ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00738.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Books reviewed in this article:SOLUTE MOVEMENT IN THE SOIL‐ROOT SYSTEM.P. H. Nyeand P. B. TinkerREGULATION OF ENZYME SYNTHESIS AND ACTIVITY IN HIGHER PLANTS(Annual proceedings of the Phytochemical Society, Number 14). Edited by H. Smit

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00739.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractIt is widely believed that there is a growing body of evidence that sieve plate pores in functioning phloem are open and quite free from obstruction. The arguments used to establish this idea are critically examined one by one and the conclusion is reached that it has very little foundation in published work. On the contrary, the view that sieve plate pores are delicately‐occluded with P‐protein in the angiosperms has much more evidence to substantiate it. Since ‘open’ and ‘occluded’ are physiologically defined this means that the pressure‐flow hypothesis must be regarded as serio

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00740.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractAn apparatus is described which consists of an assimilation chamber mounted in the centre of a light‐integrating Ulbricht sphere, irradiated through two fibreoptic light pipes. This arrangement provides totally diffuse radiation in the sphere. The quantum flux density in die sphere is measured by an integrating quantaspectrometer connected to the sphere by eight fibreoptic light pipes. The quantaspectrometer gives the spectral and the total quantum flux density in the sphere. By measuring the quantum flux density in the sphere before and after the insertion of a plant the number of absorbed quanta per unit time and plant area can be determined. In addition, the spectral distribution of the absorbed quantum flux density is obtained.CO2‐assimilation per unit time and plant area is determined in the same apparatus. The totally diffuse radiation within the sphere minimizes mutual shading between branches and leaves. Hence, well‐defined light‐responsecurves of photosynthesis can be obtained by plotting the flux density of C02‐assimilation as a function of the absorbed quantum flux density, and the quantum yields of intact plants can be calculated.Examples of photosynthetic quantum yield determinations and quanta absorption spectra are given for some plan

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00741.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractL‐usnic acid inactivates urease by the formation of high molecular weight aggregates which can reach a maximum of 700,000 under experimentation conditions previously described. The substrate, urea, itself provokes temporary aggregation states which may be either active or inactive; the latter being reversible. However, these inactive aggregates, of 820,000 molecular weight, are irreversibly stabilized by L‐usnic acid. The active aggregates with molecular weights oscillating from 605,000 to 650,000, depending on whether they are formed in the presence or absence of inactivator, may combine with the substrate to form an apparently normal ES comp

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00742.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe air‐flow regime over aPopulusleaf was investigated using a constant temperature hot‐film sensor which could be glued on the abaxial surface. The leaf was exposed to a laminar or turbulent flow of air in a wind‐tunnel, while being free to undergo normal motion. In the laminar air‐flow the boundary layer remained laminar, despite the fluttering of the leaf, until a Reynolds number of 2.3 × 104was reached. When the air incident on the leaf was made turbulent, to resemble natural conditions, the boundary layer became turbulent at a Reynolds number of 0.4 × 104. The experiments suggest that the boundary layers over leaves are always turbulent in the nat

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00743.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractWatermelon (Citrullus vulgarisSchrad.) cotyledons were excised from the seed after 24 h of imbibition and incubated for different times (ranging from 1 to 240 min) on filter paper saturated with 0.1 mM BA (benzyladenine) solution. After the incubation in BA the cotyledons were thoroughly rinsed in water and grown for 5 days in darkness on filter paper saturated with distilled water.Continuous presence of BA is not a prerequisite for optimal growth. Several effects of the hormone (stimulation of expansion growth, acceleration of lipid breakdown, enhancement of hydroxypyruvate reductase activity, increase in carotenoid content) are more intensive if the cotyledons are treated with BA for a relatively short time and then grown in water. Maximal effects are observed after a 4 h exposure to BA. A single 1 min exposure is sufficient to elicit measurable effects on growth, hydroxypyruvate reductase and carotenoid content. The sensitivity to very short exposures is considerably different for different hormone effects. Carotenoid content and hydroxypyruvate reductase activity are enhanced much more than expansion growth.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00744.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractUsing seedlings ofRicinus communisL. sucrose export from the cotyledons to the hypocotyl and roots was measured at different levels of sucrose concentration in the cotyledons. Sucrose export followed Michaelis‐Menten kinetics with a half‐saturation of export at 35 mM sucrose in the cotyledons. A maximal export flux of 90 μmol h−lg−1fresh weight of the cotyledons was obtained. Both these figures coincide with those obtained for sucrose uptake into the cotyledons. It is postulated that sucrose uptake and sucrose export occurs by the same mechanism and possibly by the same cells which then would have to be part of the phloem. Since sucrose uptake has been shown to proceed as proton‐sucrose co‐transport, phloem loading might also be energized by the protonmotive potential difference. The data, furthermore, are difficult to reconcile with the symplastic route of ph

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00745.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractUsing an open‐system leaf chamber, gas exchange measurements on attached leaves of 3‐4‐year‐old Golden Delicious apple trees, made through two seasons, provided data from which the parameters of a leaf photosynthesis model could be derived. The equation is:where C1is internal CO2concentration and Qpis the incident quantum flux. There was considerable leaf to leaf variation in the values of the parameters but no clear seasonal trends were established. The initial slope (a) had an average value of about 2.5 × 10−3mg μmol−1† (i.e. quantum yield ∼ 0.057); the mesophyll conductance (gm) was about 3.5 mm s−1in extension leaves of trees carrying fruit and 2.5 mm s−1in extension leaves of defruited trees. Differences between the values of gmfor spur leaves with and without subtending fruits were not significant; 2.5 mm s−1may be used. Dark respiration (Rd, mg m−2s−1) increased exponentially with temperature (T°C); Rd∼ 0.006 exp (0.09 T). At saturating photon flux density Pnwas linearly related to Ci, up to Ci∼ 250 mg m−3. Optimum temperatures for Pnwere slightly different in the two y

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00746.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe theoretical basis for correcting infra‐red gas analyser readings for changes in reference tube CO2concentration is developed, but in practice the corrections made are empirical. Analyser gain (GA) is related to reference tube concentration (A) in hyperbolic manner. The constants in the equation are determined by plotting 1/GAagainst A. Calibration and operating procedure for a particular type of analyser are described and a numerical example give

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00747.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY