摘要:

AbstractGreen calli obtained from leaves of the CAM‐inducible plantKalanchoe blossfeldianacv. Montezuma were grown either under long‐day or short‐day regimes in the Phytotron of Gif‐sur‐Yvette. Callus cells were found to be CAM inducible by the short‐day treatment, according to levels and diurnal oscillations of malate pools and phosphor‐enolpyruvate (PEP) carboxylase (EC.4.1.1.31) capacity.De novosynthesis of PEP carboxylase was shown to occur under the short‐day regime. In spite of continuous net CO2output, CAM‐like patterns of CO2exchange by calli were obtained under the short‐day treatment. After 2 months under both photoperiodic conditions, spontaneous organogenesis in callus tissues gave rise to numerous shootlets which were determined as photoperiod dependent for CAM; the same was so for plants originating f

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01822.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractCrassulacean acid metabolism (CAM) was studied in mixotrophic callus tissue cultures ofKalanchoë blossfeldianahybr. Montezuma and compared with plants propagated from the calli.The ultrastructural properties of the green callus cells are similar to mesophyll cells of CAM plants except that occasionally abnormal mitochondria were observed. There was permanent net CO2output by the calli in light and darkness, which was lower in darkness than in light. The calli exhibited a diurnal rhythm of malic acid, with accumulation during the night and depletion during the day.14C previously incorporated by dark CO2fixation into malate was transferred upon subsequent illumination into end products of photosynthesis. All these data indicate that CAM operates in the calli tissue. The results revealed that the capacity for CAM is obviously lower in the calli compared with plantlets developing from the calli, or with ‘adult’ plants. The data suggest also that CAM in the calli was not limited by the activities of CAM enz

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01823.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe concentration dependence of phosphate uptake was studied using root sections of corn (Zea maysL. cv. Ganga 5). Detailed and wide‐range (57 concentrations in the range 1 μmol m−3‐75 mol m−3), precise (average SEM<2.5%,n= 6) and reproducible (similar patterns in three independent experiments and for 5, 10, 15, 20, 25 and 30°C) data revealed six (or seven) concentration‐dependent phases separated by ‘jumps’ or sharp breaks. These transitions were independent of temperature and occurred over relatively narrow concentration ranges (0.0001–0.0004, 0.08–0.31, 1.0–3.5, (7.5–10), 18–20 and 57–59 mol m−3). The intermediate phases obeyed Michaelis‐Menten kinetics, whereas sigmoidal kinetics were observed at lower concentrations. Uptake within each of the two highest phases increased more rapidly with increasing external phosphate concentration than predicted from Michaelis‐Menten kinetics but also saturated more rapidly. The latter finding is not consistent with free diffusion across the plasmalemma at high external phosphate concentrations. Kinetic models yielding continuous isotherms, e.g. the sum of one or two Michaelis‐Menten terms and a diffusio

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01824.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractBorstlap (1983) has alleged that (a) there are no abrupt changes in curves for the concentration dependence of solute uptake in plants, and (b) many such uptake isotherms may be described by the sum of two Michaelis‐Menten terms and a linear term. These claims are considered in detail in connection with the recent finding (Nandi, Pant&Nissen, 1987) that phosphate uptake by corn roots increased more rapidly within the higher phases, i.e. at high external phosphate concentrations, but also levelled off faster than predicted from Michaelis‐Menten kinetics. Similar deviations are, in retrospect, also found for uptake of other solutes and result in fewer phases at high external solute concentrations. The simplified and strikingly similar multiphasic patterns in the present paper show that (a) the abrupt changes in published isotherms are not due to error in the data, and (b) uptake isotherms cannot be adequately represented by the sum of two Michaelis‐Menten terms and a linear term, or by similar continuous functions, if sufficiently detailed and precise data are used. These findings are not consistent with the existence of multiple uptake mechanisms, including free diffusion, in the plasmalemma. Uptake occurs instead by a single, multiphasic mechanism for each solute or group of related solutes. The similarities in the multiphasic patterns indicate, furthermore, that influx of the various solutes may be co

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01825.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractMoisture content and germination percentages on agar‐solidified medium were determined for pollen ofJuglans regiaandJ. nigraat the time of release from anther and at 24‐h intervals until germination fell to zero. Moisture content of freshJ. regiapollen ranged from 4.6 to 12.1%, and from 3.9 to 4.0% forJ. nigrapollen;in vitrogermination percentages were uniformly high throughout these ranges. Germination declined as pollen moisture fell below 5% inJ. regiawith regression analyses predicting 50% germination at 3.9–4.4% moisture. After 4 d at ambient laboratory conditions, all pollen had lost the ability to germinate when incubated directly on medium. This pollen was incubated in chambers where humidity was maintained at saturation and 33% saturation, and retested. Pollen up to 22 d old and having moisture contents as low as 2.6% regained the ability to germinatein vitrowhen it was incubated in a water‐saturated environment before being placed on the agar‐solidifi

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01826.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractRoots of sterile‐grown, intact 6‐day‐old seedlings ofRicinus communispossess at least two independent active amino acid uptake systems, one for neutral and one for basic amino acids. The kinetics of uptake of L‐proline and L‐arginine, which were taken as representative substrates for the two systems, are biphasic. At low concentrations (0.01–0.5 mol m−3) Michaelis ‐Menten kinetics prevail, changing to a linear concentration dependence at higher substrate concentrations (1–50 mol m−3). L‐glutamate uptake velocity is linear over the whole substrate concentration range.For comparison the uptake kinetics of nitrate and ammonium were determined as well as interactions among the different nitrogen sources. The Kmvalue for nitrate uptake was 0.4 mol m−3, and for ammonium 0.1 mol m−3. The uptake capacity for nitrate or ammonium was approximately the same as for amino acids. The interaction between the uptake systems for organic and inorganic nitrogen is small.Two hypotheses for the physiological significance of amino acid uptake by roots were considered:(i) Uptake of amino acids from the soil‐determination of amino acids in soil and in soil water indicates that they might contribute 15–25% to the nitrogen nutrition of the plant.(ii) Amino acid uptake systems of root cells serve primarily as retrieval of amino acids delivered from the phloem‐ it was found that14C L‐glutamine, which was delivered to the cotyledon and transported to the root via the phloem, was not lost by the roots, whereas it appeared in the bathing medium if L‐glutamine was applied externally to the root to compete for the uptake sites; this suggests that an apoplastic pool of amino acids in the root exists

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01827.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe germination ofSorghum bicolorseeds of 9 genotypes was tested at temperatures between 8°C and 48°C on a thermal gradient plate. Samples were tested from three regions of the panicle expected to differ in temperature during grain filling. Seeds of a tenth genotype, SPV 354, produced in controlled‐environment glasshouses at different panicle temperatures, were tested similarly. In addition, the emergence of SPV 354 was measured from planting depths of 2 and 5 cm at mean soil temperatures of 15, 20 and 25°C. Four methods of calculating mean germination rate for the nine genotypes were compared. Germination characters like base, optimum and maximum temperature (Tb, To, Tm), thermal time (θ)and the germination rate atTo(Rmaxshowed only small differences between methods. There was a range of genotypic variation in all characters: Tb8.5–11.9°C;To, 33.2–37.5°C;Tm, 46.8–49.2°C;θ, 23.4–38.0°Cd; Rmax, 0.69–1.14‐d‐1. In contrast, mean germinability (G) was between 90% and 100% over the temperature range 13–40°C. Panicle temperature had no effect on any germination character in SPV 354. However, deeper burial increased θ for emergence and decreasedG, irrespective of soil temperature except at 5 cm. Increasing panicle temperature, by reducing seed size, reducedGand increased θ by about 10

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01828.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractChanges in the phytochrome status at the end of the daily photosynthetic period result in several plant responses. To understand the causal relations among these responses it is useful to investigate species or experimental conditions where the most common correlations among responses are broken. A step in this direction is presented here withPetunia axilaris, where FR‐treated plants showed low chlorophyll content and erect leaves, but‐ contrary to other species‐higher leaf area and plant dry weight. Differences in area expansion were related to the late phase of leaf growth and were due, at least in part, to larger cells in FR‐treated plants. Effects on length/width ratio, specific leaf area, net assimilation rate, shoot/root ratio and leaf number were small or non‐existent. It is suggested that the lower chlorophyll content in FR‐treated plants was not a consequence of scarcity of

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01829.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractPhotosynthetic oxygen produced by the submerged aquatic plantEgeria densaPlanch, is partitioned into lacunar gas spaces and to the external medium. Despite an apparently linear relationship between volume of lacunar gas discharge and dissolved oxygen release under certain conditions, the partitioning is, as expected from theoretical considerations, not necessarily constant in different conditions. On this basis we believe that lacunar gas discharge is an inconsistent and therefore unreliable method of measuring photosynthesis in submerged macrophytes.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01830.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Books reviewed in this article:THE USE OF THE OXYGEN ELECTRODE AND FLUORESCENCE PROBES IN SIMPLE MEASUREMENTS OF PHOTOSYNTHESIS. By D. Walkerwith illustrations by R. Walker

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01831.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY