摘要:

The influences of light (1.5 W m−2, 24 W m−2), temperature (5°C, 15°C, 25°C) and nitrogen nutrition (1 mmol 1−1NH4NO3, 2 mmol 1−1NH4NO3, 8 mmol 1−1NH4NO3) treatments on the fatty acid composition of galactolipids from young and older leaves of oil‐seed rape (Brassica napusL. varoleiferacv. Quinta) were tested. The linolenic acid (18:3) content of lipids from young leaves was mainly affected by light and temperature. However, older leaves reacted in the first instance on nitrogen and light. For young leaves a significant light/temperature interaction was obvious. The highest level of 18:3 (72%) was observed at 5°C/1.5 W m−2. Changes in the fatty acid composition in older leaves indicated a retarded senescence by an increased nitrogen‐supply. The 8 mmol 1−1NH4NO3/24 W m−2treatment resulted in the highest percentages of unsaturated fatty acids. The results are discussed in relation to the importance of the first‐order interaction of environmental factors to the galactolipid fatty acid composition. Additionally, the relevance of l

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06025.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Ferredoxin‐nitrite reductase (EC 1.7.7.1.) from the cyanobacteriaAnabaenasp. 7119 has been purified 763‐fold with a specific activity of 21.5 units/nig protein (0.358 μkatals/mg). The enzyme has a molecular mass of 52,000 daltons with a Stokes radius of 3.09 nm and a sedimentation coefficient of 4.07 S. The cellular level of nitrite reductase activity gradually increases in response to the addition of increasing amounts of iron to the culture medium.When partially purified nitrite reductase preparations are subjected to sucrose‐density‐gradient centrifugation there is a dose correspondence between nitrite reductase activity and absorbance at 400 nm. This suggests the association of a heme chromophore with the enzyme. Furthermore, the presence of an iron‐sulfur center is suggested by a close association of acid‐labile sulfide with nitrite reductase activity. Carbon monoxide inhibits nitrite reductase activity. The nature and kinetics of this reaction are comparable to other siroheme‐containing nitr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06026.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

In roots of low‐salt barley (Hordeum vulgareL.), translocation of K+, as well as of several other ions, from the root to the shoot starts after a lag‐time. Its length is independent of external concentration. The onset of upward translocation can be remarkably abrupt. Three hypotheses that could explain the lag‐phase were tested:1It is the result of successive loading of the concentric root cell layers centripetally from the epidermis.2It is the result of successive loading of the root basipetally from the apex.3It is the result of induction of the mechanism(s) responsible for upward translocation.All three hypotheses are rejected. Within the whole root radial as well as longitudinal equilibration appears to be very rapid. The simple model of compartmentation is rejected. A more complex compartmentation of the cytoplasm (symplasm) in which the endopiasmic reticulum could play a predominant role is suggested. The mechanisms of vacuolar accumulation and upward translocation appear biochemically re

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06027.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Previous studies have shown increases in the concentration of ethylene in the soil and roots of plants when the soil is water saturated (flooded). InZea maysL. this occurs in association with an overall reduction in growth but without extensive foliar senescence and in conjunction with the development of an adventitious root system. We have assessed the possibility that ethylene may be involved in these responses to flooding. Mixtures of the gas in air were therefore supplied to the roots and stem‐base ofZ. maysgrowing in nutrient solution.Seven or 14 d exposure to ethylene (1 or 5 νl 1−1) inhibited seminal root elongation and growth in dry weight and accelerated the emergence of adventitious roots, although their final length and dry weight were depressed. Leaf extension was inhibited by 0.1,1.0 or 5.0 μl 1−1ethylene around the roots; leaves extending rapidiy at the start of treatment were the most sensitive. Final shoot fresh and dry weights were depressed by the gas but tie shootrroot dry weighl ratio and percentage dry matter were not affected greatly. Leaf chlorosis was not observed but the concentration of phosphorus in the shoots was 26 to 31% below normal.When aeration of the nutrient solution was stopped, the concentration of dissolved oxygen declined and the concentration of ethylene in the roots increased. Similar changes occur in response to soil flooding. Root and shoot growth was slowed by non‐aeration although the shootroot dry weight ratio remained unchanged. The phosphorus concentration of the shoots was depressed but there was little chlorosis or leaf death. The similarity in these respects between the effects of ethylene and non‐aeration suggests that in floodedZ. mays, ethylene contributes to their development by accelerating the emergence of adventitioos roots, inhibiting phosphorus accumulation in the shoots and by a non‐toxic inhibition of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06028.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The inhibitory action of four herbicides (atrazine, dalapon, moiinate, propanil) on the membrane transport of sulfate by excised roots was evaluated in tolerant (Oryza saliva) and susceptible (Pisam sativum, Hordeum vulgare) cultivated species, and in a tolerant and susceptible variety of a weed (Brassica rapa). A parallelism between the response of the root transport activity and the general response of the genotype was ascertained, irrespective of the metabolic target of the herbicide. The inhibition mechanism of sulfate uptake was either competitive, non competitive, or uncompetitive, but this aspect was not correlated with the response of the genotype to the herbicide. The kinetics of absorption14C atrazine by excised roots and by chloroplasts ofBrassica rapawere strictly related: the amount of atrazine binding to roots and to chloroplasts was higher in the susceptible than in the resistant variety. The Sevel of atrazine inhibition of sulfate transport in roots was correlated to that of the Hill reaction; both were higher in the susceptible variety. The membrane transport within the roots appears to summarize and anticipate the metabolic response of genotypes to herbicides.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06029.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Tissues from the aquatic macrophyte speciesScirpus subterminalis, Najas flexilis, Ceratophyllum demcrsum, Potamogeton zosteriformis, and Nuphar advenacontain cAMP in quantities similar to those reported in algae.Scirpus, Najas, andCeratophyllumreleased cAMP into the extracellular media in quantities which varied interspecifically and intraspecifically in differing media. Macrophytic release of cAMP may be an important source of dissolved cAMP in lakewater.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06030.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Seedlings ofVigna catjangEndl. were subjected to water stress for 6, S and 10 days by withholding water to investigate the activities of some oxidative enzymes and the pattern of senescence in leaves of 17‐day‐old seedlings undergoing water stress. Increasing duration of stress produced a proportional increase in the activities of IAA‐oxidase, AA‐oxidase, peroxidase and glycolate oxidase but decreased catalase activity and the contents of both chlorophyll and protein, hastening senescence. Leaf water potential and relative water content were also lowered with incresing duration of stress. Permeability was increased in leaf tissue undergoing water stress for 8 days. Seed treatment with CaCl2(10−2and 10−14M) for 6 h improved the water status of leaves, decreased tissue permeability, activities of oxidative enzymes, decline of chlorophyll and protein contents and delayed senescence compared to untreated water stre

