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.

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.

The copy number of genes encoding 5S ribosomal RNA has been found to be constant in Petunia hybrida plants regenerated from protoplast and leaf disc-derived callus cultures. However, in one somaclone a heritable change in the length of the major 5S rDNA repeat has arisen. Despite the constant copy number of 5S rRNA genes, that of the 18S-25S rRNA genes is found to very by at least ten-fold. The relevance of these findings to ribosomal RNA gene variability and to somaclonal variation is discussed.

The activity of acetylcholinesterase (AChE) isolated from coleoptiles of etiolated oat seedlings is strongly inhibited by neostigmine and less so by eserine. The optimum of the enzyme activity occurs at pH 7.2 and a temperature of + 36 °C. The enzyme Michaelis constant is 280 μM. Choline within the range of concentration from 0.001 to 10 mM does not affect the enzyme activity. Calcium ions at 5 mM concentration cause inhibition, while magnesium and manganese ions do not affect the enzyme activity.
AChE isolated from oat seedlings differs in a number of properties from AChE occurring in the tissues of other plants.

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.

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.

The stomatal density on abaxial epidermis of the second wheat(Triticum aestivum L.) leaf increased step by step from the leaf base to its tip. On adaxial epidermis, this increasing tendency was generally maintained, but close to both the base and the apex two maxima were determined. In the direction perpendicular to leaf length, maximum stomatal density was close to the edges, and minimum one was in the central part of the leaf blade.

The effect of NaCl at sublethal concentration was observed on germinating seeds of salt-sensitive and -resistant rice cultivars with respect to the level of proline regulatory enzymes and the growth of seedlings on different days of early germination period. The two enzymes of proline biosynthesis and catabolism, Δ-pyrroline-5-carboxylate reductase and L-proline dehydrogenase, were taken into consideration to observe the effects of 100 mM NaCl on their activities in both rice cultivars. The activity of Δ-pyrroline-5-carboxylate reductase in salt-resistant cultivar was increased twice after 5 d in 100 mM NaCl. Simultaneously, the activity of L-proline dehydrogenase was decreased significantly. High activities of Δ-pyrroline-5-carboxylate reductase may be regarded as a biological marker for screening the sensitive and resistant cultivars of rice seed under NaCl-salinity.

A comparative study of the isoenzyme patterns of esterase and peroxidase and overall peroxidase activity in stamens of male-sterile (MS) lines of Pearson ms-35 and P ms-35aa and of the respective male-fertile (MF) tomato plants have been conducted. The study has been made at two stages of stamens development - tetrad and pollen. Higher activities of the esterase isoenzymes in the MF stamens than that of MS in both ontogeny stages have been found. The slow moving esterase isoenzymes both of the MF and the MS stamens are the major isoenzymes in the early stage and are connected with tapetum development while the fast moving esterase isoenzymes are connected with pollen formation in the later ontogeny stage. Overall peroxidase levels in the MS stamens were higher than those of MF. The peroxidase patterns of the MS lines are also characterized by the greater number of isoenzymes and also the presence of specific isoenzymes, the contrast between the MF and the MS stamens being more strongly expressed at the later stage of development. A strong similitude between esterase and peroxidase patterns behaviour in both MS lines has been found.