Pepper species and cultivars, Capsicum annuum cv. Bell Boy, C. annuum cv. Kulai and C. frutescens cv. Padi, differing in drought tolerance were investigated for their water relations, stomatal responses and abscisic acid (ABA) content during water stress. C. frutescens cv. Padi exhibited a greater osmotic adjustment than C. annuum cultivars. Stomatal conductance of cv. Bell Boy was more sensitive to water stress than that of cvs. Kulai and Padi. In all pepper genotypes, stomatal closure was triggered in the absence of a large decrease in leaf water status. ABA content in xylem sap and leaf was higher in C. annum cultivars compared to C. frutescens cv. Padi.

Total genomic DNA isolated from maize hygromycin B resistant cell line(hygr-G204) was used to transform the maize hygromycin B sensitive cell line(hygs-G204) to the hygr-phenotype using polyethyleneglycol treatment and the transformed calli were selected using hygromycin B. The primary transformant maize plants were regenerated and analysed at the molecular level using DNA hybridization, transgenome rescue and histochemical β-glucuronidase assay. The results indicated that genomic DNA-mediated transformation can lead to transfer, expression and stable integration of a DNA fragment into the host genome.

After treatment with increased quantities of nitrogen and Azotobacter strains, activities of antioxidant enzymes superoxide dismutase, peroxidase and catalase, content of chlorophylls and carotenoids, soluble proteins and dry matter in leaves of sugar beet increased.

The first step during shoot primordia development in Papaver somniferum L. was the differentiation of globular meristemoids, resulting from localized cell division in callus tissue. During meristemoid maturation differences observed were in mitotic activity, cytoplasmic density, starch distribution, and in cell size, cell shape, and nucleus size to cell size ratio between peripheral and central meristemoid cells. Cell specialization within the meristemoids is a prerequisite for shoot primordia development.

Growth rate of fruit of Actinidia deliciosa (A. Chev.) Liang and Fergusoncv. Hayward, measured as increase in fresh mass, followed a simple sigmoidal trend showing two stages in all the seasons studied (1987 - 1989). However, growth profiles were statistically different from year to year in both shape and mean reached. The data suggest an important effect of climatic factors on growth, mainly rainfall, which may explain the differences in growth curves between seasons. Significant correlations between relative growth index and length and/or diameter were found which can be used for a non-destructive determination of Actinidia deliciosa fruit growth.

A spermine-resistant mutant of Arabidopsis thaliana (L.) Heynh. was isolated from M2 population of ethylmethanesulphonate-mutagenized seeds. The mutant was resistant to seed germination inhibition by spermine, but was as sensitive as the wild-type to spermidine and putrescine. In addition, the mutant displayed developmental abnormalities such as frequent cauline leaves, increased number of branches with inflorescence, reduced apical dominance, flowers subtended by bracts, disrupted floral organs with homeotic conversions. Genetic analysis indicated a single recessive nuclear mutation that was allelic to apetala2-1 (AP2-1). The new mutant allele of AP2 locus was accordingly numbered as AP2-10.

Zygotic embryos of Karwinskia parvifolia, isolated from seeds obtained from different regions of Mexico, were cultured on Woody Plant Medium (WPM) supplemented with 0.06 µM indole-3-acetic acid, 0.03 µM gibberellic acid, and 2 µM 6-benzylaminopurine. The growth of embryos and multiplication of shoots from stem segments were achieved. Rooting of excised shoots could be initiated on basal WPM medium with prolonged subculture period to 2 months, or on WPM medium supplemented with 10 µM 1-naphthaleneacetic acid. Multiplication capacity of shoots and rooting of K. parvifolia differed in dependence on the origin of explant material. The shoot multiplication was much lower than that of Karwinskia humboldtiana. The rooting depended on the origin of K. parvifolia seeds. The regenerated plants were successfully transferred to glasshouse.