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06031.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Photosynthate availability directly controls the maturation, senescence and distribution of bacteroids (inoculumRhizobium meliloti102 F28) in alfalfa (Medicago salivaL. cv. Buffalo) nodules. Mature, dinitrogen‐fixing bacteroids were located principally in the middle section (region) of 6‐ to 8‐week‐old nodules in light‐grown alfalfa plants. Upon dark treatment of the plants, bacteroids in the middle region of a nodule were induced to senescence while those in the tip region began to mature faster. Senescence and deterioration of bacteroids in the basal region of a nodule also were more advanced in the dark‐treated plants. Sugar supplied exogenously during the dark period retarded the senescence process. Exposure of the dark‐treated plants to light partially restored nitrogenase activity. The distribution of bacteroids in the rejuvenated nodules was similar to that of the light

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06032.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The role of atmospheric oxygen on root water absorption in Helianthus annuus. The effect of atmospheric anoxia on root water absorption was studied. The experiments were carried out on intact young sunflowers in controlled temperature, light and gas environment; roots were kept in aerated nutrient solution at constant temperature. The evolution of root water absorption and transpiration rate was measured continuously. Before the experiment, the plant was preconditioned at a high transpiration rate by illumination or by CO2free air in darkness. Then the atmospheric oxygen was suppressed for 1 h, after which the normal conditions were restored.In anoxia and darkness, the root water absorption cannot balance transpiration, so that an important water stress develops in the plant; the light compensates this effect through the photosynthetic oxygen. The supply of oxygen, in darkness or in light, immediately removes inhibition of stomatal closure and of root water absorption. Two mechanisms control water absorption by roots: the fast one occurs in the leaves and the slower one cannot develop without the root system.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06033.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The effect of cultured soybean (Glycine max(L.) Merr. cv. Acme) cells and extracts thereof on acetylene reduction byRhizobium japanicum61A76 was determined under two culture conditions. In the first (submerged culture)Rhizobiumgrowing on solid medium were submerged in an aqueous layer containing soybean cell suspension or extract; both soybean cells and crude cell extract inhibited free living rhizobial nitrogenase measured by acetylene reduction. In the second culture condition (surface culture)Rhizobiumwas grown on the surface of an agar medium which contained expressed soybean cell sap (7.4% v/v), which caused an increase in free living rhizobial nitrogenase activity. Larger concentrations (12.9 to 19.4% v/v) of soybean cell extract inhibited acetylene reduction also in surface culture, inhibition in submerged culture or surface culture was found after autoclaving of cells or extract, or treating the extract with pH extremes or withStreptomycesprotease. Each of these treatments destroyed stimulatory activity of cell extract in surface cultures. Fractionation of the soybean cell extract on a Biogel P‐6 column showed that there are three inhibitory fractions and at least one stimulatory fraction. Using column data and the fact that stimulatory and inhibitory factors were dialysable against 0.1Mphosphate buffer, we estimated the molecular weights of the factors. The stimulatory factor has a molecular mass (Mr) between 6,000 and 14,000. The inhibitory factors have molecular masses less than 6,000. Crude extracts from cultured carrot (Daucus carota(L.) cv. Danvers) cells gave results similar to those seen with soybean cell extract Extracts from cultured winged bean (Psophocarpus tetragonolobus(L.) DS. cv. TPt2) cells gave inhibition but no stimulatio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb06034.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY