摘要:

Conidiation inAlternaria cichoriiNattras is reversibly stimulated by near ultraviolet radiation (NUV, ca 313 nm) and inhibited by blue light (ca 450 nm) and seems to be a mycochrome‐mediated process. After induction with plane‐polarized NUV, blue light polarized perpendicularly to the NUV was more effective in counteracting the induction than was blue light polarized parallel to the NUV. From this the conclusions are drawn that (a) both the blue‐absorbing component (presumably a flavo‐protein) and the PNUVof the mycochrome system are membrane‐bound and that (b) the transition moment associated with blue light absorption in the presumed flavoprotein forms an angle of at least 53° with the transition moment associated with NUV absorpti

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04910.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Leaf‐specific conductivities (LSCs – hydraulic conductivity per dry weight of supplied leaves). Huber values (transverse sapwood area per dry weight of supplied leaves), specific conductivity (hydraulic conductivity per transverse sapwood area) and tracheid diameters were measured throughout the trunk and crown of 20‐year‐old trees ofAbies balsamca(L.) Mill. Measured specific conductivity was proportional to the radius to the fourth power of tracheids. LSCs, which indicate the relative water availability to different plant parts, are much higher in the trunk than in first order branches, and lowest in second order branches. The structural basis for this “hydraulic hierarchy” lies both in Huber values and in tracheid diameters. For similar diameter stem segments, there was no statistically significant difference for trunks versus branches in specific conductivity. However, in old parts of the tree, trunks are wider than supported branches and producer wider tracheids resulting in greater specific conductivities than in branches. In vigorous trees with strong apical control, Huber values were 12.0 times greater in the trunk than in similar diameter branch segments. In slow‐growing trees with weak apical control, Huber values were 2.2 times greater in the trunk versus similar br

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04911.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Stems of cottonwood (Populs deltoidesBartr. ex Marsh.) plants grown under different conditions were examined to determine the relation between net endogenous auxin yields and the acropetal advance of the primary‐secondary vascular transition zone (TZ). In all treatments, the internode yielding maximum net auxin activity, as determined by theAvenacurvature bioassay, closely corresponded with the internode in which the TZ occurred. Under short‐day (SD) dormancy‐inducing conditions, auxin yield declined steadily while the maximum auxin peak and the TZ shifted toward younger internodes. Auxin yields from these plants were extremely low after 5 weeks of SD compared with those from long‐day (LD) plants. The only consistent auxin yield was obtained from internodes subtending young leaves beneath the apical bud. Plants placed in SD for 3 weeks and then returned to LD conditions showed an immediate increase in auxin yield in the stem, and the progressive acropetal advance of the TZ under SD was reversed. Therefore, within 7 LD the positions of the TZ and peak auxin yield corresponded to those observed before the imposition of SD Fully dormant plants placed in LD showed a dramatic rise in auxin yields during the first 2 weeks of renewed growth. Although low levels of auxin were found in the newly developing shoots after 6 LD, yields increased rapidly after 9 and 14 LD. The position of the TZ corresponded with the peak of net auxin activity after 9 an

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04912.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A nodule cytosol nitrite reductase was isolated from soybean [Glyine max(L.) Mer. cv. Tracy] grown in the presence of nitrate. Enzyme activity increased when increased amounts of nitrate were supplied to the plant. A purification procedure involving ammonium sulfate precipitation, gel filtration, DEAE Sephadex and Blue Sepharose chromatography resulted in an activity capable of forming 6.7 μmol ammonia (mg protein)−1min−1. This represented a 235‐fold increase in specific activity. The molecular weight, estimated by gel filtration, was 55 000. The pH optimum for activity was 7.1. Ammonia formed stoichiometrically as nitrice was consumed. From Lineweaver‐Burk plots, Kmvalues of 0.5mMfor nitrite and 0.2mMfor methyl viologen were calculated. Spectral data suggest the association of a heme chromophore with th

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04913.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

During leaf senescence and abscission, total nitrogen in leaves of mulberry (Morus albaL. ev. Shin‐ichinose) declined substantially whereas total nitrogen in buds, bark and stem wood increased markedly, suggesting translocation of nitrogen from senescent leaves in the autumn. After leaf abscission the winter buds and stems remained almost unchanged with respect to fresh and dry weight and total nitrogen until bud break in spring. In burst buds these parameters then increased drastically during the new growth while they decreased markedly in stems. Free arginine in the stem bark accumulated in parallel with the accumulation of total nitrogen in buds and stems in the autumn. Accumulation of proline in the wood, bark and buds also started in October but continued even after leaf‐fall, increasing until mid‐January (wood), mid‐February (bark) and the new growth (buds). Prior to and in the early stage of bud break, proline in bark and wood decreased significantly and arginine in stem bark decreased slightly. Simultaneously, proline and arginine in the dormancy‐releasing buds and asparagine, aspartic acid and glutamic acid in the buds and stems increased appreciably, suggesting that this increase in free amino acids was mainly derived from free amino acids (proline and arginine) stored in stems. The resulting marked decrease in total nitrogen and the drastic increase in asparagine in the stems and sprouting buds/new shoots were primarily due to a breakdown of protein stored

