The mode of transport and regulative properties of phenylacetic acid (PAA) were studied in 11-cm long segments of pea epicotyls capable of growth. The transport of PAA m both the basipetal and aeropetal direction was limited to tissues situated immediately below and/or above the site of its application. PAA was able to promote the flow of¹⁴C-ABA in the acropetal direction. PAA-initiated thickening growth was probably the cause of this promotion.

Data point fields of values of the dependence of nitrogen and potassium concentration in shoot dry matter on dry matter weight in the course of the vegetation cycle at four stages of development of spring barley (Hordeum vulgare L. cv. Ametyst) plants were derived from a four-year-cycle of stationary field nutrition experiments at two localities. Three selection procedures of the boundary data are described. Graphical outputs and their subsequent mathematical expression enable an objective construction of regressive upper and lower boundary curves of the data point fields. The shape of the curves is characteristic of each investigated element. The position of the upper boundary curve can characterize the maximum uptake ability, that of the lower curve the maximum efficiency of utilization of absorbed nutrients, and their amplitude the requirement extent of the species or cultivar investigated. The boundary curves can be objectively constructed for individual nutrients from a sufficiently vast set of data from a very broad spectrum of ecological conditions (for example from stationary field nutrition experiments at various localities).

Mustard (Brassica juncea) Coss., chickpea (Cicer arietinum L. and barley (Hordeum vulgare) L. were grown under different moisture levels. Diurnal changes in leaf water potential showed lower values and higher fluctuation in mustard, chickpea and barley grown with no irrigation as compared to one supplemental irrigation. Diurnal maximum of adaxial stomatal conductance in mustard and barley was higher under one irrigation treatment. In mustard stomatal conductance of abaxial surface of leaf remained higher than adaxial surface of leaf throughout the day, whereas the reverse was true in barley. Also the leaf and soil temperature and reflectance were slightly higher in all the three crops under no irrigation.

Neutral proteinase was found in the leaves ofRicinus communie as assayed with α-casein and H-D-Val-Leu-Lys-pNA as substrates. The enzyme is maximally active at pH around 7.4. A selective adsorbent for serine proteinase was prepared by attaching aprotinin to aminoalkyl-porous glass.
When partially purified leaf proteinase was passed through a column containing this adsorbent, the proteinase activity present was bound to the porous glass. The proteinase eluted at IM NaCl was inhibited by aprotinin, leupeptin, DFP, phenylmethylsulfonyl fluoride (PMSF) and serine proteinase inhibitor fromR, communis leaves, whereas pepstatin, EDTA, EGTA, and DTT had no effect on the enzyme. This inhibition profile suggests the leaf proteinase is a neutral proteinase, such as a serine proteinase.

Young seedlings ofGmelina arborea Roxb. were subjected to 2 weeks of drought. Despite the gradual reduction in stomatal conductance, leaf and root growth was not affected until the later part of the stress period. This was attributed to solute adjustment in the roots of the plants. As the severity of water stress increased, root growth was prolific in all the soil segments. As a result, water in the lowest soil segment was used to maintain plant turgor, which in turn sustains the leaf and root growth during the water-stress treatment. The influence of soil water content and soil water potential upon soil water uptake rate was also evaluated on soil profile basis. Rates of extraction began to decline in all soil segments as soon as soil water potential fell below -0.06 MPa, presumably as a result of vapour gaps between the root and soil (root: soil interface resistance). It is suggested that the growth of roots ofGmelina plants away from drying soil will minimize the resistance to water uptake.

Some of the effects of oxygen concentration in the external medium bathing castor bean cotyledons were investigated.
At 700 μM O₂, the sucrose-dependent proton influx was dependent on external pH while sucrose influx was independent of pH between 4,5 and 6; proton influx and sucrose influx were both dependent on external sucrose concentration; both were saturated above 50 mM sucrose. The stoichiometry H+/S decreased with increasing pH and sucrose concentration. These data were consistent with the results obtained in stirred or aerated external medium.
Oxygen consumption, acidification of the medium, sucrose-dependent proton influx and sucrose uptake increased with increasing oxygen concentration up to 700 μM where saturation was reached. Bubbling with air (O₂, 160 μM) resulted in the same increase despite lower oxygen concentration. It is suggested that not only O₂ concentration but also CO₂ concentration act on O₂ consumption, and proton and sucrose fluxes.

