Secondary somatic embryos appeared on the cotyledons and radiculi of embryos derived from suspension and anther cultures of Aesculus hippocastanum L. The highest number of secondary somatic embryos formed on a hormone-free medium.

Seed protein profiles of 40 cultivated and wild taxa of Chenopodium have been compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The relative similarity between various taxa, estimated by Jaccard's similarity index and clustered in UPGMA dendrogram, is generally in accordance with taxonomic position, crossability relationships and other biochemical characters. Eight accessions of C. quinoa studied are clustered together and show genetic similarity with closely related C. bushianum and C. berlandieri subsp. nuttalliae. The taxa included under C. album complex are clustered in two groups which show that these taxa are a heterogenous assemblage and their taxonomic affinities need a reassessment. Other wild species studied are placed in the dendrogram more or less according to their taxonomic position.

Diurnal changes of sucrose-phosphate synthase (SPS) activity in different seasons were measured in Prosopis juliflora (Swartz) DC. leaves. SPS activity showed large variations with two distinct peaks, one around 09:00 and another at 21:00. The diurnal pattern was apparently not due to circadian rhythm since the activities were directly related to the changes in environmental parameters (irradiance, temperature, and leaf to air vapour pressure deficit) in different seasons. During the day, the enzyme showed changes in kinetic properties, differential sensitivity to allosteric modulators, differential response to ATP concentration, to concentration of endogenous sucrose, and to protein phosphatase inhibitors. These results taken together indicate the modulation of SPS in synchrony with photosynthesis and suggest the existence of multiple levels of modulation, presumably as an adaptive response to changing environmental extremes.

Oat (Avena sativa L.) plants cultured in soil and hydroponic culture were treated with cadmium [0.154 mg g^-1 (dry soil) and 100 μM CdSO₄, respectively] for 21 d and growth rate and various biochemical processes were studied. Applied cadmium reduced plant growth and chlorophyll content. Changes in activity of enzymes involved in C, N and S metabolism and in guaiacol peroxidase activity were observed. In particular, O-acetylserine sulphydrylase (OASS; EC 4.2.99.8) activity was increased by Cd exposure in both growth conditions, probably as a resistance mechanism to cadmium based on the production of phytochelatins. Results show that both field and hydroponic conditions represent suitable systems for investigating Cd effects on plant growth and metabolism.

Salix paraplesia was used as an experimental model to investigate the effect of short day photoperiod (SD) and low temperature (LT) on development of freezing tolerance and on endogenous abscisic acid (ABA) contents. We characterized differences in SD and LT-induced cold acclimation in three ecotypes from different altitudes. The results demonstrated that cold acclimation could be triggered by exposing the plants to SD or LT alone, and that a combination of the different treatments had an additive effect on freezing tolerance in all ecotypes studied. However, the high altitudinal ecotype was more responsive to SD and LT than the low altitudinal ecotype. Development of freezing tolerance induced by SD and LT was accompanied by changes in ABA contents which were ecotype-dependent. Although the stem had higher initial freezing tolerance, the leaves developed freezing tolerance more quickly than the stem and thus leaves may provide an interesting experimental system for physiological and molecular studies of cold acclimation in woody plants.

Chrysanthemum morifolium cv. Regol Time plants were found to be infected with Chrysanthemum B carlavirus (CVB). They were made CVB-free by using meristem tip culture, chemotherapy and thermotherapy. The plants were indexed by biological assay, double antibody sandwitch enzyme linked immunosorbent assay (DAS-ELISA) and reverse transcriptase polymerase chain reaction (RT-PCR). The maximum number of virus-free plants (26.7 %, as indexed by RT-PCR) was obtained with 2-thiouracil at 0.04 g dm^-3 concentration. Only 12 % plants were found to be virus-free, after being kept at 38 °C for 30 d. For indexing CVB in chrysanthemums, RT-PCR was found to be the most reliable method.

