Showing papers in "Planta in 1972"

Development and differentiation of haploid Lycopersicon esculentum (tomato).

Abstract: Haploid callus cultures of selected races of Lycopersicon (tomato) species can be obtained from anther culture. This is a further demonstration of a proposed general method of haploid culture developed with Arabidopsis thaliana. Differentiation of haploid callus of Lycopersicon esculentum can be controlled both in the dark and the light by hormones added to defined minimal media. Development to plantlets is achieved only in the light. Callus cells can be induced to develop into seedless pseudo-fruits. Chromosome counts on callus cells or root-tip cells establishes haploidy (n=12).

Sporopollenin in the cell wall of Chlorella and other algae: Ultrastructure, chemistry, and incorporation of 14 C-acetate, studied in synchronous cultures

Abstract: Cells of Chlorella fusca var. vacuolata (Cambridge 211/8p) resisted efforts aimed at producing naked protoplasts by enzymatic degradation of the cell wall, and a study of the development and composition of the wall was therefore undertaken. 1. After cytokinesis has produced naked autospores within the mother cell wall, cell wall formation commences outside the autospore plasma membrane with the appearance of small trilaminar plaques. These enlarge while inter-autospore granular material diminishes in quantity, and they eventually fuse to produce a complete trilaminar sheath around each autospore. 2. A microfibrillar, cellulase digestible, layer is deposited between the trilaminar component and the plasma membrane. Meanwhile the corresponding microfibrillar component of the mother cell wall is digested leaving only its resistant trilaminar component. 3. The trilaminar component includes a substance considered to be the polymerized carotenoid, sporopollenin, on the basis of its resistance to extreme extraction procedures including acetolysis, and its infra red absorption spectrum. 4. Two phases of sporopollenin biosynthesis were detected by means of pulse and pulse-chase treatments with 14C-acetate at intervals during the cell cycle in synchronous cultures. One coincides with the formation of the sporopollenin-containing trilaminar wall component, and the other is 6–8 hours earlier while the cells are in karyokinesis. The former yields labelled sporopollenin directly and the latter probably represents formation of a precursor. 5. Of five other strains of Chlorella tested, only one possesses sporopollenin, and so does one Scenedesmus and two out of three strains of Prototheca. 6. Examination of the wall structure of the above algae suggest a relationship between the presence of sporopollenin and the development of an outer, trilaminar wall component. 7. A survey of the literature gives support to this hypothesis and further suggests that the ability to synthesise sporopollenin is related to the ability to produce secondary carotenoids. 8. The significance of the findings is discussed.

In-vitro auxin binding to particulate cell fractions from corn coleoptiles.

Abstract: When low concentrations (e.g. 10-6 M) of labelled 3-indoleacetic acid (14C-IAA) or α-naphthaleneacetic acid (14C-NAA) are added in vitro to homogenates of corn coleoptiles, radioactivity is reversibly bound to pelletable particles. From the saturation kinetics of the binding it is possible to estimate an apparent K M between 10-6 M and 10-5 M and a concentration of specific sites of 10-7–10-6 M per tissue volume. The binding is auxin-specific. Among many compounds tested, only auxins and such auxin analogues that are known to interact directly with auxin in transport and/or growth were found to interfere with this binding. For instance, the growth-active d-dichlorophenoxyisopropionic acid at 10-4 M inhibits 14C-NAA binding more than the less active l-isomer. The auxin-binding fractions are practically free of DNA and cytochrome-C oxidase and contain binding sites for 1-naphthylphthalamic acid. The results are discussed in context with the hyothesis—derived mainly from physiological data—that auxin receptors are localized at the plasma membrane.

Stomatal responses to changes in humidity in plants growing in the desert.

Abstract: The stomata of plants growing in the Negev Desert, namely the stomata of the mesomorphic leaves of Prunus armeniaca, the xeromorphic stems of Hammada scoparia, and the succulent leaves of Zygophyllum dumosum, respond to changes in air humidity. Under dry air conditions diffusion resistance increases. Under moist air conditions diffusion resistance decreases. When the stomata close at low air humidity the water content of the apricot leaves increases. The stomata open at high air humidity in spite of a decrease in leaf water content. This excludes a reaction via the water potential in the leaf tissue and proves that the stomatal aperture has a direct response to the evaporative conditions in the atmosphere. In all species the response to air humidity is maintained over a period of many hours also when the soil is considerably dry. The response is higher in plants with poor water supply then in well watered plants. Thus for field conditions and for morphologically different types of photosynthesizing organs the results confirm former experiments carried out with isolated epidermal strips.

The chemical composition of Ricinus phloem exudate.

Abstract: The chemical composition of exudate obtained from incisions made in the bark of the stem of actively growing Ricinus plants has been determined. The exudate had a high dry matter content (100–125 mg/ml), a high sugar content (80–106 mg/ml) which was solely sucrose, reducing sugars being absent. The amino acid composition was mainly glutamic and aspartic acids and threonine with a total amino acid concentration of 35.2 mM. The exudate had a pH of 8.0–8.2. Potassium was the major cation (60–112 mM) with sodium present at a lower concentration (2–12 mM). Of the divalent cations, calcium was at a low concentration (0.5–2.3 mM) and magnesium relatively higher (4.5–5.4 mM). Chloride was the major inorganic anion (10–19 mM). Phosphate concentration was relatively high (3.7–5.7 mM) and low concentrations of sulphate (0.3–0.5 mM) and bicarbonate (1.7 mM) were also present. Nitrate was absent. The ionic balance was maintained by the presence of relatively large quantities (30–47 meq/l) of organic anions, mainly malate. Bioassays revealed auxin, gibberellin and cytokinin activities in chromatographed exudate. Adenosine triphosphate was found in the exudate (0.40–0.60 mM). The analysis is dicussed with respect to the composition of phloem sap reported for other plant species.

Tubular and filamentous structures in pollen tubes: Possible involvement as guide elements in protoplasmic streaming and vectorial migration of secretory vesicles

Abstract: An ultrastructural study of the pollen tubes of Lilium and Clivia has demonstrated three different classes of longitudinal structures which could influence patterns of protoplasmic streaming and/or serve as “guide elements” in the vectorial migration of secretory vesicles: (a), cortical and noncortical microtubules; (b), microfilaments; and (c), subcortical tubules and cisternae of the endoplasmic reticulum (“subsurface cisternae”) Morphological details of these structures are described Colchicine concentrations which lead to the complete disappearance of the microtubules affect neither germination of the pollen nor cytoplasmic streaming and tip growth of the elongating pollen tubes Tip growth is initially uninhibited by cycloheximide, and cytoplasmic streaming is insensitive to this inhibitor However, both of these processes are sensitive to cytochalasin B and vinblastine Our results suggest that neither microtubules nor subsurface cisternae are essential for cytoplasmic streaming and directional secretion of cell surface materials in the pollen tube but would be consistent with an involvement of microfilamentous structures in these processes Additionally, the possible importance of the lateral cross-link elements interconnecting all three types of structures is discussed

Sensitivity of cell division and cell elongation to low water potentials in soybean hypocotyls.

Abstract: The response of cell division and cell elongation to low cell water potentials was studied in etiolated, intact soybean hypocotyls desiccated either by withholding water from seedlings or by subjecting hypocotyls to pressure. Measurements of hypocotyl water potential and osmotic potential indicated that desiccation by withholding water resulted in osmotic adjustment of the hypocotyls so that turgor remained almost constant. The adjustment appeared to involve transport of solutes from the cotyledons to the hypocotyl and permitted growth of the seedlings at water potentials which would have been strongly inhibitory had adjustment not occurred. Growth was ultimately inhibited in hypocotyls due to inhibition of cell division and cell elongation to a similar degree. The inhibition of cell elongation appeared to result from a change in the minimum turgor necessary for growth. On the other hand, when intact hypocotyls were exposed to pressure for 3 h, osmotic adjustment did not occur, turgor decreased, and the sensitivity of growth to low cell water potentials increased, presumably due to inhibition of cell elongation. Thus, although cell division was sensitive to low cell water potentials in soybean hypocotyls, cell elongation had either the same sensitivity or was more sensitive, depending on whether the tissue adjusted osmotically. Osmotic adjustment of hypocotyls may represent a mechanism for preserving growth in seedlings germinating in desiccated soil.

