Glutamate dehydrogenase (GDH) activity, protein and total nitrogen contents in the secondary leaves of maize(Zea mays L. cv. Ganga Safed-2) seedlings increased during early seedling growth and then declined after reaching a peak level at either 10 d (GDH) or 12 d (metabolites). While the effect of kinetin on enzyme activity was statistically insignificant, benzyladenine supplied with nutrient solution increased GDH activity in secondary leaves of both 10-d as well as 14-d seedlings. However, both growth regulators increased the contents of total soluble proteins, total nitrogen, chlorophyll(a+b) and carotenoids in both 10 and 14-d old leaves.

Plasmalemma-enriched fractions were isolated from Jerusalem artichoke tubers along the time course of dormancy break produced by cold treatment. A decrease of membrane fluidity was noted from the 3^rd to the 8^th week of this treatment, as well as a decrease of plasmalemma NADH dehydrogenase activity from the 5^th to the 8^th week. The plasmalemma lipid extracts studied revealed two major phospholipidic components: phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Their respective quantities decreased until the 12^th week, where the phosphatidylcholine level is lower than the phosphatidylethanolamine one. The observed changes are discused in relation to dormant and non-dormant states of tubers and the breaking of dormancy.

The efficiency of turnip mosaic virus (TuMV) acqusition fromSinapis alba L. without sinigrin andBrassica nigra (L.) Koch with a high content of sinigrin by non-fastedMyzus persicae (Sulz.) andBrevicoryne brassicae (L.) was investigated in order to determine the effect of the phagostimulatory glucoside sinigrin on virus transmission. There was a significantly higher acquisition of TuMV fromS. alba byM. persicae than fromB. nigra. Conversely,B. brassicae acquired the virus more efficiently fromB. nigra than fromS. alba. The efficiency of transmission was positively correlated with the response of both aphid species to sinigrin. Saturation ofS. alba leaves with a 1 % solution of sinigrin did not significantly affect the acquisition of TuMV, in neitherM. persicae norB. brassicae, whether the aphids were fasted or not.

The influence of the mineral composition and acidity of media, saccharose level, brand and quantity of agar onin vitro shoot rooting of P 60 and P 2 apple and quince S 1 root-stocks were compared. Among the tested salt compositions (full WMP and 1/2 WMP, full MS and 1/2 MS) the most suitable for rooting was composition of WMP. Further modifications in quantity of nitrogen, H₃BO₃ CaCl₂ and MgSO₄ of WMP medium did not have a positive effect on rooting. 30 g l^-1 saccharose gave better results than 20 g l^-1. Acidity of WMP medium tested in a pH range of 4.0 to 6.5 did not affect rooting of P 60 rootstock but media adjusted to pH 4.5 and 5.0 were better for rooting of recalcitrant P 2 rootstock. Among 4 agar brands (Difco Bacto, Oxoid No.1, Japanese commercial fibre and Japanese commercial powder) tested at 6 g l^-1, the most effective was the last one, but its quantity had no effect in the range of 3 to 10 g l^-1 for rooting of P 60 rootstock.

Cytological and cytophotometric analysis of root tips of regenerated plants, derived from rhizome expiant ofKniphofia nelsonii andKniphofia uvaria, revealed marked difference in behaviour of chromosomes and level of 4C nuclear DNA content. Karyotypic stability could be retained in all 52 regenerants of K. nelsonii whereas inK. uvaria out of 75 regenerants analysed, 12 plants were exclusively diploid and the rest 63 plants were predominantly diploid comprising variable amount of aneuploid and tetraploid cells. Cytological data was further confirmed by nuclear DNA content estimation. Alteration in the structure of chromosomes could also be noted in 57 regenerants ofK. uvaria giving rise to two new karyotypes. The use of polysomatic tissue for securing variantsin vitro inK. uvaria has been suggested.

Diurnal variations in endogenous IAA levels inFatsia japonica leaves, maintaining constant other external factors such as temperature and relative humidity, were studied. Plants were cultivated in a growth chamber (20 °C, 75 % RH, 16 h photoperiod, 400 µmol m^-2 s^-1 PAR). IAA analyses were carried out by analytical IP-HPLC with on-line spectrofluorimetry. Rhythmic variation of endogenous IAA levels was found. At the onset of the light period the IAA concentration dropped very rapidly from 1070 pmol g^-1 (fr.m.) to 144 pmol g^-1 (fr.m.). This concentration was nearly constant throughout the entire light period. During the subsequent dark period the IAA levels increased again to about 1000 pmol g^-1 (fr.m.) at the end of the dark phase. These results were not confirmed in open field conditions where many other external factors probably influence the endogenous IAA content.

Exogenously supplied cadmium and nickel considerably affected the ethylene biosynthesis in soybean cuttings. Cadmium stimulated ethylene production by increasing production of free ACC and stimulating EFE activity. Nickel inhibited ethylene production by depressing EFE activity, but stimulated the production of free ACC. Both heavy metals did not apparently affect cell membrane integrity.

Somatic embryogenesis was induced in immature zygotic embryos of pea (Pisum sativum L.), synthetic auxins α-naphthalene acetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram, PIC) being used. Only one (line HM-6) of 46 genotypes tested exhibited good potential for somatic embryogenesis. 2,4-D was found as the best somatic embryo inductor. Three different ways of somatic embryo conversion have been described. Plantlets from individual somatic embryos were micropropagated as somaclones and subsequently rooted. A sterile morphological mutant has been found within a group of fertile plants of T₀-generation. Sufficient amount of T₁-seeds is available for somaclonal variation studies.

Nitrate content in lucerne stems and leaf blades immersed by cut ends in distilled water or in KNO₃ solution increased with the increase in KNO₃ concentration and with the duration of exposure under irradiance of 100 or 230 W m^-2 PAR. The nitrate content increased from basal stem parts to apical stem parts and leaves. Nitrate was transported mainly with transpiration stream. Some flow variations occurred in stems causing time changes in nitrate content in different parts of stems.

Sunflower (Helianthus annus L. cv. PSH-7) plants were subjected to different osmotic potentials, using polyethylene glycol-6000 (PEG-6000), after, prior to and during SO₂ fumigation. Total soluble proteins and nitrate reductase activity (NRA) decreased, and free proline content increased with the increasing water stress. These biochemical parameters were more adversely affected in fumigated plants than in non-fumigated ones, when mild water stress was provided prior to and during fumigation. When severe water stress was given prior to and during fumigation, total soluble proteins, NRA and free proline content were nearly the same in fumigated and non-fumigated water-stressed plants; it is because the stomatal closure was observed in water-stressed plants. The leaf water potential decreased with the increasing water stress; however, it was not significantly affected due to SO₂ fumigation.

The effect of different phenolic compounds:p-hydroxybenzoic acid, resorcinol and chlorogenic acid (mono-, di- and polyphenol) was studied on nodulation and related metabolic processes in pigeonpea (Cajanus cajan L. cv. Al-15). Nitrogenease activity, leghaemoglobin and ascorbic acid content of the nodules increased with the application of phenols. Phenols increase the contents of amino acids, proteins and total soluble carbohydrates in the nodules as reserve food materials.

The properties of a virus causing walnut ringspot ofJuglans regia L. which had been identified by the visual examination of symptoms on leaves and fruits of walnut trees in Slovakia were studied. The virus was transmitted mechanically toChenopodium quinoa Willd.,Chenopodium amaranticolor Coste et Reyn.,Nicotiana clevelandii Gray,Phaseolus vulgaris L. cv. Bountiful. Purified virus was used for antiserum production. The thermal inactivation point of the virus lies between 48 and 50 °C and the dilution end-point between 10^-1 and 10^-2. The obtained antiserum had a titer 1:256. Virus isolates gave a positive immunological reaction with the Mircetich's antiserum against the cherry leaf roll virus obtained from walnut tree.

The effect of kinetin (10 g m^-3) presowing seed soaking treatment on water relations, chlorophyll (Chl) and nucleic acid contents, and photosynthetic and respiration rates in wheat (Triticum aestivum L.) grown in a greenhouse under three salinity levels (i.e. 0,6 and 9 dS m^-1 ECe) was studied. Relative water content and osmotic potential showed a progressive decline with increase in the salinity but there was an increase in chlorophyll (a+b) content in the leaves. Salinity decreased RNA content and net photosynthetic and respiration rates. Seed soaking either in water or kinetin enhanced the relative water content of leaves but reduced osmotic potential under both saline and non-saline conditions.

