The specificity of IAA-binding site from the wheat shoots was investigated in an attempt to confirm its receptor function. Several monofluoro-, monochloro-, dichloro- and monobromo-substituted indol-3-ylacetic acids were allowed to displace¹⁴C-IAA from the binding site. Displacement abilities of these halogenated IAAs were closely related to there activities in wheat coleoptile straight growth biotest. This finding indirectly confirms thephysiological significance of this binding site.

Agrobacterium tumefaciens binary vectors carrying kanamycin resistance gene and either C58 T-DNA gene 4 for cytokinin synthesis or genes 1 and 2 for auxin synthesis were constructed and used for transformation of a short-day tobacco Maryland Mammoth. Kanamycin resistant plants were regenerated from a small fraction of transformed tissue and the presence of T-DNA in their genome was verified by Southern blotting. The level of endogenous cytokinin in plants transgenic for gene 4 and the level of endogenous IAA in those transgenic for genes 1 and 2 increased by more than 100 %. A number of morphological characteristics distinguish them from untransformed controls.

Four Yugoslav cultivars of alfalfa were investigated in order to determine nitrogen fixing (nitrogenase), nitrogen assimilation (nitrate reductase, glutamine synthetase, glutamate dehydrogenase) and antioxidant (Superoxide dismutase, catalase, peroxidase) enzymes activities. The level of lipid peroxidation and protein content were also investigated. On the basis of the results obtained a resistant cultivar with high nitrogen fixing and a cultivar with high nitrogen assimilation abilities were chosen. The cultivar with high nitrogen fixing ability had high activities of nitrogenase, Superoxide dismutase, peroxidase and catalase, and also a low level of lipid peroxidation. The cultivar with high assimilation ability had high activities of nitrate reductase, glutamine synthetase and glutamate dehydrogenase and high soluble protein content.

Thein vitro activity of glutamate dehydrogenase (NADH-GDH), from dark-treated root segments of maize seedlings responded differently to amino acids threonine, glutamate and methionine than that from light-treated root segments, and to the amino acid methionine in dark- and light-treated shoot segments. In most cases amino acids inhibited GDH activity, the inhibition increased with amino acid concentration. However, methionine activated GDH from dark-treated roots and light-treated shoots, while aspartate had little effect on enzyme activity.

Phosphatidylinositol 4,5-bisphosphate specific phospholipase C has been detected in a membrane preparation fromPharbitis nil cotyledons. The enzyme has a pH optimum of 6.8 and activated by calcium ions, deoxycholate, phosphatidylinositol and phosphatidylethanolamine. The enzyme is inhibited to varying degrees by Tween 20, Triton XI00, zinc, copper, cobalt and manganese ions and phosphatidylserine. G-protein activators do not affect the activity ofPharbitis nil phospholipase C. Analysis of the products of the reaction by HPLC shows inositol 1,4,5-trisphosphate from phospholipase C and inositol bisphosphate from inositol-1 and -5 phosphatase activity.

The effect of twelve amino acids and lactalbumin hydrolysate in concentration of 200 mg 1^-1 on rooting of the dwarf apple rootstocks P 2 and P 60 was testedin vitro. Arginine, omithine, glutamic acid and glycine enhanced root number of the P 60 rootstock; proline and lactalbumin hydrolysate were neutral; and asparagine, tyrosine, methionine, cysteine and glutamine lowered the root number. Tyrosine, methionine, cysteine and glutamine reduced almost completely rooting of P 60. In the recalcitrant P 2 rootstock aspartic acid, glutamic acid and omithine significantly enhanced the number of roots and rooted shoots, arginine and tryptophan increased the root number only slightly, asparagine was neutral, and proline reduced the root number.

