Showing papers in "Functional Plant Biology in 1977"
TL;DR: The duration of linear grain growth was scarcely influenced by illuminance, but was greatly reduced as temperature rose, with pronounced effects on grain yield per ear, and the cessation of grain growth did not appear to be due to lack of assimilates.
Abstract: Controlled-environment conditions were used to examine the effects of cultivar and of temperature and illuminance after anthesis on grain setting and on the duration and rate of grain growth. After an initial lag period, which did not differ greatly between cultivars, grain dry weight increased linearly under most conditions until final grain weight was approached. Growth rate per grain depended on floret position within the ear, varied between cultivars (those with larger grains at maturity having a faster rate), and increased with rise in temperature. With cultivars in which grain number per ear was markedly affected by illuminance, light had relatively little effect on growth rate per grain. With those in which grain number was less affected by illuminance, growth rate per grain was highly responsive to it, especially in the more distal florets. In both cases there was a close relation between leaf photosynthetic rate as influenced by illuminance, the rate of grain growth per ear, and final grain yield per ear. The duration of linear grain growth, on the other hand, was scarcely influenced by illuminance, but was greatly reduced as temperature rose, with pronounced effects on grain yield per ear. Cultivars differed to some extent in their duration of linear growth, but these differences accounted for less of the difference in final weight per grain than did those in rate of grain growth. Under most conditions the cessation of grain growth did not appear to be due to lack of assimilates.
455 citations
TL;DR: The grain was the tissue most flexible in its responsiveness to changes in assimilation under the conditions of the summer experiment, and the growth response to CO2 enrichment was relatively greater under the low radiation than the high radiation regime.
Abstract: Wheat (cv. WW15) was grown as a crop stand in different CO2 concentrations (ambient, ambient plus 200 ± 20 vpm CO2, ambient minus 150 ± 20 vpm CO2) from germination to maturity in naturally lit growth cabinets under winter or summer light conditions, at 21°C by day and 16°C at night. Ambient CO2 concentration during the daylight hours averaged 280-300 vpm. CO2 level had little effect on phenology of the mainshoot; most of the growth response was through tillering. From data on flag leaves in the winter light experiment, there was no indication of any positive or negative feedback on growth acting through maximum leaf net photosynthesis rate. Leaf area index was increased by CO2 at low light and the related self-shading acted as a negative feedback partially countering the effect due to an enhanced rate of CO2 uptake per unit leaf area. Dark respiratory CO2 loss represented a greater proportion of CO2 uptake in the light for the CO2-depleted crop than for the control crop. But the reciprocal effect was not evident for the enriched crop. Contrary to classical ideas on growth responses to variation of colimiting factors, the growth response to CO2 enrichment was relatively greater under the low radiation than the high radiation regime. The grain was the tissue most flexible in its responsiveness to changes in assimilation under the conditions of the summer experiment. For this crop, for which the grain yield of the control was very high (0.97 kgm-2), response of yield to CO2 enrichment corresponded to 0.25% per vpm.
144 citations
TL;DR: Plants of five cultivars of wheat were grown under controlled-environmental conditions in order to analyse the effect of cultivar and of temperature and illuminance after anthesis on the accumulation of nitrogen and phosphorus by grains in relation to dry matter.
Abstract: Plants of five cultivars of wheat were grown under controlled-environmental conditions in order to analyse the effect of cultivar and of temperature and illuminance after anthesis on the accumulation of nitrogen and phosphorus by grains in relation to dry matter. The water relations of the grain during maturation were also examined, using calcium content as an index of water entry. The nitrogen and phosphorus contents of grains increased linearly throughout the grain growth period. The percentage of nitrogen and phosphorus in grains fell sharply during the first few days after anthesis but rose progressively thereafter. The higher the temperature, and the lower the illuminance, the higher was the percentage of nitrogen in the grain of all cultivars. Such conditions also reduce final grain size, but their effects on nitrogen concentration in the grain were apparent early in grain development. No evidence was found of a flush of nitrogen or phosphorus into the grain late in its development. Water entry into the grain continued at a steady rate until maximum grain dry weight was reached, then ceased suddenly. No evidence was found of an increased rate of water loss by the grain at that stage, and the rapid fall in water content at the cessation of grain growth may have been due to blockage of the chalazal zone of entry into the grain by the deposition of lipids. Accumulation of dry matter, nitrogen and phosphorus and entry of water into the grain all ceased at the time of lipid deposition in the chalazal zone.
