In an open gas exchange system with a thermocouple psychrometer the transpiration rate of the first leaf in 8-day plants of spring barley was measured in dependence on the water saturation deficit (ΔW _sat). The plants were cultivated in Richter's nutrient solution, either complete, or deficient in nitrogen or phosphorus. The cuticular transpiration (as measured in the dark) was unaffected by N and P deficiency. The N deficiency reduced the transpiration rate by increasing stomatal resistance since full water saturation of the leaf (67% rate of the control variant) up to stomatal closing at Δ W_sat = 14%. The P deficiency does not affect the transpiration rate at initial phases of wilting, but the stomata close only at a higher Δ W_sat (25%) than those in the control.

A lectin was isolated fromCanavalia brasiliensis Mart. seeds by combining solubility fractionation with affinity chromatography on Sephadex G-50. The lectin showed a carbohydrate specificity for D-mannose (D-glucose) binding and a requirement for Ca²⁺ and Mn²⁺. All the hemagglutinating activity was found in the cotyledons and the presence of the lectin was followed during the first 15 days of plant germination, through the activity against rabbit erythrocytes, the presence of the "lectin peak" in Sephadex G-50 affinity chromatography, presence of the "lectin bands" in SDS-polyacrylamide gel electrophoresis and the "lectin arcs and rockets" in immunoelectrophoresis in agarose gel. On application of all these methods the lectin showed a differentiated metabolism, disappearing more slowly than the other high molecular weight proteins of the seed.

In five-day-old etiolated pea seedlings an increase in IAA content and in L-tryptophan aminotransferase (TAT) and L-tryptophan dehydrogenase (TDH) activities in the apical part of the epicotyl was found 12 h after root excision, which was followed by a decrease up to 48 h. In ten-day-old seedlings a continuous decrease in IAA, TAT and TDH levels in the apical part of the epicotyl was recorded up to 48 h after root excision. This indicates a growth-correlative effect of the root becoming evident in dependence on plant ontogenesis in changes of IAA content and activities of the above enzymes catalysing IAA synthesis.

Proteins diffusing from tobacco pollen grains exhibit different phosphohydrolytic activities. Molecular sieving produces nuclease fractionation into forms I, II and III with apparent molecular masses ≥ 60 × 10³, 32.9 × 10³ and 24.6 × 10³, respectively, and separation of principal forms II and III from phosphatase and major part of 5'- and 3'-nucleotidase activities. These forms did not differ in the mode of substrate attack and were combined for further enzyme characterization.
The preparation had 3'-nueleotidase activity even after further purification by DEAE-cellulose chromatography. The enzyme is an endonuclease with preference for single stranded molecules. The endolytical cleavage of native DNA occurs simultaneously in both strands and generates limit products of about 58 pairs of nucleotides. DNA duplex polymers are also cleaved by a terminally-directed, exonuclease-like process. The products of DNA degradation are oligonucleotides and 5'-mononucleotides. In the presence of NaCl, both endolytical and exonucleaselike activities on bihelical DNA are inhibited and the proportion of mono-to oligonucleotides produced increases. The enzyme can rapidly convert superhelical plasmid DNA to a nicked open circular form, and then to a unit-length linear molecule.
On the basis of these properties and of those found earlier (sugar-unspecificity, acidic pH optimum, activation by Zn²⁺ ions), the extracellular nuclease of tobacco pollen can be classified as plant nuclease I (EC 3.1.30.x).

The effects of PEG 6000 priming on germination performance of aged wheat seed lots have been studied. A correct application of osmopriming treatment indicated a relationship between the pattern of water absorption, the reactivation of mitotic activity and the start and synchronization of germination. The possibility of controlling pregerminative events by means of this treatment is discussed on the physiological basis of seed germination.

A number of amino acids have been tested for their ability to inhibit the cytokinininduced synthesis of betacyanin inAmaranthus caudatus cotyledons. Under the conditions employed there was not any serious inhibition of pigment synthesis at amino acid concentrations belowca. 20 μg ml^-1. Amino acids such as methionine, γ-aminobutyric acid and leucine did not give rise to serious inhibition belowca. 200 μg ml^-1. At amino acid concentrations ofca. 2000 μg ml^-1, inhibitions of pigment synthesis was in all instances complete.

3-day-old seedlings ofVicia faba L. were put onto a diluted Knop's solution containing the tested substances within the intentional concentration range and left there for 7 days. In comparison with controls in plain nutrient solution, the DHPA treated plants revealed a suppression of shoot and root development. The main root growth was less sensitive than root branching. 8 h exposure was sufficient to gain a distinct effect. Microscopically the block of mitosis and/or cytokinesis, the formation of binucleate cells and local tissue damage were revealed. Under the given conditions, the cytokinins (BAP, (9R)BAP, iP, (9R)iP) proved to be much more powerful inhibitors than DHPA, whereas adenine and adenosine were less impairing.