Growth of nine field grown cowpea genotypes was characterized using plastochron index. Attainment of the final plastochron index was considered as a point of completion of a vegetative phase. The population under study completed a vegetative phase within 50 d and exhibited flower initiation in 55 d. The gap between completion of the vegetative phase and flower initiation indicated the prevalence of juvenility in cowpea. The maturity period was found to be a sum of the periods for plastochron completion, lag I, pod development and lag II. Lag I and Lag-II periods existed due to variation in the relative sensitivity of successively formed leaves to the normal inductive conditions. A high genotypic variation for the two lag periods indicated a scope for designing an efficient plant architecture of cowpea either for grain or for vegetable purpose.

The Effect of Nitrogen and Saccharose on Tuberizationin Vitro. The tuberization rate increased and tuber mass decreased to one half or one quarter in potato plantlets in a modified MS-medium with 3 % saccharose and decreased nitrogen content in comparison with normal MS-medium. Decreasing nitrogen content prolonged the time necessary for tuberization. The increase of sucrose concentration to 4 % decreased the inhibitory effect of higher contents of nitrogen on tuberization rate.

The speciesVicia bithynica andVicia narbonensis, from the same subgeneric section ofVicia faba, show variations in nuclear DNA content Nuclear DNAs, extracted from root tips of the twoVicia species, were characterized by thermal denaturation, analytical ultracentrifugation and reassociation kinetics. The thermal denaturations of DNA, the number of DNA components reassociating with second order kinetics, the proportion of repeated DNA sequences, the frequency of the repeated DNA classes are reported and compared to previous data onVicia faba DNA. Feulgen absorptions at different thresholds of optical density⁺ of interphase nuclei in cytological preparations of the root meristems ofV. bithynica andV. narbonensis are determined and compared withV. faba analogous determinations. The results, confirming that plant genome is highly flexible, are discussed in relation to other data on the interspecific variations of the nuclear DNA content.

The results of long-term investigations of variations of rates of water transport through the trunk xylem, its diameter, the leaf water potential and the transpiration rate of the apple tree showed that the daily rhythm of the relative rate of moisture flow in the trunk xylem is an obvious index of the state of the apple tree water exchange. This enables us to determine the period of its unbalance at intensive transpiration as well as the level of the forming water deficit with high accuracy and operativeness. Moreover, by the daily curve of the relative rate of xylem flow one can judge the role of contribution of the trunk reservoir to transpiration.

DNA methylation of two repetitive sequences in tobacco nuclear genome was studied in the course ofin vitro dedifferentiation and differentiation. Using 5-mC sensitivè restriction enzymes and DNA/DNA hybridization with 25S-rDNA probe it has been shown that during the early phase of callus induction prominent changes in the methylation pattern occur which are stably maintained during subsequent callus growth. The following protoplast recovery and plant regeneration have again displayed some more modifications of the methylation status. Comparing the patterns of R₀ plants with the original plant material and the calli it can be assumed that both share in the resulting methylation status. The experiments analyzing the HRS60 family of non-transcribed highly repetitive sequences have displayed a quite monotonous methylation status thus indicating no random methylation perturbations in silent DNA sequences.

In one- and two-year-old green needles ofPinus pinaster growing downwind from a coal-fired power station (main airborne pollutant SO₂), mesophyll chloroplast alterations consisted in swelling of the lamellae (ranging in intensity from slight to pronounced), reduction of grana number, and granulation of the stroma. The most severely affected chloroplasts were almost spherical, with highly dilated and corrugated lamellae and lacunae in the stroma. There was a large increase in the amount of lipid-like material present as droplets in cytoplasm, vacuole and stroma chloroplasts; these droplets appeared to be expulsed from the chloroplasts to the cytoplasm and vacuole. The trees with the most severely affected chloroplasts stood southwest of the power station,i.e. downwind with respect to the winds prevailing most of the year. Chloroplasts from two-year-old needles were more affected than those from one-year-old needles.

