Planta

Wardlaw, I.; Moncur, L.

doi: 10.1007/BF00390309pmid: 24430683

An analysis of the pattern of movement of 14C-labelled flag leaf assimilates in wheat (Triticum aestivum l. c.v. Gabo) during grain development, indicated that the greater the requirement for assimilates by the ear the more rapid was the speed of movement of these through the peduncle to the ear and also the lower their concentration. Experiments with [14C] indoleacetic acid ([14C]IAA) suggested that auxin production by the grains was not responsible for the control of assimilate translocation through the peduncle. Limiting the supply of available assimilates by shading the lower parts of the plant, did not significantly alter the speed of movement of 14C-photosynthate through the peduncle, while severing half of the vascular tissue in the peduncle altered the pattern of movement of 14C to the ear and enhanced the speed of movement of 14C through the remaining functional conducting tissue. These results are discussed in relation to the mechanism of translocation.

Bowles, Dianna; Northcote, D.

doi: 10.1007/BF00390310pmid: 24430684

The polymers contained within pellets rich in either dictyosomes or the endoplasmic reticulum have been investigated. These were detected by the incorporation of radioactivity from D-[U-14C]glucose into the sugars in the intact root. Three types of material were obtained 1) water-soluble 2) soluble in chloroform 3) insoluble. The relative proportions of each of these 3 fractions were different in the 2 membrane preparations. The dictyosome pellet contained a high proportion of water-soluble material, some of the water-soluble polysaccharides contained in both membrane preparations had a molecular weight greater than 40,000. These polymers resembled the pectins and xylans deposited in the cell wall. Some of the insoluble material could be rendered soluble by incubation with proteolytic enzymes and all of this from the dictyosome pellet had a molecular weight greater than 4,000 whereas most of that obtained from the endoplasmic reticulum had a molecular weight less than 4,000 and it did not contain fucose.

Jeschke, Wolf; Stelter, Wilfried

doi: 10.1007/BF00390311pmid: 24430685

A method is described by which the Na+ and K+ content in 0.5 mm sections of single roots of Hordeum distichon L. and Atriplex hortensis L. can be determined by use of flameless atomic absorption spectroscopy. By this method the longitudinal profiles of K+ and Na+ along low salt roots and roots which had been equilibrated with or grown in K+-free 1 mM Na+-solution were determined. The profiles reveal that high K+/Na+ ratios in the cytoplasm are maintained also in K+-free solutions. In solutions containing 1 mM Na+ a high K+/Na+ selectivity was found to be dependent on sufficient aeration. From the ion profiles the cytoplasmic (110 mM) and vacuolar (20 mM) K+ concentration in low salt barley roots—values which are unobtainable by compartmental analysis—could be estimated.

Schönherr, J.

doi: 10.1007/BF00390312pmid: 24430686

The upper astomatous cuticle of Citrus aurantium L. leaves was isolated enzymatically or chemically, extracted with lipid solvents and used for the determination of water diffusion (P d ) and osmotic water permeability (P f ). The water permeability was strongly dependent on the pH value and the cations of the buffer solutions. In presence of monovalent alkali metal ions P d increased almost five fold between pH 3 and 11. The shape of the plot P d vs. pH suggests the presence of 3 different dissociable groups fixed to the membrane matrix. They are tentatively identified as two carboxyl groups dissociating between pH 3 to 6 and 6 to 9, respectively, and as phenolic hydroxyl groups dissociating above pH 9. The carboxyl group dissociating between pH 6 and 9 discriminated between alkali metal ions according to their ionic radius. Water permeability was lowest in the Li+ from and increased in the order Li+<Na+<K+<Rb+. The water permeability of membranes in Ca2+ form was only slightly higher than that of membranes in H+ form and little dependent on pH. The energy of activation which amounted to 13 kcal mol−1 was constant over the temperature range of 5 to 40°C and pH independent. Since P f was greater than P d it was concluded that the cutin matrix contained polar pores and that water transport caused by a chemical potential gradient was both by diffusion and by viscous flow. The porous nature of the membranes was also confirmed by the fact that they are permselective according to size of the permeating molecule. Using the empirical equations of Paganelli and Solomon (1957) and Nevis (1958) the equivalent radius of the pores was estimated to be 0.46 and 0.45 nm, respectively. This estimate is in good agreement with the observations that (a) [14C]urea (molecular radius r s =0.264 nm) and [3H]glucose (r s =0.444 nm) penetrated the membranes and (b) the reflection coefficient was equal to one for raffinose (r s =0.654 nm) and sucrose (r s =0.555 nm) but 0.95 for glucose and 0.78 for urea. Both, the reflection coefficient and the pore radius estimates were pH independent, hence the increase in water permeability with increasing pH was due to an increase in the number of pores per unit area (1 cm2) from 5x1010 at pH 3 to 15.8x1010 at pH 9.

Johnson, C.

doi: 10.1007/BF00390313pmid: 24430687

Nitrate reductase in the cotyledons of etiolated seedlings of Sinapis alba L. responds rapidly to the addition of nitrate. The response is inhibited by cycloheximide at low concentrations. The enzyme is also under phytochrome control. Five minutes of red light irradiation leads instantaneously to a 45% increase in enzyme activity. Increases in activity, linear with respect to time and with no lag phases are promoted by continuous far-red or blue irradiation. These increases are insensitive to cycloheximide. Thus, light and nitrate act through different mechanisms in controlling nitrate reductase activity and phytochrome does not act via controlling the rate of synthesis of the enzyme.

