for stomatal closure. It is now proposed that leaf ABA contents are regulated by chloroplast permeability and a mechanism for this is described. ABA and its conjugate occur in the protoplasm of citrus fruit vesicle cells; considerably less is in the vacuolar sap.
Recovery Growth Following Water Deficits of Different Duration in Prairie Grass
Authors: Chu ACP , Mcpherson HG , Halligan G
Published: January 2006

Recovery of rates of leaf emergence, leaf extension, tiller number, leaf number, leaf area and shoot dry weight per plant following water deficits lasting for between 10 and 28 days was measured in Bromus catharticus in a controlled environment.
The rate of leaf extension recovered to the rate of control plants within 4-6 days of rewatering and then exceeded the control rate for up to 28 days. During this time, four or five new leaves emerged. The maximum rate of leaf extension for individual leaves during recovery was up to 20% higher than rates typical for leaves of the same insertion on well watered control plants.
During an initial recovery phase which followed the 28-day water deficit, and which lasted 20 days from rewatering, the rates of increase in tiller number, leaf number, and leaf area per plant were greater than control rates by 38, 48 and 51%, respectively. Rates for these components of yield then normalized. Relatively small differences among treatments were measured for rate of shoot dry matter accumulation. Final shoot dry weight was approximately proportional to the number of 'non- drought' days, which were defined as those days on which the leaves showed no sign of wilting. This also corresponded to day-time leaf water potentials higher (less negative) than - 1400 kPa.
Effect of Early Mycorrhizal Infection on Nodulation and Nitrogen Fixation in Trifolium subterraneum L
Authors: Smith SE , Nicholas DJD , Smith FA
Published: January 2006

Three experiments are described. Rapid establishment of vesicular-arbuscular mycorrhizas in roots of T. subterraneum cv. Mt Barker, using natural soil inoculum, was associated with improved nodulation, increased nitrogenase activity per plant (nmol C2H2 reduced per plant per hour) and increased nodule efficiency on the basis of nodule volume (nmol C2H2 reduced per mm� nodule per hour). In two experiments (on soil low in nutrients), this increase occurred before any positive growth response to mycorrhizal infection was apparent. In all experiments, mycorrhizal roots had a higher phosphorus concentration (%P) than did non-mycorrhizal roots. This difference, which was evident before any differences in total plant phosphorus were detected, was not accompanied by an increase in nodule phosphorus concentration, so that differences in nodule efficiency could not be attributed to differences in this parameter.
In the third experiment (on soil with higher nutrient levels), establishment of mycorrhizas was also accompanied by increased growth, phosphorus and nitrogen contents within a 35-day experimental period. Phosphorus inflow into roots (moles P per cm root per second) was higher in mycorrhizal plants. Delay in formation of mycorrhizas (by reduction in the amount of inoculum in soil) was accompanied by lower inflow, and delay in both the establishment of high root phosphorus concentration and in the onset of enhanced nodulation and nitrogenase activity.
Electrical Assessment of Injury and Mortality of Eucalyptus obliqua L'hérit. Seedlings After Heat Stress and Decapitation
Authors: Moore GM
Published: January 2006

A wide-range a.c. bridge was used to assess injury and mortality in E. obliqua seedlings following heat stress. The impedance ratio of the lower stem was correlated with other methods of assessing injury such as the degree of defoliation and the capacity for subsequent growth. Seedlings were also decapitated and the extent of injury was compared with heat-stressed plants. It seems that the effect of decapitation is a major component of the injury caused by heat stress.