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04914.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Membranes isolated from vegetative cells ofAnabaena variabilis(ATCC 29413) oxidine NADPH and NADH in a cyanide‐sensitive reaction, NADPH being the better donor. In addition, both act as reductants for photosystem I in the light and in the presence of DCMU. An NADH‐regenerating system has been introduced experimentally, functioning as donor system for photosystem I ofAnabaenamembranes. This NADH dehydrogenation is strictly light‐dependent, sensitive to DBMIB, establishes a transhydrogenase system with NADP+was hydrogen acceptor and competes with oxygen. Kinetic analysis of oxygen uptake with reference to nucleotide concentration exhibited different Km‐ and Vmax‐values for NADPH and NADH in the light and in

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04915.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Soybean {Glycine max(L.) Merr. ev. Essex} was grown from seed in a greenhouse under ultraviolet‐B (UV‐B, 280–320 nm) radiation supplied by filtered FS‐40 sunlamps. On a weighted, total daily dose basis these plants received either 0 (control) or 2875 effective J m−2day−1UV‐BBE. When weighted with the generalized plant action spectrum (Caldwell 1971), this simulated the solar ultraviolet‐B irradiance expected to occur at College Park, Maryland, USA (39°N) in the event the global stratospheric ozone column is reduced by 23%. The effects of ultraviolet radiation on the photosynthetic recovery from water stress were measured with an infrared gas analyzer. These effects were examined in plants which were either well‐watered or previously preconditioned to water stress, during two distinct phenological stages of development. During the early stages of soybean growth, enhanced levels of UV‐B reduced net photosynthesis by 25%, and water stress also reduced photosynthesis to nearly the same extent (by 20%). The combination of these two stresses resulted in smaller biomass than that produced by plants exposed to either stress independently. Photosynthesis in older, larger plants was much more sensitive to water stress and was reduced by as much as 50–60% in non‐preconditioned plants. Although non‐irradiated, non‐preconditioned (control) plants recovered to only within 60% of their prestressed value, preconditioned plants recovered to within 70–80% during the 3 day recovery period. Both water stress and UV‐B radiation affected non‐stomatal conductance, while stomatal conductance was

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04916.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Morphometric characteristics ofLemna gibbaL. cells have been estimated. The mean relative volumes of the wall, of the cytoplasm and of the vacuoles were 0.03, 0.32 and 0.65, respectively. The distribution of the individual values has been studied: for instance 29% of the cells had a mean relative volume of the vacuoles close to 0.73, 39% to 0.68, 19% to 0.61 and 13% to 0.51. The mean value and distribution of the surface areas of the tonoplast and plasmalemma were also determined. This allows us to discuss the active or passive character of the transport of various substances at the plasmalemma and at the tonoplast, according to the usual flux‐ratio approach. The feasibility of such an approach in ordinary (non‐giant) living cells is discussed with regard to the degree of reliability of the measurements which can be performed with such ce

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04917.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Auxin‐induced changes in cell wall polysaccharide composition and enzyme activity of seta segments from the liverwortPellia epiphylla(L.) Corda were studied using colorimetric, gas chromatographic, radioactive tracer, and viscometric techniques. Extension‐growth of segments doubled in the presence of aqueous 10 μMindole‐3‐acctic acid (IAA) ± 50 mMglucose. IAA‐enhanced growth was accompanied by (1) enhanced synthesis of all wall polysaccharides but cellulose, (2) increase in the relative glucose content of neutral wall sugars, and (3) change in the activity of wall‐bound glycosidase relative to controls, but no change in the activity of cellulase. Galactose and mannose (50 mM) suppressed auxin enhancement of both growth and wall synthesis. These findings suggest that auxin‐mediated extension‐growth ofPelliasetae is dependent upon the maintenance of non‐cellulosic

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04918.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effects of nitrogen (N) nutrition on growth, N uptake and leaf osmotic potential of rice plants (Oryza sativaL. ev. IR 36) during simulated water stress were determined. Twenty‐one‐day‐old seedlings in high (28.6 × 10−4M) and low (7.14 × 104M) N levels were exposed to decreased nutrient solution water potentials by addition of polyethylene glycol 6000. The roots were separated from the solution by a semi‐permeable membrane. Nutrient solution water potential was −0.6 × 105Pa and was lowered stepwise to −1 × 105, −2 × 105, −4 × 105and −6 × 105Pa at 2‐day intervals. Plant height, leaf area and shoot dry weight of high and low nitrogen plants were reduced by lower osmotic potentials of the root medium. Osmotic stress caused greater shoot growth reduction in high N than in low N plants. Stressed and unstressed plants in 7.14 × 104MN had more root dry matter than the corresponding plants in 28.6 × 104MN. Dawn leaf water potential of stressed plants was 1 × 105to 5.5 × 105Pa lower than nutrient solution water potential. Nitrogen‐deficient water‐stressed plants, however, maintained higher dawn leaf water potential than high nitrogen water‐stressed plants. It is suggested that this was due to higher root‐to‐shoot ratios of N deficient plants. The osmotic potentials of leaves at full turgor for control plants were about 1.3 × 105Pa higher in 7.14 × 10−4Mthan in 28.6 × 10−4MN and osmotic adjustment of 2.6 × 105and 4.3 × 105Pa was obtained in low and high N plants, respectively. The nitrogen status of plants, therefore, affected the ability of the rice plant to adjust osmotically during water stress.Plant water stress decreased transpiration and total N content in shoots of both N treatments. Reduced shoot growth as a result of water stress caused the decrease in amount of water transpired. Transpiration and N uptake were significantly correlated. Our results show that nitrogen content is reduced in water‐stressed plants by the integrated effects of plant water stress per se on accumulation of dry matter and transpiring leaf area as well as the often cited change

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04919.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY