The influence of exogenous DNA of different origin on the mitosis and chromosomes of irradiated meristematic cells ofVicia faba

In this paper we compare the influence of heterologous and isologous DNA on the radiation damage repair of primary root meristematic cells ofVicia faba. Roots, irradiated by exposure of 150 r were cultivated at different time intervals either in tap water, or in a solution of heterologous or isologous DNA. In comparing mitotic activity of meristematic cells it was found that both types of DNA studied enhance the recovery of irradiated cells. The frequency of postmetaphase chromosomal aberrations of irradiated cells was influenced also by post-irradiation action of exogenous DNA. While heterologous DNA exhibited synergical effect with radiation in the sense that it increased the post-irradiation incidence of aberrations in all time intervals studied, isologous DNA had a strong repair effect—the application caused a significant decrease of the percentage of post-metaphase aberrations. Both kinds of DNA caused changes in the relation of chromosome to chromatid aberrations; a higher percentage of chromatid aberrations was registered. The study of the distribution of aberrations between large and small chromosomes ofVicia faba showed that the post-irradiation application of heterologous DNA increases damage of small chromosomes while isologous DNA caused an increased repair ability in this chromosomal group.     

Comparison of the effects of radiation and deoxyribonucleic acids on the mitosis in roots ofVicia faba

Differences as well as similarities in the action of ionizing radiation and deoxyribonucleic acids from various sources on mitosis in root cells ofVicia faba were established. The time course of occurrence of aberrations were examined. Whereas in irradiated broad beant the maximum percentage of aberrations was observed immediately after irradiation, the aps plication of non-isologous DNA was followed by maximum aberrations after 8–16 hours. As all the time-intervals studied, an incraasad number of aberrations was found during metaphase-as compared with anaphases, both after irradiation and after application of DNA. A comparison of isologous, homologous and heterologous DNA as inductors of chromosomal aberrations supported our previous findings and showed that the efficiency of DNA depends on the genetic difference between donor and acceptor. During a study of distribution of aberrations between large and small chromosomes of meristematic cells ofVicia faba, at various time-intervals it was obsarved that after irradiation the distribution of aberrations between individual chromosomes is proportional to their total length, whereas the effect of heterologous DNA is mostly in the damage to small chromosomes. It was also found that aftar irradiation mostly chromatid aberrations are formed at shorter time-intervals and only later chromosomal aberrations will appear. On the other hand, heterologous DNA brings about in all time-intervals a predominance of chromatid aberrations.     

Contribution to the study on the reparative effect of exogenous DNA in the irradiated meristem ofVicia faba

The present report is focused on the study of participation of exogenous DNA in the process of postirradiation reparation of meristematic cells ofVicia faba primary roots. It is aimed at comparison of the positive reparative effect of isologous DNA with postirradiation action of heterologous DNA in its native, thermally denatured and DNAase-degraded forms, or DNA degraded by ultrasound, and with the effect of other biologically important macromolecules (RNA, histone, heparin, and dextran sulphate). For this purpose, the roots ofVicia faba irradiated by 150 r exposure were cultivated in solutions containing the above substances for an appropriate time interval. In squash slides both mitotic activity of the investigated cell population and frequency of postmetaphase chromosomal aberrations induced by radiation were evaluated. It was shown that a stimulation of cell division and reparation of chromosome damages were supported exclusively by isologous DNA. On the contrary, exogenously applied heterologous DNA increased postirradiation frequency of aberrations; maintenance of native structure of applied DNA was an essential condition for the above effect. Other macromolecules investigated on the course of postirradiation reparation ofVicia faba meristematic cells were without effect.     

Nativity of the macromolecule of isologous DNA as a condition for its reparative effect on radiation damage

The effect of isologous DNA on the course of postirradiation reparation of meristematic cells ofVicia faba primary roots was studied in detail. A considerable interest was devoted to determinations of fundamental qualitative and quantitative conditions of the above effect of isologous DNA. Main criteria of the effect were both mitotic activity of irradiated cellular population and dynamics of chromosome aberrations induced by radiation. One set of experiments compared the course of reparation as occurred in regard to applied dose of ionizing radiation in native isologous DNA, DNA denaturated by heat and degraded by DNAase, and post-irradiation reparation of induced damages was favorably affected by native isologous DNA only. Another set of results evaluated the dependence of positive reparative effect of native isologous DNA on the length of the molecule demonstrating that in the process of reparation the presence of a complete DNA macromolecule was not essential. The last experimental group was focused on observations on the dependence of the rate of native isologous DNA effect on concentration of applied solution of the macromolecule.     

