摘要:

AbstractMitochondria were isolated from 7‐day‐old wheat roots (Triticum vulgareVill. cv. Svenno Spring Wheat) grown in either a full‐strength culture medium (100%) or in the same medium diluted 100 times (1%). Outer membrane integrity was assayed using the cytochromecreduction assay. This indicated about 20% damage. Using an oxygen electrode the respiration of the mitochondria was measured with either malate or succinate as the substrate (both 40 mM). KCN (3 mM) and salicylhydroxamic acid (SHAM, 1 mM) were used as inhibitors. The properties of the isolated mitochondria (STATE 3 rate, ADP/O ratio, and KCN‐sensitivity) depend upon the ionic concentration of the growth medium of the roots. In the mitochondria isolated from roots grown in the 1% medium (1% mitochondria) there is a synergistic effect of KCN and SHAM. This means that electrons can be shifted from one pathway to the other when only one of the inhibitors is added. This flexibility between the electron pathways is almost nil in the mitochondria isolated from roots grown in the 100% medium (100% mitochondria). The maximal capacity of the alternative electron pathway (= rate in the presence of KCN) is higher in 1% (40 nmol O2min−1(mg protein)−1) than in 100% mitochondria (20 nmol O2min−1(mg protein)−1. In 100% mitochondria the alternative pathway seems to be operating at maximal capacity in the absence of KCN with both substrates and in both STATES 3 and 4. In 1% mitochondria the alternative pathway functions at>50% of its capacity in the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02540.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe affinity of respiration for oxygen in the roots of sixSeneciospecies studied was low compared with the affinity of cytochrome oxidase for oxygen. Half saturation values of approximately 22 μMoxygen were measured. Root respiration was to a large extent insensitive to cyanide in flood‐tolerant as well as in flood‐sensitive species. The evidence presented suggests that high activity of salicylhydroxamic acid (SHAM)‐sensitive oxidase inSenecioroots was the basis for the low oxygen affinity and for the high cyanide‐insensitivity of root respiration in theSeneciospecies. Methods are described to determine thein vivoactivity of the SHAM‐sensitive oxidase. It was estimated that it contributed 70% to the total root respiration.The presence of SHAM‐sensitive oxidase activity could explain a higher efficiency of root growth respiration under a low oxygen tension if this alternate oxidase was inhibited at a low oxygen concentration in the root medium. However, the SHAM‐sensitive oxidase was not specifically involved in either growth respiration or maintenance respiration. Its significance in regulation of the redox state of the cell

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02541.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractBy washing out14C‐solutes or K+from the free space of stem segments ofVicia fabaL. andUrtica dioicaL., efflux from stem tissues was measured. At 25°C the efflux of14C or K+from non‐parasitized stem parts was found to be comparable with the pattern known for parenchyma cells. The efflux pattern from parasitized stem parts kept at 0°C was also a normal one, but at 25°C a more complicated pattern was found. After addition of metabolic inhibitors, however, the efflux pattern appeared to be comparable with the pattern found in 0°C experiments. Also, after washing stem segments for several hours in water at 0°C, Phloem unloading was shown to start unimpeded after transfer to 25°C. Stem parts parasitized byCuscutacan be regarded as a model system for studying the fundamental processes underlying movement out of sieve tubes in strong sin

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02542.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe growth response (increase in weight) of cultured explants from seedling date (Phoenix dactyliferaL.) and mature coconut (Cocos nuciferaL. cv. Malayan Dwarf) palms to source and concentration of organic nitrogen. carbohydrate, auxins, cytokinins and gibberellins was examined. Growth was strongly stimulated by the presence of auxins (10−7to 10−6M), cytokinins (10−6to 10−5M), high concentrations of sucrose (0.2M), and in the absence of NH4Cl, by organic sources of reduced nitrogen. Higher concentrations of auxin (2,4‐D or NAA at 10−6to 10−5M) which still stimulated growth of Phoenix tissue, proved inhibitory to growth of freshly excised Cocos tissues.Explants from both palms initiated roots when subcultured on a medium with increased levels of auxin (NAA, 2.5 × 10−6to 2.5 × 10−5M) and reduced levels of cytokinin (6‐BAP, 5 × 10−8M). Isolated roots excised from these explants continued growth and produced new laterals when subcultured on media with GA3(5 × 10−7M) and reduced levels of auxin, cytokinin, and

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02543.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractA method was described to determine root growth respiration and root maintenance respiration rate of plants, grown in culture solutions of high and low oxygen concentrations, during linear growth. Root growth respiration of aerobically grown plants was three to four times lower in the flood‐intolerantSenecio jacobaeaL. than in the flood‐tolerant species.Senecio aquaticusHill. Root growth respiration ofSenecio aquaticusHill decreased by a factor two to three upon transplantation to a culture solution of low oxygen tension. The difference in root growth respiration between aerobically and anaerobically grownSenecio aquaticusHill was ascribed to the presence of a highly active non‐phosphorylating ox

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02544.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractIn water culture experiments with potato plants (Solanum tuberosumL. cv. Ostara), the influence of continuous nitrogen nutrition (constant supply of NO3−) and discontinuous nitrogen nutrition (interruption of NO3−supply, i. e., nitrogen withdrawal for 6 days) on the endogeneous cytokinin level in the roots, shoots and exudate of decapitated plants was studied. Harvests took place at intervals of 3 days. The chlorophyll formation test (cucumber cotyledons) and soya callus test were used to determine the cytokinin activity.With continuous nitrogen, the cytokinin activity decreased slightly with time in both roots and shoots but rose in the exudate. With discontinuous nitrogen, the nitrogen withdrawal led to a temporary, pronounced increase in cytokinin activity in the roots; at the same time, the cytokinin activity in the exudate decreased sharply. It is assumed that this temporary increase in cytokinin activity in the roots is a reflection of increased meristem activity in the roots. In the shoots, the cytokinin activity decreased during the nitrogen withdrawal period. These nitrogen‐induced changes in cytokinin activity in the roots and shoots of potato should presumably have an important influence on the physiological age of the shoot, with all its consequences in the further development of the plant. Zeatin riboside was likely the main cytokinin component inv

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02545.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe linear uptake of zinc by excised barley roots (Hordeum distichonL.) in the time range from 20–120 min is not continued over periods of 20–28 h. In concentration dependent uptake experiments with intact barley roots three phases in the range up to 1.38 mMzinc could be detected independent of the tested uptake period. The kinetic constants increased with higher phases and the transition points were lowered with increasing time. The presence of copper did not inhibit the uptake of zinc competitively. On the contrary a slight stimulation in the uptake rates was observed indicating an interaction with the transition site. It is concluded that zinc and copper are taken up by separate mechani

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02546.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractDefined media that promote the initiation and undifferentiated growth of callus derived from stem explants of four cultivars of cassava,Manihot esculentaCrantz, are described. Growth rates and yields of cassava callus after 4 weeks of culture are shown to be comparable to those of callus ofNicotiana tabacumL. cv. Wisconsin No. 38. Nitrogen sources of ammonium nitrate or of ammonium chloride plus succinate supported growth of all four cultivars. Sucrose was superior to glucose as a carbon source. The cassava cultivars differed in their response to increasing concentrations of sucrose between 0.5% (w/v) and 3%, two of them increasing in dry matter with increasing sucrose concentrations of up to 3%. When cultured in the light on defined media that contained higher ratios of cytokinin to auxin, callus of the latter two cultivars turned green. Roots but not shoots differentiated from the callus of all cultivars. The influence of hormone concentrations, sucrose level, and nitrogen source on greening and root formation is summarized.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02547.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractTypical abnormalities were observed on French‐bean roots when the plants were cultivated in the presence ofRhizobium phaseoli, under hydroponic conditions. Substantial quantities of cytokinins were detected in the plant culture medium and their concentration remained high until the 9th day after inoculation, when the first nodules appeared. The presence of both partners, plant and bacteria, was required for this synthesis. Exogenous cytokinin production was responsible for morphological alterations of the roots observed before nodulatio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02548.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractIn uptake experiments from nutrient solutions containing 2.0 mMK+labelled with86Rb+, the relationship between potassium uptake efficiency and internal potassium concentration of the roots, [K+]iwas found to be partly sigmoidal for intact plants of spring wheat (Triticum aestivumL.), glasshouse cucumber (Cucumis sativusL.), birch (Betula verrucosaEhrh.), lingonberry (Vaccinium vitis‐idaeaL.), Scots pine (Pinus silvestrisL.) and Norway spruce (Picea abies(L.) Karst.), The results were interpreted in terms of sigmoidal enzyme kinetics for allosteric regulation. Hill plots of the data gave straight lines at specific [K+]iintervals for the species. The slopes of the lines are the Hill coefficient, which could be regarded as a measure of the minimal number of allosteric sites. The Hill coefficient varied between ‐ 14.4 and ‐ 15.9. When divided by four, these values are fairly consistent with those in the literature. It is suggested that four active uptake sites interact with four groups of allosteric sites, each group containing four such sites, or that one active uptake site interacts with all the allosteric sites. Thus the results are evidence that the mechanism regulating K+uptake is basically similar for the investigated plants. It is the interval of [K+]imediating highly negatively cooperative allosteric regulation that differs among species.For some of the species,ndecreased from about 15 and approached unity at high [K+]ivalues. This may indicate that only few sites are still available, making cooperativity unimportant. Alternatively high vacuolar [K+]iconcentrations may give rise to an incorrect evaluation of data from Hill plots, since the cytoplasmic K+content likely regulates the allosteric mechanism. Moreover, it is suggested that gene‐controlled carrier synthesis is responsible for the varying maximum K+uptake efficiency among

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb02549.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY