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1.
The host suitability of five zucchini and three cucumber genotypes to Meloidogyne incognita (MiPM26) and M. javanica (Mj05) was determined in pot experiments in a greenhouse. The number of egg masses (EM) did not differ among the genotypes of zucchini or cucumber, but the eggs/plant and reproduction factor (Rf) did slightly. M. incognita MiPM26 showed lower EM, eggs/plant, and Rf than M. javanica Mj05. Examination of the zucchini galls for nematode postinfection development revealed unsuitable conditions for M. incognita MiPM26 as only 22% of the females produced EM compared to 95% of the M. javanica females. As far as cucumber was concerned, 86% of the M. incognita and 99% of the M. javanica females produced EM, respectively. In a second type of experiments, several populations of M. arenaria, M. incognita, and M. javanica were tested on zucchini cv. Amalthee and cucumber cv. Dasher II to assess the parasitic variation among species and populations of Meloidogyne. A greater parasitic variation was observed in zucchini than cucumber. Zucchini responded as a poor host for M. incognita MiPM26, MiAL09, and MiAL48, but as a good host for MiAL10 and MiAL15. Intraspecific variation was not observed among the M. javanica or M. arenaria populations. Cucumber was a good host for all the tested populations. Overall, both cucurbits were suitable hosts for Meloidogyne but zucchini was a poorer host than the cucumber.  相似文献   
2.
The peptide mastoparan from wasp venom and the peptide melittin from bee venom stimulated growth in etiolated zucchini (Cucurbita pepo L.) hypocotyls. Both peptides were only effective in hypocotyls with abraded cuticles. At concentrations of 2 g ml–1 peptide growth was stimulated 72% by mastoparan and 50% by melittin after 2 h as compared to the controls. Mastoparan (5 g ml–1), melittin (10 g l–1) and 2,4-dichlorophenoxyacetic acid (5×10–4 M) stimulated accumulation of 14C-choline-labeled lysophosphatidylcholine in less than 10 min in cultured soybean cells (Glycine max L.), all to about the same extent. The effects of these peptides are among the first to be reported on plant cells and may be related to important events coupled to growth stimulation.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid  相似文献   
3.
The effects of illumination, temperature, deficiency of water or oxygen, phytohormones, and seedling age on the proportion of cytoskeleton-bound polysomes (CBP) in plant tissues were studied. This proportion was shown to vary depending on factors affecting protein synthesis: it decreased under the influence of factors inhibiting protein synthesis and reducing the relative content of polysomes in tissues (oxygen and water deficiencies, seedling aging) and vice versaincreased under the influence of the factors promoting translation (cytokinin, light). The significance of reversible polysome attachment to the cytoskeleton as a mechanism controlling protein synthesis is discussed.  相似文献   
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We tested the possible cytokinin effect on the functioning of the active transport system involved in the assimilate loading into the phloem as a cause for the cytokinin sink and retention effect. This effect is manifested in the deceleration of substance export from and the stimulation of substance import to the sites of local phytohormone application to the mature detached leaf from untreated leaf areas. To affect the membrane mechanisms of the substance transport, we used leaf treatment with the phytotoxin fusicoccin, an enhancer of plasmalemmal H+-ATPase and a potential stimulator of assimilates export, and with the phytohormone ABA affecting transport, metabolism, and plant growth. However, fusicoccin did not enhance 14C-sucrose export from the leaf blade and did not interfere with the cytokinin-induced export deceleration. ABA reduced substantially 14C export from the leaf but eliminated the cytokinin effect on this process. Similar results were obtained for broad bean (Vicia faba L.) leaves with apoplastic phloem loading, involving H+-ATPase activity, and pumpkin (Cucurbita pepo L.) leaves with symplastic phloem loading, that is, occurring without sucrose transmembrane translocation and without H+-ATPase involvement. The conclusion is that the cytokinin-induced development of sink zones in source leaves is not related to the membrane mechanisms of the substance transport in the mesophyll–phloem system. The data obtained support the idea that the cause for the cytokinin sink and retention effect is the enhancement of elongation growth and total activation of metabolism in the mesophyll cells of the detached leaf.  相似文献   
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从印度南瓜自交系HL中发现了一个梭形果突变体HL-fu。该突变体的花、果、茎等多器官的生物学特性同时发生了明显变异:雌花及雄花花器中异性花蕊的残存度较野生型高;果实为梭形,果形指数达野生型5倍;节间呈现长短交替分布的排列状态,叶序类似于对生。以突变体HL-fu与野生型HL杂交分别构建了正、反交F1,正交F2,BC1(P1)F1、BC1(P2)F1群体进行遗传分析,推测该变异类型为隐性多效单基因突变,突变性状受1对隐性核基因fu控制。探讨了梭形果突变体在南瓜育种及相关基础研究方面的潜在价值。  相似文献   
8.
