摘要:

The carbon allocation to current‐year shoots of the deciduousVaccinium uliginosumL. and the evergreenV. vitis‐idaeaL. was studied in a field experiment using14C. During the first week after labelling, 0–50% and 30–80% of the initially assimilated14C was lost inV. vitis‐idaeaandV. uliginosumrespectively. Later on, the losses were smaller. After leaf fall inV. uliginosum, 30, 10 and 8% of the initially assimilated14C was recovered in the abscised leaves, in plants labelled 1 July, 1 August and 1 September, respectively. The amounts found in the oldV. vitis‐idaealeaves the year after labelling were 33, 20 and 10%. Only traces of past‐year assimilates were found in the current‐yearV. vitis‐idaealeaves, while it was estimated that theV. uliginosumleaves contained 10–15% of the past‐year label. It is concluded thatV. vitis‐idaeais mainly dependent on early summer assimilates ‐ produced by leaves that have overwintered – for the current year shoot growth, while past‐years' assimilates probably make an important contribution to the leaf expansion inV. uliginosum.When fruits occurred, a large fraction of the14C assi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02809.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The uptake of glycylsarcosine (Gly‐Sar) into scutella separated from germinating grains of barley (Hordeum vulgareL. cv. Himalaya) is inhibited by other peptides; in most cases the inhibition is not purely competitive but of a mixed type (simultaneous increase in the apparent Kmand decrease in Vmax) (Sopanen, T. 1979. FEBS Lett. 108: 447–450). The aim of the present experiments was to elucidate the mechanism of the mixed inhibition by studying how peptides already taken up into the cells affect the uptake of Gly‐Sar.When scutella were preincubated in the presence of various peptides, 11 of the 13 peptides tested inhibited the subsequent uptake of Gly‐Sar by 10 to 45%. The inhibition, studied in detail with leucylleucine and prolylproline, was due to a decrease in Vmax. The two peptides having no effect were glycylglycine and D‐alanyl‐L‐alanine which are the only peptides known to date acting as purely competitive inhibitors when present together with the substrate Gly‐Sar.Preincubation with leucine, proline and alanine was not inhibitory, although preincubation with the corresponding dipeptides was. This result, together with the demonstration of intact leucylleucine in the scutella after preincubation with leucylleucine, indicates that the inhibition was caused by the intact peptides.The results support the notion that in the mixed type inhibition the increase in the apparent Kmis due to competition for the carrier at the outside of the membrane, while the decrease in Vmaxis due to peptides taken up and binding to the carrier at the inside

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02810.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Plants ofUrtica dioicaL., a very nitrophilous species, were grown in a nutrient solution containing either high (100%) or low (2%) nutrient supply. Part of these plants were subjected to a sudden switch from 100% to 2% or vice versa. Plant weight, sugar and organic nitrogen (both soluble and insoluble) and nitrate content were measured during growth. The activities of two nitrogen assimilating enzymes, nitrate reductase (NR) and glutamine synthetase (GS) were determined.Growth ofUrtica dioicawas retarded at low nutrient supply. Root growth was limited by another factor than nitrogen. This was shown by a higher protein content. In the first period after a switch from 100% to 2%, redistribution of nitrogen from shoot to root could be demonstrated, and leakage from the root into the nutrient solution. It is suggested that in these conditions GS in the root reacted to this downward flux. Comparison with earlier findings on the less nitrophilousPlantago lanceolatashowed that at 100% nutrient supply a correlation occurs between nitrate reduction and glutamine synthetase activity in that plant part which exported reduced nitrogen: the root inP. lanceolataand the shoot inU. dioica.In the importing plant part, glutamine synthetase was influenced by nitrate reduction as well as by imported reduced nitrogen.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02811.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Spinach (Spinacia oleraceaL. cv. Melody hybrid) leaf glycerate kinase (EC 2.7.1.31) was partially purified and characterized. The enzyme did not exhibit any absolute stereospecificity towards the two enantiomers of glycerate, but the affinity for the D‐isomer was 15‐fold greater. The enzyme exhibited a broad pH optimum of 7.5–9.0 and a requirement for divalent cation, satisfied by Mg2+. The reaction product was identified as 3‐phosphoglyceric acid. The observed high glycerate kinase activity together with its strategic localization exclusively in the chloroplast stroma are considered adequate for an efficient coupling of photosynthetic and photorespiratory carbon p

