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1.
The plant growth regulators, gibberellic acid (GA3), ethephon and chlormequat chloride (CCC) were sprayed on young lettuce, cauliflower and bean (Phaseolus vulgaris) plants, which had either been given or not been given a mechanically-induced stress (MIS) treatment. MIS was applied by brushing the plants with paper for 1.5 minutes each day. GA3 increased extension growth of bean and leaf length of lettuce in unbrushed plants as much as in brushed ones. CCC and ethephon were less effective at reducing the height of brushed bean plants compared to unbrushed ones. The effects of CCC on the growth of cauliflower and lettuce plants was not influenced by brushing, whereas unbrushed plants responded more readily to ethephon than did brushed ones. The effects of CCC on growth were generally similar to those of MIS whereas the effects of ethephon were in many ways different to MIS.The results are discussed in relation to the use of PGR and MIS treatments for modifying plant growth. 相似文献
2.
3.
H. M. Koop M. Valentijn-Benz A. V. Nieuw Amerongen P. A. Roukema J. De Graaff 《Antonie van Leeuwenhoek》1989,55(3):277-290
Twenty-seven oral strains of the genera Actinomyces (5), Bacteroides (3), and Streptococcus (19) were tested for aggregation by human whole saliva, as well as the effect of culture medium, Ca-ions, and bacteria concentration thereupon. Of the media tested, GF-broth gave rise to less interference by autoaggregation or higher aggregation titers than BHI and TSB, and was used throughout this study. In most cases, Ca-ions (1 mM) only enhanced the rate of induced aggregation, whereas raising the bacteria concentration increased the rate of both induce- and autoaggregation. The final titers, ranging from 1–64, were hardly affected by these parameters, except those of S. rattus HG 59 and S. mutans HG 199, which were respectively increased and decreased by Ca-ions. Saliva-induced aggregation was observed for 21 strains of A. viscosus, A. naeslundii, A. israelii, B. gingivalis, B. intermedius, S. cricetus, S. mutans, S. rattus, S. sanguis, and S. sobrinus, mostly within 15 min to 3 h. Seventeen of these strains also showed autoaggregation, usually well after the onset of induced aggregation. Any potential induced aggregation of B. gingivalis HG 91 was always masked by autoaggregation, as well as that of the S. mutans strains under a particular set of conditions. The aggregation rate and titer varied considerably in a mutually unrelated and strain-dependent way. These microtiterplate data were matched by the 5 spectrophotometric patterns observed for saliva-bacterial interaction, which moreover, gave the better differentiation between induced and autoaggregation. In conclusion, most strains tested can show rapid saliva-induced aggregation in a strain-dependent way, yet strongly affected by the experimental conditions and interference from autoaggregation. 相似文献
4.
Ion accumulation in the cell walls of rice plants growing under saline conditions: evidence for the Oertli hypothesis 总被引:10,自引:3,他引:7
Abstract. When plants of rice ( Oryza saliva L.) are subjected to mildly saline (50mol m−3 NaCl) conditions, the leaves show symptoms of water deficit, even though ion accumulation has been more than sufficient to adjust to the decrease in external water potential. After a few days of exposure to salt, there is a negative correlation, in a population of leaves, between the leaf water concentration (g water per g dry weight) and their sodium concentration (mmol Na per g dry weight). Ion concentrations in the cell walls and the cytoplasm of cells of plants grown in low salinity were measured by X-ray microanalysis. The NaCl concentration in solution in the apoplast was calculated to be around 600mol m−3 in leaves of plants whose roots were exposed to only 50 mol m−3 NaCl. This constitutes strong evidence that an important factor in salt damage in rice is dehydration due to the extracellular accumulation of salt as suggested in the Oertli hypothesis. The implication, that changes in tissue ion concentration and solute potentials equivalent to the external medium is not evidence of plant osmotic adjustment to salinity, is discussed. 相似文献
5.
Comparative studies of diurnal variations of nitrate reductase activity in wheat, oat and barley 总被引:1,自引:0,他引:1
Diurnal variations of in vitro and in vivo (intact tissue assay) nitrate reductase (EC 1.6.6.1) activity and stability were examined in leaves of wheat ( Triticum aestivum L. cv. Runar), oat ( Avcna saliva L. cv. Mustang) and barley ( Hordeum vulgure L. cv. Agneta and cv. Gunillu). Nitrate reductase activity was generally higher for wheat than for oat and barley. However, the diurnal variations of nitrate reductase activity and stability were principally the same for all species, e.g. the high activity during the photoperiod was associated with low stability. All species showed a rapid (30-60 min) increase in the in vitro and in vivo activity when the light was switched on. When light was switched off the in vitro activity decreased rapidly whereas decrease in in vivo activity was slower. These experiments support the hypothesis that an activation/ deactivation mechanism is involved in the regulation of diurnal variations in nitrate reductase activity. Red light enhanced nitrate reductase activity in etiolated wheat and barley leaves. In green leaves, however, the daily increase in nitrate reductase activity was not induced by a brief red light treatment. Indications of different regulation mechanisms for the diurnal variations of nitrate reductase activity among the cereals were not found. 相似文献
6.
Apparent phytotoxicity of mononuclear hydroxy-aluminum to four dicotyledonous species 总被引:3,自引:0,他引:3
It has long been assumed that Al3+ is an important rhizotoxic ion in acid soils around the world, but the toxicity of Al3+ relative to mononuclear hydroxy-Al [AlOH2+ and Al(OH)+ 2 ] has been examined in detail only for an Al-sensitive wheat variety ( Triticum aestivum L. cv. Tyler). That plant appears to be sensitive to Al3+ but not to AlOH2+ and Al(OH)+ 2 . New experiments, and reanalyses of previously published experiments, provide evidence that dicotyledonous species may be sensitive to mononuclear hydroxy-Al and that Al3+ may be nontoxic, or less toxic, to those plants. Despite these consistently measured differences between wheat and the dicotyledons, the determination of relative toxicities (Al3+ vs mononuclear hydroxy-Al) may be an intractable problem. Because of hydrolysis equilibria, (AlOH2+ ) and (Al(OH)+ 2 ) are equivalent to (Al3+ )k1 (H+ )−1 and (l3+ )k2 (H+ )−2 , respectively, in which k1 and k2 are the first and second hydrolysis constants (braces denote activities). Thus, any expression of root elongation as a function of mononuclear hydroxy-Al can be alternatively expressed as a function of (Al3+ ) and (H+ ). Toxicity attributed to mononuclear hydroxy-Al may actually be Al3+ toxicity that increases as pH rises (i.e. Al3+ toxicity ameliorated by H+ ). 相似文献
7.
Nagilactone E, a norditerpene dilactone isolated from a gymnosperm, Podocarpus nagi (Podocarpaceae), was able to stimulate the growth of cultured cells of Lactuca sativa cv. Grand Rapids at 0.1 g ml-1 but not at 0.01 or 1 g ml-1. Cell wet weight/unit time and cell number/unit wet weight were increased when they were recorded at the end of the 14-day incubation period. Also, the population of cells treated with that concentration of nagilactone E had a higher percentage of cells with shorter cell length compared to the control (untreated). 相似文献
8.
Analysis of total aromatic amino acid (free and bound) in some cucumber accessions selected previously for resistance to western flower thrips, Frankliniella occidentalis (Pergande) [Thysanoptera: Thripidae], indicated that low concentrations of these essential nutrients, relative to total leaf protein, were correlated with a reduction in damage by the insect. Further analysis of samples of four important horticultural crops (lettuce, tomato, pepper and cucumber) with unknown levels of resistance to thrips showed a significant genotypic variation in the concentrations of total aromatic amino acids relative to the total leaf protein. Accessions from each crop with low or high concentrations of aromatic amino acids in proteins were exposed to thrips larvae. Regression analysis showed a highly significant positive correlation between aromatic amino acid concentration in leaf protein and thrips damage, regardless of crop species. It is concluded that higher concentrations of aromatic amino acids in plant proteins are important for successful thrips development. These results provide plant breeders with a promising tool for indirect selection without using undesirable insect bioassays. 相似文献
9.
The effects of an aqueous plant-derived smoke extract, octanoic acid and ethylene on germination of light-sensitive Grand Rapids lettuce seeds were investigated. The smoke extract brought about a concentration dependent increase in germination and a complete inhibition of germination at high concentrations. Octanoic acid could not induce germination. Ethylene at concentrations over 5 L L–1 increased lettuce seed germination, but not to the same degree as smoke. Aqueous smoke in combination with ethylene showed a synergistic effect on germination at suboptimal smoke concentrations. At high smoke concentrations the effect of ethylene was almost completely inhibited. Octanoic acid in combination with ethylene brought about a higher level of germination than with ethylene alone, but only at the highest concentration of octanoic acid tested (1 mM). Standardized hexane and dichloromethane-partitioned smoke extracts and octanoic acid were subjected to TLC separation. The R
f
-fractions in the smoke lanes showing activity in the lettuce seed bioassay did not correspond to the R
f
-value of octanoic acid. As aqueous smoke can withstand autoclaving and can be separated by TLC and HPLC without loosing activity it is unlikely that the activity of aqueous smoke is linked to ethylene. It thus appears that the active compound in smoke is neither octanoic acid nor ethylene.Abbreviations TLC
thin layer chromatography
- HPLC
High performance liquid chromatography 相似文献
10.
Interaction of the salivary low-molecular-weight mucin (MG2) with Actinobacillus actinomycetemcomitans 总被引:2,自引:0,他引:2
J. Groenink A. J. M. Ligtenberg E. C. I. Veerman J. G. M. Bolscher A. V. Nieuw Amerongen 《Antonie van Leeuwenhoek》1996,70(1):79-87
Periodontitis is associated with the presence of certain Gram-negative bacteria in the oral cavity, among these Actinobacillus actinomycetemcomitans. In order to determine which types of salivary components interact with A. actinomycetemcomitans two strains (HG 1175 and FDC Y4) were incubated with whole saliva and individual glandular secretions, viz. parotid, submandibular, and sublingual saliva. Immunochemical analysis by immunoblotting of bacteria-bound salivary proteins showed that IgA, the low-molecular mucin MG2, parotid agglutinin, and a 300 kDa sublingual and submandibular glycoprotein, were bound to the bacterial strains tested. In addition, adherence of A. actinomycetemcomitans to salivary proteins in a solid-phase was studied. After electrophoresis and transfer of salivary proteins to nitrocellulose membranes A. actinomycetemcomitans adhered only to MG2. In this assay periodate treatment, mild acid hydrolysis or neuraminidase digestion of the saliva glycoproteins abolished binding of two clinical isolates (HG 1175 and NY 664), suggesting that sialic acid residues on MG2 are involved in the binding. In contrast, adherence of the smooth laboratory strain Y4 was not affected by removal of sialic acid residues or even periodate treatment of MG2.Abbreviations S-IgA
Secretory IgA
- MG1
high-molecular-weight mucin
- MG2
low-molecular-weight mucin
- EP-GP
extra parotid-glycoprotein
- PRPs
proline-rich proteins
- SNA
Sambucus nigra agglutinin
- MAA
Maackia amurensis agglutinin
- PNA
peanut agglutinin
- UEA
Ulex europaeus agglutinin 相似文献