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161.
The gibberellin (GA) 2-hydroxylases in mature and immature seeds of Pisum sativum have been partially purified and characterised. The enzymes are unstable when stored below pH 7.0 or in the absence of a thiol reagent. The optimum assay pH is between 7.4 and 7.8 and activity is dependent upon the presence of -ketoglutarate, Fe2+ and ascorbate. The 2-hydroxylase activities for GA1, GA4, GA9 and GA20 are chromatographically inseparable and correspond to a protein of Mr 44000. The rate of GA 2-hydroxylation varies according to substrate and some evidence indicates that the 2-hydroxylase activities for GA1 and GA4 and for GA9 and GA20 may reside in different proteins. During pea seed maturation, the specific activity of the enzyme(s) increases dramatically and reaches a maximum at a time when endogenous GA9, GA20, GA29 and GA51 are also at their greatest concentration. This correlation is not the result of substrate induction of enzyme activity. Since the GA 2-hydroxylases operate at maximal rate at low substrate concentrations they are incapable of rapidly 2-hydroxylating excessive quantities of (exogenously applied) GA1 or GA20. On the basis of the kinetic parameters of the GA 2-hydroxylase activities, a generalised model is discussed for the control of the steady-state levels of bioactive hormone under normal physiological conditions.Abbreviations DTE
dithioerythritol
- EDTA
ethylenediaminetetraacetic acid
- GAn
gibberellin An
- HPLC
high-performance liquid chromatography
- HSS
high-speed supernatant
- LSS
low-speed supernatant
- PMSF
phenylmethane sulphonyl fluoride 相似文献
162.
The effects of ultraviolet-B radiation on plant competition in terrestrial ecosystems 总被引:3,自引:0,他引:3
Evidence regarding the interaction of ultraviolet-B (UV-B, 280-320 nm) radiation and plant competition in terrestrial ecosystems is examined. The competitive interactions of some species pairs were affected even by ambient solar UV-B radiation (as exists without ozone depletion), when compared to control pairs grown without UV-B. Also, the total shoot biomass of these species pairs was depressed under ambient UV-B. Relatively large increases in UV-B radiation (approximating a 40% ozone layer reduction when weighted with the generalized plant action spectrum) altered the competitive interactions of some species pairs grown in pots under field conditions, but did not affect the total shoot biomass production of those pairs. Recent field experiments have examined the competitive interactions of wheat ( Triticum aestivum L. cv. Bannock) and wild oat ( Avena fatua L.) under a simulated increased UV-B regime resulting from a 16% ozone layer reduction when weighted with the generalized plant action spectrum. This increase in UV-B altered the competitive interactions of these two species without affecting the total shoot biomass production of the species pair. The manner in which increased UV-B affected the relative competitive abilities of the two species was highly dependent upon the environmental conditions during the early life stages of the plants. The implications of these results for both agricultural and natural plant communities are discussed. 相似文献
163.
Studies using [3H]chlorogenic acid and [3H]rutin demonstrated that the kinetics of uptake of these plant phenolics into the haemolymph of 5th-instar Heliothis zea (Boddie) following actue oral administration is a first-order process. The total quantity of either phenolic present in the haemolymph within 1 hr amounts to 5% or less of the total ingested dose. Based on TLC analyses, 80% or more of the radioactivity in the haemolymph occurs as the parent phenolic. Retention of [3H]-chlorogenic acid or [3H]-rutin in H. zea following chronic feeding from 1st to 3rd-instar larvae is also linearly related to dietary dose. Chlorogenic acid and rutin are both equitoxic and equivalent in bioavailability to H. zea.Loss of [3H]-rutin from the haemolymph of 5th-instar larvae following injection is biphasic. One half of the injected dose is excreted in the frass in the first 6 hr after injection; the other half is thereafter eliminated at 1/20th of the initial rate. Analyses of extracts of frass by thin-layer chromatography indicate that after either chronic or acute feeding 90% of the ingested phenolic is excreted unchanged. Possible sites and modes of action of phenolics in insects are discussed in light of these findings. 相似文献
164.
N. Hammatt B. Jones M. R. Davey 《In vitro cellular & developmental biology. Plant》1989,25(7):669-672
Summary Plants have been regenerated from nodular, green callus derived from cotyledon, petiole and leaf lamina explants ofG. argyrea, a perennial relative of the soybean (G. max). The degree of response obtained was governed primarily by the genotype used, accession G1626 proving the most responsive.
