The possibility to improve the recovery of sugar beet plants after water stress by application of synthetic cytokinins N⁶-benzyladenine (BA) or N⁶-(m-hydroxybenzyl)adenosine (HBA) was tested. Relative water content (RWC), net photosynthetic rate (P_N), transpiration rate (E), stomatal conductance (g_s), chlorophyll (Chl) a and Chl b contents, and photosystem 2 efficiency characterized by variable to maximal fluorescence ratio (F_v/F_m) were measured in control plants, in water-stressed plants, and after rehydration (4, 8, 24, and 48 h). Water stress markedly decreased parameters of gas exchange, but they started to recover soon after irrigation. Application of BA or HBA to the substrate or sprayed on leaves only slightly stimulated recovery of P_N, E, and g_s in rehydrated plants, especially during the first phases of recovery. Chl contents decreased only under severe water stress and F_v/F_m ratio was not significantly affected by water stress applied. Positive effects of BA or HBA application on Chl content and F_v/F_m ratio were mostly not observed.

Contents of various organic and inorganic osmotica in the leaves, shoots and roots of Zostera marina L. were determined and their contributions to the osmotic adjustment to seawater were calculated. The inorganic ions, especially Na⁺, were the main osmotica. X-ray microanalysis indicated that vacuoles in the parenchymatous cells are the main sites in leaves accumulating toxic ions.

Embryogenic cultures of chir pine (Pinus roxburghii Sarg.) were cryopreserved successfully in liquid nitrogen. It was found that using sorbitol and dimethyl sulfoxide (DMSO) as cryoprotectants was essential for the survival of the tissue. Among the different concentrations of the cryoprotectants used, the most effective treatment was observed to be 0.3 M sorbitol and 5 % DMSO. On staining the cryopreserved tissue with fluorescein diacetate, it was observed that only a few meristematic embryo heads survived and resumed growth after a very short initial lag phase. The recovered cultures showed normal regrowth on proliferation medium and, it was also observed that washing off the cryoprotectants was necessary for the cultures to survive. The results indicate that cryopreservation can be used for conserving the germplasm, and in maintaining the embryogenic capacity of the tissue.

Micropropagated plants of two annual haloxerophytic Asiatic Salsola species (S. pestifer and S. lanata) were obtained from zygotic embryos cultured on Murashige and Skoog (MS) agar medium supplemented with 0.5 µM benzylamino-purine (BAP) and 0.3 µM indole-3-acetic acid (IAA) or with 0.5 µM 6 γ, γ-dimethylallylaminopurine and 0.3 μM IAA. The callus induction from shoot and leaf explants derived from plants propagated in vitro were obtained on MS agar medium with various concentration of auxins and cytokinins. The best medium for growth and proliferation of calluses of both studied species was MS medium containing 9.0 µM 2,4-dichlorophenoxyacetic acid. It was also determined that beginning of plant regeneration from callus of S. lanata was induced by 8.8 µM BAP.

Simple, fast and cost-effective method for preparation of DNA with high molecular weight (HMW DNA) from plant nuclei and mitotic chromosomes has been developed. The technique involves mechanical homogenization of formaldehyde-fixed root tips, purification of nuclei and/or chromosomes on sucrose gradient, embedding in low-melting-point agarose, and DNA isolation in agarose plugs. Alternatively, nuclei and chromosomes may be purified using flow cytometry. Majority of DNA obtained is megabase-sized and well digestible by restriction endonucleases. The method is highly efficient as microgram amounts of DNA can be obtained from only several milligrams of plant tissue. Handling negligible amounts of plant material reduces the consumption of chemicals. Furthermore, the use of root tips makes it possible to obtain high-quality DNA even from plant species with leaves that are rigid or rich in secondary metabolites such as polyphenols. It is expected that preparation of HMW DNA from root tip nuclei will facilitate long-range mapping and construction of large-insert DNA libraries also in these species. Successful isolation of HMW DNA from flow-sorted chromosomes opens a way for construction of chromosome-specific large-insert libraries in plants.

The protection compound benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) was applied to soybean roots or leaves in a dose of 20 cm³ of a solution containing 25 μg g^-1 of the active ingredient. Electrophoretic profiles of chitinase and superoxide dismutase were not altered by the product. Increased activity of two root anionic peroxidases and three differential isoforms of these enzymes were observed in plants with roots treated by BTH, which can be used as biochemical markers of the BTH effect.

Non-vernalized scions were grafted onto vernalized stocks in winter rape (Brassica napus L. var. oleifera, cv. Górczański). The grafted plants were subjected to electric current (30 V for 30 s or 6 V for 24 h) and the percentage of flowering scions was recorded. The negative polarity with cathode (-) attached to the scion and anode (+) left close to the roots inhibited greatly the percentage of flowering. The reverse polarity enhanced flowering markedly under short days and only slightly promoted flowering under long days. Attachment of electrodes without passing a current had no effect on flowering.