This paper is a sequential analysis of qualitative and quantitative nuclear evolution inSesbania rostrata (Leguminosae) stem nodules. Before infection, the nuclei of the root primordia (nodulation site) cells show a 2G level of DNA. Immediately upon infection, the cells cease their mitotic activity and the nuclei begin synthesizing DNA up to a 32C level after the onset of the infection. The increase in the diameter of the nuclei of the infected cells is concomitant with the rise in the level of DKA. In the final phase of the evolution of these nodules, the nuclei of the infected cells undergo degenerative changes.

The possible implication of ethylene on the growth regulation of etiolated lupin hypocotyls was investigated. Excised hypocotyl sections from actively growing seedlings produced ethylene at a rate of 3 nmol h^-1 g^-1 min^-1. The rate of ethylene production was increased about 7 times when sections were treated with 10 mM 1-aminocyclopropane-1-carboxylic acid (ACC). Measurement of endogenous ACC showed that 95 % of total ACC (64.2 nmol g^-1 min^-1) corresponded to conjugated ACC.
Treatments to intact seedlings with the ethylene precursor ACC, and the ethylene generating compound, 2-chloroethyl phosphonic acid (ethephon) during the cell elongation phase of the hypocotyl (from 7 to 21 dage), modified the cell growth of the organ. ACC (1 or 5 mM) or low concentrations of ethephon (0.66 mM) produced a transient decrease in the growth rate without modifying the final length of the hypocotyls. Higher concentrations of ethephon reduced the final length; the younger the seedlings were, the greater the reduction. Simultaneously to inhibition of cell elongation, ethephon produced stimulation of the radial expansion of cells in pith and cortex.
The growth inhibition period, which lasted for 2 days after the treatments, was followed by another period in which the growth rate of treated plants surpassed that of the control. In both cases differences were observed along the hypocotyls due to the different growth status of the cells. It is suggested that the sensitivity to ethylene and the metabolism of ethylene depend on the growth status of the cells.

A pre-treatment of 40 °Cprovided thermoprotection to wheat seedlings against 43 °C, which was otherwise a lethal temperature. Due to temperature pretreatment, the rate of protein synthesis at 45 °C increased in both plumules and radicles. The HPLC profile of plumule and radicle proteins of thermoprotection-acquired seedlings was different from the plumules and radicles of non-treated seedlings.

Primary roots ofVicia faba were grown for 24 h in the presence of tritiated thymidine (1.85-18.5 kBq ml^-1) and then irradiated with a dose of 1.5 Gy of⁶⁰Co-gamma- rays. The aim of these experiments was to determine whether low-level endogenous beta-irradiation from incorporated radioactive thymidine could influence the frequencies of sister chromatid exchanges (SCEs) and the numbers of micronuclei induced by subsequent external irradiation with high doses of gamma-rays. The results demonstrated that the pretreatment with³H-dTh had no significant effect on the frequencies of SCEs in gamma-irradiated root tip cells ofVicia faba. In contrast to SCEs, the yields of micronuclei in the³H-dTh pretreated cells were altogether less than the yield induced by gamma-rays alone (protective effects).

Spring barley seedling were grown in the dark for 21 d and respiration rates of the whole plant (including the seed), of the shoots, and of the roots were determined. A function describing the growth and maintenance components of respiration was interpolated through the experimental points and its parameters in plants under different mineral nutrition were compared. The plants grown in a complete nutrient solution showed the highest growth rate in the initial phase of development and thus reached the maximum respiration rate earlier than plants in the other variants. The highest proportion of substrate was respired in the shoot. Plants grown under deficiency of phosphorus and magnesium had a slower respiration rate than plants grown in the complete nutrient solution (NP), whereas the amount of respired substrate in plant parts was similar to that recorded in the NP plants. Plants grown in distilled water showed the lowest growth efficiency and respirated the highest proportion of substrate in the root.