Oscillations in stomatal conductance and plant functioning associated with stomatal conductance: Observations and a model.

Abstract: Measurements of transpiration, leaf water content, and flux of water in a cotton plant exhibiting sustained oscillations, in stomatal conductance are presented, and a model of the mechanism causing this behaviour is developed. The dynamic elements, of the model are capacitors—representing the change of water content with water potential in mesophyll, subsidiary and guard cells—interconnected by resistances representing flow paths in the plant. Increase of water potential in guard cells causes an increase in stomatal conductance. Increase of water potential in the subsidiary cells has the opposite effect and provides the positive feed-back which can cause stomatal conductance to oscillate. The oscillations are shown to have many of the characteristics of free-running oscillations in real plants. The behaviour of the model has been examined, using an analogue computer, with constraints and perturbations representing some of those which could be applied to real plants in physiological experiments. Aspects of behaviour which have been simulated are (a) opening and closing of stomata under the influence of changes in illumination, (b) transient responses due to step changes in potential transpiration, root permeability and potential of water surrounding the roots, (c) the influence of these factors on the occurrence and shape of spontaneous oscillations, and (d) modulation of sustained oscillations due to a circadian rhythm in the permeability of roots.

Localization and activity of various peptidases in germinating barley.

Abstract: Germinating barley grains contain at least eight different peptidases: three carboxypeptidase (pH optima 4.8, 5.2, and 5.7), three aminopeptidases which act on aminoacyl-β-naphthylamides (pH opitima in the hydrolysis of di- and tripeptides at pH 5.8–6.5), and two peptidases which hydrolyse Ala-Gly and Leu-Tyr optimally at pH 7.8 and 8.6 respectively. We have determined the activities of these enzymes in the different tissues of non-germinated grains and followed the changes in the activities during a 5-day germination at 16°C.

The effect of SO 3 (--) on the activity of ribulose-1,5-diphosphate carboxylase in isolated spinach chloroplasts.

Abstract: SO 3 -- inhibits the activity of ribulose-1,5-diphosphate carboxylase in isolated spinach chloroplasts. It shows a non-competitive inhibition pattern with respect to ribulose-1,5-diphosphate and Mg++ but a competitive one with respect to HCO 3 - . The K i -values are 14 mM SO 3 -- and 9.5 mM SO 3 - respectively for the non-competitive inhibition but only 3.0 mM SO 3 -- in the case of competitive inhibition with HCO 3 -- as a substrate. Thus it is concluded that the competitive inhibition type will predominate at low SO 3 -- and low internal CO2 concentrations.

Electrical coupling between cells of higher plants: A direct demonstration of intercellular communication.

Abstract: Electrical coupling between adjacent cells of Elodea canadensis has been demonstrated using a microelectrode technique in which the membrane potentials were recorded during the passage of a current pulse from the vacuole of one cell to the external solution. The changes in membrane potential resulting from the passage of the current may be simulated by an equivalent circuit in which the tonoplast:plasmalemma:plasmodesmata resistances are in the ratio 1.0:5.6:2.2. On this basis, the specific resistances are 3.1 kΩ cm2 for the plasmalemma, 1.0 kΩ cm2 for the tonoplast and 0.051 kΩ cm2 for the junction between the cells. Although the plasmodesmata permit the passage of current, it is estimated that they have a resistance about 60 times higher than would be the case if they were completely open channels. Electrical coupling has also been demonstrated between parenchymal cells in oat coleoptiles and between cortical cells in maize roots. The significance of these findings is discussed in relation to the symplastic transport of ions and other small molecules and in relation to the quantitative measurement of membrane resistance in multicellular tissue.

The in-vitro acid-growth response: Relation to in-vivo growth responses and auxin action.

