Influence of boron on somatic embryogenesis in papaya (Carica papaya L.) cv. Honey Dew was investigated. Immature zygotic embryos were grown in the induction medium containing Murashige and Skoog basal salts, with B₅ vitamins, picloram (1 mg dm^-3) or 2,4-dichlorophenoxy acetic acid (2 mg dm^-3) and different concentrations of boric acid (30 to 500 mg dm^-3). Maximum somatic embryo initiation was observed at 62 mg dm^-3 boric acid irrespective of the growth regulator used. The cotyledonary stage somatic embryos were germinated on MS basal medium devoid of growth regulators. The regenerated plantlets were hardened under greenhouse conditions and transferred to field.

The physiological function of glutamate dehydrogenase (GDH) was investigated by treating germinating peanut (Arachis hypogaea L.) seeds with nucleoside triphosphate (NTP) solutions in order to alter the isoenzyme distribution patterns. The free nucleosides and nucleotides of the GTP-treated peanut were the highest [8.7 μmol g^-1(f.m.)], and they decreased through the ATP-treated peanut [5.8 μmol g^-1(f.m.)], and CTP-treated peanut [5.5 μmol g^-1(f.m.)], to the UTP-treated peanut [4.1 μmol g^-1(f.m.)]. The combination of 4 NTPs induced 20 % higher content of Pi [173 nmol g^-1(f.m.)] than in the control, but the combined ATP+UTP treatment induced the lowest (93.0 nmol g^-1(f.m.)] Pi. The 4 NTP treatment also induced the highest number of GDH isoenzymes (28) followed by the purine NTP treatments (15 to 20), but the pyrimidine NTP treatments and the combined purine + pyrimidine NTP treatments induced the lowest numbers (<15) of isoenzymes. The deamination/amination ratios were generally higher in the UTP (0.11), and CTP (0.06) treated peanuts than in the GTP (0.04), and ATP (0.07) treated peanuts. There were mutual relationships between higher numbers of GDH isoenzymes present in the GTP-, and ATP-treated peanuts and higher RNA (236.5 and 239.4 μg g^-1, respectively) contents on one hand, and between the lower numbers of isoenzymes in the CTP-, and UTP-treated peanuts and lower RNA (162.0 and 152.5 μg g^-1, respectively) contents. The recurrent relationships of the effects of the NTP treatments of peanut were UTP > ATP > CTP > GTP.

We examined morphological and ultrastructural differences in chloroplasts of cotton leaves and the fruiting organs, bract, and capsule wall to advance our understanding of their commonly observed differences in photosynthetic efficiency. Chloroplasts from leaves were large (7.1 μm long in cross section), lens shaped with a well developed membrane system differentiated into grana and stroma lamellae that occupied the large cross-sectional area (12.3 μm²) of the organelle. A few small plastoglobuli and starch grains were scattered in the stroma region. The bract chloroplasts were correlative of leaf chloroplasts in size (6.8 μm in length) and shape with the exception that the bract chloroplasts exhibited greater thylakoid number per granum (15.8) than the leaf chloroplasts (10.5). In contrast to leaf and bract, the capsule wall chloroplasts were smaller in size (4.3 μm) and cross sectional area (6.8 μm²) than either the leaf or bract. The most intriguing feature of the capsule wall chloroplasts was its domination by large starch granules (5.3 μm²) in the stroma which filled the whole chloroplast coercing the membrane system to move towards the periphery of the organelle. Grana number and thylakoids per granum were lowest in the capsule wall chloroplasts.

Developmental changes and effects of various abiotic stresses on peptidyl prolyl cis-trans isomerase (PPIase) activity were studied in the seedlings of sorghum [Sorghum bicolor (L.) Moench cv. CSH-6]. The PPIase activity of sorghum seedlings markedly decreased after two days of germination. Up to 90 % of the PPIase activity was inhibited by cyclosporin-A. Maximal increase in specific PPIase activity in the 3-d-old seedlings was observed in response to osmotic stress and it was transient in nature. The stress-induced enhancement in PPIase activity, depending upon tissue and stress treatment, was due to induction of cyclophilins as well as other PPIases. Osmotic stress-induced enhancement in PPIase activity in the drought susceptible cv. SPRU-94008B was maximal in roots, as compared to shoots in the drought tolerant cv. ICSV-272.