The effect of derivatives of benzoic and cinnamic acids, quereetin,p-benzoquinone, and 2,5-dimethylbenzoquinone on oxygen consumption mitoehondrial suspensions and on the activity of some respiratory chain enzymes was studied. Benzoquinone and 2,5-dimethylbenzoquinone highly significantly inhibited the respiration and phosphorylation rates and malate- and succinate dehydrogenase activities. Chlorogenic acid, similarly as the quinones, very significantly inhibited the activities of the studied dehydrogenases but did not affect cytochrome oxidase. Oxygen consumption by intact mitochondria was not inhibited, only the oxidativo phosphorylation was significantly uncoupled. Quereetin significantly enhanced dehydrogenase activities and completely inhibited cytochrome oxidase activity. The respiration and phosphorylation activities of the mitochondria were significantly inhibited by quereetin. The effect of the other phenolic compounds studied on respiration and phosphorylation activities was not significant. Succinate dehydrogenase activity was the most affected enzyme among the respiratory chain enzymes. It was significantly inhibited by all the above phenolic compounds at 1^-4M or 5 10^-5M concentrations with the exception of gallic acid.

Protease activity inSpinacia oleracea leaves, but not roots, increased when sodium sulfite, hydrogen peroxide and sodium azide, but not sulfuric acid, were injected through the petiole under light conditions. On the other hand, protease inhibitory activity in both the leaves and roots decreased by the injection.
Protease activity inRicinus communis leaves increased when hydrogen peroxide and sodium sulfite were injected through the petiole and kept for 4 h under light conditions. No visible injuries were caused to the leaf. On the other hand, protease inhibitory activity in leaves decreased by the injection of hydrogen peroxide.
Changes in the activity of protease caused the senescence of leaves such as chlorosis and necrosis which were observed with leaves injected with hydrogen peroxide after one week. These results suggested that in the healthy leaf, the protease inhibitor protects the cellular components from the protease.

It has been found that cytokinins, as a class, can be separated from co-occurring phenolics by column chromatography using polyvinylpyrrolidone (PVP) with methanol as eluant. Subsequent fractionation of the cytokinins can then be achieved by HPLC on a C₁₈ODS reversed phase system using methanol: water (60: 40) as the mobile phase. The system shows considerable promise as an extremely mild separation process and has been used to separate two unknown cytokinins from seedlings ofHordeum vulgare cv. Steptoe.

After infection ofNicotiana tabacum cv. Samsun with tobacco mosaic virus (TMV) crude extracts from dark-green spots of upper leaves had a more strongly marked inhibitory effect upon TMV addedin vitro than crude extracts from the surrounding light-green tissue. Likewise, crude extracts from leaves ofNicotiana tabacum cv. Samsun showing recovery after infection with tobacco ringspot virus (TRV) were seen to have a marked inhibitory effect on TMV addedin vitro. The results obtained suggest that virus inhibitors are produced after virus infections not only in hypersensitive hosts but also in systemic hosts. Necrotizing processes are not an indispensable prerequisite of the production of virus-induced virus inhibitors.

Adsorption, absorption and translocation of sodium were compared in three species showing an ascending degree in tolerance to salinity: red cabbage (tolerant) shows higher Root Cationic Exchange Capacity than tomato (sensitive) or radish (intermediate). At low NaCl concentrations, tomato accumulates the greatest quantities of sodium; but Na⁺ translocation remains proportional to the quantity absorbed in the three plants. At high salt concentrations, diffusive phenomena explain similar accumulation in every plant, but red cabbage quickly localises 50% of Na⁺ amount in cotyledons, while this element stays stored in tomato roots. The consequence of these three nutrition phases was discussed in relation to the behaviour observed at the germination time of these same plants.

