EDTA对蚕豆根尖细胞微核的诱变作用

为探讨EDTA对高等植物细胞的诱变作用 ,以及验证EDTA对金属离子的螯合作用 ,本试验用不同浓度的EDTA处理蚕豆根尖细胞 ,进行微核试验 ,并以Pb(NO3 ) 2 作为阳性对照 ,以无离子水作为阴性对照 ,发现EDTA能使蚕豆根尖细胞微核率有明显增加。由此证明EDTA对高等植物细胞有一定的诱变作用     

Effect of Auxins (2,4-Dichlorophenoxyacetic acid, Indole-3-Acetic Acid and Naphthaleneacetic Acid) on the Accumulation of {gamma}-Aminobutyric Acid in Excised Rice Root Tips

-Aminobutyric acid (GABA) accumulation occurs in cultured ricecells when ammonium is added to the medium [Kishinami and Ojima(1980) Plant Cell Physiol. 21: 581–589]. Whether thisphenomenon occurs in rice plant tissues was examined with respectto exogenously supplied auxins: 2,4-dichlorophenoxyacetic acid(2,4-D), indole-3-acetic acid (IAA) and naphthalene-acetic acid(NAA). In intact rice plants grown in medium containing ammonium withoutauxin, glutamine first increased, then asparagine graduallyincreased. In both shoots and roots, the asparagine contentbecame the highest among four amino acids after 4 days of cultureperiod. GABA did not increase at all, its level remaining lowin both shoots and roots throughout the culture period. GABA accumulation was observed in excised rice root tips whenthey were incubated in the medium containing ammonium in thepresence of 2,4-D, IAA or NAA. In the absence of auxin, however,excised rice root tips accumulated asparagine and glutamine,but not GABA. Rice root segments obtained from a region in whichroot cells had already developed to maturity did not accumulateGABA but asparagine and glutamine in the presence of both ammoniumand 2,4-D. These results suggest that GABA accumulation occurs in rapidlygrowing and dividing tissue, such as the apical meristem ofrice root in the presence of auxin during ammonium assimilation. (Received June 15, 1987; Accepted March 14, 1988)     

Na2SeO3对蚕豆根尖细胞遗传损伤作用的研究

采用蚕豆根尖微核实验和姊妹染色单体交换实验,研究亚硒酸钠(0.01～10.0 mg·L-1)对蚕豆根尖细胞的遗传损伤效应.结果表明一定浓度的亚硒酸钠(Na2SeO3)可导致蚕豆根尖细胞有丝分裂指数下降,间期细胞微核频率明显增高,且Na2SeO3的上述效应具有一定的剂量效应关系;同时Na2SeO3可诱导细胞姊妹染色单体交换(SCE)频率显著增高.研究表明,亚硒酸钠对蚕豆根尖细胞具有遗传毒害作用,并有可能对人体产生遗传损伤.     

乙酸铜对蚕豆根尖细胞致畸效应

采用蚕豆根尖细胞的微核试验和染色体畸变试验方法,以不同浓度的乙酸铜为诱变剂,选择不同的处理时间,测定蚕豆根尖细胞的有丝分裂指数、微核率和染色体畸变率。结果表明：乙酸铜能诱发较高频率的微核率,处理6h、12h时微核率均随着乙酸铜浓度的升高而增加,具有明显的剂量效应;处理24h时在实验浓度范围内,其微核率随乙酸铜浓度的升高而增加,但高于一定浓度后反而呈下降趋势。不同浓度的乙酸铜在不同处理时间均使蚕豆根尖细胞有丝分裂指数增大。乙酸铜还能诱导蚕豆根尖细胞产生较高频率的染色体畸变,且产生多种类型的染色体畸变。因此,乙酸铜对蚕豆根尖细胞具有明显的致畸效应。     

Growth Rates of a Pseudomonad on 2,4-Dichlorophenoxyacetic Acid and 2,4-Dichlorophenol

The growth of a pseudomonad on 2,4-D (2,4-dichlorophenoxyacetic acid) and 2,4-DCP (2,4-dichlorophenol) was studied in batch and continuous culture. The optimum growth rate using 2,4-D was 0.14/h at 25 C in a pH range from 6.2 to 6.9. Highest specific growth rate using 2,4-DCP was 0.12/h at 25 C in a pH range from 7.1 to 7.8. Growth was strongly inhibited by 2,4-DCP above a concentration of 25 mg/liter whereas no appreciable inhibition was observed with 2,4-D at concentrations up to 2,000 mg per liter. Growth on 2,4-DCP was described by Monod kinetics at subinhibitory concentrations but the inhibition by 2,4-DCP exhibited an unusual linear response to substrate concentration, and did not fit a model based on noncompetitive inhibition. The lag phase of batch cultures was found to depend on both 2,4-DCP concentration and prior adaptation of the inoculum. A study such as this on the kinetics of growth on related substrates may be useful as a method of finding the rate-limiting step in a metabolic sequence.     

