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51.
Abstract. 1. Collards (Brassica oleracea L.) grown in clumps were more difficult for unstarved, early instar cabbage white caterpillars (Pieris rapae L.) to find than collards spaced at regular intervals, although total plant densities were identical.
2. Early instar, unstarved larvae are less mobile than later instar larvae (our data) or starved larvae (Jones' 1977 data).
3. Starved larvae and late instar larvae tend to find plants more readily than do unstarved or younger larvae.
4. We contend that larval mobility governs the success of searching caterpillars and their sensitivity to variations in plant dispersion.
5. Our results show that the dispersion of targets can influence searching success even though target density is constant. This means that the degree of clumping in host plants is capable of influencing their availability to herbivores. 相似文献
2. Early instar, unstarved larvae are less mobile than later instar larvae (our data) or starved larvae (Jones' 1977 data).
3. Starved larvae and late instar larvae tend to find plants more readily than do unstarved or younger larvae.
4. We contend that larval mobility governs the success of searching caterpillars and their sensitivity to variations in plant dispersion.
5. Our results show that the dispersion of targets can influence searching success even though target density is constant. This means that the degree of clumping in host plants is capable of influencing their availability to herbivores. 相似文献
52.
Stimulation of de novo synthesis of δ-aminolevulinate dehydralasc of radishes grown under far-red light .
Density labelling studies of δ-aminolevulinate dehydratase (ALAD) in cotyledons of radish ( Raphanus sativus L. cv. Longue Rave Saumonée) seedlings demonstrate that far-red light stimulates de novo synthesis of ALAD and that the turn-over of this enzyme is very poor. Cycloheximide reduces considerably both the increase of ALAD activity and the incorporation of deuterium in ALAD, which indicates that ALAD synthesis depends upon cytoplasmic ribosomes. 相似文献
Density labelling studies of δ-aminolevulinate dehydratase (ALAD) in cotyledons of radish ( Raphanus sativus L. cv. Longue Rave Saumonée) seedlings demonstrate that far-red light stimulates de novo synthesis of ALAD and that the turn-over of this enzyme is very poor. Cycloheximide reduces considerably both the increase of ALAD activity and the incorporation of deuterium in ALAD, which indicates that ALAD synthesis depends upon cytoplasmic ribosomes. 相似文献
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55.
超干处理对几种芸苔属植物种子生理生化和细胞超微结构的效应 总被引:1,自引:0,他引:1
几种芸苔属植物种子经过超干处理后,发芽力和活力不受影响,耐藏性大为提高。超干及老化后种子的脱氢酶、超氧物歧化酶、过氧化物酶、过氧化氢酶等酶系统保持完好;丙二醛和挥发性醛类物质等劣变产物相应减少;电导率测定表明,细胞膜系统的完整性良好;透射电镜(TEM)和扫描电镜(SEM)观察表明,细胞超微结构及功能保持完好。不同干燥方法和不同干燥剂的系列实验证实,生石灰的脱水效果并不亚于冰冻真空干燥法,且经济实用。 相似文献
56.
Summary
Brassica napus and Brassica juncea were infected with a number of Agrobacterium tumefaciens strains. Tumourigenesis was very rapid and extremely efficient on B. juncea with all but one of the strains. Tumourigenesis on B. napus varied widely. It was very efficient with the nopaline strains, was reduced with the succinamopine strain A281 and was very weak with the octopine strains. The latter observation was confirmed with six different B. napus rapeseed cultivars. The selectivity was due to differences in the virulence of Ti plasmids with B. napus, rather than the tumourigenicity of the T-DNA or virulence of the chromosomal genes associated with the strains. An exception was strain LBA4404. The virulence of the octopine strains was increased by coinfection with more virulent disarmed strains and by induction with acetosyringone. 相似文献
57.
Paul A. Wiersma John E. Hachey William L. Crosby Maurice M. Moloney 《Molecular & general genetics : MGG》1990,224(1):155-159
Summary The expression of an acetolactate synthase (ALS) gene isolated from the cruciferous plant Brassica napus was investigated in Salmonella typhimurium. Using an expression plasmid containing the highly active trc (trp-lac) promoter, several plant ALS constructs were made containing successive in-frame truncations from the 5 end of the coding region. Functional complementation by these plant ALS constructs of a S. typhimurium mutant devoid of ALS enzymic activity was assayed on minimal medium. Truncations which eliminated a large portion of the transit peptide coding sequence proved to act as efficient ALS genes in the bacterial host. Truncations close to the putative processing site of the plant protein were inactive in the complementation test. A full length copy of the gene, including the entire transit peptide coding region, was also inactive. The efficiency of the complementation, estimated by comparison to the growth rate of wild-type S. typhimurium, was found to correlate with levels of ALS activity in the transformed bacteria. Specific mutations, known to produce herbicide resistance in plants, were introduced into the truncated ALS coding sequence by site-directed mutagenesis. When expressed in bacteria these constructs conferred a herbicide resistance phenotype on the host. The potential of this system for mutagenesis and enzymological studies of plant proteins is discussed. 相似文献
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59.
Sergio M. Cocucci Silvia Morgutti Alessandro Abruzzese Chiara Alisi 《Physiologia plantarum》1990,80(2):294-300
The effect of increasing osmotic values of the medium (mannitol) on the growth and the response mechanisms of seeds of radish ( Raphanus sativus L., cv. Ton do Rosso Quarantino) during the early phase of germination was investigated in the presence or absence of fusicoccin (FC). Decreasing the water potential in the medium inhibited the growth and the evolution of protein synthesis and enhanced H+ extrusion, net uptake of K+ and malic acid synthesis. FC, which stimulates these latter functions, counteracted the inhibitory effect of the decreasing water potential of the medium on growth and protein synthesis. Neither in the absence nor in the presence of FC did decreasing water potential of the medium enhance the synthesis of soluble sugars and amino acids to support the osmotic pressure of the seeds. The osmotic and water potentials of the seeds increased during germination. FC made the increase more rapid, while mannitol kept both potentials low. The pressure potentials of the seeds also decreased with time, and both FC and mannitol enhanced this change. If the seeds were without turgor, the development of protein synthesis was blocked. The seeds counteract the effect of decreasing water potentials in the medium by: a) enhancing H+ extrusion (and, as a consequence, wall loosening and transport mechanisms) and the synthesis of malic acid as apparent in the presence of FC; b) regulating the osmotic potentials of the cells (with a lower dilution of the osmotic compounds present in the seeds due to the diminished uptake of water); c) controlling the growth through the effects of a) and b) on the pressure potentials (internal hydrostatic pressure) of the seeds and on protein synthesis. 相似文献
60.
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