The physiological responses of alfalfa (Medicago sativa L. cv. Gilboa) to salinity (100 mM NaCl) and some inorganic nutrients (K+, Ca2+ and N as NO3-) were investigated. Salinity caused a substantial reduction in biomass, carbon assimilation rate, stomatal conductance, water use efficiency, leaf area, relative growth rate, NO3- content and nitrate reductase activity, whereas, transpiration rate was slightly affected. Inclusion of K+, Ca2+ and N as NO3- in plant nutrient medium in combination or alone brought about a marked stimulation in control plants and moderated the salinity caused reductions in NaCl treated plants. In addition, plants also exhibited differences in these parameters at two growth stages.

Effect of two important mycotoxins, aflatoxin B1 and citrinin (concentration 2 g m-3) at various combinations (i.e., 1:1, 1:2, 2:1, 1:3 and 3:1, v/v) on seed germination, seedling growth, chlorophyll, carotenoid, starch, sugar, protein and nucleic acid contents, α-amylase activity, and respiration quotient was studied in maize cv. Suwan composite. The maximum and minimum inhibitions were recorded in most of the above parameters (except starch) at 3:1 and 1:3 combination ratios of these toxins, respectively. However, the inhibition rates varied with the treatments.

We obtained transformed bean shoots by electroporation of intact bean cells with the plasmid pDPG165 containing bar gene conferring herbicide resistance to plants. Transformed shoots were selected from electroporated callus on herbicide containing media. Data of molecular analysis (PCR and Southern blotting) confirmed the insertion of bar gene in the genome of herbicide resistant shoots. Detailed procedures for obtaining regenerative bean callus, optimization of electroporation of intact cells and transgenic shoots are given.

Cadmium, copper and zinc ions at high concentrations partially released scarified freshly-harvested seeds ofStylosanthes humilis from physiological dormancy. This response to toxic metals increased along with seed postharvest ageing. Cobalt and silver ions, and abscisic acid impaired metal-promoted germination.

Supply of 0.01 to 1.0 mM lead acetate to greening pea(Pisum sativum L.) leaf segments either in the absence or in the presence of inorganic nitrogen lowered total chlorophyll (Chl) content. During a time course study, there was not any appreciable effect of Pb²⁺ upto 4 h but thereafter Pb inhibited Chl synthesis. While supply of succinate, cysteine dithiothreitol, 5,5-dithio-bis-2-nitrobenzoic acid and NH₄C1 had no protective action against Pb²⁺ toxicity, and glycine, glutamate 2-oxoglutarate, MgCl₂, KH₂PO₄, CaCl₂, KC1 protected only partially, reduced glutathione (GSH) could completely overcome the inhibition of Chl biosynthesis by the metal. It is suggested that Pb²⁺ interferes with Chl biosynthesis through GSH availability

When the proper stimuli are given, somatic plant cells may form adventitious embryos, roots or shoots. The three pathways of regeneration show apparent similarities. They consist of three analogous phases: 1) dedifferentiation (during which the tissue becomes competent to respond to the organogenic/embryogenic stimulus), 2) induction (during which cells become determined to form either a root, a shoot or an embryo), and 3) realization (outgrowth to an organ or an embryo). The first phase may involve a period of callus growth (indirect regeneration), but often cells present in the explant become competent without cell division or without cell division at a large scale (direct regeneration). In an explant, only very few cells show the organogenic/embryogenic response. In direct regeneration, the three regenerative pathways start from cells in different tissues. This is most obvious when the different types of regeneration occur in the same explant. The hormonal trigger for the dedifferentiation phase is a general one, probably auxin. During the induction phase, each pathway requires specific hormonal triggers. During the realization phase, hormones should be absent or at low concentration. The successive steps in the regeneration process coincide with events on the molecular and biochemical levels, but so far no coherent picture has emerged. In particular during the early stages of regeneration, research on these levels is hampered by a technical problem, viz., the very low proportion of cells that participate in the process of regeneration. New methods may overcome this problem.

The localization of peroxidase in cells of horse-radish (Armoracia lapathifolia Gilib.) tumour and teratoma tissues was studied. Both tissue lines were derived from the same primary crown-gall tumour induced on the leaf fragments by a wild type of Agrobacterium tumefaciens B6S3. Enzymatic activity was measured in cell walls, high-density heterogeneous membrane fraction, microsomal and soluble (no particulate) fractions. The subcellular localization of enzymatic activity was distinct for each transformed tissue. Both tumour and teratoma showed similar isoenzyme patterns, but one soluble acidic isoperoxidase could be considered as a marker of cell differentiation.