A 2,4-D dependent cell line, accumulating only traces of indole alkaloids under standard conditions of subculture, was grown in two different production media. Removal 2,4-D from maintenance culture medium enhanced the production of ajmalicine and serpentine and increased the activities of the NADPH-producing enzymes: glucose 6-phosphate dehydrogenase, 6-phospho-gluconate dehydrogenase, malic enzyme and cytosolic isocitrate dehydrogenase.
Adding zeatin to a 2,4-D depleted medium further increased the alkaloid content but the activities of the NADPH-producing enzymes remained unchanged.

Two forms of α-glucan phosphorylase were isolated fromDioscorea cayenensis by ammonium sulphate gradient solubilization and further purified using starch adsorption and ion exchange chromatography on DEAE-Sephadex A-25 colunm. Fraction DC₁was purified 80 fold with specific activity of 400 umol min^-1 mg^-1 protein, while fraction DC₂showed 60 fold purification with specific activity of 300 umol min^-1 mg^-1 protein. Both enzyme forms were activated by AMP, magnesium, calcium and inhibited by ATP, ADP, ADP-glucose and sodium sulphate. They showed absolute primer requirement and obeyed Michaelis-Menten kinetics. The two forms have different Km values and different pH optima. The presence of amino acids and intermediates of glycolysis had no effect on the activities of the enzymes. There are no unusual properties of the enzymes which suggest that they function primarily in starch biosynthesis inD. cayenensis tuber.

Three isolates of strawberry mottle agent (SMA) from strawberry plants were regularly maintained and multiplied by mechanical inoculation onChenopodium quinoa plants showing mosaic and mottle symptoms. The use of 5 mM borate buffer pH 8.6 or tap water pH 6.6-7.9 with 4 % (m/v) charcoal for homogenization resulted usually in 100 % infection. The total of 2090 plants were infected from 2264 inoculated ones under the same conditions. The infectivity of SMA isolates in crude sap ofC. quinoa was retained from 48 h to 72 h at 20 °C. The dilution end points of SMA isolates were 10^-3 while the inactivation temperatures were between 50 and 55 °C. The infectivity of SMA isolates in frozen leaves ofC. quinoa was detected still after six months.
Purification procedure of SMA is based on using low molar 25 mM borate buffer pH 8.3 with cysteine hydrochloride, DIECA and Tween 20 for homogenization of infectedC. quinoa leaves, polyethyleneglycol precipitation, clarification with octanol, low and high speed centrifugation and sucrose density-gradient centrifugation. Partially purified preparations are highly infectious, causing mosaic, mottling and tip necrosis ofC. quinoa plants. The agent could not be completely separated from host proteins and it could not be concentrated to a high extent. Isometric virus-like particles 14-16 nm were observed in partially purified preparations.

The time-evolution of germination of oat seeds, suspended in the standard 5mm N. M. R. tube and supplied by water, was investigated continuouslyin vivo by the pulsed N. M. R. of water protons at the level of the seed. The results show that the spin- lattice relaxation time T1 yield the physiological information: in the germinated (living) seeds, the T¹'s are higher than in the killed seeds.

The enhancement of fruit abscission zone formation with ethephon treatment caused an increase in soluble proteins, endo-cellulase, exo-polygalacturonase and peroxidase activities. Exo-cellulase and endo-polygalacturonase did not show any relationship with apple abscission. The separation of cells initiated in the cortex region and progressed towards vascular tissue. Cell separation in the cortex appeared to be due to dissolution of middle lamella but vascular tissues ruptured mechanically.

During the growth of multiple-shoot cultures of Ruta graveolens, oxygen and carbon dioxide exchanges were continuously and simultaneously measured. The shoots subcultured on a medium containing 166 mM glucose showed a marked respiration rate. Even under light, CO₂ concentrations reached 4000 to 6000 cm³ m^-3. Photosynthesis never compensated for respiration. These cultures were photomixotrophic. A change of respiration and photosynthesis occurred between the 30th and the 32nd day of culture, with a high respiration rate. When the shoots were subcultured on a medium containing 41 mM glucose, it was possible to obtain photoautotrophy after two weeks under high irradiance (150 umol m^-2 s^-2), and after three weeks under low irradiance (60 μmol m^-2 s^-1), the CO₂ concentrations being 1100 and 600 cm³ m^-3 respectively.