Gibberellin (GA) 20-oxidases are multifunctional enzymes that catalyse reactions at an important branch point in the GA biosynthetic pathway. These enzymes oxidise the C-20 methyl group of a diterpene carboxylic acid precursor (e.g. GA12) to form an alcohol (in our case GA15-open lactone) and an aldehyde (GA24). The aldehyde is either oxidised to a tricarboxylic acid (GA25) or, with loss of carbon-20 and lactonisation, to a C19-GA (GA9). This branching is interesting to study, because C19-GA derivatives function as plant hormones in different tissues, whereas the C20-GA tricarboxylic acids have no known function. We have constructed chimaeric proteins by combining a GA 20-oxidase from immature seeds of Cucurbita maxima L., which produces mainly C-20 carboxylic acids, with a 20-oxidase from Marah macrocarpus immature seeds, which forms predominantly CC19-GAs. The cDNAs encoding these two very similar 20-oxidases were digested with restriction endonucleases Van 911. Bcl 1, and Bsa WI, and six chimaeric sequences were produced by recombination of the DNA fragments. The pCM1 -construct was obtained by exchanging nt 303–809 of the Cucurbita cDNA with the homologous DNA from the March 20-oxidase. In pCM2, pCM3, pCM4, pCM5 and pCM6, nt 810–992, nt 993–end, nt 303–992, nt 810–end, and nt 311–end were exchanged, respectively. All constructs were cloned in a pUC18 vector and functionally expressed in E. coli NM522 cells. GA 20-oxidase activity was detectable in cell-lysates from the transformed E. coli, but the extent and kind of conversion depended on the construct. Highest conversion of GA12was found with pCM1 and pCM3, one-tenth of this conversion was observed with pCM5 and pCM6, and one-hundredth was obtained with the hybrid proteins from pCM2 and pCM4. With pCM2 and pCM4, neither the C19-end product, GA9, nor the C20-end product, GA25-was formed. However, after transformation with constructs pCM1, pCM3, pCM5 or pCM6. GA9accounted for 30, 40, 60 and 90%, respectively, of the end products formed. Thus, the segments originating from M. macrocarpus conferred upon the chimaeric proteins an increasing ability to direct the biosynthetic flow into C19-GAs in this order. Although GA24is the immediate precursor, much less end products were formed by using this substrate.  相似文献   
9.
以黑籽南瓜(Cucurbita ficifolia)种子为试材, 研究了外施不同浓度的NaHS对NaHCO3胁迫下种子萌发及生理特性的影响。结果表明, NaHCO3胁迫显著抑制了黑籽南瓜种子的发芽率、胚轴长和胚根长, 降低了种子萌发过程中的可溶性糖含量, 抑制了α-淀粉酶、β-淀粉酶、SOD及POD活性。而外施不同浓度的NaHS显著促进了NaHCO3胁迫下黑籽南瓜萌发种子胚轴和胚根的生长, 提高了可溶性糖含量及α-淀粉酶、β-淀粉酶、SOD和POD活性, 降低了MDA含量; 外施其它盐类(Na2S、Na2SO4、NaHSO4和NaHSO3)及不同pH值(pH5.8–7.8)的Na2HPO4-NaH2PO4缓冲液对NaHCO3胁迫下黑籽南瓜种子的萌发则无影响。外施NaHS可有效缓解NaHCO3胁迫对黑籽南瓜种子萌发的抑制作用, 其缓解效应可能与其释放的H2S有关。  相似文献   
10.
The effect of pectic oligomers (OG) on ethylene biosynthesis, electrolyte leakage (EL), and CO(2) production was studied in discs excised from zucchini fruit (Cucurbita pepo L.) and stored at 20 or 2.5 degrees C. At 20 degrees C, OG enhanced ethylene biosynthesis and had a transient effect on decreasing EL, but showed little effect on respiratory rate; both the amount and size of the oligomer were important in changing both ethylene synthesis and EL. At 2.5 degrees C, OG increased both ethylene biosynthesis and respiratory rate with a maximum effect at 100 microg of oligomer and peaking at 6 h; shorter oligomers demonstrated an even greater effect on ethylene biosynthesis, but differences were smaller in respiratory rate. EL at 2.5 degrees C was affected most by 1 microg of OG and by monomeric galacturonic acid, with transient increases that peaked at 8 h. We suggest a signaling role for OG in the early steps of cold acclimation or chilling injury.  相似文献   
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