127 citations
TL;DR: It is clear that mycorrhizal enhancement of phosphate uptake and nitrogen fixation precedes any effect on growth and the results indicate the importance of the time factor in the development of this tripartite symbiosis between legume, Rhizobium and mycorRHizal fungus.
Abstract: Nodulated Medicago sativa cv. Europe plants, both non-mycorrhizal and mycorrhizal (inoculated with Glomus mosseae), were grown in sand or soil with a range of phosphate levels. The following parameters were measured: intensity of mycorrhizal infection, intensity of nodulation, growth, phosphate content, nitrogenase activity (acetylene reduction) and nitrogen content. Both nodulation and mycorrhizal infection had occurred within 2 weeks of inoculation with the appropriate endophytes. Major increases in dry weight of mycorrhizal plants were not apparent until approximately 10 weeks from inoculation. However, mycorrhizal plants showed more extensive nodulation, coupled with higher rates of nitrogenase activity from 2 weeks onwards, and at the final (12-week) harvest had higher values of % N. Phosphate content of mycorrhizal plants (µg P/g dry wt) was also greater than non-mycorrhizal plants at 7 weeks. By 10 or 12 weeks, when significant mycorrhizal enhancement of growth was apparent, the total nitrogen and total phosphorus per mycorrhizal plant were also higher, but nitrogenase activity and phosphate content measured on a dry weight basis showed no significant differences between mycorrhizal and non-mycorrhizal plants. It is clear that mycorrhizal enhancement of phosphate uptake and nitrogen fixation precedes any effect on growth and the results indicate the importance of the time factor in the development of this tripartite symbiosis between legume, Rhizobium and mycorrhizal fungus.
98 citations
TL;DR: Water-soluble arabinogalactan-proteins have been isolated from tissue-cultured rye grass endosperm cells and their culture medium by precipitation with the β-glucosyl Yariv artificial antigen and show homologies both in their peptide and polysaccharide portions.
Abstract: Water-soluble arabinogalactan-proteins have been isolated from tissue-cultured rye grass endosperm cells and their culture medium by precipitation with the β-glucosyl Yariv artificial antigen. The intracellular and extracellular polymers are similar in composition and molecular size (apparent mol. wt 2.2 — 2.8 × 105). The protein portion represents up to 7% of the molecule and is rich in hydroxyproline, alanine and serine. The carbohydrate portion (84%) consists solely of arabinose (36%) and galactose (64%) and methylation analysis shows it to be a branched 1,3 : 1,6-galactan substituted by arabinofuranosyl residues. The carbohydrate compositions and methylation analyses for polymers precipitated by the β-glucosyl Yariv antigen from lima beans, cashew, tomato, silver beet and asparagus and an arabinogalactan-peptide from wheat endosperm are compared. As a group, they show homologies both in their peptide and polysaccharide portions. A histochemical method, based on precipitation with the β-glucosyl Yariv antigen, showed the binding polymers to be localized in discrete irregular vesicles in the tissue-cultured rye grass endosperm cells. Native rye grass endosperm cells show staining between starch granules, and staining is also seen in the aleurone cells of barley, wheat and rye grass.
85 citations
TL;DR: The pattern of the photosynthetic responses to growth temperature was generally similar for all populations but the material from the lowest-elevation, warmest, site showed the highest temperature optimum and significantly higher rates of net photosynthesis at the highest growth temperature.