When seedlings of two rice (Oryza sativa L.) cultivars Ratna and Jaya were raised under 100 and 500 µM cadmium nitrate in the medium, a high proline content was noted in Cd²⁺ stressed seedlings compared to controls. Seedlings grown under 500 µM Cd(NO₃)₂ maintained increased proline level compared to non-stressed seedlings. Kinetic properties of RNase extracted from control grown and Cd²⁺ stressed seedlings showed a marked alteration in Km due to Cd²⁺ treatment. The RNase isoforms were purified from 15-d-old rice seedlings with a total purification of 22.25 fold and 74.75 % yield using conventional biochemical techniques. Three RNase isoforms, namely I, II and III were eluted from DEAE-Sephacel column. The isoform RNase II had Km value of 3.2 mg(RNA) cm^-3. The in vitro osmotic stress created by incorporation of PEG in the enzyme assay medium led to decreased affinity of enzyme towards its substrate with increase in Km. This loss in affinity was partially restored by the addition of 1 M proline in the assay medium, suggesting the possible protective role of proline on RNase under osmotic stress.

In Sedum fabaria, the ovule is anantropus, bitegmic and crassinucellate. The development of the nucellus conforms to the Sedum type. The development of the embryo sac is of the Allium type. The antipodal cells in unfertilized embryo sac occasionally divide and one of them forms four-celled structures resembling embryos and remaining once elongate in the form of haustoria. The entry of the pollen tube is porogamous. After division the primary endosperm nucleus forms two cells: the apical one develops into cellular endosperm according to the Acre type and the basal one acts as the endosperm haustorium of the Sempervivum type. The embryogeny corresponds to the Caryophyllad type.

Secondary somatic embryogenesis and shoot organogenesis from primary somatic embryos of Papaver somniferum L. are described. The embryos became malformed, the root meristem expressed dividing activity without position-dependent cell differentiation, causing abnormal development or arrested growth of primary somatic embryos. The adventitious shoots regenerated from embryo hypocotyl, but secondary somatic embryos had an epidermal origin close to the root meristem. The regeneration occurred without hormonal treatment, indicating endogenous nature of triggering signals. These signals are probably related to the integrity loss of morphogenetic steps during development of primary somatic embryos, which appeared to induce an activation of cells competent to regeneration.

Ten-days-old bean plants (Phaseolus vulgaris L., cv. Cheren Starozagorski) were treated with simulated acid rain (pH 2.4, 2.2, 2.0 and 1.8). Anatomical changes in the primary leaves were studied 3, 48 and 168 h after a single treatment. This treatment induced: 1) change in the shape of palisade cells, contraction of their contact surfaces and expansion of spongy cells (pH 1.8, 3 h after treatment); 2) reduction of symplast connections among palisade cells and of apoplast in the spongy mesophyll (pH 1.8, 48 h after treatment); 3) destruction of adaxial epidermis and portions of palisade mesophyll, plasmolysis of spongy cells (pH 1.8, 168 h after treatment); 4) full destruction of mesophyll (pH 2.4, 2.2, 2.0 and 1.8, 168 h after treatment). The structure of abaxial epidermis was more stable than that of the adaxial one. With respect to anatomical parameters the studied species could be considered as comparatively resistant to acid rain.

Effects of a short-term pre-irradiation of etiolated wheat seedlings by radiation of various wavelengths and various irradiances on the rates of photophospho-rylation, Hill reaction, and chlorophyll accumulation were studied. The curves, constructed for the dependence of inhibitory effect in different processes on pre-irradiance doses, have a saturation level corresponding to photostationary state of the phytochrome system and a pre-threshold site where the inhibition is absent. For an interpretation of the experimental data we suggest a general model that includes both the threshold concept of Mohr and the presence of an additional control mechanism not sensitive to far-red radiation. According to the model, the phytochrome-controlled biological effect is pro-portional to the time during which the level of active phytochrome is higher than the threshold one and may be analysed according to the inhibition degree. The difference in control by red (RR) and green radiation (GR) pretreatments is attributed to the difference of the phytochrome photoconversion rate under RR and GR.