Size variability of uninucleate microspores was studied in horse chestnut (Aesculus hippocastanum L.). Microspores were isolated from buds of different size (3, 4, and 5 mm) taken from lower, middle and upper segments of inflorescences. All analyzed buds showed bimodal distribution of microspore size which confirmed the presence of pollen dimorphism.

This study was conducted to examine the individual developmental stages of Colchicum autumnale. We identified the sclerenchymatic tissue in the middle part of the protuberance. This tissue supports the function of protuberance as a kind of hollow diverticulum. On the boundary of the new corm and the shoot a meristematic layer was recognized. We assume that this abscission zone-like structure can initiate dying back of the above-ground part regularly at the end of annual life-cycle. The major part of starch is reutilized in the mother corm during the autumnal stage, supporting sprouting which takes place in the soil. Decline of starch content is paralleled by increasing of total amylolytic activity. From amylolytic enzymes α-amylase, β-amylase and α-glucosidase have been identified. The presence of pullulanase and starch phosphorylase was not observed. From free sugars glucose, fructose and sucrose were identified in corms. The level of sucrose increased significantly during winter season.

Apical and basal halves of 3 cm long apical segments of in vitro cultured juvenile, adult and rejuvenated Sequoia sempervirens shoots were analyzed for total and tyrosine phosphorylated proteins. The latter was detected by a phosphotyrosine specific antibody. Younger tissues, or the apical halves of shoot terminals, showed larger amounts of 36, 44, 46 kDa proteins and lesser amounts of 29 kDa proteins. These are proposed as age-related changes. Phase-related proteins were also evident. Adult tissues contained more of the 34 and 36 kDa proteins than juvenile and rejuvenated shoots. Western blotting with a phosphotyrosine specific antibody revealed more of 25, 39, and 54 kDa protein in the younger tissues. In addition, tyrosine phosphorylated proteins of 25 and 34 kDa were higher in the adult, than in juvenile or rejuvenated tissues. Our findings showed that protein tyrosine phosphorylation, or the signal transduction pathway, is involved in phase- and age-related processes.

Activities of acid and alkaline invertases and sucrose synthase were determined in roots and nodules of lentil at various stages of development. Alkaline invertase and sucrose synthase were both involved in sucrose metabolism in the nodule cytosol, but there was only a small amount of acid invertase present. Activity of sucrose metabolizing enzymes in roots was significantly less than that observed in the nodules. Amongst sugars, sucrose was found to be the main component in the host cytosol. Lentil neutral invertase (LNI) was partially purified from nodules at 50 days after sowing (DAS). Two forms of invertase were identified, i.e., a major form of 71 kDa which was taken for enzyme characterization and a minor form of 270 kDa which was not used for further studies. The purified enzyme exhibited typical hyperbolic saturation kinetics for sucrose hydrolysis. It had a Km of 11.0 to 14.0 mM for sucrose depending upon the temperature, a pH optimum of 6.8 and an optimum temperature of 40 °C. Compared with raffinose and stachyose, sucrose was better substrate for LNI. The enzyme showed no significant hydrolysis of maltose and p-nitrophenyl-α-D-glucopyranoside, showing its true β-fructosidase nature. LNI is completely inhibited by HgCl₂, MnCl₂ and iodoacetamide but not by CaCl₂, MgCl₂ or BaCl₂.

