摘要:

AbstractThree experiments were designed to investigate to what extent adaptation to water stress take place. Wheat (Triticum aestivumL. cv. Kolibri) was grown in water culture at constant temperature, air humidity, and light intensity. When the plants were 16 days old, the potential of the root medium (ψr) was lowered by 1 bar every second day by means of polyethyleneglycol 1500 down to −4 or −7 bar and then remained at these levels. As a control one experiment was grown at −0.7 bar. By regression it was found that when ψrwas lowered by I bar, osmotic potential in leaf (ψπ) decreased 1.46 bar, and leaf water potential (ψt) 0.68 bar, which mean an increase of turgor of 0.78 bar. At the same time the leaf water content did fall 0.30 g per g dry matter. Specific transpiration rate increased significantly after ψrwas kept constant, but the increase in area of fresh leaves was strongly reduced due to wilting of old leaves.After an “adaptation” period during which ψrremained at −0.7, −4, and −7 bar, respectively, for at least 1 week. ψrwas altered so as to cover the range from 0 to −14 bar and ψπ, ψr, transpiration and diffusion resistance in stomata (rs) were measured. The levels of ψπand ψ1were lower (more negative) and turgor potential higher in plants grown at low ψr. The transpiration in pre‐stressed plants showed less sensitivity to the alteration of ψrthan in the non‐stressed plants. The values of ψrat which rsincreased greatly, were found to be about −13, −15, and −18 bar for plants

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03952.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractChlorfenprop‐methyl (the herbicidal component of BIDISIN®), and to a lesser extent the free acid, chlorfenprop, inhibit auxin mediated cell responses in coleoptiles ofAvena sativaL. andZea maysL., such as cell elongation, auxin‐uptake, ‐transport and ‐metabolism, acidification of growth media, and binding of naphthyl‐I‐acetic acid to auxin‐specific binding sites in homo‐genates of corn coleoptiles. Within a very narrow concentration range (1 to 2μM) chlorfenprop‐methyl arrests growth from 0 to 100% in sensitive cultivars. The compound displays neither auxin‐nor anti‐auxin‐activity, and only thel(—)‐enantiomer is active. The interaction of the herbicide with auxin at the l

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03953.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe protochlorophyll(ide) present in primary roots of dark‐grown corn (Zea mays) seedlings has anin vivoabsorption maximum at 634 nm. Red light converts the pigment to chlorophyll(ide)awith an absorption maximum at 675 n

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03954.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractObservations that deciduous larch species can show annual growth increments equal to or greater than evergreen conifers, and that the saturating light intensity for photosynthesis in needles ofLarix leptolepiswas almost twice those for several evergreen conifers, led to a study of the photosynthetic mechanism in L. leptolepis. Several features of photosynthesis in L. leptolepis placed this species in an intermediate position between classical C3and C4plants. Incorporation of14C from14CO2by enzyme preparations of larch needles was eight times greater with PEP as substrate than with ribulosebisphosphate; a chlorophyll a/b ratio of 3.5 was obtained; needles possessed a green starch‐containing endodermis but with little orientation of mesophyll cells to this “bundle sheath”; no clear ultrastructural dimorphism was observed between chloroplasts of mesophyll and endodermal cells; a CO2‐compensation point of 20 μl‐l−1was recorded; and the first measurable product of photosynthesis appeared to be malate rather than phospho‐glyceric acid. These results are discussed in relation to the deciduous habit of L. leptolepis and its high productivity in comparison with

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03955.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractArtificially induced parthenocarpic fruits of apples, pears and tomatoes, as well as seeded fruits treated with 2,3,5‐triiodobenzoic acid, frequently show symptoms of Ca deficiency and a low Ca content. It was concluded that auxins, probably produced by the seeds, play a significant role in Ca translocation into fruits. Exogenous indoleacetic acid but not 4‐chlorophenoxyacetic acid applications could replace the effect of seeds in this respect. Auxin transport, rather than auxin accumulation, seems to be necessary for Ca transport, as can be concluded from the effect of auxin transport inhibit

