Subeellular localization of the enzymes which phosphorylate hexoses was studied in photosynthesizing tobacco leaves by means of differential centrifugation and centrifugation in sucrose gradient. More than 80 % of the total hexokinase activity of leaf tissues were found to be associated with the particulate fraction of mitochondria; however, the ratio of the particulate hexokinase fraction to the soluble fraction was influenced by the extraction medium applied. The particulate hexokinases showed a high affinity to glucose (Km = 26.8 μM) and a relatively low affinity to fructose (Km = 17.6 mM). They had a broad pH optimum, because 81 % of the phosphorylating activity obtained for glucose and 75 % of the activity obtained for fructose occurred in pH range from 7.9 to 9.1 (Tris-HCl buffer). The hexokinases were Mg2+ dependent with the highest activity occurring at equimolar Mg2+ and ATP concentrations. Their activity was enhanced by KC1, NaCl, and (NH4)2SO4 at 30 to 120 mM concentrations.

Growth of Dunaliella tertiolecta was retarded when the alga was exposed to high boron (B) concentrations between 50 and 200 g m-³. Photosynthetic oxygen evolution as well as respiratory oxygen uptake were significantly suppressed with the rise of B concentration. Similarly the contents of chlorophyll, glycerol, lipid and proteins were lowered, while that of saccharides was raised.

Sulphate ion is accumulated in the cells of the algaHydrodidyon reticulatum to a concentration approximately 30 mmol 1^-1. The rate of SO₄ ^2- uptake is increased markedly in the light, however, the effect is observable only after the cells have been kept in the light for about one hour. Uptake of sulphate is strongly inhibited by phosphorylation uncouplers and also by DIDS. The two-phase sulphate uptake kinetics, reported earlier was confirmed in experiments in which competition with phosphate anion was tested. Phosphate competes with sulphate only in the range of higher substrate concentrations (from 0.2 mmol 1^-1) and does not affect the system which works at low substrate concentrations. Efflux of SO₄ ^2- is very slow; the reason of the flux hindrance is not yet known.

InTradescantia, clone 4430, diethyldithiocarbamate (DEDTC) markedly decreased the frequency of somatic mutations induced by maleic hydrazide (MH) and N-nitrosodiethylamine (NDEA). In contrast, DEDTC had no such effect on N-methyl-N-nitrosourea-induced mutagenesis. The putative degradation and conversion products of MH (maleic acid diamide, succinic acid, maleic acid, lactic acid and hydrazine) exhibited no mutagenic activity in theTradescantia mutagenicity assay.

Respiration rate of foliarPelargonium discs was insensitive to ageing. The addition of BAP or GA₃ to the ageing medium did not produce any effect.
The presence of GA₃ or BAP in the ageing medium induced an increase (27 %) or a decrease (45 %) of the phosphate uptake. The analysis of phosphorylated compound labelling showed that these two hormones decreased³²P incorporation in the non-acid soluble fraction and increased³²P incorporation in the acid soluble organic fraction. GA₃ and BAP had little effect on the distribution of radioactivity between the different acid soluble compounds, but they increased the ATP level.
These results suggest that both GA₃ and BAP increase the basal metabolism, but they seem to act differently on the development of the uptake mechanism during ageing.

The present investigations were designed to elucidate the linkage of medium acidification to metabolism and to study the influence of phytohormones (IAA, ABA) and fusieoccin (FC) on H+ extrusion from peeled leaf tissue of Vicia faba. H+ release, which was sensitive to the metabolic inhibitors sodium azide, vanadate, DCCD, and cycloheximide, was promoted by 5 to 50 μM IAA and 10 μ FC, but transiently diminished by 10 μM ABA. FC was a much more powerful inducer of H+ extrusion than IAA. Other weak acids such as acetate and citrate had no effect on H+ extruding activity of Vicia leaf tissue indicating that the IAA effect is specific. These results support the view that IAA and ABA control of cell growth can be attributed entirely to a modulation of H+ pump activity.

Xylogenesis was induced in cultures of calli ofHaplopappus gracilis (NUTT.) A. Gray by metabolic shocks brought about by changes in nutrition. Xylogenesis was observed to occur in response to three changes in callus nutrition, caused by the following modifications of Eriksson's nutrient medium and culture conditions: i) omission of sucrose in the medium for 3 to 6 days and then transfer of the calli onto complete Eriksson's medium; ii) replacement of sucrose by 0.36*mol l_-1 xylose for the whole culture period; iii) omission of nitrogen sources(i.e. glycine and NH₄NO₃ omission and replacement of KNO₃ with equimolar KCI) for the whole culture period.
The induction of xylogenesis in response to nutritional stress inH. gracilis can be used as a suitable model system for research concerning plant cell differentiation.