Abstract: We have examined in detail the characteristics of the hydrogen-ion extension response in frozen-thawed Avena coleoptile sections (in-vitro acid-growth response). These data allow us to compare the in vitro response with the in-vivo extension responses initiated by auxin and hydrogen ions. The in-vitro response has three characteristics in common with the in-vivo responses: a similar Q10 (3–4 between 15 and 25°C, but almost 1 between 25 and 35°); a minimum yield stress; and a lack of stored growth (i.e., an inability to induce a potential for growth during periods of reduced wall tension). Both the in-vivo and in-vitro acid-growth responses have a threshold pH of about 4.5 and give an optimum response at pH values of 3 and below. These similarities suggest that the in-vitro and in-vivo acid-growth responses have a common wall-loosening and wall-extension mechanism. We have also examined the effects of Pronase, sodium lauryl sulfate (SLS), elevated temperatures, calcium, and potassium ions on the in-vitro acid-growth response. We suggest that hydrogen ions do not activate wall-associated enzymes, but act to hydrolyze non-enzymatically some acid-labile linkages in the cell wall. Furthermore, we suggest that auxin induces cell elongation either by causing the release of hydrogen ions from the protoplast or by causing the appearance in the wall of an enzyme which can hydrolyse the acid-labile linkages.

Cell division and plant development from protoplasts of carrot cell suspension cultures.

Abstract: Cell regeneration and sustained division have been observed in protoplasts from carrot cell suspension cultures. Carrot plants were produced from the protoplasts by embryogenesis.

Adventive plants from ovules and nucelli in Citrus.

Abstract: 1- to 8-week-old ovules and nucelli from three Citrus cultivars—Shamouti and Valencia (Citrus sinensis) oranges and Marsh Seedless (C. paradisi) grapefruit—were cultured in vitro. No embryo differentiation was observed in the explants prior to culture. The Shamouti ovules had degenerated and were apparently unfertilized. Embryoids formed on Murashige and Tucker nutrient medium supplemented with 500 mg/l malt extract. Whole plants developed on the same basal medium supplemented with kinetin and indole-3-acetic acid (IAA), coconut milk or gibberellic acid (GA3). A higher kinetin/IAA ratio or the addition of coconut milk favoured stem elongation more than root formation while a lower kinetin/IAA ratio favoured root formation and inhibited stem elongation. The addition of GA3 to the basal medium stimulated rooting and stem elongation. These results can be of aid in mutation research, allowing irradiation at stages prior to embryonic development.

A nickel-accumulating plant from Western Australia.

Abstract: A small shrub Hybanthus floribundus (Lindl.) F. Muell. Violaceae growing in Western Australia accumulates nickel and cobalt to a very high degree. Values of up to 23% nickel in leaf ash may represent the highest relative accumulation of a metal on record. The high accumulation of nickel poses interesting problems in plant physiology and plant biochemistry.

Exploration of the nitrogen transport system of a nodulated legume using 15 N

Abstract: Feeding experiments using (15)N2 or (15)NO3 are described investigating the transport of nitrogen in the field pea (Pisum arvense L.). Nitrogen assimilated by root or nodules moves preferentially upwards to the shoot through the xylem. Parts of the root below or distal to a region of assimilation can benefit from this nitrogen but do so to a much greater extent when the shoot is left attached than when it has been removed. A considerable proportion of the nitrogen received by a shoot from the root or nodules is apparently returned to the root in the translocation stream, this "cycled" nitrogen being especially important in the nutrition of outlying parts of nodulated roots growing in media lacking combined nitrogen.Nitrogen from nitrate fed to a mature leaf is exported in quantity to all parts of the plant except older regions of the shoot. Leaf and stem segments immediately above the fed leaf, and the root and its nodules receive large shares of this nitrogen, although the root's share declines noticeably as the plant ages.The root appears to be extremely inactive in transferring nitrogen from the downward translocation stream across to the stream of nitrogen leaving the root in the xylem. This may act as a major obstacle to the free circulation and mixing of nitrogen within the plant body.A scheme is proposed embracing the main quantitative features of the transport system for nitrogen in the species.

Lipids of membranes and of the cell envelope in heterocysts of a blue-green alga.