A critical analysis of karyotype and meiosis ofBowiea volubilis Harv. showed normal bivalent formation with considerable irregularities in meiosis. Asynchrony is manifested to a significant extent within the anther where the range is between pollen grains and early stages of pollen mother cells.

Rapid multiplication of axillary shoots of oak and linden has been achieved on broad-leaved tree medium (BTM) and woody plant medium (WPM) containing low level of cytokinin (BAP 0.2-1.0 mg l^-1). High rooting percentages (80-95%) were obtained on low salt, low sucrose media, containing low level of auxins. Rooted plants were transplanted into pots containing a mixture of peat and perlite. Most of the plants (90-95%) survived the transfer. After the hardening off period the new plants were planted in the field.

Salicylate administered to detached tobacco (Nicotiana tabacum L.) leaves kept in the light rapidly induced an increase in stomatal resistance. This effect was not the result of water stress. Both the concentration of salicylate and the duration of the application to leaves affected the extent of the stomatal response. Application of salicylate for short periods showed that, once the stomatal response started, it was maintained for long period of time in the absence of further supply. K⁺ or Ca²⁺ were able to lower the stomatal resistance induced by salicylate, but only when both the ions were administered together with salicylate the stomatal closure was prevented. The results suggest that salicylate elicits some alterations interfering with the control of, stomatal movements, possibly affecting the integrity of cell membranes.

A low reproducibility of some characteristics in the life cycle of the volvocal algaChlamydomonas geitleri was observed in repeated experiments. The sets of the cultures were very similar in the number of the studied characteristics, but some of them differed significantly in one or several characteristics whereas the others agreed in a whole set. This is documented by the growth in a nitrogenless medium, the formation of zygotes, and their maturation and germination. The results of a small representative set of experiments were treated by an analysis of variance. Some possible explanations are discussed.

The occurrence of polysomaty was noted in a diploid cytotype ofUrginea indica with B chromosomes. These accessories could be clearly distinguished from the other chromosomes in their stainability, very small size, morphology, variability and irregular behaviour. The variant nuclei were hyperdiploid, hypertriploid and hypertetraploid. B chromosomes were noted only in diploid cells and no accessories could be recorded in cells showing higher chromosome number.
The amount of DNA content as indicated by the absorbance is rather low as compared to the diploid without accessories which may be due to the shorter size of the chromosomes. Under ultrastructural study subterminal centromeric region of B chromosome show low electron dense appearance.

On rooting the poplar stem cutting, the growth processes are coordinated so as to ensure optimum development of the new, vegetatively acquired individual. At first, adventitious roots develop on the cutting from latent root primordia. A part of them is short-lived, but in the meantime other, the so-called wound adventitious roots initiate from the callus on the lower cut surface of the cutting, which complement the permanent root system. In this way, conditions are prepared for a rapid growth and development of the stem, which forms from the upper bud on the cutting. The action of apical meristems providing the elongation of the stem and root, is followed by the action of vascular cambium. By the radial growth of organs controlled by cambium, the capacity of substance transport increases relatively to progressing development of the new plant. In the buried stem cutting cambium is the first to start functioning. Its reactivation is slow, discontinuous, and at the beginning it depends on local stimulating sources of the cutting itself. It was observed for the first time that, in addition to expanding buds, activated root primordia are also such sources of stimuli. The overall induction of cambial activity in the cutting occurs only in the period of rapid growth and development of the new stem, which thus becomes the main source of factors controlling the cambial activity of the cutting. In comparison with the growth of stem and cutting, the radial growth of adventitious roots is limited and there are considerable differences in the thickness of radial increments between individual roots.

Salinity caused a consistent reduction in the growth of cowpea plants and water content in their leaves. The total as well as the pigment fractions, except carotenoids, exhibited lower values than those of control plants at almost all salinity levels. With the rise of salinization, the total nitrogen and potassium contents in the leaves were decreased but the sodium content was increased and phosphorus content was not significantly affected as compared with the controls.
The application of IAA to salt-treated plants increased the water content in the leaves but it had no effect on the number of leaves and the stem length. The pigment contents in the leaves were either promoted or inhibited with the application of IAA, depending upon the level of salinization. The application of IAA to plants irrigated with water of the highest salinity level was effective in increasing the potassium content in the leaves as compared with the control, but it had no effect on the other mineral elements.

Supply of 0.01 to 5.0 mM salicylic, caffeic and gallic acids, either during imbibition of seeds for 24 to 48 h or during seedling growth increased anthocyanin production in maize (Zea mays L. cv. Ganga safed-2) roots. While tyrosine had no effect, phenylalanine either in the presence or absence of the phenolic acids increased anthocyanin content. Glucose in a concentration range of 1 to 20 mM and shikimic acid in 0.01 to 5.0 mM range also increased pigment level, which was higher in the presence of salicylic acid than in it.s absence. The experiments demonstrate the possibility of some indirect effects of salicylic acid and other phenolic acids on anthocyanin synthesis.