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03956.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractIn attached cotyledons ofCucurbita pepoL. protein, chlorophyll, RNA, DNA and carbohydrates were found to increase to a maximum level 14 days after commencement of germination, followed by a sharp decline thereafter. Cotyledons excised and planted in a nutrient solution 14 days after sowing showed maximum levels of protein, chlorophyll, RNA, DNA and soluble and insoluble sugars 52 days after planting. The increase in these compounds coincides with the full development of the root system. Excision earlier or later than 14 days resulted in lower levels of protein and other compounds. The decrease in the level after 52 days was parallel to the senescing phase of the cotyledons.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03957.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractTwo methods for determining critical respiratory oxygen pressure in whole plants are described.By a polarographic method involving the use of cylindrical platinum electrodes the following critical oxygen pressures for root respiration were found: Rice (cv. Norin 36). 0.024 atm: Rice (cv. Norm 37). 0.026 atm:Eriophorum angustifolium. 0.02 atm. These values contrast markedly with those obtainedin vitro, and support earlier criticisms ofin vitromeasurements: they call into question the use of such data in the modelling of root aeration. When the results were assessed by an electrical analogue system, it was concluded that the respiratory activity in the intact root does not follow the normally accepted hyperbolic relationship with oxygen partial pressure. The experimental data were simulated most closely by assuming the critical oxygen pressure to be a function of respiratory responses in the low porosity (high diffusional impedance) tissues of the root meristem and stele, and respiratory activity in the moderately porous root cortex to be unaffected at values greater than 0.001 atm.A critical oxygen pressure of 0.025–0.04 atm forE. angustifoliumwas found from analyses of the gas phase oxygen in the leaves of whole plants after submergence in the dark. It was concluded that the higher value found by this method was most likely a function of respiratory responses in root tissue remote from the leaf and should not be regarded as the critical oxygen pressure for leaf respiration. The form of the oxygen concentration vs. time plot again suggested a very much lower critical oxygen pressure for certain of the plant tissue

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03958.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractSimultaneous measurements of bioelectric potentials of the vacuole and cell wall in cells ofNitella mucronatawere made by inserting glass microelectrodes into the vacuole and cell wall respeclively. During the oscillation of the bioelectric potential of the vacuole. induced by sudden changes of the external bathing solution or by the impalement of the cell with a microelectrode. the cell wall potential also exhibited fluctuations of variable intensities in phase and concomitant with spikes of the vacuolar potential oscillation. However, the polarity of the pulses of the cell wall potential was reverse to that of the spikes of the vacuolar potential. These results suggest that the same event is registered at both sides of the plasmalemma membrane across which these phenomena are occurring. The results also support the voltage clamp and tracer flux measurements on these cells which indicate that during the generation of single action potentials, induced by current, the plasma lemma transiently increases its permeability to Cl−and K+ions expelling them from the cell. The variable intensity of the transient hyperpolarizations of the cell wall potential is explained by the distance of the microelectrode in the cell wall from the plasmalemm

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03959.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractCarbon dioxide (optimum concentrationc.1.0%) is essential to the initiation of the growth in suspension culture or on agar plates of cultured sycamore cells. By effective flushing of the cultures with CO2‐free air it is possible to demonstrate this requirement with initial cell densities up to 50 × 103cells ml−1. This growth‐promoting activity of carbon dioxide is not related to any effect it may have on the pH of the culture medium. The cells fix applied carbon dioxide into organic and amino acids but attempts to replace the carbon dioxide requirement by non‐toxic levels of organic or amino acids have not been su

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03960.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractAfter one month of cultivation in the dark in inorganic medium the chloroplasts of protonemata ofCeratodon purpureushave larger grana than chloroplasts from light‐grown cultures. Incubation of dark‐grown material with ALA increases the chlorophyll content and chlorophylla/bratio. On polyacrylamide‐gel electrophoresis, a préferential labelling of chlorophyll‐protein complex I is obtained after treatment with (3H) ALA in darkness. In contrast, in light, much higher activity is found in chlorophyll‐protein complex II. The free pigment zone is highly labelled in both en

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03961.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY