bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dependence of starch storage on nutrient availability and photon flux density in small birch Betula pendula Roth)
Authors: McDONALD A. J. S. , ERICSSON A. , LOHAMMAR T. 
Published: April 2006

Abstract Small birch plants (Betula pendula Roth) were grown in a climate chamber at different levels of nutrient availability and at two photon flux densities. The extent to which starch storage was dependent upon nutrient availability and photon flux density was investigated.Acclimated values of starch concentration in leaves were highest at low nutrient availability and high photon flux density. Starch storage in roots was only found at the lowest nutrient availability. However, the relative rate of starch storage (starch stored per unit plant dry weight and time) was higher in plants with good nutrition.The data suggest that, at sub‐optimal nutrient availability, the momentary rate of net shoot photosynthesis is unlikely to limit the structural (as opposed to carbon storage) growth of the plant. Although photosynthetic rate per unit leaf area (as measured at the growth climate) was slightly lower in plants with poor nutrient availability, photosynthetic rate per unit leaf nitrogen was higher. These data suggest a priority of leaf nitrogen usage in photosynthesis, with limiting amounts of leaf nitrogen (and possibly other nutrients) for subsequent growth processes. This argument is consistent with the higher concentrations of starch found in plants with poor nutrient availability.
A 13C method of estimation of carbon allocation to roots in a young chestnut coppice
Authors: MORDACQ L. , MOUSSEAU M. , DELEENS E. 
Published: April 2006

Abstract A method is described in which 1 year‐old chestnut coppice was fed in situ with air highly enriched in 13CO2 (23%). After 3 days, 13C concentration increases in shoots were measured by mass spectrometry. Respiratory losses between 13C feeding and harvest were estimated using two different methods: (i) a model involving the temperature response of respiration and (ii) direct measurement of 13C content of the CO2 respired by the shoots during the night.Carbon allocation to roots was deduced by subtracting from the given amount of 13C, the amount remaining in shoots and the 13C respired by the shoots.The method was tested twice during the growing season. Very little carbon was allocated to roots in late July, but over 80% of assimilated 13C went to roots at the end of September. Despite some approximations in the 13C respiratory losses estimations, the method allowed evaluation of carbon allocation to roots with an error of about 5%.
Cation exchange in isolated xylem cell walls of tomato. II. Direct determination of chemically bound and electrostatically attracted Cd2+ by γ‐γ‐directional correlation measurements
Authors: WOLTERBEEK H. Th. , BODE P. , DE BRUIN M. 
Published: April 2006

Abstract Xylem cell walls were isolated from internodes of tomato plants (Lycopersicon esculentum Mill, cv. Tiny Tim). Purification was carried out in Triton X‐100. Experiments were conducted in which the adsorption of Cd2+ (applied as 115CdCl2) in the cell walls was measured. The application of γ‐γ‐directional correlation measurements permitted the direct determination of chemically bound cell wall Cd in experiments where the total adsorption of Cd was also measured. A set of equations is presented by which the adsorption of Cd could be described, thereby considering the presence of co‐ions in the polyelectrolyte phase. In experiments with simultaneous ll5CdCl2 and K82Br applications, measurements were carried out of the presence of 82Br− in the Donnan Free Space (DFS), indicating Cl− action in the process of CdCl2 adsorption.The cell wall contents of the relevant ions were determined in such a manner that the measurements gave access to the undisturbed equilibrium concentrations. The very small Br− concentrations in the DFS indicated that, at small applied concentrations, internal free Cd may be considered to exist entirely of Cd2+. The results suggest that simultaneous measurement of internal free counter‐ion and co‐ion concentrations may be a relatively easy way to check the reliability of values for apparent formation constants in single cation adsorption experiments. From experiments in which the cell walls were incubated in solutions of varying Cd concentrations, the apparent dissociation constant (KCd2+) for the formation of R2Cd complexes could be calculated as 51±6 mol m−3. The exchange coefficient (KCd2+H+) was shown to vary with the internal free proton concentration and the applied Cd2+ concentration, due to the buffering capacity of the carboxylic acid exchanger.
The relationship between respiration and temperature in leaves of the arctic plant Saxifraga cernua
Authors: McNULTY AMY K. , CUMMINS W. R. 
Published: April 2006

Abstract Saxifraga cernua, a perennial herb distributed throughout the arctic and subarctic regions, shows high levels of dark respiration. The amount of respiration exhibited by leaves and whole plants at any temperature is influenced by the pretreatment temperature. Plants grown at 10°C typically show higher dark respiration rates than plants grown at 20°C. The levels of alternative‐pathway respiration (or cyanide‐insensitive respiration) in leaves of S. cernua grown at high and low temperatures were assessed by treating leaf discs with 0.25 mol m−3 salicylhydroxamic acid during measurements of oxygen consumption. Alternative pathway respiration accounted for up to 75% of the total respiration. Tissues from 20°C‐grown plants yielded a Q10 of 3.37 for normal respiration, and of 0.97 for alternative‐pathway respiration. Tissues from 10°C‐grown plants yielded a Q10 of 2.55 for normal respiration, and of 0.79 for alternative‐pathway respiration. The alternative pathway does not appear to be as temperature sensitive as the normal cytochrome pathway.A simple energy model was used to predict the temperature gain expected from these high rates of alternative‐pathway respiration. The model shows that less than 0.02°C can be gained by leaves experiencing these high respiration rates.
Photosynthesis in frost‐hardened and frost‐stressed leaves of Hedera helix L.
Authors: BAUER H. , KOFLER RENATE 
Published: April 2006

Abstract The purpose of this study was to determine the respective extents to which winter reduction of photosynthetic capacity in ivy (Hedera helix L.) is caused by direct frost injury to the photosynthetic apparatus and by preceding protoplasmic changes connected with the acquisition of frost tolerance. Potted juvenile ivy plants were placed in the open under natural weather conditions whilst others were hardened under controlled conditions and subjected to the desired frost stress.Low non‐freezing temperatures induced frost tolerance in ivy leaves down to about – 12°C (50% injury = TL50) without impairing net photosynthetic rate as measured under standard conditions (20°C, light saturation, natural CO2 level; = Standard‐Fn. Only if the leaves froze (below − 3°C to −4°C) was a reversible inhibition of Standard‐Fn observed. As long as the temperatures did not fall below approximately −8°C the inhibition was small and Standard‐Fn reached about 80–90% of the control. In this case the stomatal opening narrowed, giving a poorer supply of CO2 to the mesophyll cells. Maximal frost tolerance (TL5O−20°C to −24°C) developed only with severe frosts below about − 10°C. After such frosts, Standard‐Fn was reduced to less than 20% of the control. The dependence of the rate of net photosynthesis on the internal CO2 concentration showed a lower initial slope, thus indicating disturbances of chloroplast functions. However, neither in outdoor plants nor in those artificially frosted at – 20°C could there be found an appreciable inhibition of the electron transport capacity from H2O to dichlorophenol indophenol or of ribulose bisphosphate carboxylase.If intact, severely frosted ivy plants were then held at higher temperatures (20/15°C), Standard‐Fn recovered completely in approximately 10 d. Furthermore, following a frost period with temperatures down to −12°C, mild weather caused a distinct improvement in Standard‐Fn in outdoor plants, and there was no loss of maximum frost tolerance. Thus it can be concluded that the inhibition of Standard‐Fn after severe frosts is not due to the development of maximal frost tolerance, but rather may be attributed to frost damage to the photosynthetic apparatus.
Water flow and water storage in Agave deserti: osmotic implications of crassulacean acid metabolism
Authors: SMITH J. A. C. , SCHULTE P. J. , NOBEL P. S. 
Published: April 2006

Abstract Water flow and water storage were investigated for Agave deserti, a desert succulent showing crassulacean acid metabolism (CAM). The anatomy and water relations of the peripheral chlorenchyma, where CAM occurs, and the central water‐storage parenchyma were investigated for its massive leaves so that these tissues could be incorporated as discrete elements into an electrical‐circuit analogue of the whole plant. The daily cycling of osmotic pressure was represented by voltage sources in series with the storage capacitors. With soil water potential and leaf transpiration rate as input variables, axial water flow through the vascular bundles and radial flows into and out of storage during the day/night cycle were determined.The predominantly nocturnal transpiration was coincident with increases in cell osmotic pressure and in titratable acid of the leaf chlorenchyma. In the outer layers of the chlorenchyma, water potential was most negative at the beginning of the night when transpiration was maximum, while the water‐storage parenchyma reached its minimal water potential 9 h later. The roots plus stem contributed 7% and the leaves contributed 50% to the total water flow during maximal transpiration; peak water flow from the soil to the roots occurred at dawn and was only 58% of the maximal transpiration rate. Over each 24‐h period, 39% of the water lost from the plant was derived from storage, with flow into storage occurring mainly during the daytime. Simulations showed that the acid accumulation rhythm of CAM had little impact on water uptake from the soil under the conditions employed. In the outer chlorenchyma, water potential and water flows were more sensitive to the day/night changes in transpiration than in osmotic pressure. Nevertheless, cell osmotic pressure had a large influence on turgor pressure in this tissue and determined the extent to which storage was recharged during the latter part of the night.
Suberin lamellae in the hypodermis of maize (Zea mays) roots; development and factors affecting the permeability of hypodermal layers
Authors: CLARKSON D. T. , ROBARDS A. W. , STEPHENS J. E. , STARK M. 
Published: April 2006