Role of superoxide dismutase isozymes and other antioxidant enzymes was studied in relation to leaf age in sunflower (Helianthus annuus L. cv. ACC 1508) at pre-flowering and grain filling stages. Relative water content (RWC) did not change much in leaves of different age and at the two stages. Protein content declined continuously from the youngest to the oldest leaf, while chlorophyll (Chl) and carotenoids (Car) contents increased down to 7^th/9^th leaf and declined in subsequent older leaves. Protein, Chl and Car contents were higher at pre-flowering than at seed filling stage. Superoxide dismutase (SOD), its isozymes, and ascorbate peroxidase (APO) and catalase (CAT) activities were highest in the 9^th leaf and declined in subsequent older leaves. SOD and APO activities were higher at seed filling, except in oldest senescent (13^th, 15^th) leaves. Among SOD isozymes, Cu/Zn-SOD and Mn-SOD activities accounted for most of the total SOD, and only marginal activity was observed for Fe-SOD. Peroxidase activity increased from youngest to the oldest leaf at pre-flowering stage and down to 13^th leaf at seed filling stage.

The effect of different radiation sources - blue (B), red (R), R plus B (RB), B plus far red (BFr), R plus far red (RFr) - was tested on the growth of hairy roots and betalain accumulation in Beta vulgaris L. (red beet). Light emitting diodes were used as radiation sources. The growth of hairy roots under different radiation treatments depended on radiation quality. Highest biomass accumulation was under the BFr treatment. BFr treatment efficiently induced betalain pigmentation in hairy roots. Total sugar and sucrose contents of hairy roots were also greater in this treatment. Thus, the betalain pigmentation in the cultured hairy roots can be influenced by radiation quality and BFr is most suitable for accumulation of betalains.

Mature and immature cotyledon explants of cowpea were cultured on Murashige and Skoog's (MS) medium supplemented with 0.1 - 2.0 mg dm^-3 benzyladenine (BA). Shoot organogenesis was observed from the minimal greenish calli formed at proximal cutting edges of the immature cotyledon explants after 15 - 20 d of culture. Among whole immature zygotic embryo and seven explant types we tested, single whole cotyledon was suitable for shoot organogenesis. Nearly 67.5 % of the explant types produced adventitious shoots on MS medium containing with 1 mg dm^-3 BA, and the shoot number (10.1) per explant was higher than other explant types. From the histological studies, the shoot primordia originated from the procambial strands of immature cotyledon explants. When the shoots were transferred to 1/2 MS basal medium, formed roots within 20 d of culture. The rooted plants were subsequently transferred to the pots and to the field.

Salix alba L. and Populus×euroamericana cv. Robusta cuttings were grown in 10 μM Cd(NO₃)₂ (direct treatment) or in Knop solution and afterwards in Cd(NO₃)₂ (indirect treatment). Cd impact on rooting of directly treated plants and its impact on normally formed roots and shoots of indirectly treated plants were studied. The cumulative length, number and biomass of willow roots, pigment and starch contents, leaf net photosynthetic rate and dry mass/leaf area ratio of willow leaves were positively influenced by indirect treatment. However, indirectly treated poplars were more sensitive to Cd than directly treated ones. Indirect treatment lowered root Cd uptake in willow, Cd accumulation in cuttings of both species and Cd accumulation in poplar shoots. Cd-caused structural changes were similar in both species and in both treatments. Root apices, rhizodermis and cortex were the most seriously damaged root parts. In directly treated willow, the structure of central cylinder (0.5 - 1 cm from apex) remained unchanged in contrast to indirectly treated plants. Formation of cambium close to the apex indicated shortening of root elongation zone of indirectly treated plants. Directly Cd-treated poplar roots exhibited unusual defence activity of root apical meristem and accumulation of darkly stained material around central cylinder.

The present paper tests the hypothesis, that a periodic fluctuation of mitotic activity of the embryonal tissue of the Norway spruce (Picea abies (L.) Karst.) is synchronnous with synodic lunar cycling. The increased mitotic index (MI) was observed under full moon, and the decreased MI around the first and third quarter.

Two wheat (Triticum aestivum L.) genotypes differing in their sensitivity to water deficit (stress tolerant - C306 and stress susceptible - HD2329) were subjected to osmotic stress for 7 d using polyethylene glycol (PEG-6000; osmotic potential -1.0 MPa), at initial vegetative growth. The plants were either supplemented with 1 mM CaCl₂ (Ca²⁺) alone or along with verapamil (VP; calcium channel blocker) to investigate the involvement of calcium in governing osmoregulation. Relative elongation rate (RER), dry matter (DM) production, water potential (Ψ_w), electrolyte leakage (EL), contents of proline (Pro) and glycine betaine (GB) and activities of γ-glutamyl kinase (GK) and proline oxidase (PO) in shoots and roots were examined during stress period. C306 showed relatively higher accumulation of Pro while HD2329 accumulated more GB under stress. RER, DM and Ψ_w were relatively higher in C306 than HD2329. Roots compared to shoots showed lower content of osmolytes but had faster rate of their accumulation. Presence of Ca²⁺ in the medium increased the activity of GK and decreased that of PO while in the presence of its inhibitor, decrease in activity of both the enzymes was observed. Ca²⁺ appeared to reduce the damaging effect of stress by elevating the content of Pro and GB, improving the water status and growth of seedlings and minimizing the injury to membranes. The protective effect of Ca²⁺ was observed to be more in HD2329 than C306.