7 days or 7 weeks old alfalfa plants (Medicago sativa L.), susceptible (S) and resistant (R) to bacterial wilt, were inoculated withCorynebacterium michiganense pv.insidiosum and on day 8 and 15 after inoculation the levels of acid-soluble phosphate esters (P-esters) were determinated by means of³²P labelling in the shoots or roots. The most significant changes were recorded in the roots of the older R plants grown in full Knop nutrient solutions on day 8 after inoculation. The marked reduction of inorganic phosphate (P₁) uptake by whole R plants is accompanied by a decrease in the levels of fructose-l, 6-bisphosphate (Fru-P₂), glucose-6-phosphate (Glc-6-P), fructose-6-phosphate (Fru-6-P), adenosine mono-, and diphosphate (AMP and ADP), phosphorylcholine (P-choline) and a proportional increase in the level of P₁. In the S plants, infection affected neither P₁ uptake nor P₁ proportions. In the plants grown after inoculation in diluted Knop's solutions (0.147 mM KH₂PO₄), infection induced a reduction of the radial transport of P₁ to the segments of R roots whereas a reduction of the levels was only recorded in some P-esters [AMP, ADP, dihydroxyacetone phosphate (DHAP), and P-choline, but no decrease of Fru-P₂, Glc-6-P and Fru-6-P]. In the S plants, P₁ transport and the levels of P-esters were increased by the infection. P₁ transport exhibited considerable metabolic dependence (DNP, DCCD). Bacterial infection probably had no influence on the activity of the plasma membrane ATPases.

Application of kinetin to four interspecific crosses in Brassica, either singly or in combination with NAA, resulted in larger length and retention time of ovaries, increased frequency of ovules with embryos and aided embryo development.

The cross B. campestris ssp. japonica x B. oleracea var. botrytis fails due to incompatibility barrier at the stigma. To realize this cross, irradiated compatible pollen (mentor pollen) was used before the incompatible pollination. The presence of mentor pollen stimulated the incompatible pollen to germinate and effect fertilization and seed set. One hybrid was thus obtained. Most of the seeds were inviable. Of the 5 plants raised one was a hybrid and 4 resembled the female parent.

The quantitative changes of chlorogenic acid in shoots and leaves of two groups of grape vines differing in their flower- and fruit-formation have been studied. It was established that in most cases the acid level was lower in both shoots and leaves of grape vines with suppressed growth and intensified generative processes. The results obtained suggest that the lower content of chlorogenic acid is related to the reduced growth of shoots and acceleration of generative processes.

In negatively photoblastic seeds of Cucumis anguria L. the scarification of micropyle overcame the inhibitory effect of "white light ", although far-red radiation inhibited the germination in both intact and scarified seeds. The moistened testa powder transmitted more far-red than red radiation. Thus the testa could act as a filter of radiation and maintain a high far-red/red ratio at the photosensitive site of the embryo, which must be localized near the micropyle.

The effect of potassium administration in early germination of wheat (Triticum durum L., cv. Appulo) was studied by incubating isolated embryos at different viability levels with 1 mM KC1. The stimulation of germination and growth in aged embryos by K⁺ was accompanied by a significant increase in (³H) leucine incorporation into protein and in phospholipid synthesis as evidenced by TLC analysis of embryo phospholipids extracted after 24 h of imbibition. The metabolic improvement mediated by the cation would in turn repair aging damage occurring at subcellular sites including membranes.

Vitrification of stem explants of carnation was brought about by culturing in liquid medium. Cellulose and lignin levels were decreased in vitrified stems and leaves. Isolated cell walls of vitrified tissues were also characterized by low calcium content, low Ca²⁺/uronic acids ratio, low ratio of uronic acids to neutral sugars due to higher amounts of the latters. All these characteristics may account for the high wall plastic potential previously measured in vitrifying internodes.

