The blade area and the number of stomata were studied in the cotyledons of five cultivars ofBrassica oleracea L., cultivated in a growth chamber and in the greenhouse, respectively. Characteristic differences between different varieties were found in the number of stomata per unit area as well as in their occurrence on both the adaxial and abaxial surfaces.

A relatively high auxin level was found in old leaves from the lower part of long shoots of young apple trees using the straight growth bioassay on wheat coleoptile segments. The auxin level remains almost constant during summer and autumn.

Cotyledons of 15 day-old seedlings of fiveBrassica oleracea L. varieties were surveyed to identify salient anatomical features. Both palisade parenchyma cells present in the first subepidermal layer and stomata were found to differ in size.

The paper deals with the problem of the significance of Ca²⁺ for the growth of algae, its participation in the process of nitrate and ammonium nitrogen utilization, and with the possibility of substituting Sr²⁺ for it. It was revealed that calcium represents a microbiogenous element for the algae tested, which takes part in the utilization of nitrate nitrogen. It cannot be replaced by strontium especially at a high growth rate of mixotrophically cultivated algae (ina glucose medium).

A previous report on the mechanism of diurnal oscillations is supplemented here by data concerning causes of irregularities in their oscillation trajectories. Cinematographic records showed that the final trajectory is significantly influenced by the circumnutation oscillations of the stem. Amplitudes of these oscillations which are small(ca 0.7 mm as compared with 5 X larger amplitudes of leaves when measured at the leaf tip) can be enlarged up to 10 times the value at the apical tip of the leaf. These nutations are responsible for side-deviations of space spirals of growing leaves in the direction of their shorter half axis. This explanation is based on the occurrence of side-deviations of leaf trajectories which correlate with the actual position of the nutation phase of the stem. Concurrent frequencies of the two oscillations (= diurnal rhythm) indicate that nyctinastic oscillations of the leaves are controlled by the same mechanism as is the circumnutation of the stem.

Allopolyploids were raised by oolchicine treatment of vegetative buds in the triploid hybrid of tetraploidPhaseolus species xP. calcaratus cross. They had 70 per cent pollen fertility and produced many viable seeds. The average chromosome configuration per cell at MI in them was 1.56_IV + 0.01m + 29.30_II + l.llr. It has been concluded that the increased fertility in allopolyploids was due to more regular meiosis and the low frequency of quadrivalents indicated the occurrence of preferential pairing.

Studies underin vitro conditions withCuscuta stem tips have revealed that the parasite depends on the host for the supply of all essential requirements for its growth. The vestigial photosynthetic apparatus inCuscuta cannot meet its total requirements. Thus for supply of energy it depends primarily on the host. Inorganic nutrients seem to be of secondary importance and perhaps help to some extent in its independent metabolic pool. Carbohydrates, particularly sugars, are presumably tapped by the parasite from the translocating channels of the host and further utilised for its own growth. Besides sugars, which form the carbon and energy source, amino acids and growth substances are also found to be utilised. The mechanism of carbohydrate utilization inCuscuta has been postulated.

The action of exogenously applied hormones in the induction of morphogenesis inLimnophila chinensis (Osb.) Merr. tissue culture has been demonstrated. Stem expiants were grown on Murashige and Skoog's medium containing various levels of kinetin, gibberellic acid and indole-3-acetic acid. Formation of roots, shoots (normal or abnormal), plantlets and friable, hard or nodulated calluses depended largely on the hormone levels used. The formation of normal shoots and roots were stimulated by treatment with kinetin. GA₃ treatment stimulated the bud differentiation but inhibited the root initiation. A combination of kinetin and GA₃ gave variable results.

Biologioal activities of humic acid (Na salt), hymatomelanic acid (Na salt), lignofulvic acid and of fulvic acids isolated from peat were studied by means of the auxin-, gibberellin-, and cytokinin- bioassays. All the four tested fractions showed higher or lower stimulating activity in these bioassays. However, the stimulating effect is considerably lower and cannot be interpreted as phytohormone activity. Some fractions in some concentrations also showed inhibitory effects. The manner of biological action of the studied fractions might bo the result of interaction of their respective components.

The interaction of nutation oscillation and phototropic curvature mechanisms of growing pine hypocotyl(Pinus silvestris L.) was investigated. Nutation parameters of growing hypocotyl are not affected by continuous lateral illumination. Frequency and nutation amplitudes undergo changes which are dependent on plant development and are nearly the same when plants are illuminated from one side or from above. Lateral illumination, however, induces a phase shift. This deviation from a normal nutation rhythm usually disappears after a period of time equal to three nutation revolutions,i.e. after 12 h.
The positive phototropio response of nutating hypocotyl is dependent on the phase in which the hypocotyl is exposed to the lateral illumination:(a) nutation perihelium,(b) ahelium and(c) nutation interphase. These response-variants are compared with the expected gradients of plant hormones at the opposite sites of the hypocotyle. Analysis of location of the individual movement reactions(i.e. oscillations as a component of the geocontrol system and phototropic curvature) together with the determination of the zone of maximum elongation indicates the existence of different receptory centres of these two movement systems. In the case of the phototropic response reaction it is possible to consider the presence of different photo- and biochemical mechanisms at least for a part of this system.

The lowering of the cultivation temperature allows one to alter the growth intensity and micromorphology of tobacco cell strains specifically. By a long-term low temperature treatment the effect is deepened, by transferring inocula into normal cultivation temperature it is repaired. Both the growth and morphogenic effects of the low temperature correspond to those of cytokinins, exhibiting even the same strain specificity.