The partitioning of¹⁴C-assimilates was studied in pigeonpea(Cajanus cajan L.) at vegetative and flowering stages (40 and 70 d after sowing, respectively) exposed to moderate and severe drought induced by withholding the irrigation. At vegetative stage, the ethanol soluble fraction in shoot decreased from 99 to 43.16 % between 0 and 120 h, whereas in underground part it increased from 1% to 56.84 % with maximum amount in nodules (35.51 %). Similar trend was observed in ethanol insoluble fraction. At moderate drought, a significant increase in soluble fraction (11.31 %) in nodules was observed. Stem showed significant reduction of assimilates (13.09 %). After flowering, the assimilates produced in leaves were exported to reproductive parts, especially under drought. In plants recovering from severe drought, 14C in soluble and insoluble fractions in reproductive parts was reduced to 85 % and 43 %, respectively, whereas leaf and nodules showed a significant increase. Thus the assimilate partitioning to different plant parts was dependent on growth stage and affected by drought.

A simple and rapid method for the estimation of the proportion of diploid and tetraploid perennial ryegrass in a mixed sward is described, based on the measurement of the nuclear DNA content of the leaf tissue cells by flow cytometry. The error of estimation was less than 5 %.

During the germination, wheat and sorghum plants tolerated salinity up to 10 mM NaCl. Seedling growth and dry matter production remained more or less unchanged up to 10 mM NaCl in case of wheat and up to 5 mM NaCl in case of sorghum. The water content of test plant species exhibited nearly constant values irrespective of the salinity level applied. The proline and carbohydrate content increased with elevating NaCl, while free amino acids content decreased. Irrigating of seedlings with tryptophan had non significant effect at all salinity levels used.

Possibilities of adventitious buds induction on the cotyledons obtained from sterile seedlings ofAbies concolor xAbies grandis hybrid were investigated. The following variables influencing bud induction and their further development were studied: the effect of expiant age, the effect of different growth regulators and their concentrations and duration of their application. The most suitable expiants proved to be the cotyledons of 7 d old seedlings. The most efficient cytokinin was benzylaminopurine (S mg l^-1) in combination with napthaleneacetic acid (0.01 mg l^-1). The most optimal duration of treatment was 17 to 21 d culture of explants on induction medium. Shoot growth was achieved on basal medium to which 14 mg 1^-1 spermidine was added.

Changes in the phenylalanine ammonia-lyase (PAL) activity, accumulation of phenolic acids and ionically-bound peroxidase activity in thein vitro selected embryogenic and nonembryogenicMedicago sativa callus cultures resistant to the filtrate ofFusarium spp. were found. The PAL activity in bothin vitro selected cultures during a 4-week cultivation on a medium with phytotoxins was higher than in the control calli grown on a medium without toxin. The filtrate fromFusarium spp. evoked an increase in the contents of all determined phenolic acids in the selected calli. They occurred predominantly bound as esters. The most pronounced portions in the elevated acids level were of ester-bound p-hydroxybenzoic, vanillic, p-coumaric and ferulic acids. The ionic cell wall-bound peroxidase activity in both selected calli cultivated on a medium with a filtrate was twice as high as the activity determined in the control cultures. The activity of soluble peroxidase was not influenced by challenge with a filtrate. No significant differences were found between thein vitro selected embryogenic and nonembryogenic alfalfa callus cultures in the response to the phytotoxic filtrate.

One-month-old plants of two chickpea (Cicer arietinum L.) cultivars were exposed to salinity of 4 and 8 dS m ^-1 in pots in a greenhouse. The cultivar BG 312 performed better than Pusa 209 in terms of visible injury and dry mass accumulation. Tissue water content of the various plant organs was affected differently by salinity. Expression of Na⁺ and Cl ^- concentrations on a dry mass basis indicated retention of Na⁺ and Cl ^- by roots, thereby keeping the leaves free of ion accumulation, but their expression on a tissue water basis did not indicate Cl ^- retention and showed less Na ^- exclusion. Changes in the apparent exclusion mechanisms resulted from a higher water content in the roots than in the shoots. On a dry mass basis, roots appeared to retain K⁺, but on a tissue water basis stems appeared to act as a reservoir of K⁺; leaves and nodules received K⁺ preferentially. The exclusion mechanisms and their efficiency differ with cultivar and salinity. The expression of ion concentrations on a tissue water basis appears to be more useful then on a dry mass basis in studies of salinity tolerance.