The overall washing out of ions, especially⁸⁶Rb⁺ (as the tracer for K⁺), from hypocotyl segments of pumpkin (Cucurbita pepo L.) into distilled water or a CaCl₂ solution was studied, during plasmolysis with a saccharose solution and during deplasmolysis. Compartimental analysis was used to evaluate the⁸⁶Rb⁺ washing out kinetics. During plasmolysis, the washing out of⁸⁶Rb⁺ increases, due to two processes whose half-times are lower than those during washing out into the CaCl₂ solution. During deplasmolysis, the permeability of plasmalemma and tonoplast is substantially descreased, leading to washing out of most⁸⁶Rb⁺ from the cells. Plasmolysis differs from a mere decrease in the turgor pressure in the fact that after exchange for a hypotonic solution the membranes are irreversibly damaged.
The aim of this work was to monitor the changes in the cell membrane permeability due to a change in the water potential of the cells, especially during plasmolysis and deplasmolysis.

A study was made on the effect of increasing photon fluence rate (I) at a unilateral irradiation of adaxial (normal leaf position) and abaxial (inverse leaf position) blade surface of maize leaves of various insertion levels on net photosynthetic CO₂ uptake (P _n ) by the leaves, as well as the contribution of individual surfaces toP _n of the leaves, and the significance of, or relationship between the stomatal (g _s ) and intracellular (gm) conductances at the CO₂ transport.P _n of leaves of various age according to their insertion level was unaffected by the direction of incident irradiation. Upon irradiation of the leaves in normal and inverse position the contribution of the adaxial and abaxial surfaces toP _n ,g _s and g_m was different. On irradiating the leaves in normal position, the contribution of the irradiated adaxial surface to the characteristics mentioned made on the average 55% of total values, the contribution of the abaxial surface irradiated in inverse position made on the average 70% inP _n andg _m , and 80% ing _s . At lowerI's g _m was higher thang _s both in irradiated and non-irradiated surfaces. The ratio ofg _s to g_m gradually got square with increasingI. In the irradiated adaxial surface the equilibrium (g _s /g _m = 1.0) took place at the highestI's, in the irradiated abaxial surface between 500 to 1000 μmol m^-2 s^-1. The significance of the ratiog _m in the CO₂ transport through the individual surfaces is discussed.

Cholinesterase activity was studied in 2 to 10-week-old pea plants cultivated under artificial illumination. Free and membrane-bound forms of the enzyme were separated by extracting the enzyme from pea shoots with buffers differing in ionic strength. The ratio of the free cholinesterase to the membrane-bound one fluctuated between 1 : 1 and 1 : 2.5. The free cholinesterase was inhibited by neostigmine (0.1mmoll^-1) by 50%, the membrane-bound enzyme by 90%. The pH optimum of cholinesterase activity was 8.5, the temperature optimum 37 °C. The enzyme activity was increased by some cations in this order: Mg²⁺ < < K⁺. The K^m value for the substrate S-acetylthiocholine iodide was 250 μmoll^-1, the enzyme activity being inhibited by concentrations higher than 3 mmoll^-1 of this substrate.
The activity of the membrane-bound enzyme was demonstrated in the roots, leaves, stems, fruits, seeds and carpels, but could not be reliably detected in the blossoms. The highest activity expressed per fresh matter was found in older leaves and in the fruits, the lowest in the roots and stems. Cholinesterase activity in plant parts markedly varied during the investigated growth period.

The effects of vanadium and tungsten on growth of the heterocystous cyanobacteriumNostoc linckia (Roth.) Born. and the activity of its nitrogenase and nitrate reductase were studied. While vanadate stimulated the growth of molybdate-limited cells and also their acetylene-reducing ability, it did not stimulate nitrate reductase activity. Tungstate inhibited growth in molybdate-limited cells and also their acetylene reducing and nitrate reductase activities. Acetylene reduction response of cells grown in a tungstate-containing medium indicated certain difference between the modes of action of vanadium and molybdenum. Tungstate caused a slight increase in heterocyst frequency both in nitrogen-fixing and nitrate-grown material. Cyanophycin granules and polyhedral bodies disappeared in molybdate-deficient cells in which thick deposition of polyglucan-like granules occurred throughout the breakdown of cytoplasm and the thylakoids.

Leaf form and stomatal characteristics play an important part in the strategy of tall fescue (Festuca arundinacea Schreb) to limit water losses. Transpiration rates of artificially rolled leaves measured by potometer at varying wind velocities support this assertion.

