Developmental changes in the gibberellin-induced growth response in stem segments of light-grown pea genotypes

The effects of GA on stem elongation were studied using segments from one tall and three dwarf light-grown pea genotypes varying in endogenous hormone content. Stem segments were cut at two distinct ages: when the fourth internode was at about 6–13% of full expansion (early-expansion) or at 18–25% of full expansion (mid-expansion). Light microscopy and flow cytometry were used to demonstrate that GA does not induce cell division in excised pea stem segments. The growth studied here was strictly elongation. Measurement of final segment length after 48 hours and high resolution measurement of growth kinetics over 20 hours using an angular position transducer were done on segments treated with hormone solutions. Our data indicate that the action of GA on stem elongation can be classified into two distinct modes. The first, apparent in early-expansion stem segments, shows distinct growth kinetics and is independent of the endogenous IAA concentration of the segments. Quantitation of IAA by GC/MS in early-expansion segments of wild type pea incubated with gibberellin shows that an increase in IAA concentration is part of the GA response in such segments. The second mode of GA action is evinced in mid-expansion segments. Whereas there is no short term (<20 h) response to GA alone (as determined by growth kinetics), there is a long term (48 h) response whose magnitude decreases across the genotypes with decreasing endogenous hormone content. Growth responses indicate that in mid-expansion segments exogenous GA acts by enhancing IAA action but appears to be unable to augment endogenous IAA content. Contradictory reports of the response of excised stem segments to GA can be reconciled when tissue genotype and developmental stage are considered.     

Inhibition of auxin-stimulated growth of pea stem segments by a specific nonasaccharide of xyloglucan

Hemicellulose extracted from cell walls of suspension-cultured rose (Rosa Paul's Scarlet) cells was digested with cellulase from Trichoderma viride. The quantitatively major oligosaccharide products, a nonasaccharide and a heptasaccharide derived from xyloglucan, were purified by gel permeation chromatography. The nonasaccharide was found to inhibit the 2,4-dichlorophenoxy-acetic-acid-induced elongation of etiolated pea (Pisum sativum) stem segments. This confirms an earlier report (York et al., 1984, Plant Physiol. 75, 295–297). The inhibition of elongation by the nonasaccharide showed a maximum at around 10^-9M with higher and lower concentrations being less effective. The heptasaccharide did not significantly inhibit elongation at 10^-7–10^-10M and also did not affect the inhibition caused by the nonasaccharide when co-incubated with the latter.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - XG xyloglucan - XG7 xyloglucan heptasaccharide (Glc₄·Xyl₃) - XG9 xyloglucan nonasaccharide (Glc₄·Xyl₃·Gal·Fuc)     

Effect of galactoglucomannan-derived oligosaccharides on elongation growth of pea and spruce stem segments stimulated by auxin

Galactoglucomannan-derived oligosaccharides (GGMOs) (degree of polymerization 4–8) isolated from the wood of poplar (Populus monilifera Ait.) were shown to be inhibitors of the 2,4-dichlorophenoxyacetic acid-stimulated elongation growth of pea (Pisum sativum L. cv. Tyrkys) and spruce [Picea abies (L.) Karst] stem segments. A dependence on the concentration of GGMOs (between 10^-5-10^-10M) as well as plant species was ascertained. Pea stem segments were much more sensitive (10^-10M) than spruce (10^-8M). The GGMOs did not exhibit toxicity even at high concentrations and during long-term bioassays. The timing of the action of GGMOs and auxin in the growth process was also studied.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - d.p degree of polymerization - GGMOs galactoglucomannan-derived oligosaccharides This research was supported by the Slovak Grant Agency for Science.     