The growth and water relations of Paulownia fortunei in photoautotrophic cultures (nutrient medium lacking sucrose and growth regulator) with CO₂ enrichment (PWAH) or without CO₂ enrichment (PWAL) were compared with those in photomixotrophic shoot (PWC; 30 g dm^-3 sucrose and 0.3 mg dm^-3 N⁶-benzyladenine) and root cultures (PWR; 0.3 mg dm^-3 indole-3-butyric acid). The photoautotrophic and photomixotrophic cultures were incubated under photosynthetic photon flux 125 and 60 μmol m^-2 s^-1, respectively. 100 % sprouting and significantly higher number of shoots (1.6) were obtained with PWAH as compared to PWAL and PWC. PWAH and PWAL stimulated spontaneous rooting from the cut end of axillary shoots. In PWAH, 84 % of shoots rooted with an average of 5.9 roots per shoot and 4.0 cm of root length in 21 d. Rooting of photomixotrophic shoot cultures were stimulated by an auxin treatment. In this case, 98.3 % of shoots were rooted with an average of 4.6 roots per shoot and 1.9 cm length. A microscopic observation on leaf abaxial surface prints from photomixotrophic shoot and root cultures showed widely open (6 - 8 μm) spherical stomata (12 - 14 μm) and from photoautotrophic cultures elliptical stomata (10 - 12 μm) with narrow openings (3 - 4 μm). Leaves from photomixo-trophic cultures had higher stomatal index as compared to photoautotrophic cultures. The rate of moisture loss from detached leaves was not varying significantly in different cultures.

Studies on stem (and leaf) structure and histology of a semi-natural grassland community, permanently growing in mini-FACE rings under elevated concentrations of atmospheric CO₂ (560 μmol mol^-1) are presented. Histochemical analysis of stem sections from legume plants grown under high CO₂ concentration revealed both a reduction of lignin deposition in spring vascular bundles of Trifolium repens L., and a decrease in size of the xylem vessels in Vicia hybrida L. and Vicia sativa L. Thus, the effects of elevated CO₂ on the stem histology of the species investigated are rather species-specific and/or organ-specific, and of major account especially in the early phases of vegetative growth, in particular as regards lignin deposition mechanisms. In leaves, neither differences as to lignification nor any other anatomical structure modification were found under CO₂ enrichment.

Putative transcription factors bearing a particular DNA-binding domain called "MADS-box", have been mainly involved in processes related to flower development. It is generally accepted that MADS-box genes may have played a central role in the evolution of plant reproductive structures. During the last years increasing evidence points to more general roles of these factors that spans to the control of the flowering time, but also to other non-reproductive processes. Moreover, sequencing of the Arabidopsis genome has led to the recognition of above hundred MADS-box genes in this model organism, most of them still uncharacterized. This opens the possibility of uncovering new roles for MADS-box genes in plant development and evolution.

Chlamydomonas reinhardtii was grown in medium with different carbon (acetate, CO₂, or both), and nitrogen (ammonium chloride, peptone, urea) sources and under light of different spectral composition. The light-dark cycles were found more suitable for mixotrophic growth than continuous irradiation. Both blue (BR) and red (RR) radiations decreased photosynthetic capacity of mixotrophic cells compared to "white light" (WL). Effect of RR was associated with photon distribution favouring photosystem 1 (PS1) suggesting increased cyclic phosphorylation. Mixotrophic growth in 10 mM NH₄Cl increased photosynthetic oxygen evolution compared to standard concentration of 5 mM NH₄Cl used for growing C. reinhardtii. Autotrophic growth stimulated the photosynthetic capacity compared to mixotrophic one. However, higher photosynthetic capacity was achieved for mixotrophic cells by growing them at high NH₄ ⁺/K⁺ ratio and high phosphate concentration.

Isolated pistils of dimorphic buckwheat (Fagopyrum esculentum Moench.) flowers were treated with phosphatase inhibitors (ocadaic acid and cantharidin) and with calcium antagonists (verapamil, La³⁺, and A23187). They were subsequently cross- or self-pollinated, and the growth of pollen tubes was observed under the fluorescence microscope. All treatments suppressed inhibition of pollen tubes growth suggesting that protein phosphatases and calcium signaling may be involved in self-incompatibility signal transduction in buckwheat.

Changes in contents of reactive oxygen species (O₂ ^- and H₂O₂) and non-enzymatic antioxidants, activities of antioxidant enzymes and lipid peroxidation were investigated during senescence of detached cucumber cotyledons dipped in water (control) and 20 mg dm^-3 triadimefon (TDM). O₂ ^- and H₂O₂ accumulation and lipid peroxidation were observed during senescence of cucumber cotyledons, which coincided with a drop in the contents of carotenoids (Car) and ascorbic acid (AsA), and the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), and an increase in the activity of peroxidase (POD). However, TDM could significantly inhibit the accumulation of O₂ ^- and H₂O₂, and lipid peroxidation by preventing the decrease of CAT, APX, Car and AsA and the increase of POD, while TDM had little effect on SOD activity during the senescence. Therefore we can draw a conclusion that TDM protects the membrane system and retards the senescence of detached cucumber cotyledons.

Somatic embryogenesis was achieved from mature embryos excised from stored hybrid Abies alba × Abies cephalonica seeds. Embryogenic tissue formation occurred on SH medium supplemented with 1 mg dm^-3 benzyladenine. The formation of embryogenic tissue was influenced by the time of storage of seeds. Initiation frequencies 27.2 - 29.0 % were obtained in embryos isolated from 6 month and 1 year stored seeds. Embryos excised from 4-year stored seeds showed no response. Embryogenic structures appeared on the surface of hypocotyl. They originated without previous callus formation. Embryogenic tissues were maintained in long-term cultures. After maturation treatment cotyledonary somatic embryos developed and germinated in small plantlets.

Activities of ammonium assimilating enzymes glutamate dehydrogenase (GDH), glutamine synthetase (GS), glutamate synthase (GOGAT), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) as well as the amino acid content were higher in nodules compared to roots. Their activities increased at 40 and 60 d after sowing, with a peak at 90 d, a time of maximum nitrogenase activity. The GS/GOGAT ratio had a positive correlation with the amino acid content in nodules. Higher activities of AST than ALT may be due to lower glutamine and higher asparagine content in xylem. The data indicated that glutamine synthetase and glutamate synthase function as the main route for the assimilation of fixed N, while NADH-dependent glutamate dehydrogenase may function at higher NH₄ ⁺ concentration in young and senescing nodules. Enzyme activities in lentil roots reflected a capacity to assimilate N for making the amino acids they may need for both growth and export to upper parts of the plant.

The contents of three major steviol glycosides (SGs) (stevioside and rebaudiosides A and C) in vegetative and generative organs during ontogeny of Stevia rebaudiana Bertoni were analysed with HPLC. Plant organs contained different amounts of the SGs, which declined in the following order: leaves, flowers, stems, seeds, roots. The highest content of the SGs was found in upper young actively growing shoot sections, whereas lower senescent shoot sections exhibited the lowest amount of such compounds. During ontogeny a gradual increase in the SG content was observed in both mature stevia leaves and stems, and this process lasted up to the budding phase and the onset of flowering.

Effect of NaCl was studied on chlorophyll (Chl) synthesis and its intermediates (protoporphyrin IX, Mg-protoporphyrin IX, and protochlorophyllide), dry mass, ethylene evolution, and activities of superoxide dismutase (SOD) and peroxidase (APX) in wheat (Triticum aestivum L.) seedlings at 24, 48, and 72 h after germination. A conspicuous decrease in Chl synthesis, associated with increase in ethylene evolution and SOD and APX activities, was noted as NaCl concentration was increased from 0 to 100 mM.

A liquid culture technique has been developed to study lipid metabolism in seeds of Brassica campestris L. grown in vitro from terminal inflorescences detached 4 to 46 days after anthesis. Seeds developed under these conditions exhibited pattern of growth, deposition of storage products and lipid composition similar to those from intact plant.

Cowpea (Vigna sinensis L.) plants were inoculated with arbuscular mycorrhizal fungus (Acaulospora laevis) to investigate the effects of different concentrations of di-n-butyl phthalate (DBP; 0, 10, and 100 mg kg^-1) added to soil on their growth. Mycorrhizal plants were less affected by high concentration of DBP (100 mg kg^-1) than non-mycorrhizal ones. Also the uptake and transformation of DBP by mycorrhizal plants differed from that of non-mycorrhizal plants.

Application of NaCl (electrical conductivity 4.0 mS cm^-1) resulted in about 52, 50 and 55 % reduction in total nitrogen contents in mung bean [Vigna radiata (L.) Wilczek] leaf, root and nodule, respectively. In nodule, nitrogenase activity was reduced by about 84 % under stress as compared with the control set. Glutamine synthetase activity was reduced by about 31, 16 and 23 %, glutamate oxoglutarate aminotransferase activity was reduced by 78, 57 and 42 % and glutamate dehydrogenase activity was reduced by 9, 8 and 42 % in leaf, root and nodule, respectively, under salt stress. The pretreatment with indole-3-acetic acid, gibberellic acid and kinetin, each ranging from 0.1 to 10 µM, in restoring the metabolic alterations imposed by NaCl salinity was investigated in mung bean. The three phytohormones used were able to overcome to variable extents the adverse effects of stress imposed by NaCl solution.

Free proline content, superoxide-dismutase activity, and lipid peroxidation were measured in sixteen Yugoslav and introduced genotypes of soybean. More tolerant genotypes with higher free proline content and high superoxide-dismutase activity, and low lipid peroxidation were chosen. The selected genotypes could be used in field production, as well as in breeding.

Identification of individual chromosomes in Lupinus is not possible due to gradient in size and similar morphology. To overcome this problem, molecular cytogenetics was developed for Lupinus. As an initial step in karyotype analysis, fluorescent in situ hybridization (FISH) was performed to determine genomic distribution of rRNA genes in L. hispanicus, L. luteus and L. × hispanicoluteus. It was found that all three diploid species posses two chromosome pairs carrying 18S-5.8S-25S rDNA and one chromosome pair carrying 5S rDNA. The use of probes for rDNA permitted unambiguous identification of three different pairs of chromosomes and revealed conservation of the number of rDNA loci among the three species. The study represents the first step in physical mapping of Lupinus genome through FISH by providing distinct chromosome landmarks.

Expression of alcohol dehydrogenase loci was used to estimate hybridity of Lycopersicon esculentum Mill. in 1012 seeds. The banding patterns were obtained by means of vertical block electrophoresis in polyacrylamide gels. It was established that qualitative variation of locus Adh-2 can be applied to prove hybridity of F₁ tomato seeds. This genetic marker is indicative for hybrids with fertile maternal line or with position male sterility line and not only for maternal line with pollen male sterility.

Influence of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and two ethylene inhibitors, silver nitrate (AgNO₃) and cobalt chloride (CoCl₂), on direct somatic embryogenesis were tested in vitro using leaf cultures of Oncidium cv. Gower Ramsey. Leaf cells of tips, adaxial sides and cut ends could directly form somatic embryos on a hormone-free 1/2-strength MS medium. The frequency of embryo-producing explants was 55, 52.5 and 30 %, respectively. The embryo numbers per embryo-producing explant was 20.3. ACC at lower concentrations (5 and 10 μM) significantly retarded direct embryo formation from cut ends. However, higher concentrations of ACC (20 and 50 μM) significantly promoted embryogenic response of leaf tips and adaxial sides. All concentrations of AgNO₃ and CoCl₂ significantly retarded direct embryo formation. The best response was found on 20 μM of ACC, and the frequency of embryo-producing explants were 90, 85 and 35 % on leaf tips, adaxial sides and cut ends, respectively. The embryo numbers per embryo-producing explant was 32.2.