An improved method for the isolation of leaf mesophyll protoplasts ofSolanum tuberosum L. cvs. Xenia and Bintje, their culture and regeneration to plants is described. The improvements involve the culture of nodal stem explants on Schenk and Hildebrandt (SH) medium supplemented with AgNO₃ (7.5 mg 1¹) and Alar 85 (5 mg 1^-1), and the pre-treatment of donor plants for 2-3 weeks at a short photoperiod (6 h), a low irradiance (17 (μmol m^-2s^-1) and a low temperature (20 °C). Regeneration of cell wals was observed within 2-3 d and cell divisions within 7-12 d after resuspending freshly isolated protoplasts in Sidorov et al. (SW) medium. The resulting microcalli were cultured on solid media containing zeatin (1-2,5 mg 1^-1) and/or NAA (0.1 and/or 0.01 mg 1^-1) and subsequently on medium with BAR (0.25 mg1^-1) and GA^-3 (0.1 mg 1¹) for shoot regeneration.

Changes in the activity and localization of nonspecific esterase, acid phosphatase, α-galactosidase and β-glucosidase inL. regale pistils after pollination with μ-irradiated pollen were studied. In the embryo sac and in the ovule reduction of AS-esterase and α-galactosidase and, at the same time, enhancement of α-esterase, acid phosphatase and β-glucosidase activities were observed. The changes in hydrolytic enzyme activities are discussed as manifestations of lethal factors resulting from structural disturbances of DNA in the generative nucleus and in sperms caused by irradiation.

The effect of crude volatile oils from the leaves ofEucalyptus globulus andE. citriodora and the pure terpenes - cineole and limonene from these oils, (in vapour form) was studied onPhaseolus aureus, Lens esculentum, Hordeum vulgare and Avena sativa. The parameters like germination of seeds, seedling growth, values of cell survival, and content of water and chlorophyll of the crops formed the system of bioefficacy study. The allelopathic impact of the oil vapours from the eucalypt tree becomes evident from the negative response of the parameters studied. The impact of the E. citriodora oil vapours compared to that ofE. globulus oil or the pure terpenes was seen to be relatively greater in almost all parameters under investigation. A strong reciprocal correlation that exist between the concentration and the seedling growth or the water content of the crops under study supports the dose linked allelopathic phenomenon. It is suggested that oil vapours ofEucalyptus exert their effect through impairing the respiratory as well as photosynthetic ability of the target plants.

Cytokinins in addition to nitrate induce nitrate reductase activity (NRA) in some plants. Effects of cytokinins onNRA was investigated in stem pith parenchyma of kale, intact wheat and barley seedlings and isolated cucumber cotyledons.
The most profound effect onNRA was found in barley and wheat seedlings.NRA in seedlings sprayed with 100 μM 6-benzylaminopurine (BAP) for three subsequent days was increased in leaves and decreased in roots. These changes were further enhanced in seedlings grown in nutrient solution lacking nitrate:NRA in wheat and barley leaves was increased by 57% and 202%, respectively, in plants supplied with nitrate theNRA increase was not significant: in wheat and barley leaves by 22% and 9%, respectively.
Similar effect of BAP and kinetin was found in kale stem parenchyma and cucumber cotyledons. The cytokinin kinetin or BAP alone increasedNRA about twice in kale and three times in cucumber. Addition of nitrate to the medium enhanced the effect of kinetin in kale discs, but the two effects were not additive. Additive effect of nitrate and BAP onNRA was found in cucumber cotyledons in light.
In general NRA was more affected by cytokinins in intact seedlings of wheat and barley as compared to explanted tissue of kale and cucumber, and lack of nitrogen made their effect more expressive.