Abstract: The photosynthetic responses of three altitudinal populations of snow gum, E. pauciflora Sieb. ex Spreng., were examined on material grown at a range of day/night temperatures from 8/4 to 33/28°C. The pattern of the photosynthetic responses to growth temperature was generally similar for all populations but the material from the lowest-elevation, warmest, site showed the highest temperature optimum and significantly higher rates of net photosynthesis at the highest growth temperature. In a corresponding way, the material from the highest-elevation, coldest, site showed the lowest temperature optimum, and significantly higher rates of net photosynthesis at the lowest growth temperature. This pattern, also reflected in the responses of rI, the intracellular resistance, and rI, the gas-phase resistance, supported the view that E. pauciflora shows continuous variation in physiological responses through its altitudinal range. The peak values of net photosynthesis were high for all populations, but were greatest, 81 ng cm-2 s-1, in the lowest elevation material and decreased to 72 ng cm-2 s-1 in the highest-elevation material. Corresponding values of rI ranged from 2.5 - 3.0 s cm-1, and for rI from 2.4 - 3.3 s cm-1. These levels compare favourably with levels reported for other woody species.
80 citations
TL;DR: The rate of elongation of sunflower hypocotyl sections was found to be dependent on the rate of growth of the outermost cell layers of that tissue, and it is speculated that the peripheral cell layers are the site of both geoperception and georesponse.
Abstract: The rate of elongation of sunflower (Helianthus annuus L.) hypocotyl sections was found to be dependent on the rate of growth of the outermost cell layers (peripheral cell layers) of that tissue. Hypocotyl sections from which those layers had teen peeled grew but did not show typical geotropic curvature. A model of geotropic curvature is proposed where the differential growth causing curvature is due to a differential rate of elongation between the upper and lower peripheral cell layers of a horizontal shoot. In the model it is speculated that the peripheral cell layers are the site of both geoperception and georesponse. The model does not involve a lateral movement of a growth regulator and experiments with longitudinally bisected hypocotyl sections provided evidence consistent with this model but inconsistent with the Cholodny-Went theory of geotropism.
79 citations
TL;DR: Photosynthetic temperature response curves were measured on seedlings of E. pauciflora grown from seed collected at high (1770 m) and low (915 m) elevation sites, in the Snowy Mountains and similar response patterns were observed in intracellular resistance, ri, and gas phase resistance, Ri.
Abstract: Photosynthetic temperature response curves were measured on seedlings of E. pauciflora grown from seed collected at high (1770 m) and low (915 m) elevation sites, in the Snowy Mountains. The material was grown in contrasting day/night temperature regimes (33/28 and 15/10°C) in the Canberra phytotron. The material from the high elevation site showed a temperature optimum at about 20°C when grown at 15/10°C and at about 25°C when grown at 33/28°C. By comparison, the temperature optimum for the low elevation material was near 25° when grown at 15/10°C and shifted to about 30° when grown at 33/28°C. The general form of the temperature response curves was similar for both sets of material, although net photosynthesis of the higher elevation material dropped off more rapidly at temperatures above and below the optimum. When grown at 15/10°C, peak Ievels of net photosynthesis were higher in the high elevation material (66 ng cm-2 s-1 v. 54 ng cm-2 s-1). When grown at 33/28°C, peak levels were higher in the low elevation material (78 ng cm-2 s-1 v. 60 ng cm-2 s-1). Similar response patterns were observed in intracellular resistance, ri, and gas phase resistance, ri, although there was relatively more change in ri, and relatively less change in ri, with respect to growth temperature and material, than in net photosynthesis. The most conservative parameter that was measured was the CO2 compensation point, Γ. Although it showed a strong dependence on measurement temperature, Γ was not significantly influenced by growth temperature or site location at the levels of probability used.
66 citations
TL;DR: Net assimilation rates of fruiting plants exceeded those of deflorated plants, and these differences appeared to be associated with alterations in assimilate demand, indicating that leaves of these plants retain their photosynthetic capacity long after full expansion.
Abstract: 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.
60 citations
TL;DR: The relationship between the observed photosynthetic temperature optimum and the day temperature of the growth regime indicated a preferred temperature for photosynthesis of 20.0°, and a tendency for the temperature optimum to shift by 0.34° per degree shift in the day growth temperature.