Different species of yam tubers were examined for the presence of pyruvate kinase and phosphatase activities, Pyruvate kinase was purified 25 fold with a yield of 50 %. using ammonium sulphate precipitation and ion exchange chromatography on DEAE-Sephadex. Partially purified enzyme showed normal Michaelis-Menten kinetics. However, pyruvate kinase from crude extract of dormant yam tuber showed slight sigmoid response towards phosphoenol-pyruvate and magnesium and to a certain extent ADP. The enzyme is activated by AMP and inhibited by ATP and citrate in both crude and partially purified preparations. Further studies on the effect of energy charge on the enzyme strongly suggest that pyruvate kinase from D. alata is a regulatory enzyme. No evidence was found for the presence of more than one pyruvate kinase in germinating D. alata tuber. With the exception of D. dumentorum, all the other three species of yams studied contain very little or no detectable phosphatase activity during dormancy. However, phosphatase activity increased during germination in all the species, thus excluding the use of sprouting yam tubers for kinetic study of pyruvate kinase.

Uptake of³⁵S-sulphate by bundle sheath strands (BSC) from leaves of maize plants (Zea mays L. ev. Dekalb L 72 A) was higher than that by isolated mesophyll protoplasts (MC) of maize. Ion uptake followed the Michaelis-Menten kinetic satuiation curves. SO² ₄-uptake increased after addition of malate, NADPH, malate + NADP+ to BSC suspensions, but not to MC susp: nsions.

The season of collection of shoot tips from field-grown plants ofChrysanthemum morifolium cv. Birbal Salmi was found to be crucial for their proliferation and establishment of plants in vitro. Shoot tips collected only during the period of March to April proliferated and survived. Shoot apices and segments of leaf, stem (nodal und internodal) and root, excised from aseptically established plants, were cultured on Murashige and Skoog's medium supplemented with different concentrations and combinations of Kn, BAP, IAA and NAA. A maximum number of 9 off-shoots differentiated, without intervening callus formation, from a shoot tip in a treatment containing 1.5 mg l^-1 BAP and 0.1 mg^-1 NAA in 60 days. A single-node stem segment produced less shoots in the same treatment. Other kinds of expiants produced only callus. About 2-cm-long shoots, excised from cultures of proliferating shoots, were rooted 100 %, acclimatized and grown in soil. They grew normally and flowered true-to-type.

The change in protein composition of whole cotyledons and cotyledon aleurone grains ofLupinus luteus L. during seed germination was studied. SDS-polyacrylamide gel electro-phoresis showed a clear change in composition of cotyledon proteins as well as in composition of the aleurone grains during 5 days of seed germination. At this time, both in whole cotyledons as well as in aleurone grains, two subunits of β-conglutin with mol. m. 53 000 and 39 000 were rapidly hydrolyzed. After 5 days of germination traces of α-conglutin subunits could be detected in the cotyledons, whereas in aleurone grains this globulin fraction disappeared. In whole cotyledons and in cotyledon aleurone grains the γ-conglutin subunits with mol. m. 28 000 and 17 000 were not mobilized during the study period. These results indicate that the protein components with lower mol. m. were degraded later than those withhigher mol. m. during seed germination.

The effect of choline, acetylcholine, carbamylcholine and of the acetylcholinesterase inhibitors, eserine and neostigmine, on the germination of seeds exhibiting different photosenitivities was studied in two light variants. Both in the darkness and in continuous white light the substances in question had no effect or only slightly modified germination of photoblastically neutral seeds. On the other hand, the above substances, particularly aeetylcholine and carbamylcholine, stimulated germination of photoblastically positive seeds, and inhibited germination of photoblastically negative seeds in continuous white light.

High rates of oak shoot multiplication were achieved on low salt nutrient media (BTM, WPM) supplemented with adenine type cytokinin or BAP. Low concentration of (0.2-0.6 mg 1^-1) stimulated formation of a large number of axillary shoots and their elongation. Thidiazuron in very low concentration (0.001 - 0.002 mg 1^-1) promoted shoot proliferation, in high concentration stimulated formation of large callus. More than twelve thousand micropropagated shoots were rooted in low salt agar media supplemented with low concentration of auxin (IBA or NAA 0.2 - 0.5 mg 1^-1). High rooting percentages (81 %) were obtained. Survival of the mieropropagated plantlets transplanted into soil was high (78 %). Micropropagated trees planted in the field withstood severe winter frosts without significant losses. At the end of the fifth growing season trees attained considerable size.

The rooting ability of 2 cm long shoots ofPisum sativum L., derived from differentin vitro shoot-tip cultures in two pea cultivars Bohatýr and Kleine Rheinländerin was evaluated. In three mutually independent experiments the full and half-strength Murashige-Skoog medium (containing full or half concentration of macro and microelements), with sucrose concentrations 10-30 g l-¹, and with various NAA and IAA combinations, was tested. The variant with half concentration of macro- and microelements, supplemented with 30 g l¹ sucrose, and with growth regulators in the quantity of 1 μM proved optimum.