Shoots were also recovered from about 6.0% of cotyledon protoplasts of this genotype. The implications of these results are
discussed in relation to genetic manipulations using this species. 相似文献
165.
玉米花粉单倍体植株染色体上异染色质的变异 总被引:4,自引:1,他引:3
我们用Giemsa BSG C-带技术检查了玉米花药培养获得的花粉单倍体植株根尖细胞染色体上异染色质的变异,观察结果表明,有的植株所显示的C-带数目是与供体植株的相一致,有的植株所显示的C-带数目则发生了显著变化,其中有的增加,有的减少。并讨论了异染色质发生变异的可能原因。还相应地观察到间期核中染色中心的变化是与中期染色体上C-带数目的变化相一致。 相似文献
166.
Red clover (Trifolium pratense L.) seedlings were screened for the ability to regenerate plantlets from hypocotyl-derived callus tissue. Media sequences described by Beach and Smith (1979) and Collins and Phillips (1982) and a variation using media from both sequences were tested. Plantlets were regenerated from three out of 642 genotypes. In all three cases, callus was initiated on B5C medium and regeneration was accomplished on SPL medium. Attempts to regenerate plants from petiole-derived callus tissue have so far been successful only with regenerants of clone F49. Petiole callus from epicotyl-derived F49 plants proved to be non-regenerative. Pollen viability varied significantly among individuals regenerated from callus cultures of clone F49. Root tip squashes from F49 regenerants revealed the normal diploid chromosome number (2n=14). The frequency of regeneration within progeny from reciprocal crosses between F49 regenerants and several non-regenerative genotypes was 29%.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- BAP
benzylaminopurine
- KN
kinetin
- NAA
-naphthaleneacetic acid 相似文献
167.
Plant resistance, plant traits, and host plant choice of the leaf-folding sawfly on the arroyo willow 总被引:1,自引:0,他引:1
Abstract. 1. The hypotheses that genetic variation in host plant resistance of the arroyo willow affected leaf folder ( Phyllocolpa sp.) (Hymenoptera: Tenthredinidae) density and that genetic variation in shoot length and leaf length was correlated with resistance were tested.
2. Willows grown in pots and exposed to ovipojsition by the leaf folding sawfly in cages had significantly different densities among clones, indicating variation in resistance caused by genetic differences among conspecific host plants.
3. There was a general correspondence between leaf folder density on potted cuttings and on the plants in the field that were the sources of cuttings.
4. In behavioural choice experiments, susceptible clones (with highest leaf fold densities) had the highest oviposition activity of female leaf folders compared to clones that were resistant to the leaf folder.
5. Clones differed significantly in shoot length and leaf length among clones grown in pots, among clones in the field, and between shoots with galls and shoots without galls on clones in the field.
6. Leaf folder density was significantly positively correlated with mean shoot length on field clones in 1985 and 1986, but was not correlated with leaf length, although leaf length and shoot length were correlated.
7. Leaf length variation among willow clones accounted for a significant portion of the variation in resistance of potted willows, but shoot length was unimportant. 相似文献
2. Willows grown in pots and exposed to ovipojsition by the leaf folding sawfly in cages had significantly different densities among clones, indicating variation in resistance caused by genetic differences among conspecific host plants.
3. There was a general correspondence between leaf folder density on potted cuttings and on the plants in the field that were the sources of cuttings.
4. In behavioural choice experiments, susceptible clones (with highest leaf fold densities) had the highest oviposition activity of female leaf folders compared to clones that were resistant to the leaf folder.
5. Clones differed significantly in shoot length and leaf length among clones grown in pots, among clones in the field, and between shoots with galls and shoots without galls on clones in the field.
6. Leaf folder density was significantly positively correlated with mean shoot length on field clones in 1985 and 1986, but was not correlated with leaf length, although leaf length and shoot length were correlated.
7. Leaf length variation among willow clones accounted for a significant portion of the variation in resistance of potted willows, but shoot length was unimportant. 相似文献
168.
Plant hormone response mutants 总被引:4,自引:0,他引:4
I. M. Scott 《Physiologia plantarum》1990,78(1):147-152
A variety of plant hormone response mutants has now been described, and is surveyed in this article. In addition to hormone-insensitive mutant phenotypes with defects in hormone-related features, there exist mutants apparently constitutive for the gibberellin responses, and also a mutant hyper-responsive to gibberellin. Although there is still little biochemical evidence on the nature of these mutants, the emerging picture of their genetic dominance relationships has given rise to tentative suggestions of the involvement of represser functions in hormonal control systems. 相似文献
169.
170.