Abstract: Photosynthetic temperature response curves were measured at leaf temperatures from 10 to 40°C on seedlings of E. pauciflora grown from seed collected at tree-line (elevation 1905 m) in the Snowy Mountains area and at three lower elevations, 915, 1215 and 1645 m, which correspond to those used in an earlier field study (Slatyer and Morrow 1977). The material was grown in naturally lit, temperature-controlled greenhouses at day/night temperatures of 8/4, 15/10, 21/16, 27/22 and 33/28°C. Comprehensive measurements were made on the tree-line population, in which peak rates of net photosynthesis, Pamb, reached 75 ng cm-2 s-1 at a temperature of 20°°C, from material grown at 21/16°. Minimum levels of intracellular resistance, rt, were 2.8 s cm-1, and of leaf gas-phase resistance to CO2 transfer, r1, were 3.2 s cm-1. Changes in rt and r1, with measurement temperature, appeared to be of approximately equal importance in mediating the overall photosynthetic temperature response. Changes in the CO2 compensation point, Γ were of increasing importance at higher measurement temperatures. The photosynthetic temperature optimum was markedly affected by the growth temperature regime. In the tree-line population, it increased from about 16° when grown at 8/4° to 24° when grown at 33/28°. The relationship between the observed photosynthetic temperature optimum and the day temperature of the growth regime indicated a preferred temperature for photosynthesis of 20.0°, and a tendency for the temperature optimum to shift by 0.34° per degree shift in the day growth temperature. A similar effect of growth temperature on the photosynthetic temperature optimum was noted in the three lower-elevation populations, in which preferred temperatures of 21.5, 24.2 and 27.2° were calculated for the material collected at 1645, 1215 and 915 m respectively. These temperatures were several degrees higher than the field-observed temperature optima, although the gradient of preferred temperature with elevation was comparable to that noted in the field study.
58 citations
TL;DR: Although there is no absolute requirement for long days to induce flowering in S. alba, light reactions cther than photosynthesis probably contribute to photoperiodic induction in this species.
Abstract: Flowering can be induced in the long-day plant Sinapis alba in 8-h photoperiods provided that the irradiance is close to that at which leaf photosynthesis is light-saturated (e.g. 96 J m-2 s-1). Three such 8-h cycles result in 10% flowering and six are required for full flowering, whereas only one long-day cycle of 16-20 h duration at a much lower irradiance (25 J m-2 s-1) is required for full flowering. High irradiance during the single long day promotes flowering when given for the first 8 h of a 16-h photoperiod, but is inhibitory over the last 8 h. Photosynthetic CO2 uptake is crucial for this response to high irradiance, as both its inhibitory and promotive effects on flowering are reversed by the removal of atmospheric CO2 during the period of high irradiance. Compared with plants kept in short days (8-h photoperiod), export of 14C-labelled assimilates from the leaf during a 24-h period was only 50-60% greater in plants exposed to a long day (20-h photoperiod), because plants in short days compensated to a degree for their shorter photosynthetic period by mobilizing leaf reserves during darkness. However, flowering can occur with no evident enhancement of supply of assimilate to the shoot apex, for example following dis- placement of the short day or on removal of atmospheric CO2 during the last 12 h of exposure to a 20-h long day. Also, the flowering response to radiant flux density during the second half of a long day shows an optimum between 15 and 70 J m-2 s-1, with reduced flowering both above and below this irradiance. Thus, although there is no absolute requirement for long days to induce flowering in S. alba, light reactions cther than photosynthesis probably contribute to photoperiodic induction in this species.
TL;DR: 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 and, consistent with the water potential data, the leaves of the mature forest had higher resistance to water loss than did those of the regrowth.
Abstract: 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.
TL;DR: The photosynthetic capacity of leaves of fruiting Capsicum plants that expanded during or shortly after anthesis remained steady throughout the growth of the fruit, and 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.
Abstract: 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.
TL;DR: The water potential of spikelets was appreciably higher than that of flag leaves, especially at low values of the latter, and hence, spikelets survived longer periods of water deficit than leaves.
Abstract: 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.
TL;DR: 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, is supported.
Abstract: The activities of two soluble enzymes which hydrolyse L-leucyl s-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 µmol per min per cotyledon (cv. Melbourne Market, dwarf) or 0.84 and 1.32 µmol 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.
TL;DR: 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.
Abstract: 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.
TL;DR: In pear leaf tissue, sorbitol may be segregated into a non-metabolic pool, thus serving as a specific storage compound in place of sucrose as in other plants.
Abstract: Pear (Pyrus domestica Medik.) leaf slices, which form sorbitol photosynthetically, took up sorbitol from solution by an active transport mechanism. Uptake was linear with time, was sensitive to metabolic inhibitors and cold, occurred against a concentration gradient, and was not reversed by washing the tissue. Glucose uptake was similar to sorbitol uptake, but showed consistent differences in response to tissue aging, sugar concentration, light, and to competing sugars and sugar analogues. There was little competition between sorbitol and glucose, suggesting that the two may be taken up by separate mechanisms. The relationship of uptake to concentration could be interpreted as biphasic with constants resembling those for sugar uptake in other tissues: for sorbitol, (a) Km 3 × 10-3M and Vmax 1000 nmol per g fresh wt per h, (b) Km 1 × 10-1 M, Vmax 19 500; and for glucose, (a) Km 1 × 10-3 M and Vmax 600, (b) Km 0.6 × 10-1 M and Vmax 10 500. The ability of various species to accumulate sorbitol was compared. Species which normally contain sorbitol accumulated it as readily as glucose, while other species accumulated it much less rapidly. In pear leaf tissue, sorbitol was poorly metabolized while glucose was largely converted to sorbitol. In rose (Rosa sp., cultivated) leaf tissue (which does not contain sorbitol), sorbitol and glucose were both extensively metabolized to sucrose and other compounds. In pear, sorbitol may be segregated into a non-metabolic pool, thus serving as a specific storage compound in place of sucrose as in other plants.
TL;DR: Values for plasmalemma influx of K+ into excised barley roots, from solutions containing 0.05 mM KCl plus 0.5 mM CaSO4, were reduced by 50-60% following a 6-h pret treatment period, independent of DNA, RNA and protein synthesis during the pretreatment period.
Abstract: Values for plasmalemma influx of K+ into excised barley roots, from solutions containing 0.05 mM KCl plus 0.5 mM CaSO4, were reduced by 50-60% following a 6-h pretreatment period in 50 mM KCl plus 0.05 mM CaSO4 solution. This reduction of influx, associated with increased internal K+ concentration, was independent of DNA, RNA and protein synthesis during the pretreatment period as indicated by its insensitivity to the presence of 5-fluorodeoxyuridine, actinomycin D, cycloheximide, p-fluorophenylalanine or anisomycin in the pretreatment solutions. Roots of plantlets grown from gamma-irradiated barley seeds, which were incapable of under-going cell division and capable of only limited protein synthesis, were nevertheless able to reduce K+ influx values in response to increased internal K+ concentration. The measurement of K+ influx from 0.05 mM KCl solutions following pretreatment periods as short as 15 min in 50 mM KCl gave no evidence of any lag period in the development of reduced influx associated with increased internal K+ status. The above experiments are discussed in terms of a model for the regulation of K+ influx which ascribes a direct 'allosteric' role to internal K+ in controlling influx.
TL;DR: 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).
Abstract: 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.
TL;DR: Simultaneous measurements of the separate plasmalemma and tonoplast capacitance and conductance (as a function of frequency) are described and the frequency dependence of the capacitance determined from vacuolar measurements was nearly the same as that of the plas malemma alone.
Abstract: Simultaneous measurements of the separate plasmalemma and tonoplast capacitance and conductance (as a function of frequency) are described. For frequencies > 1 Hz, the capacitance of both membranes increased with decreasing frequency. Below 1 Hz, two distinctly different types of behaviour were observed: either the membrane capacitances continued to increase, reaching values of 0.5 F/m² (50 µF/cm²) at 0.07 Hz, or the membranes became inductive at very low frequencies. At frequencies > 10 Hz, the tonoplast capacitance was 1.5-3 times higher than that of the plasmalemma and increased more rapidly with decreasing frequency. Notwithstanding this, in each case the frequency dependence of the capacitance determined from vacuolar measurements (i.e. tonoplast, cytoplasm and plasmalemma in series) was nearly the same as that of the plasmalemma alone. The conductance of the tonoplast at all frequencies was 4-10 times higher than that of the plasmalemma.