Elimination of Material that Obscures Stained Chromosomes in Squashes of Vicia faba Root Tips

A procedure for elimination of cytoplasmic debris from Vicia faba root tip cells is: (1) a root tip previously fixed in 3:1 absolute alcohol-acetic acid and stained by the Feulgen method is placed on a slide and squashed in a small drop of water, (2) a cover slip is applied and the cells are flattened with a hand-operated lever device supplying 35 pounds pressure onto a 22 × 22 mm cover glass, (3) the slide is quick-frozen, the cover slip is removed, and the slide is dropped immediately into water, (4) the slide is cleared through an alcohol-xylene dehydration series and permanently mounted. The significant result of this procedure is the consistent presence of clear, flat cells showing excellent definition of chromosomes.     

镉离子对蚕豆根尖细胞分裂的影响

蚕豆根尖经孙同浓度（0.1-10.0ppm）的CdCl2溶液处理24-48小时后,根的生长受到不同程度的抑制。对根尖细胞分裂的毒害则表现为低毒C-有丝分裂和高毒的染色体断裂、粘连和液化。此外,对Cd++的毒害机理进行了简略讨论。     

Nucleic Acid Metabolism of Vicia faba during Germination and Growth

During the growth of Vicia faba seedlings in the absence of an external nitrogen supply, the cotyledons decreased rapidly in dry weight and nucleic acid content. In the developing shoot the dry weight increased rapidly for four weeks and then very slowly over the next two weeks growth; the nucleic acid content of the shoot increased to a maximum after 4 weeks growth and decreased in amount during the next 2 weeks. On the other hand the roots increased in both dry weight and nucleic acid content throughout the growth period, although they only accounted for a small proportion of the total dry weight and nucleic acid content of the plant. These changes during germination and growth are discussed in relation to those occurring during these developmental stages in other plants.     

The Emergence and Early Growth of the Lateral Root in Vicia faba L.

The duration of the mitotic cycle, as well as the proportionof cells with long and short cycle times and quiescent cells,have been investigated in the apical meristems of young lateralroots of Vicia faba. No changes took place in the duration ofC or in the phases of the mitotic cycle as the lateral rootemerged from the primary root, though the proportion of proliferatingcells increased and the quiescent fraction of cells decreased.It is suggested that the low frequency with which newly emergedlateral roots label with ³H-TdR is a result of the formationof a large endogenous pool of TdR in the meristems during theperiod they are temporarily quiescent. The changes which tookplace in the parameters of cell proliferation during the earlygrowth of the lateral root have been correlated with those inroot apical meristems following the onset of seed germination.     

Changes in Lipid and Fatty Acid Metabolism of Vicia faba Mesophyll Protoplasts

The metabolism of the major polar and neutral lipids of Viciafaba protoplasts isolated from ¹⁴CO₂-fed leaves has been examined.The results show large losses in the radioactivity found inphosphatidylcholine and monogalactosyldiacylglycerol while thatof phosphatidylglycerol was stable. This loss was accountedfor by a rapid increase in the ¹⁴C content of the neutral lipids,particularly the triacylglycerols. Analysis of the fatty acidradioactivity in the lipids suggests that protoplast isolationinhibited fatty acid desaturation on phosphatidylcholine andpossibly on other lipids. These results also suggest a roleof phosphatidylcholine in the donation of fatty acids for triacylglycerolsynthesis in mesophyll protoplasts. The results are discussedin terms of the regulation of lipid metabolism and protoplastbiology. (Received April 20, 1984; Accepted August 27, 1984)     