Crown galls induced onArabidopsis thaliana plants by octopine or nopaline strains ofAgrobacterium tumefaciens were grownin vitro on different media. Dark growth of all tumor tissues was strictly hormone-dependent. In contrast, hormonal autonomy was observed in the light where crown gall calli readily differentiated into teratomas and (sometimes fertile) plants. Differentiating tissues always grew more vigorously than subtended calli. The growth of transformed calli was stimulated by vitamins and partly inhibited by growth regulators in concentrations used for the maintenance of untransformed calli. Crown gall calli, teratomas and sometimes regenerated plants were shown to express lysopine or nopaline dehydrogenase activities.

The metabolism of exogenously supplied abscisic acid (ABA) during translocation attracted under the influence of indolyl-3-acetic acid (IAA) was studied in etiolated segments of pea (Pisum sativum L.). After 8 and 24 h 90% and 60% of the ABA, respectively, were found in the segments in unchanged form. Phaseic acid, dihydrophaseic acid and the glucose ester of ABA were found as ABA metabolites. Results indicated that the growth processes initiated by the application of IAA were associated neither with an increased immobilization nor increased metabolization of this growth regulator.

The growth ofArabidopsis thaliana calli on media without growth regulators was studied Calli under study showed autonomy for cytokmms independently whether cultivated on the light or m the dark When cultivated in intense light, they were able to grow, either transiently or permanently, on the medium without any growth regulators In the dark, they were strictly dependent on 2,4 D m the medium Both the intensity of growth and the duration of the transient growth on the medium without growth regulators m the light decreased with the duration of the previous cultivation on the medium with growth regulators The intensity of growth on the medium without grow th regulators was best and the growth was permanent m the callus clone of spontaneous origin which was never treated by growth regulators The degree of chromosomal variability (assessed as the number of chromocentres) m this callus line was lower than that in calli induced on media with growth regulators and then transferred onto medium without growth regulatois.

The mature nodules ofLens esculenta Moench. contained higher levels of indolyl acetic acid (IAA), cytokinins (CK), gibberellic acid (GA)-like substances and more active in nitrogenase (N₂-ase) activity than young or old ones. Synthesis of IAA and its metabolism was found to be controlled by tryptophan (tryp) and phenol metabolism, respectively, in nodules of different ages. An abscisic acid (ABA)-like substance being a 'late growth phase' hormone, was highest in old nodules.
IAA and CK were highest in winter when N₂-ase activity was also highest but then GA and ABA were low. The IAA metabolic pattern of both roots and nodules was regulated by phenols. The hormones hardly changed seasonally in the roots and showed higher activities of IAA oxidase, MeOx reductase, peroxidase and polyphenol oxidase than nodules.
The nodular anabolic changes are more pronounced in winter as lentil is a winter crop. The size of nodules at a particular age was the same in different seasons, even though their hormone content varied with the season showing that the nodular hormones were not solely utilized for nodule development and growth.

Effects of cyclic AMP and traumatic acid on adventitious bud initiation inTorenia stem segments culturedin vitro were examined. Both the compounds stimulated bud initiation at relatively low concentrations. Simultaneous addition of an anticytokinin did not counteract the stimulatory action of the 2 chemicals. Their stimulatory effects were also clear when expiants were pre-incubated for 2 h with 1 μM of either of the 2 substances. The treatment with cyclic AMP and traumatic acid may favourably modify some physiological process which is triggered by excising expiants (wounding) and leads to adventitious bud initiation.

At pollination of maize plants, the old leaves, those of medium age, and young leaves, cut into segments transversally (10 segments) and longitudinally (8 segments and main vein), were sampled and concentrations of N, P, K, Ca, and Mg were determined. Then concentration gradients of these elements in maize leaves of different age were evaluated. The results obtained show that concentration gradient of N was the most evident in transversal segments of leaves of different ages, in particular in young leaves, that of K in the old leaves, and the Ca concentration gradient in leaves of medium age. The phosphorus concentration gradient was weakly expressed and in the young leaves not recorded at all. In longitudinal segments, concentration gradients of elements varied in leaves of different ages.