Abstract: Heterocysts of Anabaena cylindrica, isolated rapidly in the cold, were found—in contrast to earlier reports—to contain all of the same lipids and lipophilic pigments, and in about the same proportions, as vegetative cells. In broken filaments and in heterocysts damaged during isolation, the membrane lipids and certain pigments (myxoxanthophyll and an unidentified red pigment) break down rapidly. The glycolipids specific to heterocyst-forming blue-green algae are localized in the laminated layer of the heterocyst envelope. A possible role of the laminated layer is discussed.

Polyphenol synthesis in cell suspension cultures of Paul's Scarlet rose

Abstract: 1. In dark-grown cell suspension cultures of Paul's Scarlet rose (Rosa sp.), polyphenol accumulation is essentially restricted to late- and post-exponential phase cells. The range of polyphenols synthesised is extensive, involving at least fourteen different compounds which show a characteristic pattern of development over the growth cycle. 2. The duration of polyphenol accumulation is largely determined by the availability of carbohydrate, while the initiation and initial rate of synthesis is largely influenced by a complex of factors of which auxin concentration and light are most important. High 2,4-D concentrations (5x10-5M) supress accumulation by delaying initiation and reducing the subsequent rate of synthesis. High intensity illumination (6000 Lux) partially reverses the inhibition of polyphenol synthesis at 5x10-5M 2,4-D, and enhances accumulation at lower auxin concentrations (5x10-7M 2,4-D). 3. Illuminated cultures also accumulate anthocyanin. Initiation of pigment synthesis is insensitive to the auxin concentration of the medium, and higher hormonal levels (5x10-5M 2,4-D) increase net anthocyanin accumulation by prolonging the period over which it is synthesised.

Fine structural observations on the epidermis : I. The epidermal cell wall.

Abstract: The organization of the wall of epidermal cells in the petiole of species of Apium, Eryngium, Rumex, and Abutilon as well as that of the epidermis of Avena coleoptile has been investigated The outer and inner tangential walls consist of layers in which the cellulose microfibrils are oriented alternately parallel or transverse to the longitudinal cell axis This organization resembles that previously described for collenchyma cell walls (Wardrop, 1969; Chafe, 1970) On the radial (anticlinal) walls the orientation of the microfibrils is transverse and these appear continuous with the layers of transverse orientation of the outer and inner tangential walls Variation in thickness of the outer tangential, and radial, and inner tangential walls appears to result from the variation in thickness of those layers in which the microfibrils have a longitudinal orientation The extent to which these observations can interpreted in terms of some type of modified "multi-net" growth is discussed

The function of the aleurone layer during galactomannan mobilisation in germinating seeds of fenugreek (Trigonella foenum-graecum L.), crimson clover (Trifolium incarnatum L.) and lucerne (Medicago sativa L.): A correlative biochemical and ultrastructural study.

Abstract: The reserve endosperm galactomannans of fenugreek (Trigonella foenum-graecum L.), crimson clover (Trifolium incarnatum L.) and lucerne (Medicago sativa L.) are broken down to free galactose and mannose in dry-isolated endosperms (devoid of embryo) incubated under germination conditions. Breakdown is prevented by inhibition of protein synthesis or of oxidative phosphorylation in the aleurone layer. Resting aleurone cells contain inter alia a large number of ribosomes more or less regularly distributed in the ground plasma. At the onset of germination, before galactomannan breakdown begins, polysomes are formed and seem, at least partly, to become associated with vesicles and flat cisternae both probably newly formed and derived from ER. Concurrently with galactomannan breakdown in the reserve cells, wall corrosion occurs in the aleurone layer, the contents of the aleurone grains disappear and the rough vesicles and cisternae proliferate. Later a large central vacuole is formed which incorporates smaller vacuoles emerging from the cytoplasm, and at the same time the rough ER vesicles and cisternae become highly distended.It is concluded that the cells of the aleurone layer are responsible for the synthesis and secretion into the storage cells of the enzymes necessary for galactomannan degradation. The physiology of galactomannan breakdown is compared and contrasted with that of starch mobilisation in the endosperm of germinating cereal grains.

Reproduction induced by blue light in female gametophytes of Laminaria saccharina.

Abstract: In red light at 15°C, female gametophytes of Laminaria saccharina continue to grow indefinitely without becoming fertile, but 6–12 hours' irradiation with blue light induces the production of eggs. At lower temperatures, some gametophytes become fertile in red light, but blue irradiation increases the percentage of fertile gametophytes.

The dosage-response curve for auxin-induced cell elongation: A reevaluation.

Abstract: The dosage-response curve for auxin-induced growth of coleoptile sections has been reevaluated, using initial growth rates than rates obtained hours after application of auxin. The curve is sigmoid rather than the “classical” bell-shape; i.e., the growth rate increases as the IAA concentration is raised from 10-8 M, but then the same optimal rate prevails over the range of 3×10-7 to 10-3 M. In the absence of sucrose this sigmoid shape persists, but with sucrose present the shape slowly changes into a modified bell-shaped curve. It is suggested that the classical bell-shaped curve is due, at least in part, to an auxin-sucrose interaction, and that it is not a true reflection of the kinetics of auxin-induced elongation.

The early ontogeny of embryoids and callus from pollen and subsequent organogenesis in anther cultures of Datura metel and rice.

Abstract: Haploidy induction through anther culture has been examined in Datura metel and rice with a view to tracing the precise sequence of development of the pollen, either directly or through an intervening callus, into an embryo and seedling. In D. metel, the vegetative cell of the young pollen grain assumes the major role in formation of embryos whereas the generative cell and its few derivatives degenerate. Embryos and seedlings arising directly from pollen without an intervening callus phase always proved to be haploids, whereas those differentiating from pollen-derived callus gave haploid, diploid and even triploid plants. Cytological analysis of callus tissue showed cells of various ploidy levels ranging from haploid to triploid, and in rare instances even with higher chromosome numbers.In rice anther cultures the embryoids arose from an initial callus phase. Of 15 different rice cultivars tried, only four produced a callus, and in only one, was there differentiation of plants, both haploid and diploid ones. Among other species tried, egg plant has also yielded plantlets through a callus phase whereas only callus production has been achieved in jute, tea and petunia. No response has been obtained in wheat, maize, cotton and coconut.Coconut milk (CM) appears to be the most important component of the medium for the initial induction of embryoids and callus in anther cultures of most of the species tried. However, further growth and differentiation of plants may require a simpler medium; in D. metel, continued culture on CM led to dedifferntiation.

An electrophysiological study of regeneration in Acetabularia mediterranea.

Abstract: Polar regeneration of anucleate posterior stalk segments (PSS) of Acetabularia mediterranea has been studied electrophysiologically. 1. During regeneration the PSS develops a longitudinal, steady potential gradient, U, which is shown to reflect a spatial difference in the transmembrane potential, ΔVm,of 5 to 10 mV, i.e. about 5% of Vm.While regeneration becomes visible at about tr=45 h after its light-triggered onset, its sign can be predicted from U not later than at t=29 h, because regeneration occurs at that cell pole where Vmis highest, i.e. where the cytoplasm is more negative (Fig. 3, Table 1). 2. Clamping U to comparable values by external circuitry causes the regeneration again to occur where Vmis highest, although in this case the flow of the current, I, which controls U is opposite to the direction of the self-generated current, or even changes its sign (Fig. 11, Table 2). 3. Clamping U to zero, i.e. eliminating any transcellular potential gradient, inhibits polar regeneration at least up to t=60 h (Table 3). 4. Spontaneous spikes of U (Fig. 4) and of I (Fig. 12), occur as early as at t=8 h (Fig. 5). These spikes arise at the presumptive regenerating pole with refractory intervals of 10–25 min. They obviously reflect the propagating action potential (Figs. 7–9) although, under the conditions of our present experiments, they spread along the PSS only electrotonically (Fig. 6). 5. Both signals, U and the spikes, are presumably due to changes in the electrogenic Cl-dependent component of Vm,rather than its K+-controlled, diffusive component. 6. The data allow to substantiate our working-hypothesis (p. 242) that the mechanism of spatial differentiation involves voltage-dependent plasmalemma properties including excitation.

