During 195-min light exposure following 5 d in dark, nitrate content was studied in different organs of lucerne plants in early bud stage. Nitrate content varied considerably especially in stems. Rapid diurnal variations in nitrate content were found in lower and upper halves of stems, in petioles and in leaf blades. The results reflected discontinuous nitrate movement in lucerne shoots. The positive correlation between the diurnal course of the nitrate and potassium contents in different plant organs showed that the K⁺ transport followed the NO₃ ^- transport. Similar diurnal changes were found also in Na⁺ and Ca²⁺ contents. Discontinuous salt movements occurring in xylem sap flow were in contrary to continuous transpiration stream and could be a consequence of temporary adsorption or binding of salts in xylem vessels.

The effect of growth in saline medium on the activity of two ATP utilizing enzymes was studied. Hexokinase in carrot (Daucus carota L.) cells grown in suspension culture either in the absence or presence of 150 ml NaCl, and tonoplast H⁺-ATPase in tobacco (Nicotiana tabacum L. cv. Wisconsin 38) cells grown in suspension culture either in the absence of presence of 428 mM NaCl. There was no difference in the pH profiles, NaCl sensitivity and kinetic parameters towards glucose of hexokinase activities from carrot cells grown in the presence or the absence of NaCl, but the activity from cells grown in the presence of NaCl was more resistant to inhibition by N-ethylmaleimide and to inactivation by heat. Two separate apparent Km values toward ATP were delineated in the extract from cells grown in presence of NaCl while extracts from cells grown in the absence of NaCl had only one apparent Km value. The tonoplast H⁺-ATPase from NaCl grown tobacco cells showed changed kinetic compared to this activity from cells grown in the absence of NaCl. These data may indicate that growth in NaCl results in the appearance of isozymic activity that enhances the ability of plant cells to utilize metabolic energy more efficiently.

Four-year-old seedlings ofQuercus petraea (Matt.) Liebl. andNothofagus procera (Poepp. et Endl.) Querst were grown outdoors in pots while subjected to full, medium and low irradiances. Shading and decrease in height of leaf attachment generally increased specific leaf area, the diameters of chloroplasts and of palisade and spongy mesophyll cells, but decreased leaf thickness, number of palisade cell layers, length of palisade and spongy mesophyll cells, number of chloroplasts per mesophyll cell and epidermal cell and cuticle thickness, stomata and hair densities per unit leaf area, hair length, maximum hair breath and cell wall thickness in the two species. However, inN. procera grown under full irradiance, leaves at the upper and middle positions had hairs on both upper and lower epidermes, whereas those in other treatments and all leaves in all treatments inQ. petraea, had theirs only on the upper epidermis.

Seven barley(Hordeum vulgäre L.) cultivars tested varied greatly in their responses to root medium salinity (electrical conductivity of 3, 5, 10, 15 and 20 dS nr^-1)-lant growth was relatively more adversely affected than seed germination. Dry/fresh mass ratio increased at higher salinity levels in all barley cultivars indicating reduced water uptake. Higher K/Na ratio in plant shoots compared to that in the root medium solution indicated selective uptake of K that seems to be among processes involved in tolerance of cultivars to salinity stress.

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.

D-amino acid were searched in wilted tomato leaves. D-Isomers of free amino acids were not revealed by the treatment with L- and D-amino acid oxidases. The noncationic fraction of the extract contained N-malonyl-D-tryptophan and no other N-acylated amino acids. A special search for endogenous N-malonyl-D-phenylalanine gave negative results. Exogenous¹⁴C-malonate was only incorporated in one Chromatographic zone corresponding to N-malonyl-D-tryptophan. It is concluded that drought stress does not induce the appearance of D-amino acids except for D-tryptophan which is accumulated in the malonylated form.

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.