UV-B (0.4 W m^-2) irradiation and cadmium (2 and 8 μM) treatments separately inhibited the survival, growth, pigment content, and photosynthetic electron transport in Plectonema boryanum. Phycocyanin was the main target to UV-B and Cd and it was followed by chlorophyll a and carotenoids. UV-B and Cd caused strong inhibition on activities of photosystem 2 (PS2) and the whole electron transport chain, whereas photosystem 1 (PS1) was the least affected. UV-B and Cd treatment accelerated respiration, lipid peroxidation, and the activities of superoxide dismutase and catalase. However, enhancement in catalase activity was considerably less (5 - 50 %) as compared to SOD activity. As compared to individual treatment, the effect of their combination (UV-B + Cd) was more detrimental to the above parameters. A synergistic interaction of UV-B and Cd is probably due to increased cadmium uptake as a result of increased membrane permeability caused by lipid peroxidation in P. boryanum after UV-B exposure.

Tobacco plants infected with the potato virus Y (PVY) were studied during the acute-infection period. The control enzymes of metabolic pathway of host's RNA degradation tending to biosynthesis of PVY-RNA, its coarse/fine regulation and content of host's RNA were monitored. Activities of ribonucleases, phosphomonoesterases and phosphodiesterases in both the crude homogenates and the partially purified enzyme preparations from the diseased leaves were markedly increased when compared to the tissues from healthy plants. The curves of enzyme activities positively correlated with the multiplication curve of the PVY and negatively correlated with the decreased contents of host's RNA. The enzyme activity in homogenate samples did not significantly differ from the corresponding purified enzyme preparations.

In this report we describe the most suitable protocol for callus formation and plant regeneration for cotton. We screened 15 cotton (Gossypium hirsutum L.) genotypes for metal resistance and two of them, Nazilli M-503 (M503) Nazilli 143 (N-143) selected as Cd, Cu and Ni resistant. The cotyledonary nodes from these genotypes were the best explants for regeneration of shoots (more than 90 %) and roots (50 to 70 %). Shoot apex also gave good shoot regeneration (more than 90 %) but their root regeneration efficiency was low (35 %). These results show that Murashige and Skoog (MS) media containing 0.44 μM naphthaleneacetic acid (NAA) and 0.98 μM indole-3-butyric acid (IBA) was the most suitable recipe for getting high shoot and root regeneration from cotyledonary nodes of N-143 and M503 cotton genotypes.

The effect of acute ozone (O₃) fumigation on isozyme patterns of superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) in mature (ML) and young leaves (YL) of two poplar clones, contrasting in O₃-sensitivity was analysed. Untreated leaves of both the O₃-sensitive (O₃-S) clone Eridano of Populus deltoides×P. maximowiczii and the O₃-resistant (O₃-R) clone I-214 of P.×euramericana showed four distinct SOD isoforms with a relative mobility (R_f) of 0.54 (MnSOD), 0.60 (Cu/ZnSOD), 0.65 (unidentified), and 0.71 (Cu/ZnSOD). After O₃-fumigation the activity of the SOD isoforms showed only quantitative variations with respect to control plants. In ML of untreated O₃-R plants seven POD isoforms (R_f= 0.13, 0.19, 0.34, 0.59, 0.64, 0.70 and 0.75) were found, while in YL one isoform (R_f= 0.34) was undetected. Only three POD isoforms in both ML and YL of untreated O₃-S plants were resolved. The electrophoretic pattern of POD in O₃-S leaves was greatly modified by acute O₃-fumigation with the appearance of new isoforms in both YL and ML and the disappearance of an isoform (R_f= 0.13) in YL. Additionally, O₃-exposure induced the appearance of two APX isoforms in YL (R_f= 0.66 and 0.70), and one isoform in ML (R_f= 0.70) of the O₃-S clone. By contrast, the activity of the three APX isoformes (R_f= 0.64, 0.70 and 0.76) detected in O₃-R leaves showed only quantitative variation with respect to untreated plants. From these data it is concluded that: 1) in these poplar hybrids antioxidant enzyme activity is developmentally regulated and greatly affected by acute O₃ stress treatments and 2) the different enzymes activity displayed by the two poplar clones, especially for POD and APX isoformes, could partly explain their distinct O₃-sensitivity.