Prézelin, Barbara; Haxo, Francis

doi: 10.1007/BF00390314pmid: 24430688

A peridinin-chlorophyll a-protein complex (PCP) was obtained in large quantity from the marine dinoflagellates, Glenodinium sp. and Gonyaulax polyedra. The chromoproteins have similar molecular weights, 35,500 for Glenodinium sp. and 34,500 for G. polyedra. The proteins from the PCP complex of Glenodinium sp. dissociated from the chromophore on treatment with 1% sodium dodecyl sulfate (SDS) at room temperature. The protein component was a single subunit with a molecular weight of 15,500. Proteins from the PCP complex of G. polyedra were composed of a single polypeptide with a molecular weight of about 32,000. Two peridinin-chlorophyll a-proteins from Glenodinium sp. accounted for 70% of the PCP complex and had isoelectric points of 7.4 and 7.3. The PCP complex from G. polyedra was dominated by a single chromoprotein with an isoelectric point of 7.2 Chromophore analysis indicated the presence of only peridinin and chlorophyll a in a molar ratio approaching 4:1. Other pigments characteristically found in dinoflagellates were absent. Fluorescence excitation spectra of purified PCP indicated an efficient energy transfer from peridinin to chlorophyll a, an observation that lends support to the reported role of peridinin as an accessory pigment in photosynthetic oxygen evolution. In several other brown colored dinoflagellates examined, PCP representtd less than 20% of the total peridinin. However, no PCP could be isolated from cultures of Amphidinium carterae (PY-1). This study provides further evidence that PCP is a normal component of most peridinin-containing dinoflagellates, and functions as a light-harvesting component of the dinoflagellate chloroplast. No fucoxanthin-containing analog of PCP was detected in the chrysophyte, Cricosphera carterae and the dinoflagellate Glenodinium foliaceum.

Molowitz, R.; Bahn, M.; Hock, B.

doi: 10.1007/BF00390315pmid: 24430689

Fruiting body formation of Sordaria macrospora Auersw. is controlled by L-arginine and biotin when the fungus is grown on a synthetic nutrient medium containing optimal concentrations of fructose, KNO3, KH2PO4, MgSO4, and ZnSO4. Arginine and biotin operate in very low concentrations which exclude unspecific nutrient effects. In spite of the complicated interactions of arginine and biotin which are shown qualitatively (Figs. 3 and 4a) and quantitatively (Figs. 2 and 4b), the following conclusions are reached: 1. In the absence of biotin, the development of Sordaria macrospora is blocked at the stage of small protoperithecia. The external addition of biotin (optimal concentration: 3–12 μg/l) allows the formation of fertile fruiting bodies. This effect cannot be imitated by arginine. The biotin effect is discussed in connection with stimulated RNA synthesis.-2. The developmental velocity is influenced by the external addition of arginine. Without arginine but at permissible biotin concentrations, the total life cycle takes about 10 days, in the presence of arginine (1 mM), however, about 6 days.-3. The hyphal density, as well as the total number of fruiting bodies being produced, is controlled in a similar manner by biotin and arginine. The induction of fruiting body formation obviously takes place after the transgression of a critical hyphal density.

Kennedy, Robert

doi: 10.1007/BF00390316pmid: 24430690

Ribulose diphosphate (RuDP) and (PEP) phosphoenolpyruvate carboxylase enzyme activities were studied in young, mature, and senescent Portulaca oleracea leaves. While the absolute amount of both the C3 (RuDP) and C4 (PEP) carboxylase is less in senescent leaves than in mature leaves, RuDP carboxylase activity is reduced to a lesser degree. In senescent leaves, PEP carboxylase activity equals 10% of that in mature tissue, but RuDP carboxylase is 27% of that in mature leaves. The same ontogenetic series was also used to determine photorespiration rates and responses to several gas treatments. Young and mature leaves were unaffected by changes in the light regime or oxygen concentrations, and exhibited typical C4-plant light/dark 14CO2 evolution ratios. Senescent leaves, on the other hand, have photorespiration ratios similar to C3-plants. In addition, senescent leaves were affected by minus CO2, 100% O2 and N2 in a manner expected of C3-plants, but not C4-plants. These results are discussed in terms of a relative increase in activity of the C3 cycle in later developmental stages in this plant.

Steer, Barrie; Pearson, Craig

doi: 10.1007/BF00390317pmid: 24430691

The leaves of Capsicum annuum L. cv. California Wonder function as efficient carbon exporting organs for a large part of their life span. Young and old leaves export the same percentage of fixed carbon (74% within 24 hours) although fixation rates per unit area of young leaves may be three times that of old leaves. A constant feature of translocate distribution is a supply to the roots and to the terminal fruit of the main axis from both the main axis leaves and branch leaves. Carbon supply to branch fruit is flexible in that main axis leaves supply carbon to the very small fruit, but the subtending branch leaves supply more as the fruit grows and the branch node becomes more self-sufficient. Fruit are capable of carbon fixation but translocation to terminal fruit from main axis leaves supplies about 7.5 times as much carbon as direct fixation.

Wattendorff, Joachim

doi: 10.1007/BF00390318pmid: 24430692

Styloid calcium oxalate crystal idioblasts of Agave americana L. are suberized. Where the crystals do not touch the cell wall directly they are enclosed in a suberinic sheath which is connected with the suberinic wall layer. No polysaccharides are laid down as a tertiary wall layer, nor could any polysaccharides be found in the crystal sheath. These results contradict those of Arnott (1973) but agree fully with those of Rothert and Zalenski (1899).