Stable transformation and expression of transgenes was achieved in Centaurium erythraea Gillib. using Agrobacterium rhizogenes-mediated system. Five hairy root clones exhibited the transformed phenotype. Shoot regeneration, with green organized structures, was apparent in 4 clones, after the first subculture on Murashige and Skoog (MS) half strength medium. The integration of Ri-plasmid T-DNA was confirmed by polymerase chain reaction (PCR) analyses.

Nitrite, as well as the nitric oxide (NO) donor S-nitroso-N-acethylpenisilamine (SNAP), was found to increase the aperture of stoma on Vicia faba leaf peels. The results demonstrated here suggest that the nitrite-dependent NO production pathway would be involved in the signal transduction for stomatal movements.

Proline accumulation and mobilization in roots of 7-d-old seedlings of wheat genotypes varying in sensitivity towards water stress were compared. Water stress was induced by polyethylene glycol (PEG-6000; osmotic potential -1.5 MPa) in the presence of 0.1 mM abscisic acid (ABA), 1 mM calcium chloride, 0.5 mM verapamil (Ca²⁺ channel blocker), 0.5 mM fluridone (inhibitor of ABA biosynthesis). While both the genotypes did not differ in total proline accumulation, rate of proline accumulation and utilization was higher in tolerant genotype C 306 as compared to susceptible genotype HD 2380. The treatment with ABA and CaCl₂ caused further increase in proline accumulation during stress and reduced its mobilization during recovery. The membrane stability and elongation rate of roots was observed to be higher at ABA and calcium treatment in both the genotypes under stress. As was evident from inhibitor studies, the tolerant genotype was more responsive to ABA and the susceptible one to calcium.

Hexaploid triticale introgressive lines developed after recombination of A-genome with A^m-genome of diploid wheat (Triticum monococcum) were analysed in respect of grains responsiveness to exogenous ABA treatment. This was assessed by in vivo bioassay as grain germination indices, and by α-amylase assay as quantity of synthesised α-amylase measured with the technique of radial diffusion in agarose gel. The results showed an important diminishing of seedling length caused by ABA (variable in different lines) as well as genotype dependant variability of α-amylase synthesis inhibition. The differences of ABA responsiveness were seen both in whole grains and in embryoless half-grains as a direct reaction of the aleurone layer. Variation of grain sensitivity to ABA treatment compared with two sprouting resistance indices showed a significant correlation with Falling Number values in grains, but not with a dormant grains germination in spikes. This is an evidence that in triticale precocious starch decompose in unripened and ungerminated grains is dependent on genotype ABA-responsiveness of the aleurone layer.

The induction of secondary somatic embryogenesis in Abies numidica De Lann. was achieved. Precotyledonary, cotyledonary, and desiccated cotyledonary embryos were used as explants. Cotyledonary embryos before desiccation were the most suitable. The most beneficial was induction medium Schenk and Hildebrandt (SH) with 1 mg dm^-3 thidiazuron and 1000 mg dm^-3 myo-inositol. Initiation frequency was from 1 to 34 %. Maturation of somatic embryos was achieved on modified Murashige and Skoog medium supplemented with 40 g dm^-3 maltose, 100 g dm^-3 polyethylene glycol-4000 and 10 mg dm^-3 abscisic acid. Mature somatic embryos after three weeks of desiccation germinated on SH medium with 10 g dm^-3 charcoal and 10 g dm^-3 sucrose.

Contents of soluble proteins, proline and chlorophyll in winter wheat (Triticum aestivum cv. Doğu-88) and cabbage leaves (Brassica oleracea convar. acephala) during acclimation to low temperature were investigated. When both of the plants species were cold acclimated, soluble proteins, proline and chlorophyll contents were higher than in the controls (non-acclimated). Also protein patterns differed between the plants at control and cold conditions.

An efficient technique for isolation of resistant gene analogs (RGAs) in pepper from silver stained denaturing polyacrylamide gel was developed using a modified amplified fragment length polymorphism (AFLP) strategy. Pepper DNA was digested, ligated and pre-amplified as in a normal AFLP method. The selective amplification was made by using combinations with oligonucleotide primers based on conserved motifs in and around nucleotide binding site (NBS) of known NBS-leucine-rich repeats resistance proteins from known resistant genes. The amplified products were separated by using denaturing polyacrylamide gels and silver staining instead of radioactive labelling. We isolated specific polymorphic AFLP bands directly from the gels with one round of polymerase chain reaction amplification, in order to confirm, after sequencing, that these bands have homologies with products of resistance genes described so far. Two bands (R2: 250 bp and R6: 150 bp) are particularly highlighted because they could be considered as RGAs related to resistance to Phytophthora capsici in pepper, because their sequences have a very high homology with other resistant gene analogs that have already been described. Besides, they were only detected in the resistant parent and in the bulked resistant segregants but not in the susceptible parent or susceptible F₂ segregants. We can conclude that the technique used is clean, quick and efficient for the isolation of RGAs in pepper.

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.