Abstract The development of suberin lamellae in the hypodermis of Zea mays cv. LG 11 was observed by electron microscopy and the presence of suberin inferred from autoliuorescence and by Sudan black B staining in nodal (adventitious) and primary (seminal) root axes. Suberin lamellae were evident at a distance of 30–50 mm from the tip of roots growing at 20°C and became more prominent with distance from the tip. Both oxygen deficiency and growth at 13°C produced shorter roots in which the hypodermis was suberized closer to the root tip. There were no suberin lamellae in epidermal cells or cortical collenchyma adjacent to the hypodermis. Plasmodesmata were not occluded by the suberin lamellae: there were twice as many of them in the inner tangential hypodermal wall (1,14 μn−2) as in the junction between the epidermis and hypodermis (0.54 μm−2).Water uptake by seminal axes (measured by micropotometry) was greater at distances more than 100 mm from the root lip than in the apical zone where the hypodermis was unsuberized. In the more mature zones of roots grown at 13°C rates of water uptake were greater than in roots grown at 20°C even though hypodermal suberization was more marked.Sleeves of epidermal/hypodermal cells (plus some accessory collenchyma) were isolated from the basal 60 mm of nodal axes by enzymatic digestion (drisclase). The roots were either kept totally immersed in culture solution or had the basal 50 mm exposed to moist air above the solution surface. In both treatments the permeabilities to tritiated water and 86Rb were low (circa 10−5mms−1) in sleeves isolated from the extreme base. In roots grown totally immersed, however, the permeability of sleeves increased 10 to 50‐fold over a distance of 40 mm. In roots exposed to moist air the permeability remained at a low level until the point where the root entered the culture solution and then increased rapidly (> 50‐fold in a distance of 8 mm). Growth of roots in oxygen depleted (5% O2) solutions promoted the development of extensive cortical aerenchymas. These developments were not associated with any reduction in permeability of sleeves isolated from the basal 40 mm of the axis.It was concluded that the presence of suberin lamellae in hypodermal walls does not necessarily indicate low permeability of cells or tissues to water or solutes. The properties of the walls (lamellae?) can be greatly changed by exposure to moist air, perhaps due to increased oxygen availability.
Genetic engineering strategies for manipulation of the heat shock response
Authors: SCHÖFFL F. 
Published: April 2006

Abstract. The heat shock response in plants is well characterized at the levels of RNA and protein synthesis. Increasing information is becoming available about the DNA sequences of heat shock protein genes and their mechanism of transcriptional regulation. Relatively little is known about their biochemical functions and physiological importance. The heat shock response is highly conserved in nature and the heat shock proteins appear to confer thermotolerance on cells that express them.Modern genetic engineering and gene transfer techniques offer new possibilities to alter the expression of heat shock genes in transgenic plants by interference with the processes of transcription and translation. New strategies are discussed for selection of regulatory mutants of the heat shock response (trans‐active factors), genetic engineering of cis‐active promoter elements, the use of antisense RNA, and the overexpression of heat shock proteins.
The influence of water deficits on needle conductance, assimilation rate and abscisic acid concentration of seedlings of Pinus radiata D. Don
Authors: SQUIRE R. O. , NEALES T. F. , LOVEYS B. R. , ATTIWILL P. M. 
Published: April 2006