The development of protein and oil bodies in the seed of Sinapis alba L.

Abstract: The cotyledons of Sinapis alba L. seed are the storage organs and first photosynthetic organs. The development of the cotyledon cell contents was studied using electron and light microscopy. From the heart shaped embryo (11 days from petal fall) to the mature seed, nine stages were examined.

Endogenous abscisic acid in relation to photoperiodically induced bud dormancy.

Abstract: The abscisic acid contents of birch, maple and sycamore plants growing under long and short photoperiods were measured by gas-liquid chromatography No increase was observed in the abscisic acid content of extracts when plants were transferred to dormancy-inducing conditions

Genetic control of β-diketone and hydroxy-β-diketone synthesis in epicuticular waxes of barley

Abstract: Five eceriferum, (cer) mutants in barley which influence β-diketone and hydroxy-β-diketone synthesis in spike and internode epicuticular waxes have been characterized. The mutation cer-u69 blocks the synthesis of hydroxy-β-diketones and leads to a compensatory increase in the amount of β-diketones, indicating that β-diketones are precursors of the hydroxy-β-diketones. Furthermore, highly lobed wax plates were observed for the first time on barley lemmas, in addition to the characteristic wax tubes. Both diketone classes are selectively and proportionally reduced in the spike wax of cer-i16, which has shorter wax tubes. The three mutants cer-c36, -q42, and -c,u108 synthesize neither diketone class and form no wax tubes. In contrast to the variable composition of most individual barley wax classes, only a single β-diketone was identified, namely hentriacontan-14,16-dione.

Plasmalemma structure in relation to microfibril biosynthesis in Oocystis.

Abstract: The plasmalemma of Oocystis apiculata, W. West when freezeetched has been shown to bear granules of several sizes. At the earliest stage of development the outer face of the plasmalemma of the naked autospore has small (8.5 nm diameter) granules aligned in rows, in pairs. These rows are stacked together forming extensive “granule-bands” over the plasmalemma surface. The orientation of these “granule-bands” corresponds exactly to one of the major microfibril directions. Occasionally, the bands are reduced to patches, some of which are at right angles to each other. Banding of granules on the inner plasmalemma face of naked autospores is also seen. During development the plasmalemma is seen to change so that in the final stages it bears reticulate invaginations, the granule bands occurring within them. The significance of the “granulebands” in terms of cellulose microfibril biosynthesis is discussed.

P-protein distribution in mature sieve elements of Cucurbita maxima.

Abstract: Portions of the hypocotyls of 16-day-old Cucurbita maxima plants, from which the cotyledons and first foliage leaves had been removed 2 days earlier, were fixed in glutaraldehyde and postfixed in osmium tetroxide for electron microscopy. In well over 90% of the mature sieve elements examined the P-protein was entirely parietal in distribution in both the lumina and sieve-plate pores. In addition to the parietal P-protein, the unoccluded sieve-plate pores were lined by narrow callose cylinders and the plasmalemma. Segments of endoplasmic reticulum also occurred along the margins of the pores.

The effect of the source of inorganic nitrogen on growth and enzymes of nitrogen assimilation in soybean and wheat cells in suspension cultures.

Abstract: Soybean (Glycine max L. cv. Mandarin) and wheat (Triticum monococcum L.) cells were grown in media with NO3- plus NH4+ (B5) and NO3- without NH4+ (B5-NH4) as nitrogen sources. Changes in pH, [NO3-] and [NH4+] in media, and dry weight, protein content, nitrate reductase (NR) and glutamate dehydrogenase (GDH) in the cells were followed for about 170 h. With both NH4+ and NO3- in the medium, NH4+ was utilized very quickly. Soybean cells grew poorly in the absence of NH4+ while wheat cells grew equally well on media with or without NH4+. When soybean cells were grown in medium with NO3- plus NH4+, dry weight and NR activity remained relatively low for several hours after which both increased rapidly. This coincided with the time NH4+ was depleted from the medium. In the absence of NH4+, soybean cell growth and NR activity remained low. NR activity in wheat cells, and GDH activity in soybean and wheat cells, did not vary significantly in the presence or absence of NH4+.