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02812.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Rhizobium trifoliimost frequently infects its host white clover (Trifolium repensL.) by means of infection threads formed in markedly curled root hairs.Rhizobiuminfections are classified as either lateral or apical based on whether they originate in the branches or at the apex of the root hairs. A quantitative estimate of lateral and apical infection in the region of the host root (Trifolium repensL. cv. Regal Ladino) that possessed mature and immature root hairs at the time of inoculation withRhizobium trifoliiTAI (CSIRO, Canberra City, Australia) indicated that lateral infection occurred more frequently in the mature root hair region of the root. Apical infections were more common in the immature root hair region. Cell free filtrates collected fromR. trifoliicultured in association with the host roots induced branching in white clover root hairs. A partially purified preparation of the branching factor was obtained from freeze‐dried filtrates by ethanol extraction and ion exchange chromatography. Preliminary studies on the characteristics of these substances suggest that some are dialyzable and heat stable white others are non‐dialyzable and heat labile. The dialyzable, heat‐stable compounds contain neutral sugars and range between 1200 to 10000 daltons in size. In roots that were exposed to low concentrations (6–25 μg‐ml−1) of these partially purified deformation factors before inoculation, the developmentally mature root hairs were deformed at the time of inoculation. Nodules appeared in the mature and immature root hair region of these plants at the same time. In plants exposed to water, nodules were observed in the immature root hair region and mature root hair regions 3 and 5 days after inoculation, respectively. Based on these results, we conclude that the nodule development was hastened in the plants exposed to the root hair‐deforming substances because the mature root hairs of these plants were made infectible at the time of inoculation by

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02813.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Environmental and hormonal control of flowering and vivipary in four Norwegian timothy (Phleum pratenseL.) cultivars has been studied in phytotron and by aseptic culture of inflorescence explants. The critical photoperiod for flowering increased with increasing temperature (12–18°C) and it was 13 to 15 h for the southern and 14 to 16.5 h for the northern cultivars. Diurnal temperature fluctuation significantly stimulated flower formation compared to the corresponding constant temperature treatment. Plants grown in 16‐h photoperiod contained normal sexual flowers, but a high percentage of spikes developed in 12‐ or 14‐h photoperiod contained viviparous plantlets. One‐ to four‐weeks in continuous light before treatment with 12‐h photoperiod increased the number of spikes per plant, but did not enhance the frequency of vivipary. Experiments with aseptic cultures showed that generative versus vegetative development of timothy inflorescence was affected by plant hormones. Kinetin stimulated the vegetative development and induced proliferation both in inflorescence initials and in spikelets isolated a

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02814.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

A decline in nitrogenase activity (C2H2reduction) of nodules ofPhaseolus vulgarisL. cv. Contander was correlated with a decrease in their soluble protein including leghe‐moglobin. Concomitantly, two distinct proteolytic activities against leghemoglobin with acidic and alkaline pH optima were detected. The corresponding proteases were purified about 30‐fold by ammonium sulfate precipitation, gel filtration and hydroxy‐apatite chromatography. Both the acidic (pH optimum 3.5) and the alkaline (pH optimum 8.0) proteases were thiol enzymes. They were characteristic of senescing nodules, whereas only an acidic serine protease was present in functional no

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02815.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The role of endogenous ethylene during germination of non‐dormant seeds ofAmaranthus caudatusL. was investigated. The seeds readily germinated in water and darkness at 24°C. Application of ethylene or of its precursor I‐aminocyclopropane‐I‐carboxylic acid (ACC) slightly increased the rate of germination. Both compounds effectively antagonized osmotic inhibition by polyethyleneglycol. Application of aminoethoxyvinylglycine (AVG) reduced ethylene production by 90% but did not inhibit germination. However, germination was inhibited by 2,5‐norbornadiene, a competitive inhibitor of ethylene action. This inhibition was counteracted by ethylene, ethephon or ACC and enforced by AVG. It is concluded that the action of endogenous ethylene is an indispensable factor during germination of non‐dormant seeds ofA. caudatus.Ethylene action is required from the start of imbibition on. In water, low levels of endogenous ethylene are sufficient for this action. PEG increased the ethylene requirement

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02816.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Cytokinin‐like activity was assayed in stolons and tubers ofSolanum tuberosumL. ssp.andigena(Juz. et Buk.) Hawkes cv. 165 grown in pots under controlled environment conditions. The plants were allowed to tuberise without the application of environmental or other external stimuli. The soluble sugar and starch contents of stolon tips and tubers were measured. Starch accumulation was a precise indicator of tuber initiation. Cytokinin‐like activity began to increase in tubers with a diameter greater than 7.5 mm and, as assessed on a per tuber basis, was greatest in the largest size‐category analysed. However, expressed as a function of fresh and dry weight, activity was greatest in tubers of 15–20 mm in diameter. Increases in cytokinin‐like activity occurred subsequent to tuber formation, indicating that the tuberisation stimulus is unlikely to be cytokinin‐lik

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02817.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Ozone, leaf age and water stress each affected leaf conductance in soybean [Glycine max(L.) Merr. Hodgson], but there were no interactions among these factors. Exposure to increased concentrations of O3(0.01, 0.05, 0.09. and 0.13 μl l−1) resulted in linear declines in abaxial and adaxial conductances in leaves of all ages. There were no differences in relative response to O3between the two leaf surfaces. For well‐watered plants, water use efficiency also decreased with exposure to increased O3concentrations (water‐stressed plants were not tested). Abaxial conductance increased as leaves aged from 4 to 10 days and then declined with further aging. Adaxial conductance decreased with all increases in leaf age beyond 4 days, and the ratio of abaxial/adaxial conductance increased continuously throughout the leaf lifespan. During water‐stress cycles (water withheld for 2–3 days) leaves of water‐stressed plants had lower conductances than those from well‐watered plants, and there was no difference in relative response between abaxial and a

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb02818.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY