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101.
An exo-β-(1β3)-glucanase derived from Selerotinia libertiana induced growth of Avena sativa coleoptiles and degraded hemicelluloses and β-(1→4):(1→3) mixed linked glucan. However, neither endo-β-(1→4)- nor endo-β-(1→3)-glucanase activity could be detected in the enzyme preparation. Nojirimycin inhibited the glucan degradation caused by the enzyme but glucono-1,5-lactone did not. Another exo-β-(1→3)-glucanase derived from Basidiomycete QM 806 did not induce coleoptile growth and did not degrade the glucan. Growth-inducing properties of exo-β-(1→3)-glucanases are discussed. 相似文献
102.
103.
Comparative evaluation of iron solubilizing substances (phytosiderophores) released by oats and corn: Iron-efficient and iron-inefficient plants 总被引:2,自引:1,他引:1
Release of phytosiderophores from barley (Hordeum vulgare L.) in response to Fe-deficiency stress prompted further testing of other graminaceous (grass) species for phytosiderophore release and results have prompted characterization of these plants into a Strategy II designation. This classification denotes an enhanced release of phytosiderophore in response to Fe-deficiency stress with a concomitant uptake of Fe by the plant. The objective of this study was to determine if Fe-inefficient and Fe-efficient corn (Zea mays L.) differ in their release of Fe solubilizing substances in response to Fe-deficiency stress. We have not identified the specific structure of these substances but refer to them as phytosiderophores to further characterize their behavior. By our indirect method, there was no measurable release of Fe solubilizing substances (phytosiderophores) from either the Fe-efficient WF9 or the Fe-inefficient ys1 corn despite WF9 being greener and apparently more Fe efficient than ys1. Fe-efficient Coker 227 oats (Avena byzantina C. Koch.) has been found to release a phytosiderophore whereas the Fe-inefficient TAM 0-312 does not. Iron-stressed Coker 227 oats released Fe solubilizing substances when grown in the same solution with WF9 corn which resulted in greening and Fe uptake by WF9 corn. Iron efficiency in these two graminaceous species appears to be controlled by different mechanisms. 相似文献
104.
Is the wild oat embryo monocotylous? 总被引:1,自引:0,他引:1
The embryogeny of the wild oat (Avena fatua L.) was studied in detail. The pattern of embryo development was observed to be similar to the other investigated grass taxa,
conforming to thePoa variation of the Asterad type. The embryogeny and anatomy of young seedlings showed that the embryo of the wild oat was not
monocotylous, but dicotylous. The scutellum of the embryo, as reported for other grasses, was regarded as the first cotyledon,
and the first leaf primordium, which developed later into a photosynthesizing leaf and situated opposite the scutellum, was
interpreted as the second cotyledon. Observations indicated that the cotyledons of the embryo were placed lateral to the shoot
apical meristem, which was terminal in position. The cotyledons were found to be dimorphic in structure and function. The
scutellum, a modified cotyledon, functioned as a suctorial organ, transporting nutrients from the endosperm to the embryo
axis. The second cotyledon or the first true leaf supplied nutrients directly to the embryo axis through the process of photosynthesis. 相似文献
105.
Phytochrome (120 kdalton) was isolated from etiolated seedlings of Avena sativa L. cv. Pirol (Baywa, München). Low temperature spectra between −17°C and −160°C are recorded for Pr , Pfr , and irradiated phytochrome samples. The temperature-dependence of the Pr and Pfr absorption spectra is described. Difference spectra of such temperature effects can erroneously be interpreted as difference spectra of intermediates. Probable absorption spectra of intermediates are calculated from the spectra of irradiated Pr or Pfr , respectively. The calculated spectral data are compared with published data on phytochrome intermediates. 相似文献
106.
Auxin-induced cell elongation in oat coleoptile segments was inhibited by galactose; removal of galactose restored growth. Galactose did not appear to affect the following factors which modify cell elongation: auxin uptake, auxin metabolism, osmotic concentration of cell sap, uptake of tritium-labeled water, auxin-induced wall loosening as measured by a decrease in the minimum stress-relaxation time and auxininduced glucan degradation. Galactose markedly prevented incorporation of [14 C]-glucose into cellulosic and non-cellulosic fractions of the cell wall. It was concluded that galactose inhibited auxin-induced long-term elongation of oat coleoptile segments by interfering with cell wall synthesis. 相似文献
107.
Variation in stomatal aperture in leaves of Avena fatua L. observed by low-temperature scanning electron microscopy 总被引:5,自引:2,他引:3
Abstract. A novel technique to record the variability of stomatal aperture over the leaf surface is described. This combines observations of leaf surfaces using low-temperature scanning electron microscopy (LTSEM), with digital image analysis to produce the most accurate aperture measurements obtained to date. Leaf samples are rapidly immobilized by cryo-fixation in liquid nitrogen and stored in a purpose-built cryo-storage system. Specimens can be collected in the field, remote from the cryopreparation system, and stored for up to several weeks before being examined on the LTSEM. The advantages of this method are that the time frame of the measurements is accurately known, and is identical for all stomatal apertures in a sample, and the precision of the measurements is not limited by the resolving power of the microscope. Measurements of stomatal aperture were obtained from leaves of field grown Avena fatua using the above procedure. Leaf surface conductance (gsur ) was determined by porometry immediately before cryo-fixation of the same region of the leaf. Measurements of aperture size showed a high degree of variability within each specimen, with coefficients of variation similar to those found in previous studies. Stomatal conductance (gs ) was calculated from stomatal dimensions using formulae derived elsewhere. A linear regression between the computed values of gs and porometric estimates of gsur showed good agreement with the regression line passing through the origin with a slope of 1.0 (R2 =0.96). Applications of the experimental system are discussed. 相似文献
108.
Allan H. Brown ers Johnsson David K. Chapman David Heathcote 《Physiologia plantarum》1996,98(1):210-214
Gravitropic responses of dark grown oat coleoptiles were measured in weightlessness and under clinorotation on earth. The tests in microgravity were conducted in Spacelab during the IML-1 mission and those on clinostats were conducted in laboratories on earth. The same apparatus was used for both kinds of tests. In both cases autotropism and gravitropic responsiveness were determined. This allowed a quantitative comparison between the plants' responses after receiving the same tropistic stimulations either in weightlessness or on clinostats.
Autotropism was observed with oat coleoptiles responding in weightlessness but it did not occur on clinostats. Gravitropic responsiveness was measured as the ratio between the incremental bending response (degrees curvature) and the corresponding incremental g-dose (stimulus intensity times duration for which it was applied). Plants were tested at either of two stages of coleoptile development (i.e. different coleoptile lengths). From a total of six different kinds of critical comparisons that could be made from our tests that provided data for clinorotated vs weightless plants, three showed no significant difference between responses in simulated vs authentic weightlessness. Three other comparisons showed highly significant differences. Therefore, the validity of clinorotation as a general substitute for space flight was not supported by these results. 相似文献
Autotropism was observed with oat coleoptiles responding in weightlessness but it did not occur on clinostats. Gravitropic responsiveness was measured as the ratio between the incremental bending response (degrees curvature) and the corresponding incremental g-dose (stimulus intensity times duration for which it was applied). Plants were tested at either of two stages of coleoptile development (i.e. different coleoptile lengths). From a total of six different kinds of critical comparisons that could be made from our tests that provided data for clinorotated vs weightless plants, three showed no significant difference between responses in simulated vs authentic weightlessness. Three other comparisons showed highly significant differences. Therefore, the validity of clinorotation as a general substitute for space flight was not supported by these results. 相似文献
109.
Ethylene and carbon dioxide: regulation of oat mesocotyl growth 总被引:1,自引:1,他引:0
Either ethylene or carbon dioxide stimulated the growth of oat mesocotyls in darkness, although the effect was much greater for carbon dioxide. Maximum elongation was obtained in the presence of both gases. Ethylene also induced lateral expansion of the mesocotyl: the volume of the mesocotyl was increased more in air with added ethylene than in air depleted of ethylene. Ethylene also stimulated mesocotyl growth under red light. Gibberellin only slightly increased mesocotyl length under red light and acted cooperatively with ethylene in the promotion of growth. The oat mesocotyl is a unique organ in terrestrial plants because ethylene simultaneously stimulates not only longitudinal growth but also lateral expansion. The ecological significance of oat mesocotyl growth in relation to the response to ethylene and carbon dioxide is discussed. 相似文献
110.
I. Saarela 《Plant and Soil》1992,147(1):115-126
The availability of phosphorus to plants was estimated by a new method based on the diffusion of P from a thin layer of water-saturated stationary soil to a disc of iron oxide coated filter paper. Twenty-one acid Finnish soil samples were tested using four modifications of the method which differed in the duration of the diffusion time and in the thickness of the soil layer. The new diffusion tests were compared with other soil P testing methods and evaluated as indicators of the availability of P to pot-grown barley and oats. Close linear correlations were found between the initial (18 or 42 h) P diffusion rate and the water extractable P contents determined at the extraction ratios of 1:10 and 1:60, respectively (r=0.97–0.99). The amounts of P obtained by the new method were small when the diffusion time was short, but after prolonged diffusion (1 week) the test values were close to the amounts of P taken up by plants. The relationships of plant yield and P uptake with soil P test values were affected by soil acidity. Although the original soil P test values were significantly correlated, the accuracy of all methods drastically improved when the interfering effect of soil acidity was taken into account using a simple pH-correction model. The correlation coefficients (r) between the test values of diffusible P in soil and the uptake of P by plants increased up to 0.97. 相似文献