TL;DR: The seedcoats contain almost all of the acid phosphatase activity in the pea seed in the earliest stages of expansion and declines as the embryo matures, while the developing cotyledons show a later rise in acid phosph atase activity to a maximum shortly before dehydration.
Abstract: The seedcoats contain almost all of the acid phosphatase activity (EC 3.1.3.2) in the pea seed in the earliest stages of expansion. The seedcoat activity is maximal by the end of the period of rapid cell expansion and declines as the embryo matures. The developing cotyledons show a later rise in acid phosphatase activity to a maximum shortly before dehydration. The activity in the embryonic axis shows a marked increase only during dehydration. The acid phosphatase activity in the seedcoats results almost entirely from an isoenzyme with high electrophoretic mobility in 5.5% polyacrylamide gels (RF 0.97). This isoenzyme has not been detected in other tissues from the plant. The phosphatase activity in the cotyledons is accounted for by one major isoenzyme at RF 0.75 and by four minor components. The partially purified enzyme from the seedcoats shows a broad pH optimum from pH 5.0 to pH 6.0. In contrast, the preparation from the cotyledons has an optimum close to pH 5.6 and is slightly more sensitive to inhibition by 0.2 mM PI.
TL;DR: When 14CO2 was supplied as a 30-s pulse to photosynthesizing apricot leaves, the pattern of the various phosphate esters, organic acids and amino acids was consistent with the operation of the normal C3 photosynthetic pathway.
Abstract: When 14CO2 was supplied as a 30-s pulse to photosynthesizing apricot leaves, the pattern of the various phosphate esters, organic acids and amino acids was consistent with the operation of the normal C3 photosynthetic pathway. Fructose 6-phosphate became labelled much more rapidly than glucose 6-phosphate and fructose was more rapidly labelled than glucose. Sorbitol was the major end-product of photosynthesis, becoming the predominant 14C-containing compound within 10 min of starting the 14CO2 pulse, and containing more than half the total radioactivity after 30 min. Sorbitol may be synthesized by way of fructose or fructose 6-phosphate rather than glucose or glucose 6-phosphate. Sorbitol phosphate was shown to be present in the tissue as 2% of the total hexose monophosphate, and to become labelled as rapidly as the hexose monophosphates. The pathway of sorbitol synthesis may therefore follow the sequence: fructose 6-phosphate → sorbitol phosphate → sorbitol.
TL;DR: Established, field-grown, seedlings of Eucalyptus pauciflora were transferred from high- and low- elevation field sites to a controlled-environment greenhouse in Canberra and the pattern of photosynthetic acclimation observed.
Abstract: Established, field-grown, seedlings of Eucalyptus pauciflora were transferred from high- and low- elevation field sites to a controlled-environment greenhouse in Canberra (maximum/minimum daily temperature range 26/15°) and the pattern of photosynthetic acclimation observed. Levels of net photosynthesis, Pamb, intracellular resistance rI, and leaf gas-phase resistance to CO2 transfer (r1) were monitored, as were the temperature optima for these parameters. Acclimation proceeded most rapidly in the material grown at the warmer, low-elevation, site (955 m), and in the low-elevation population. Daily maximum/minimum temperatures at this site for the 10 days prior to transfer averaged 23/11°. With this material, levels of, and the temperature optimum for, Pamb reached control levels within 6 days of transfer from the field environment. By comparison, Pamb in the high-elevation population grown at the high-elevation (tree-line) site (1910 m) where the 10-day temperature averaged 15/7°, did not reach control levels until 14 days after transfer, and the temperature optimum for Pamb required 20 days to reach the control level. In general, the patterns of change in rI and r1 paralleled those in Pamb. Both the level of physiological activity in the field, and the temperature differences between the field and greenhouse environment, appeared to affect the rate of acclimation. Immediately after transfer from the field, the temperature optima of the high-and low-elevation populations were close to the daily maximum temperature of the respective field environments. The temperature optimum of the high-elevation material grown at the low-elevation site was intermediate in value. At the conclusion of the acclimation period, the temperature optima of both high-elevation populations had converged to a value similar to that of the high-elevation control (about 22°); similarly, the temperature optimum of the low-elevation populations had reached the level of the low-elevation control (27°) These various temperature optima are interpreted on the basis that each population has a 'preferred' temperature which can be modified by different effective growth temperatures to yield different optima in different thermal environments. In the field, the effective temperature appears to be intermediate between the prevailing maximum and minimum temperatures.