Abstract Seedlings of Pinus radiata, 10–20 weeks old and hitherto fully watered, responded rapidly when water was withheld. Wilting occurred 9d later, at which time soil matric water potential at dawn (Ψm) was –1.06MPa and shoot water potential (Ψ) was –1.9 MPa. Small reductions in Ψm elicited large responses in assimilation rate (A) and leaf conductance to water vapour (g). Seedlings appear to be more sensitive to small water deficits than are older Plants of P. radiata. After rewatering, significant increases of A and g occurred within one day, but neither regained the values measured prior to the imposition of a single drying cycle. This residual effect of drought on A, after one or six drying cycles, was partially caused by a decrease in photosynthetic capacity.In plants wilted for the first time, the concentration of abscisic acid (ABA) in the bulk foliage increased 3.4 times as Ψ decreased to –1.77 MPa. In comparison, pretreatment with six drying cycles significantly reduced Ψ to –2.13 MPa (indicating some osmotic adjustment) and induced only a doubling of ABA concentration. However, these differences in Ψ and ABA concentration did not Persist after the plants of all pretreatments had been watered for 7 d, although g of drought‐pretreatment Plants remained approximately half that of continuously‐watered plants.
Comparative sensitivity of ‘Prior Lisbon’ lemon and ‘Valencia’ orange trees to foliar sodium and chloride concentrations
Authors: LLOYD J. , KRIEDEMANN P.E. , ASPINALL D. 
Published: April 2006

Abstract While citrus rootstocks differ in capacity for sodium and chloride ion exclusion, citrus scion species also vary in foliar sensitivity to NaCl salinisation. Of two common scions, ‘Lisbon’ lemon appears more sensitive, whereas ‘Valencia’ orange in less sensitive to leaf salt. In an attempt to explain this difference. ‘Valencia’ orange (Citrus sinensis [L.] Osbeck) and ‘Prior Lisbon’ lemon (Citrus limon [L.] Burm. F.) were budded to rootstocks known to differ in their ability to exclude sodium ions viz, the strong excluder Trifoliata (Poncirus trifoliata [L.] Raf.), and the weaker excluder Troyer citrange (C. sinensis×P. trifoliata); neither rootstock shows strong exclusion of chloride ions. Budded trees were held under a photosynthetic photon flux density of 450 μmol m 2 S 1 and watered with nutrient solution containing either 0 or 50 mol m 3 NaCl. Growth and photosynthetic responses were measured over 58 d following onset of salinization: salinity effects on leaf gas exchange were studied in relation to changes in leaf water status, compatible solutes and foliar content of sodium and chloride ions, over that same period.Once root‐zone salinization began to influence leaf solutes (day 30 onwards), lemon showed a steeper increase in leaf chloride than occurred for orange. Although rootstock differences were without effect on this ingress of chloride ions for either scion, sodium ions were excluded from both scions to a larger extent by Trifoliata than by Troyer citrange.Carbon dioxide assimilation of scion foliage was reduced earlier and to a much larger extent by rootzone salinization in lemon than in orange. Furthermore, comparisons of CO2 assimilation in relation to leaf tissue solutes between scions (on either rootstock) showed stronger responses for both sodium and chloride ions in lemon than in orange. Faster ingress of chloride into lemon leaves was identified as the crucial factor which predisposed towards expression of that contrast between scions.Although contrasts between scions in photosynthetic responses to salinization matched a faster ingress of chloride into lemon than into orange leaves, the sharper photosynthetic response of ‘Prior Lisbon’ lemon to salinity was not solely attributable to higher concentrations of chloride ions (cell sap basis). A difference between species in subcellular compartmentation of the chloride ion under saline conditions was invoked.
Expression of C4‐like photosynthesis in several species of Flaveria
Authors: MOORE B. D. , KU M. S. B. , EDWARDS G. E. 
Published: April 2006

Abstract Photosynthetic metabolism was investigated in leaves of five species of Flaveria (Asteraceac), all previously considered to be C4 plants. Leaves were exposed to 14CO2 for different intervals up to 16s. Extrapolation of 14C‐product curves to zero time indicated that only F. trinervia and F.bidentis assimilated atmospheric CO2 exclusively through phosphoenolpyruvate carboxylase. The proportion of direct fixation of 14CO2 by ribulose‐I, 5‐bisphosphate carboxylase/oxygenase (Rubisco) ranged from 5 to 10% in leaves of F. australasica. F. palmeri and F. vaginata.Protoplasts of leaf mesophyll and bundle sheath cells were utilized to examine the intercellular compartmentation of principal photosynthetic enzymes. Leaves of F. australasica, F. palmeri and F. vaginata contained 5 to 7% of the leaf's Rubisco activity in the mesophyll cells, while leaves of F. trinervia and F. bidentis contained at most 0.2 to 0.8% of such activity in their mesophyll cells. Thus, F. trinervia and F. bidentis have the complete C4 syndrome, while F. australasica, F. palmeri and F. vaginata are less advanced, C4‐like species.
Na‐Ca interactions in barley seedlings: relationship to ion transport and growth
Authors: CRAMER G. , EPSTEIN E. , LÄUCHLI A. 
Published: April 2006