The hypocotyl and internodal segments from in vitro grown seedlings of Feronia limonia (L.) Swingle (wood apple) were cultivated on Murashige and Skoog's (1962, MS) medium supplemented with N⁶-benzyladenine (BA) or adenine (ADE) or kinetin (KN) at 0.5 to 5 µM. The optimum response was recorded on the medium containing 2 µM BA. An average of 12 and 8 shoots were developed from hypocotyl and internodal explants, respectively, after eight weeks of culture. The shoots were excised, and the residual explants were transferred to fresh medium where again they developed shoots. Up to three such passages resulted in the production of shoots from repeatedly subcultured explants and an average of 24 - 36 shoots per explant was obtained. The in vitro developed shoots produced roots when transferred to half strength MS medium supplemented with 1 µM 1-naphthaleneacetic acid (NAA). The developed plantlets were successfully transferred to mixture of soil, sand and coco-peat (1:1:1) and hardened in controlled environment. Hardened plants were transplanted to soil in greenhouse.

Organogenetic buds were induced from hypocotyl and cotyledon explants of oil crop Perilla frutescens in Murashige and Skoog (MS) medium supplemented with 5.7 μM indole-3-acetic acid (IAA) and 8.9 - 13.3 μM 6-benzylaminopurine (BA). Shoots were rooted on MS medium with 2.9 μM IAA and 1.4 μM gibberellic acid (GA3) and the regenerated plants flowered and set seeds normally.

Two sets of wheat (Triticum aestivum L.) substitution lines for the homoeologous group 5 chromosomes, 5A, 5B and 5D, carrying vernalization genes (Vrn-A1, Vrn-B1, Vrn-D1) were used to study the relationship between vernalization requirement and winter survival, with respect to the induction and maintenance of frost tolerance. Substitution lines carrying dominant Vrn loci substituted from the spring cultivars Zlatka (5A), Chinese Spring (5D) and the alternative cultivar Česká Přesívka (5B) into three different winter wheat backgrounds, Vala, Košútka and Zdar, showed lower winter survival by 20, 36, and 41 % for substitutions of 5B, 5A and 5D, respectively, compared to the original winter cultivars. Reciprocal substitution lines between two winter cultivars Mironovskaya 808 and Bezostaya 1 carrying different recessive alleles, vrn-A1, vrn-B1, vrn-D1, did not exhibit a modified induction of frost tolerance, but the duration of good frost tolerance, as well as the ability to survive the whole winter, was changed. In accordance with the model suggesting that genes for vernalization act as a master switch regulating the duration of frost tolerance, substitutions of homoeologous group 5 chromosomes induced, at first, frost tolerance at a level equal to the parental cultivar, and then, relative to the different extent of saturation of vernalization requirement, they gradually lost both frost tolerance and their ability to re-induce significant frost tolerance with a drop in temperature following warm periods in the winter.

The effects of treatment with NaCl (3, 100 and 300 mM) for 1, 2, 3 and 7 d on plant growth and ion accumulation were analyzed in 2-week and 8-week-old Annona muricata and A. squamosa plants. Fresh mass and root growth inhibition were directly related to the increase in salinity, particularly for A. squamosa. Two-weeks old seedlings were sensitive to 100 and 300 mM NaCl particularly after 7 d, whereas 8-week-old plants were shown to be more resistant to NaCl even at 300 mM NaCl. Na⁺ and Cl^- mostly accumulated in young leaves. Our results suggest that A. squamosa is more sensitive than A. muricata to salt stress and that older seedlings of both species are more tolerant than younger seedlings.

Thirty-day-old plants of two okra cultivars, Sabzpari and Chinese-red, were subjected for 30 d to normal watering or continuous flooding. Continuous flooding did not cause any adverse effect on shoot fresh and dry biomass. Leaf water potential and pressure potential of both cultivars increased significantly due to waterlogging, but there was a slight increase in leaf osmotic potential. Chlorophyll a and b contents decreased significantly and chlorophyll a/b ratio increased. Waterlogging caused a significant reduction in net photosynthetic rate, water use efficiency and intrinsic water use efficiency, but stomatal conductance and intercellular CO₂/ambient CO₂ ratio remained unchanged.

Microspore division was monitored in three triticale (× Triticosecale Wittmack) genotypes over 21 d of in vitro anther culture, on two media differing in their 2,4-dichlorophenoxyacetic acid content. After low temperature (4 °C) pre-treatment for two weeks, all the microspores were still alive, but they began to die from day one of culture. Both genotype and culture medium affected the number of microspores that aborted over time (82 - 97 % by day 21), the number of microspores that underwent the first symmetrical division (> 82 % over all), the number of microspores that attained four or more nuclei, and the number of divisions per 100 alive microspores after 21 d of culture.

The structure and development of Myrtus communis L. secretory cavities has been studied in young and expanded leaves, using light and scanning electron microscope. Secretory cavities are continuously formed during leaf development, but in mature leaves the rhythm of their appearance shows steep decrease. Each secretory cavity is developed from a single epidermal cell, which undergoes a periclinal division followed by anticlinal and several oblique cell divisions. The lumen of the secretory cavity is initiated by cell wall separation, i.e., schizogenously. The secretory cells line the cavity, where the secreted material is collected. Secretory cavities are covered by modified epidermal cells, which do not seem to form any special aperture. Essential oils seem to be discharged after mechanical treatment of the leaf.

The roles of glucose-6-phosphate dehydrogenase (G6PDH) in paclitaxel production were investigated in cell suspension cultures of Taxus chinensis. In the normal cultures, the trend of G6PDH activity was similar to that of cell growth. Addition of glutamate increased G6PDH activity, while dehydroepiandrosterone (DHEA) decreased G6PDH activity. In elicitor-treated cultures, cell growth was depressed, while G6PDH activity and taxol production were enhanced compared with the control. Glutamate recovered the depression of cell growth, and resulted in further increase in G6PDH activity and taxol production. Contrarily, DHEA exacerbated the depression of cell growth, and decreased G6PDH activity and taxol production induced by fungal elicítor. The results indicated that G6PDH played a critic role of taxol production by affecting cell viability.

In vitro propagation protocol for Haemaria discolor (Ker) Lindl. var. dawsoniana by artificial cross-pollination and asymbiotic germination of seeds has been developed. Fruit set (100 %) was obtained when the pollinia and ovules of various aged flowers were used for pollination. In vitro germination of seeds obtained from capsules of various ages was achieved on half-strength Murashige and Skoog's (MS) medium supplemented with 3 % sucrose and 0.85 % agar. The germinated seedlings were cultured on half-strength MS medium with 0.2 % activated charcoal, 8 % banana homogenate, 0.1 mg dm^-3 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea (TDZ) and 1 mg dm^-3 α-naphthaleneacetic acid (NAA). Ninety-six percent of plantlets survived after hardening in greenhouse.

Axillary buds from adult field-grown plants of Lavandula dentata L. were used to evaluate the effect of growth regulators and culture media on the in vitro shoot proliferation and growth. The highest multiplication rate was obtained using Murashige and Skoog (MS) medium supplemented with a combination of 2.2 μM of benzyladenine and 2.5 μM indole-3-butyric acid. The best condition for rooting was MS medium plus 2.5 μM naphthaleneacetic acid. Rooted plantlets were successfully transferred to soil. Short-term culture derived plants (6 month) exhibited a normal development, but a low frequency of not heritable morphological changes were detected in long term culture derived plants (more than 1 year).

Using 2-D electrophoresis, we analyzed proteins from transgenic rice overexpressing gibberellin acid (GA) catabolic enzyme, GA2-oxidase. These results indicate eight specific proteins differentially expressed in the transformed rice stems of T₁ generation, but non in case of T₂ generation. Proteins isolated from different stages of leaves of T₁ generation showed no significant differences, except one-month-old leaf, where five differentially expressed proteins are visible.

Somatic embryogenesis of European chestnut (Castanea sativa Mill.) was obtained using juvenile tissue cultured on P24 medium with 5 μM 2,4-dichlorophenoxyacetic acid plus 0.5 μM 6-benzylaminopurine (BA) for three weeks and then cultured on 0.89 μM BA. Induction frequency with ovaries ranged from 2.0 to 19.1 % and was observed in tissue collected 2 to 8 weeks postanthesis, ovules used as a starting tissue gained 0.8 to 7.8 %, 3 to 9 weeks postanthesis. Zygotic embryos collected 5 to 10 weeks postanthesis formed 10.5 to 57.1 % somatic embryos, respectively. The culture lines were maintained via secondary embryogenesis on P24 medium with 0.89 μM BA. Development and maturation were stimulated on P24 medium with increased agar concentration (1.1 %). Five plantlets were transferred to substrate and acclimatized successfully in greenhouse.