TL;DR: In this paper, different levels of water stress were induced in P. trichoglume by withholding water for various periods, and the elongation rate was measured during dark stress periods and after rewatering in both the light and the dark.
Abstract: Different levels of stress were induced in P. maximum var. trichoglume by withholding water for various periods. Leaf elongation rate was measured during dark stress periods and after rewatering in both the light and the dark. Following rewatering, elongation rates of previously stressed plants exceeded those of controls for periods up to 33 h, during which time elongation rate was more related to previous levels of water stress than to current leaf water potential. In addition, there was a transient burst of elongation when plants were rewatered in the light. It is suggested that the stimulated rates result from expansion of cells which have accumulated during the stress because cell division is less sensitive to water stress than is cell expansion. Despite the stimulated rates of elongation after rewatering, the recovery was incomplete such that the final lengths of stressed leaves were less than those of unstressed plants.
TL;DR: The capacity of the leaf enzyme to catalyse the decarboxylation of oxaloacetate to pyruvate was negligible and the properties of the enzyme are discussed in relation to its proposed role in C4 pathway photosynthesis.
Abstract: A procedure is described for partially purifying phosphoenolpyruvate carboxykinase [ATP : oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.49] from leaves of Chloris gayana Kunth. In three steps the enzyme was purified about 60-fold with 22% recovery of activity. This procedure removes enzymes, particularly malate dehydrogenase, that preclude the use of a simple spectrophotometric assay for phosphoenolpyruvate carboxykinase. The activity of the enzyme in the direction of oxaloacetate decarboxylation was about 10 times that in the reverse direction. At the optimal pH of 8.0, ATP was the preferred nucleoside triphosphate but CTP, UTP, GTP and ITP were also active. A requirement for Mn2+ could not be replaced by Mg2+. The Michaelis constants for oxaloacetate and ATP were 0.035 mM and 0.024 nM, respectively. The photosynthetic intermediates fructose 1,6-bisphosphate, 3-phosphoglyceric acid and dihydroxyacetone phosphate significantly inhibited the enzyme at concentrations in the region of 1-5 mM. Unlike the phosphoenolpyruvate carboxykinase from other sources, the capacity of the leaf enzyme to catalyse the decarboxylation of oxaloacetate to pyruvate was negligible. The properties of the enzyme are discussed in relation to its proposed role in C4 pathway photosynthesis.
TL;DR: The effects of certain treatments on ethylene were quantitatively comparable with the effects of the same treatments on anthocyanin formation in whole fruit.
Abstract: Ethylene production by immature apple fruit was stimulated by cycloheximide application, u.v. irradiation and wounding. After fruit were treated with 1 and 10 µg ml-1 cycloheximide, the rate of ethylene production increased to 2 and 10 times the control level, respectively. In skin discs cut from whole fruit (wounded tissue), the rate of ethylene production was stimulated to at least 40 times that in whole fruit. This wound-stimulated ethylene production was partially inhibited by an initial application of cycloheximide. Ultraviolet irradiation of whole fruit stimulated the rate of ethylene production to more than 25 times the control rate after 15 min irradiation. In skin discs, u.v. irradiation caused only a 50-100% increase in ethylene production rate. The effects of certain treatments on ethylene were quantitatively comparable with the effects of the same treatments on anthocyanin formation in whole fruit. Ethylene at 30 µl 1-1 stimulated anthocyanin in skin of immature apples by 16%. Possible mechanisms by which ethylene may stimulate anthocyanin synthesis are discussed.
TL;DR: From measurements and light- and CO2-response curves of intact pods, estimates of gross photosynthesis, photorespiration and dark respiration of seeds and hulls indicated that seed reassimilated slightly more CO2 than they respired when young and about two-thirds thereof at a later stage.