The influence of zinc and light conditions on the cadmium-repressed growth of the green alga Coelastrum proboscideum

The growth response of Coelastrum proboscideum Bohlin to cadmiun (3 × 10^?9M to 2.4 × 10^?7M) was studied. The inorganic media used varied in zinc concentration (1.3 × 10^?7M to 3.6 × 10^?6M). The data were evaluated by factorial analyses. The influence of zine on the growth depression by cadmium depended on the light conditions (16:8 h light:dark cycles or 24 h continuous illumination periods). Intermittent illumination caused a negative interaction of zinc and cadmium in contrast to a positive interaction or additive effects of these elements during continuous illumination.     

Identification of secretory vesicles in homogenates of pea stem segments

In homogenates of stem sections from etiolated pea (Pisum sativum L.) seedlings, secretory vesicles can be separated from Golgi-apparatus cisternae by rate-zonal centrifugation in renografin gradients. Optically, two bands of turbidity are observed, the uppermost containing the secretory vesicles and the lower one the Golgi-apparatus cisternae. The absence of glutaraldehyde in the homogenizing medium has allowed the effective characterization of marker-enzyme activities. Golgi-apparatus cisternae have been recognized by the presence of inosine-diphosphatase and glucan-synthase I activities as well as by electron microscopy. In contrast, although secretory vesicles also bear inosine diphosphatase they do not appear to possess glucan-synthase activity. Three plasma-membrane markers, NPA-binding, glucan synthase II, and KCl,Mg²⁺-adenosine triphosphatase (pH 6.5), were not detected in secretory vesicles. Pulse-chase experiments with [³H]glucose support our designation of secretory vesicles and Golgi-cisternal fractions.Abbreviations ER endoplasmic reticulum - GSI, GSII glucan, synthase I, II, respectively - IDPase inosine diphosphatase - PM plasma membrane - SV(s) secretory vesicle(s)     

The influence of methyl jasmonate on the growth processes in the pea

The influence of methyl jasmonate (MJ) on pea growth was studied. Stimulation of seed germination by MJ [10(-9), 10(-6) M] was carried out for 24 h. MJ [10(-9) M] intensifies the epicotyl growth, and MJ [10(-6) M] inhibits the epicotyl and root growth. Season dependence of mitosis regulation was determined. The maximum intensity was observed early in spring with MJ [10(-6) M], and autumn with MJ [10(-9) M], with almost one order less intensity, the latter intensity being one order less, suggesting a general loss of cell sensitivity to regulator. The peak of mitotic activity in summer was between the spring and autumn peaks due to the low concentration of effector. It is supposed that jasmonoids are able to coordinate cell entry to mitosis in different seasons.     

Turnover of cell wall polysaccharides in elongating pea stem segments

Turnover of cell wall polysaccharides and effects of auxin thereon were examined after prelabeling polysaccharides by feeding pea (Pisum sativum var. Alaska) stem segments ¹⁴C-glucose, then keeping the tissue 7 hours in unlabeled glucose with or without indoleacetic acid. There followed an extraction, hydrolysis, and chromatography procedure by which labeled monosaccharides and uronic acids were released and separated with consistently high recovery. Most wall polymers, including galacturonan and cellulose, did not undergo appreciable turnover. About 20% turnover of starch, which normally contaminates cell wall preparations but which was removed by a preliminary step in this procedure, occurred in 7 hours. Quantitatively, the principal wall polymer turnover process observed was a 50% decrease in galactose in the pectinase-extractable fraction, including galactose attached to a pectinase-resistant rhamnogalacturonan. Other pectinase-resistant galactan(s) did not undergo turnover. No turnover was observed in arabinans, but a doubling of radioactivity in arabinose of the pectinase-resistant, hot-acid-degradable fraction occurred in 7 hours, possibly indicating conversion of galactan into arabinan. None of the above changes was affected by indoleacetic acid, but a quantitatively minor turnover of a pectinase-degradable xyloglucan was found to be consistently promoted by indole-acetic acid. This was accompanied by a reciprocal increase in water-soluble xyloglucan, suggesting that indoleacetic acid induces conversion of wall xyloglucan from insoluble to water-soluble form. The results indicate a highly selective pattern of wall turnover processes with an even more specific influence of auxin.     

Developmental and genotypic differences in the response of pea stem segments to auxin

The objective of this investigation was to examine the response to exogenous auxin (indole-3-acetic acid; IAA)of stem segments at two developmental stages. The standard auxin response of excised stem segments and intact plants consists of an initial growth response and a prolonged growth response. We found that this biphasic response does not occur in internodes at very early stages. Stem segments of light grown pea of various genotypes were cut when the fourth internode was at 6–13% of full expansion (early-expansion) or at 18–25% of full expansion (mid-expansion). Length measurements of excised segments were made after 48 hours of incubation on buffer with or without auxin. An angular position transducer linked to a computerized data collection system provided high-resolution measurement of growth of stacks of segments incubated in buffer over 20 hours. Early-expansion segments of all genotypes deviated from the standard auxin response, while mid-expansion segments responded in a manner consistent with previous reports. Early-expansion segments of tall, light-grown plants were unique in showing an auxin-induced inhibition of growth. The auxin-induced inhibition correlated with high endogenous auxin content, as determined by HPLC and GC/MS, across genotypes and between early-expansion and mid-expansion segments of tall plants. Measurement of ethylene evolved from stem segments in response to auxin, and treatment of segments with the ethylene action inhibitor, norbornadiene, showed the inhibition to be mediated in part by heightened ethylene sensitivity. Growth of early-expansion segments of dwarf and severe dwarf plants was stimulated by exogenous auxin, but the growth rate increase was delayed compared to that in mid-expansion segments. This is the first time that such a growth response, termed the delayed growth response has been emonstrated. It is concluded that developmental stage and endogenous hormone content affect tissue response to exogenous auxin.     

Orientation of cell growth in the etiolated pea stem

Summary Both ethylene and IAA induce swelling in the sub-apical region of etiolated pea plants. The modified cells of these two types of swellings differ both morphologically and in their enzyme composition. In ethylene the cell walls become thickened within 24 h and the level of peroxidase is enhanced; ethylene does not affect cellulase levels. IAA induced swellings are not accompanied by early thickening of cell walls or enhanced peroxidase activity, but IAA greatly increases the level of cellulase. It is proposed that the retardation of extension growth by ethylene treatment results from the deposition of longitudinal microfibrils in the walls and that cross linking bonds in the polysaccharide matrix prevent their separation. Lateral expansion can occur, however, in the presence of auxin-induced cellulase which breaks or prevents the formation of these bonds.     

Competitive inhibition of the auxin-induced elongation by α-D-oligogalacturonides in pea stem segments

Branca, C, De Lorenzo, G. and Cervone, F. 1988. Competitive inhibition of the auxin-induced elongation by α-D-oligogalacturonides in pea stem segments. - Physiol. Plant. 72: 499–504.
α-D-galacturonide oligomers (OG) were prepared by partial hydrolysis of sodium polypectate with an homogeneous Aspergillus niger endopolygalacturonase (EC 3.2.1.15). OG, obtained after digestion for 10, 20, 30, 60, 120 min and 24 h, were assayed for their ability to interfere with the IAA-induced elongation of pea ( Pisum sativum L. cv. Alaska) stems. Maximum inhibiting activity was exhibited by oligomers with an approximate degree of polymerization higher than 8. Inhibition by longer OG was much lower, and the products of the 24 h digestion and the unhydrolysed polypectate were ineffective. The addition of OG to pea stems caused a parallel shift to the right of the IAA dose-effect curve. The shift depended on the amount of OG used, showing that oligogalacturonides behave as competitive antagonists of IAA. The presence of OG caused the disappearance of the second maximum of the elongation rate and reduced the first maximum. OG were also tested for their ability to inhibit IAA-induced ethylene evolution of pea stem segments. Maximal inhibition was obtained with OG of the same size as those that interfered with IAA-induced elongation. Inhibition of the auxin action seemed to be specific as OG did not interfere with the activity of gibberellic acid (GA₃) or kinetin. It was concluded that oligogalacturonides strongly interfere with the activity of IAA, although they are by themselves incapable to influence the elongation of pea stem segments directly.     

Inhibition of 2,4-dichlorophenoxyacetic Acid-stimulated elongation of pea stem segments by a xyloglucan oligosaccharide

Xyloglucan, isolated from the soluble extracellular polysaccharides of suspension-cultured sycamore (Acer pseudoplatanus) cells, was digested with an endo-β-1,4-glucanase purified from the culture fluid of Trichoderma viride. A nonasaccharide-rich Bio-Gel P-2 fraction of this digest inhibited 2,4-dichlorophenoxyacetic-acid-stimulated elongation of etiolated pea stem segments. The inhibitory activity of this oligosaccharide fraction exhibited a well-defined concentration optimum between 10⁻² and 10⁻¹ micrograms per milliliter. Another fraction of the same xyloglucan digest, rich in a structurally related heptasaccharide, did not, at similar concentrations, significantly inhibit the elongation.     

The influence of the phosphorus and nitrogen nutrition of pea plants on the growth of their progeny

Summary In glasshouse experiments with peas grown in nutrient cultures, seed from phosphorus-deficient plants contained much lower phosphorus concentrations than seed from plants not deficient in this element, but differences in the supply of mineral nitrogen to the plants (which were nodulated) had little effect on the chemical composition of the seed.Lower haulm weights and pea yields were obtained from sowings of low-phosphorus as compared with high-phosphorus seed when the plants were grown in cultures deficient in phosphorus. In cultures not deficient in phosphorus, there were no such differences between the performance of the seed.In field experiments carried out on a fertile soil, low-phosphorus seeds gave 20 to 25 per cent lower yields of both haulms and peas than were obtained from sowings of high-phosphorus seed.It appeared that the differences in the performance of the seeds weer related to differences in the concentration of phosphorus they contained rather than to any other variation in their composition or size.     

The influence of plant growth regulators on explant performance, bud break, and shoot growth from large stem segments of Acer saccharinum L

Benzyladenine (BA) and/or gibberellic acid (GA₃) were applied in 20% white exterior latex paint separately at 0, 0.3, 1, 3, 10, or 30 mM; and at 1, 10, or 30 mM of each plant growth regulator (PGR) in a 3 × 3 factorial to 40 cm long stem segments of Acer saccharinum L. Softwood shoots were forced from these stem segments at various times of the year in a greenhouse and in a laboratory, these resulting shoots were surface disinfested and used as explants in vitro on Driver and Kuniyuki Walnut medium with 0 or 0.01 μM thidiazuron (TDZ). There was some response to the plant growth regulators applied in paint for shoot production from the stem segments and in vitro. Explants from softwood shoots forced from stems painted with 3 mM BA and cultured on medium with 0.01 μM TDZ produced more shoots than explants taken from softwood shoots forced with other BA concentrations or controls. Callus also grew significantly more on explants from stems treated with 3 mM BA cultured on 0.01 μM TDZ than explants harvested from stems painted with other concentrations of BA excluding 10 mM BA. When stem segments treated with BA plus GA₃ were compared as a group to controls, more and longer softwood shoots grew on the stems painted with PGRs when all four runs were pooled (Sept. 2005 through Feb. 2006). Application of PGRs in paint extends the season of production of softwood shoots that may be used as explant materials and their subsequent performance in vitro.     

Short term phytochrome control of oat coleoptile and pea epicotyl growth

Continuous recordings of the effect of light on oat (Avena sativa L. cv. Victory) coleoptile and pea (Pisum sativum L. cv. Alaska) epicotyl growth were made. Using a single excised coleoptile 10 minutes of red light was found to promote growth after a latent period of 46 minutes. The stimulation was transient and was not far red-reversible. Blue and far red light also promoted growth with similar kinetics. The action of continuous red or far red light was similar to that of 10-minute light. The growth of the intact pea third internode (as well as excised segments) was strongly inhibited by red light, with a latent period of 80 minutes. This effect was far red-reversible, and far red and blue light caused only a slight inhibition of growth.     

The effect of storage and short term cultivation the proliferation of mouse bone marrow stem cells]

Suspension of stored and short-term cultured murine bone marrow cells was i. v. administered to lethally irradiated mice. We demonstrated that the cells still after 72 h of storing and 24 h of culture in liquid medium were capable of proliferation and on day 9 following transplantation could produce colony forming units in the spleens of lethally irradiated mice. We established the relative participation of individual types of cells in the recovery of haemopoiesis in the spleens.     

The slender phenotype of pea: stem growth, peroxidase levels and ethylene responses

Stem elongation growth in a slender line of Pisum sativum L. was much greater than in its two dwarf parental lines due to a greater rate of production of longer internodes. The cellular basis of the greater length of slender internodes was tissue specific. In the epidermis, greater cell length primarily accounted for the longer internodes of the slender plants, but in the outer cortex, greater cell number was the more important factor. The soluble and salt-extractable peroxidase (EC 1.11.1.7) activities of expanding internodes were much lower in slender plants than in dwarf plants. The proportional effects of ethylene treatment on epicotyl length, diameter and orientation were similar in etiolated slender and dwarf seedlings.     

Regulation of cell wall synthesis by auxin and fusicoccin in different tissues of pea stem segments

Cell wall synthesis was studied by determining the incorporation of [¹⁴C]-glucose into epidermal and cortical cell walls of etiolated Pisum sativum L. cv. Alaska stem segments. Walls were fractionated into the matrix and cellulose components, and incorporation into these components assessed in terms of the total uptake of label into that tissue. When segments were allowed to elongate, the stimulation of total glucose uptake by indole-3-acetic acid (IAA) and fusicoccin (FC) was greater than their stimulation of incorporation. IAA and FC thus did not stimulate precursor incorporation in elongating segments. When elongation was inhibited by calcium, however, IAA and FC significantly promoted wall synthesis in the cortex and vasular tissue (which shows almost no growth or acidification response to auxin). In these tissues incorporation into matrix and cellulose was promoted approximately equally. In the epidermis (thought to be the tissue responsive to auxin in the control of growth), FC promoted a significant increase in wall synthesis, although less than that in the cortex, while there was some evidence of a similar promotion by IAA. Both IAA and FC had a greater effect on incorporation into the matrix component of the wall than into cellulose. The results that FC caused a substantial promotion of cell wall synthesis which was not due solely to elongation, and that the inner non-growth responsive cortical tissues can respond to IAA. Moreover, a comparison of the effects of IAA and FC on the different components of the wall suggests that the response in the epidermis differs from that in the other tissues.     

The influence of growth conditions on the synthesis of molybdenum cofactor in Proteus mirabilis

Cell-free extracts of Proteus mirabilis were able to reconstitute NADPH-dependent assimilatory nitrate reductase in crude extracts of the Neurospora crassa mutant strain nit-1, lacking molybdenum cofactor. Molybdenum cofactor was formed in the cytoplasm of the bacterium even in the presence of oxygen during growth though under these conditions no molybdo enzymes are formed. As a consequence no cofactor could be released by acid treatment from membranes of cells grown aerobically. The amount of cofactor released from membranes of cells grown anaerobically under various conditions was proportional to the amount of molybdo enzymes formed. During growth in the presence of tungstate a cofactor, which lacks molybdenum, was found in the cytoplasm. For detection of this so-called demolybdo cofactor the presence of molybdate during reconstitution was essential. Moreover, the cytoplasmic cofactor pool in cells grown in the presence of tungstate appeared to be two to three times higher than in cells grown under similar conditions without tungstate. After anaerobic growth in the presence of tungstate, the inactive demolybdo reductases were shown to contain partly no cofactor and partly a demolybdo cofactor. The P. mirabilis chlorate resistant mutant S 556 did not contain molybdenum cofactor. In two other chl-mutants the cofactor activity was the same as in the wild type.