Micronuclei and Radiosensitiviy in the Root Meristem of Vicia faba

Percentages of cells with micronuclei in four regions of theroot meristems of Vicia faba are used as measures of sensitivityto acute X-irradiation. There are two peaks in these percentages,occurring at about four and eight days after 360 rads and twoand six days after 180 rads. Two peaks exist, probably becausethe radiation delays cells that were in G₁ much more than cellsthat were in G₂ in reaching the first post-irradiation mitosisand consequently in displaying micronuclei in the followinginterphase. The relative heights of the two peaks thereforereflect the relative numbers of cells in G₁ and G₂ as well asthe relative sensitivity of the two phases to chromosomal damage. The cells of the quiescent centre are injured least by the radiationas they are mostly held at Gt. The meristem thus obeys the lawof Bergonié and Tribondeau, but differs from that ofZea in that the meristematic cells of the cap initials and steleimmediately adjacent to the quiescent centre resemble the quiescentcentre much more closely than the stele 250 µ away inthe numbers of micronuclei produced. This is consistent withthe differences already known between the two species concerningrates of division in the different regions of the meristem andthe behaviour of the meristem after severe radiation injury.     

Organic Acid Changes in the Epidermis of Vicia faba and Their Implication in Stomatal Movement

Considerable evidence indicates that the increase in guard cell turgor resulting in stomatal opening is brought about by active K⁺ uptake into guard cells. Only a small increase in inorganic anions appears to accompany the increase in K⁺. A plausible explanation is that organic acids are produced within guard cells and act as counterions, whereas the H⁺ produced are exchanged for K⁺.     

Growth Substances in the Roots of Vicia faba

An investigation has been made into the growth regulators presentin ethanol extracts of the seedling roots of Vicia faba afterseparation on paper partition chromatograms, using segmentsof Avena coleoptiles and mesocotyls and of Pisum sativum.rootsas biological assay material. Acetonitrile purification shows the presence of at least threeauxins running in isobutanol: methanol: water, at Rfs of 0–0·25,0·4–0·6, and 0·65–0·95;the latter may represent two different auxins. A similar, butclearer, picture is shown by the ether-soluble acid fraction.Here an auxin at Rf 0–0·25 also stimulates rootgrowth and could be ‘accelerator ’. A second atRf 0–0·25 is an indole compound which inhibitsroot growth and does not seem to be be IAA. A third at Rf 0·8–1·0is also a root-growth inhibitor and gives no indole reaction.The ‘inhibitor ß’ complex was demonstrated(Rf 0·65–0·85) together with a number ofother inhibitors at lower Rf value. The ether-soluble neutral component also contains auxins orauxin precursors. The water-soluble, ether-insoluble fraction contains four readilyinterconvertible substances with auxin properties. They allappear to inhibit root growth and give no indole reaction.     

2,4—D对水稻根尖微管排列的影响

通过共焦激光扫描显微镜对经过２,４－Ｄ处理水稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）根尖的微管骨轲的排列进行了研究。结果表明,对照（未经２,４－Ｄ处理）根尖的不同生长区微管呈现不同的排列方式,生长区皮导呈管呈随机排列,伸长区微管呈横向排列,根毛区的呈斜向排列。经过２,４－Ｄ处理的根,不但皮层细胞微管表现重新定向,同时也伴随着生长受到强烈抑制。１ｍｇ／Ｌ２,４－Ｄ处理１ｈ,分生区细胞微管由随机排列变成横     

Quantitative Effects of 2,4-Dichlorophenoxyacetic Acid on Growth of Suspension-cultured Acer pseudoplatanus Cells

Using suspension-cultured Acer pseudoplatanus cells requiring 2,4-dichlorophenoxyacetic acid for growth, the dependence of the population doubling time and the maximum increase in cell population density on the auxin concentration was studied. It appears that in the range of 2,4-dichlorophenoxyacetic acid concentration from 4 × 10⁻⁸ to 4 × 10⁻⁶ M, the rate of cell division during the logarithmic growth phase is independent of the auxin concentration, while the maximum number of cell generations obtained is limited by the initial auxin concentration. The significance of these two aspects of auxin action are discussed.     

2,4-二氯苯氧乙酸的研究进展

2,4-二氯苯氧乙酸经常作为除草剂和植物生长调节剂使用,在农林业中发挥了重大作用,尤其在水果(如柑橘)保鲜中应用广泛,但其毒性问题也受到广泛关注,因此了解2,4-D的生理作用、在生物及环境中的代谢降解、残留毒性和提取鉴定等的研究进展很有必要.