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.

The content and changes in the activity of phosphogluconate dehydrogenase were followed in leaf tissues of tobacco plants infected with the potato virus Y (PVY) in the acute phase of infection. The activity of the enzyme was higher in virus-infected tissues during the entire experimental period compared with the values found in healthy control plants in both crude homogenate and partially purified enzyme preparation. The courses of the activity curves of both the crude extract and partially purified enzyme preparations were consistent and correlated with the reproduction curve of the virus. These results suggest that increased activity of the enzyme was a result of its coarse regulation and indicate its immediate involvement in"de novo" biosynthesis of the virus via the oxidative pentose phosphate pathway.

The content of endogenous cytokinin-like substances and the release of ethylene were determined in leaves of different insertion of sunflower plants during their ontogeny. The content of cytokinin-like substances was highest in the leaves on the middle part of the stem (that is in leaves just before full expansion), with a decrease occurring both towards the base and the apex of the stem, when followed at four growth phases (vegetative plants, plants with inflorescence diameter up to 0.5 cm, plants with inflorescence diameter up to 3 cm, and plants in flower). Changes in the content of cytokinin-like substances during the ontogeny of the leaf also corresponded to this pattern. Data obtained with the leaf at the third node from the basis of the stem showed that the level of cytokinin-like substances first sharply increased, and then after reaching maximal value (at the time when leaf blade area reached approximately 70 % of the final value) slowly and continuously decreased.
The highest amount of ethylene released from the leaves was recorded in basal leaves and then also in apical leaves, whereas the leaves with the largest blade area situated at the central part of the stem released the lowest amount of ethylene. This pattern was repeatedly found at all four selected growth phases of sunflower plants.

Benzylaminopurine and thidiazuron stimulated shoot proliferation ofTilia, Sorbus andRobinia. Low concentration of BAP (0.2-1.0 mg I^-1) promoted axillary bud formation and shoot elongation. Thidiazuron displayed high cytokinin activity at very low concentrations (0.002-0.05 mg I^-1). Shoot number induced on media containing thidiazuron was large. Numerous shoots were produced on the media containing BAP together with thidiazuron. Shoots produced on media containing thidiazuron or BAP together with thidiazuron rooted after transfer to medium supplemented with low concentration of auxin (IBA or NAA).

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.

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.

Fractions of humic acids (HA-K⁺) of molecular mass between 500 and 300 000 and exceeding 300 000 showed a very high nitrite depleting ability, whereas the fraction of HA-K⁺ with molecular mass lower than 500 had little or no such effect. Autoclaving HA-K⁺ (121 °C, 20 min) decreased the nitrite-depleting ability to about a half. This observation correlates with the results of mutagenic studies in Arabidopsis thaliana, demonstrating the inhibitory effect of HA-K⁺ and its fractions on the formation of mutagenic N-methyl-N-nitrosourea (MNU) from the nitrosation mixture of N-methylurea and nitrite. Nonfractionated HA-K⁺ had no inhibitory effect towards the mutagenic activity of preformed direct acting MNU or towards the activation of the promutagen N-nitrosodimethylamine to a mutagenic product.

The data of Rowet al. (1961) on endogenous indoleacetylaspartic acid in tomato plants were reexamined. It was shown that two indole compounds were present in ethanolic extract of tomato stems and leaves. The predominating substance was concluded to be N-malonyltryptophan on account of its UV- and IR-spectra, colour reactions with the Ehrlich and Salkovski reagents and products of acidic and alkaline hydrolyses. The chemical nature of the second indole compound remained unknown. It differed from N-malonyltryptophan, N-aeetyltryptophan, indoleacetylaspartic acid and indoleacetic acid and may result from non-enzymatic transformation of N-malonyltryptophan.

Recurrent application (17 administrations in 38 days) of 14 pesticides (Karathane FN 57, Fundazol 50 WP, Dithane M 45, Topsin M 70 WP, Perozin 75 B, Fademorf EK 20, Novozir MN 80, Metation E 50, Pirimor DP, Decemtion EK 20, Zeazin 50 DP, Fatex EK 80, maleic hydrazide and Ethrel) did not increase (with the exception of maleic hydrazide) the frequency of somatic mutations in a heterozygous chlorophyll mutant ofNicotiana tabacumL. var.xanthi n. c. None of the four tested pesticides (Fademorf EK 20, Decemtion EK 20, maleic hydrazide and Ethrel) were transformed in tobacco plants to a stable mutagenic or promutagenic product active in theSalmonella (Ames) mutagenicity assay.

An analysis of axillary meristem (axillary bud) localization of radish (Raphanus sativus L. cv. Tetra-Iłówiecka) was undertaken on vernalized (flowering) and unvernalized (vegetative) plants. It has been shown that the localization of these meristems can be different on successive nodes of the same plant and is connected with the development stages of the plants. The axillary meristems can arise on the stem as well as in the leaf axil or on the base of the subtending leaf. The localization of axillary meristems has been discussed in relation to growth directions and growth correlations inside the meristematic region of the shoot apex.

Crown galls and hairy roots were induced inin vitro cultivated seedlings ofAtropa belladonna by differentAgrobacterium tumefaciens andA. rhizogenes strains. During furtherin vitro cultivation, tumors and hairy roots showed high differentiation ability which persisted for at least one year ofin vitro culture. Only root cultures, induced by Ri plasmid A4, synthesized detectable amounts of alkaloids.

Effect of abscisic acid on cell permeability in leaves ofIresine u allisi hort. and roots ofBeta vulgaris L. were examined. An increase of betacyanin leakage from leaf cells was shown by ABA at 10^-4, 10^-7 or 10^-9 M concentrations in water solution at 25 °C. The efflux of batacyanin from tissues did not change during the joint action of ABA and PEG 1000. ABA could lower the betacyanin leakage fromIresine leaves and beet-root slices under severe osmotic stress, as was found by deplasmolysis. The results suggest that ABA elicits some alteration in density of tonoplast membranes under dehydration.

A haemagglutinating material was isolated and purified from the phosphate buffered saline extract of the seeds of the jack fruit using an immobilized N-aeetyl-D-galactosamine column. This material was composed of two iso-lectins of molecular masses 11 500 and 15 000. The lectins agglutinated native washed red blood cells of the human A, B and 0 groups and sheep, rabbit and mouse erythrocytes. The lectins were found to be composed of single polypeptide chains and they contained no covalently linked sugars. The lower molecular mass material was present in considerably greater quantity than the higher molecular mass component. On isoelectric focussing on PAG the lectins gave a spread of components with calculated pI between 6.0 and 8.3.

Methyl jasmonate (JA-Me) at a concentration of 0.5% in lanolin paste totally inhibited bulblets formation induced by benzyladenine in intactMuscari bulbs. Lower concentrations of JA-Me delayed development and growth of bulblets induced by benzyladenine. It seems that methyl jasmonate acts as a powerful inhibitor of cell division induced by cytokinin in used test. In comparison with methyl jasmonate, abscisic acid did not show an inhibitory effect on bulblets formation induced by benzyladenine, even in a higher concentration.