Abstract: Net CO2 uptake by soybean pods in the light was much less and output in darkness much greater than from equal areas of leaves. The net photosynthesis decreased, becoming negative, and dark respiration increased as seed filling progressed. The photochemical efficiency was the same but the diffusive resistance of pods was about twice and the internal resistance two to three times those of leaves. Fluxes into open deseeded pods were initially much greater than into intact pods but drying out of the tissue soon led to fluxes only about three times greater. From these measurements and light- and CO2-response curves of intact pods, estimates of gross photosynthesis, photorespiration and dark respiration of seeds and hulls were made. These indicated that seed reassimilated slightly more CO2 than they respired when young and about two-thirds thereof at a later stage. Hulls fixed about similar amounts but these were insufficient to prevent net effluxes from pods during the later stages of their development, even at irradiances of 190 W m-2. On a daily basis, direct uptake of CO2 made a negligible contribution to the total import of dry weight by the pod; nevertheless, photosynthesis in the seeds and hulls refixed some 50-70% of the CO2 respired by these tissues.
TL;DR: Wounding of fruit tissue, as a specific treatment or while preparing skin discs, increased the level of anthocyanin in the skin and replaced the stimulating effect on anthocianin formation of applied u.v. light or cycloheximide, and the effects of wounding and cyclo heximide decreased with increasing fruit maturity.
Abstract: Cycloheximide applied to apple skin discs inhibited anthocyanin synthesis even at very low concentrations (0.01 µg ml-1) but stimulated accumulation in whole apple skin at concentrations between 0.05 and 30 µg ml-1. When cycloheximide was applied as a drop to whole fruit, anthocyanin synthesis was inhibited in the zone of application. A region of enhanced synthesis surrounded the inhibited area when the concentration was 1 µg ml-1 or higher. Inhibition appears to be the primary effect, while stimulation is a secondary effect of the application of cycloheximide. Similarly, exposure to u.v. light for 5-60 min promoted anthocyanin accumulation. Wounding of fruit tissue, as a specific treatment or while preparing skin discs, increased the level of anthocyanin in the skin and replaced the stimulating effect on anthocyanin formation of applied u.v. light or cycloheximide. The effects of wounding and cycloheximide decreased with increasing fruit maturity. The data suggested that wounding, u.v. light, maturity and cycloheximide act through a common effector, perhaps ethylene.
TL;DR: A range of summer and winter vegetable crops has been grown under favourable conditions, and the relation between net carbon exchange and irradiance determined at several stages of growth, using large field assimilation chambers and semi-closed gas analysis systems, suggests partial stomatal closure at about midday.
Abstract: A range of summer and winter vegetable crops has been grown under favourable conditions, and the relation between net carbon exchange and irradiance determined at several stages of growth, using large field assimilation chambers and semi-closed gas analysis systems. For all crops, leaf area index was an important determinant of net carbon exchange rate during early stages of growth, and rates increased markedly from day to day during the period of rapid vegetative development. Except for cauliflower and cucumber, for which leaf area ceased to be so important as the crops developed, maximum rates of CO2 uptake were achieved at maximum leaf areas, and were in excess of 90 mg CO2 dm-2 (ground area) h-1 for sweet corn, about 64 for rockmelon, 50 for broad bean, cauliflower and cabbage, and 45 mg dm-2 h-1 for cucumber. For both rockmelon and cucumber, net carbon exchange rates in the morning were often greater than those at the same irradiances in the afternoon, which suggests partial stomatal closure at about midday. In all crops, variations in temperature of up to 10°C either side of the ambient temperature, imposed at any time during the day, generally had little effect on negative CO2 flux (uptake), but positive CO2 flux at night was strongly influenced by temperature. In cucurbits uptake was reduced at temperatures above 35°C, but rapidly recovered when the temperature was again lowered. High growth rates were achieved by all crops for most months of the year, and the efficiency of utilization of incident energy was also high compared with other reported values. However, growth rates were not related to the maximum rates of CO2 uptake in the day, for net carbon exchange over each 24 h depended also on factors such as the ratio between day- and nightlength and night temperatures.
TL;DR: Results are taken as evidence that the normal developmental pattern of accumulation of dry matter in the endosperm is determined within theendosperm itself, rather than through the provision of precursors from the rest of the plant.
Abstract: 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.