Participation of exogenous DNA in the repair processes of meristematicVicia faba cells injured by monofunctional alkylating agens ethylmethane sulphonate

The effect of exogenous DNA of syngeneic origin on the course of reparation of meristematic cells ofVicia faba primary roots followed after treatment with monofunctional alkylating agent, ethyl methanesulphonate (EMS), was tested. Time course of alternations in mitotic activity of investigated cellular population and the dynamics of formation of postmetaphase chromosomal aberrations was evaluated. A reparation of damaged cells was significantly supported by syngeneic DNA; its application induced an increased incidence of cellular division already in the early intervals of the repair which was accompanied by concomitant decrease of microscopically detectable rupture in the chromosomes. The study performed on the localization of induced damages occurring in metaphase chromosomes pointed out an increased sensitivity of small chromosomes ofVicia faba to EMS. Similarly, a reparative action of syngeneic DNA was exhibited by significant decrease of aberrations frequency, predominantly in the same chromosomal group. Per cent representation of individual types, not affected by the action of syngeneic DNA, was established by detailed classification of induced aberrations. In both cases, isochromatide breaks were found of greatest predominance.     

The effect of maleic hydrazide and exogenous DNA on chromosomes ofVicia faba

The mitotic activity of merstematic cells ofVicia faba, the frequency of chromosomal abnormalities and their interchromosomal distribution are evaluated in dependence on the concentration of maleic hydrazide (MH) and on the recovery period. The influence of exogenous DNA of different genetic origin on the course of repair of primary root cells damaged by MH was also studied. Isologous DNA which exhibited a strong repair effect in authors' previous experiments was quite ineffective in the case of maleic hydrazide. Heterologous DNA, on the other hand, had to some extent a parallel effect with MH in breaking down the structural integrity of chromosomes and increased the frequency of aberrations induced by maleic hydrazide in meristematic cells ofVicia faba.     

Action of Ypenyl [5-bis-(2-chloroethyl)-aminomethyluracil] on the chromosomes ofVicia faba

An investigation was carried out on ability of Ypenyl,i.e. 5-bis-(2-chloroethyl)-aminomethyluracil to induce structural disturbances of chromosomes and changes of mitotic activity of meristematic cells ofVicia faba. The cytostatic employed induced chromosomal aberrations mostly of the chromatide type, the greater part of which were localized in the group of small chromosomes. The frequency of aberrations was proportional to the concentration of the substance used as well as to the duration of treatment. After a 24 hour treatment with 0·01mm solution of Ypenyl the maximum incidence of aberrations was found after 8 hour recovery in water. Longer recovery periods resulted in a gradual decrease in the number of aberrant post-metaphases in the cell population studied. Increasing concentration of Ypenyl led to the decrease in mitotic activity. Short recovery periods caused a considerable decrease in the mitotic index, which was compensated as late as 16 hours after treatment with the cytostatic.     

Chromosome aberrations caused by the effect of ultrasound in the meristematic cells ofvicia faba

In our present work the formation of chromosome aberrations has been studied in dependence on the tima interval between sonication and fixation of the primary root tips of Vicia faba. Maximum occurrence of aberrations was recorded immediately after sonication. The results of our experiments pointed to the fact that the frequency of the induced changes was independent on the sonic waves intensity within the range of 0-2—3-0 W/cm² and on ultrasond treatment duration within the range of 1—20 min. Studies of the distribution of chromosome abnormalities caused by ultrasound between the large and small chromosomes of theVicia faba meristematic cells in various time intervals showed that the frequency of the aberrations in both chromosome groups was proportional to its total metaphase lengths. Analysis of the type of aberrations observed in various time intervals after sonication indicated the simultaneous formation of chromosome and chromatide abnormalities.     

Sister chromatid exchanges in Vicia faba

The relationship between chromosomal aberrations and sister chromatid exchanges (SCE's) after treatment of Vicia faba root tips with thiotepa, caffeine and 8-ethoxycaffeine (EOC) was studied by using a modified fluorescent plus Giemsa (EPG) technique. At concentrations which had little effect on the frequency of chromosomal aberrations, thiotepa strongly increased the frequency of SCE's, provided that the chromosomes were allowed to replicate between treatment and fixation. Frequently, the size of the exchanged material was smaller than the diameter of the chromatid. Post-treatments with caffeine of roots previously exposed to thiotepa strongly increased the frequency of aberrations, but had little effect on the frequency of SCE's. In contrast to thiotepa, EOC caused only a slight increase in the frequency of SCE's even at concentrations which produced a high frequency of chromosomal aberrations. Thus, there was not a close correlation between SCE's and chromosomal aberrations. Single-strand exchanges between the DNA double helices in sister chromatids were not detected.     

The cytogenetic effect of products of cytosine radiolysis: Isobarbituric acid and dialuric acid

The cytogenetic effect of two radiolytic cytosine products, i.e. of isobarbituric acid and of dialuric acid has been studied on a system of resting meristem ofVicia faba L. on chromosomal level. Both compounds produced in a concentration 10^-3 and 10^-4 M chromosomal aberrations with a relatively low frequency, about 4 aberrations per 100 anaphases after 12 h of treatment. Among the aberration types chromosomal and chromatid breaks and minutes pre-dominated.     

Cytogenetic effect of radiation products of cytosine: Parabanic and oxaluric acids

The two final products of radiolytic degradation of cytosinei.e. parabanic and oxaluric acids were investigated as regards their cytogenetic effects. Broad bean (Vicia faba L.) root meristem was used as experimental material. While the oxaluric acid was not able to induce chromosomal aberrations to a greater extent, the parabanic acid acts as a clastogenic compound. When applied on a resting broad bean root meristem at concentration from 10^-3 to 10^-2 M it induces chromosome and chromatid aberrations, especially breakages. Their frequency reaches 9–12% at the highest tested concentration. The same concentrations of the parabanic acid increases mitotic index of the first cell generation of primary root.     