Excised barley embryos were treated with methyl methanesulphonate and cultivatedin vitro in water or in a nutrient medium. The alkylating compound induced a high frequency of chromosome aberrations observed at anaphase and metaphase and depressed the mitotic division in the root-tips of excised embryos.

In contrast to their soil counterparts, algal fulvic acids were more inhibitory than the corresponding humic acids. Fulvic and humic acids fromFucus vesiculosus were more efficient than the correspondingLaminaria digitata acids in inactivating the enzyme.Laminaria humic acids, which have no phenolic hydroxyls, showed a concentration dependent inhibition hardly in accordance with the presumed role played by these groups in the activity of oxidases.

Time-lapse microcinecmatography showed that the negative prototactic response of the chloroplast lasted 11-19 min and was completed 40 min after the beginning of irradiation; the contraction reached 11% in 60 min.

A propagation method for someFreesia cultivars usingin vitro cultures is described. Bud and root formation was evoked in callus tissue culture on a modified Murashige and Skoog's medium. Reconstituted plants were transferred into soil and cultivated in the glasshouse.

The tips of the rhizomorphs ofSphaerostilbe repens transferred on agar medium regenerate some aggregated organs without an intermediate mycelium stage. Each extremity of the drawn rhizomorphs can give rise to eoremia on its air face and to rhizomorphs on the contact with tho culture medium. These heterogeneous environmental factors impose polarized regeneration, easily inverted, upon the rhizomorphs. Nevertheless, a residual and stable polarity remains; it is attributed to the apex which is more capable of bearing new organs than the other extremity. Tho efficiency to regenerate depends on the ago of collulos and on tho size of tho rhizomorph tip; howover it is very difficult to provent the formation of new aggregated organs.

Uridine-³H incorporation and RNA concentration were investigated in different parts of the shoot apical meristem ofChenopodium rubrum using autoradiography and cytophotometry. A single inductive cycle was sufficient to bring about postinductive first events in the shoot apex but not for complete flower differentiation. The initial activation of RNA synthesis manifested itself in all zones of the apex. The first increase was more conspicuous in the peripheral than in the central zone. The indications of the first events in the apices after a single inductive cycle disappear prior to morphological reversal to the vegetative state. Induction by three short days led to rapid flower differentiation. The increase in RNA synthesis and concentration was most conspicuous in the central zone in this case. The ratio of RNA synthesis and content between bud and leaf primordia (B/L) also change in relation to photoperiodic induction. In vegetative plants the B/L ratio was low while after induction it increased.
The shifts in activity of RNA synthesis observed in the shoot apical meristem are related to the changes in growth activity of the different parts of the apex. The growth ratios in the apices bear the character of growth correlations. The change in the growth correlations following photoperiodic induction together with the total activation of RNA synthesis are considered to represent one of the first events of the transition to the reproductive state.

The effect of mannitol, glucose and sucrose on the stomatal behaviour of two desert species,Merremia aegyptia andM. dissecta has been studied. Stomatal opening did not uniformly depend on the decrease in turgor of the epidermal and subsidiary cells caused by the different osmotic potential of the sugars. Sucrose caused plasmolysis of the subsidiary cells only but this was not accompanied by the opening of the stomatal pore. InM. aegyptia, no plasmolysis was seen either in epidermal or subsidiary cells, even the stomata opened; inM. dissecta, on the other hand, plasmolysis occurred in these cells without any stomatal opening, after incubation in glucose or mannitol. Mannitol is least absorbed, glucose slightly more and sucrose is absorbed to a very large extent in the guard cells when the materials were inoubated in the respective sugar solutions. However, the absorption of these three sugars was almost always larger in isolated epidermal strips than in discs; in detached intact leaves it was still more reduced.

The effect of gibberellic acid, benzyladenine and a mixture of these compounds on the activity of some hydrolytic enzymes was studied in hyacinth bulbs non-exposed to low temperatures. Plant growth regulators were applied on the heel of dormant bulbs in the middle of July. An intensive elongation of the inflorescence was observed only in the plants treated previously with GA₃ and grown in a warm greenhouse for 63 and 84 days. The activities of amylase, invertase and acid phosphatase were higher in the flower buds of unrooted bulbs treated with growth regulators than in the control plants, although growth regulators did not affect the level of extractable proteins. The elongation of the inflorescence in the plants treated with gibberellic acid was correlated with a sharp increase of invertase activity in this organ. The effect of GA₃ and BA on the activity of other enzymes in buds and scales varied with the period of plant growth.

Total activities of nitrate and nitrite reductases were higher in 4 to 20 day old maize plants in the leaves than in the roots. The ratio of activities found in the leaves and in the roots respectively was much higher in the case of nitrate reductase than in the case of nitrite reductase. On the other hand higher glutamate dehydrogenase activity in the roots than in the leaves clearly indicates that the roots play a more important role in the assimilation of ammonium than in the assimilation of nitrate. When comparing the distribution of seminal and nodal adventitious roots of maize seedlings with the assimilation of inorganic nitrogen on the basis of enzyme levels, it could be deduced that during the first 20 days of seedling growth seminal roots were more involved in the assimilation of nitrate whereas nodal adventitious roots were more active in ammonium assimilation.

Soybean (Glycine max (L.) MERR. CV. 'Amsoy') plants were grown for 40 days in nutrient solution at various concentrations of ammonium. Maximum yield of dry matter was obtained at a concentration of 715 μM. Further increase in the concentration of ammonium resulted in a reduction in growth due to ammonium toxicity which affected both root and shoot development. The pattern of nitrogen accumulation in tops was consistent with the multiphasic uptake of ammonium and can be represented by 2 phases in the range 1.78 X 10-⁵-3.57 x X 10-³ M of ammonium.