Abstract Salt‐stressed plants often show Ca deficiency symptoms. The effects of NaCl salinity (1 to 150 mol m‐3) and supplemental Ca (10 mol m‐3) on Na and Ca transport in barley (Hordeum vulgare L.) and their relationship to growth were investigated. The adjustment of Na and Ca transport was investigated by examining young seedlings exposed to short‐term (immediate) and long‐term (7 d) exposure to salinity. When the plants were exposed to long‐term treatments of salinity, the rate of sodium accumulation in roots was approximately 10 to 15% of short‐term treatments. No significant adjustment in the transport to the shoot was observed. Rates of tracer (22Na) transport were compared to calculated rates based on relative growth rates and tissue element concentrations. Comparisons between measured tracer and calculated rates of transport indicate that 22Na transport may underestimate transport to the shoot because of dilution of the tracer in the root cytoplasm. Calcium uptake showed only minor adjustment with time. Measured rates of tracer transport to the shoot correlated well with calculated values. The transport and tissue concentrations of Na were significantly affected by supplemental Ca. Calcium transport and tissue concentrations were markedly inhibited by salinity. Supplemental Ca increased Ca transport and accumulation at all NaCl treatments above that of control plants without supplemental Ca. Salinity inhibited plant growth at 150 mol m ‐3NaCl, but not at 75 mol m‐3.Supplemental Ca significantly improved root length but not fresh weight after 7d of salinity, although differences in fresh weight were detected after 9d. There were significant Na‐Ca interactions with ion transport, ion accumulation, and growth. The effects of salinity on Na and Ca transport to the shoot do not appear to play a major role in shoot growth of barley.
Stable carbon isotope fractionation by marine phytoplankton during photosynthesis
Authors: DESCOLAS‐GROS C. , FONTUNGNE M. 
Published: April 2006

Abstract. In the marine environment, the range of values of carbon isotope fractionation between particulate tissue of phytoplankton and inorganic carbon can be more than 20‰ (− 35‰ < δ13C < − 14‰). This review considers the influence of seawater temperature, lipid content of phytoplanktonic cells, kinetic fractionation, and carbon pathway on δ13C values observed at sea.In order to study the contribution of carboxylases (RUBISCO and the β‐carboxylases phosphoenolpyruvate carboxylase, phosphoenoplpyruvate carboxykinase and pyruvate carboxylase) to variations of particulate δ13C values at sea, we present results obtained simultenously on carboxylase activities and δ13C in various environmental conditions. The lowest δ13C values are clearly associated with predominance of ribulose‐1.5‐bisphosphate carboxylase activity, but it was more difficult to explain the high δ13C values. Different hypotheses are discussed.
Reduction of leaf photosynthesis and transpiration rates of potato plants by second‐stage juveniles of Globodera pallida
Authors: SCHANS J. 
Published: April 2006

Abstract. Net photosynthesis and transpiration rates of potato plants, grown in pots in the greenhouse, were measured at various light irradiances and ambient CO2 concentrations, 3d after inoculation with second stage juveniles of Globodera pallida. Gas exchange rates, both in darkness and in light, and the initial light use efficiency were strongly reduced by nematodes. Stomatal conductance of infected plants was lower than that of control plants and showed little response to decreasing ambient CO2 concentration. The maximum internal CO2 concentration of infected plants was lower than that of control plants. Globodera pallida reduced photosynthesis also by apparent non‐stomatal effects.The effects of G. pallida on gas exchange rates are similar to the effects of abscisic acid in the transpiration stream and of abiotic stresses in the root environment. Apparently, there is a general response of plant roots to adverse conditions. The reduction of photosynthesis may be an important factor in yield reduction by potato cyst nematodes.