Effects of plant extracts on the rates of parasitization ofAnagasta kuehniella [Lep.: Pyralidae] eggs byTrichogramma pretiosum [Hym.: Trichogrammatidae] under greenhouse conditions

In the greenhouse, rates of parasitization ofAnagasta kuehniella (Zeller) eggs byTrichogramma pretiosum (Riley) were significantly increased when treated with water extracts of the weed,Amaranthus retroflexus L.: 1) Parasitization rates appeared to be dose dependent with greatest percentage parasitization obtained fromVicia faba L. plants sprayed with 2.5 ml of the extract, 2) Parasitization rates increased with an exposure time of 24 h, and 3) Plants sprayed withA. retroflexus in mosaic patterns interspersed with 2 additional plant extracts (Chenopodium album L. andPortulaca oleracea L.) did not show a total increase of parasitization over control plants treated with water.     

Mitochondrial plasmid-like molecules in fertile and male sterileVicia faba L

Biochemical analysis and electron microscopy showed that mitochondria of both the fertile and the male sterile 350 and 447 cytoplasms ofVicia faba. L. contain two small supercoiled DNA molecules of mean length of 1 700 and 1 420 base pairs in addition to the main mitochondrial DNA of high molecular weight. By agarose gel electrophoresis, the male sterile cytoplasm 350 is distinguished from the fertile cytoplasm and from the male sterile cytoplasm 447 by the presence of an additional supercoiled DNA molecule of approximately 1 540 bp.     

Effect of the herbicide terbutryn on meiosis,yield and mitotic chromosomes in C2 plants ofVicia faba L.

The herbicide terbutryn induced up to 11.3 % chromosomal abnormalities in cells undergoing meiosis inVicia faba. The mean number of pods/plant and the mean number of seeds/pod were considerably reduced, but the average seed dry mass was not or was only slightly affected by this herbicide. In C₂ plants chromosomal abnormalities were observed in few but significant numbers of cells.     

Ethylene-enhanced ethylene oxidation inVicia faba

The alkene oxygenase (AO) of fababean (Vicia faba L.) converts ethylene to ethylene oxide. Treatment of fababeans with 10μl/liter ethylene increases the activity of this enzyme within 2 hours of ethylene treatment. Though other alkenes were taken up by fababean seedlings, ethylene was the most active in inducing AO activity. The ability of ethylene to increase AO was blocked 60% by cycloheximide, an inhibitor of protein synthesis, and 35% by AgNO₃, an inhibitor of ethylene action.     

Production of plant growth substances by rhizosphere mycoflora of broad bean and cotton

The culture filtrates of the rhizosphere fungi of broad bean (Vicia faba L.) and cotton (Gossypium barbadense L.) were analysed for the presence of plant growth substances of auxin and gibberellins nature. Bioassay test and chromatographic analysis indicated that these fungi, each synthesized different auxins in their culture medium. These auxins were indole compounds. Similarly the rhizosphere fungi produced in their culture medium some gibberellins and gibberellin-like substances.     

Glucose-6-phosphate dehydrogenase isoenzymes in root growth zones ofVicia faba

The specific activity of glucose-6-phosphate dehydrogenase (G-6-PD) in growth zones ofVicia faba roots is increasing with cell maturation and differentiation. Changes in the total activity of G-6-PD are not associated with a change in the number of G-6-PD isoenzymes. Five G-6-PD isoenzymes were found in all root growth zones. Some differences were found in the activity of individual isoenzymes.     

Ion transport in broad bean leaf mesophyll under saline conditions

Main conclusion

Salt stress reduces the ability of mesophyll tissue to respond to light. Potassium outward rectifying channels are responsible for 84 % of Na ⁺ induced potassium efflux from mesophyll cells. Modulation in ion transport of broad bean (Vicia faba L.) mesophyll to light under increased apoplastic salinity stress was investigated using vibrating ion-selective microelectrodes (the MIFE technique). Increased apoplastic Na⁺ significantly affected mesophyll cells ability to respond to light by modulating ion transport across their membranes. Elevated apoplastic Na⁺ also induced a significant K⁺ efflux from mesophyll tissue. This efflux was mediated predominately by potassium outward rectifying channels (84 %) and the remainder of the efflux was through non-selective cation channels. NaCl treatment resulted in a reduction in photosystem II efficiency in a dose- and time-dependent manner. In particular, reductions in Fv′/Fm′ were linked to K⁺ homeostasis in the mesophyll tissue. Increased apoplastic Na⁺ concentrations induced vanadate-sensitive net H⁺ efflux, presumably mediated by the plasma membrane H⁺-ATPase. It is concluded that the observed pump’s activation is essential for the maintenance of membrane potential and ion homeostasis in the cytoplasm of mesophyll under salt stress.