The effect of manganese chloride (10 mg Mn l^-1), EDTA (18 mg l^-1) and a mixture of these compounds on the nitrogen balance in maize xylem exudate was investigated. The compounds were applied as experimental solutions to the roots of 20 day old plants 24 h before excision. Application of Mn resulting in a lowered nitrogen level in the xylem exudate increased the relative content of the organic N-compounds in the exudate, particularly that of free amino acids. EDTA appreciably enhanced the content of total nitrogen in xylem exudate, however no significant changes were found in the proportion of inorganic and organic N-compounds in comparison with the water control. The significant features of the free amino acid exudate fraction of all experimental variants were, among others, the relatively high lysine content and the absence of proline arid sulphur containing amino acids. By gel filtration on Sephadex G-25 of xylem exudates UV (254 nm) absorbing fractions, four in the water control, five in Mn and six in EDTA variants were isolated. The UV absorbing fractions with the exception of one in each experimental variant (K_av 0.73 in water control, K_av 0.61 in Mn-variant, K_av 0.75 in EDTA and Mn + EDTA variant) were of peptide character, proline and sulphur-containing amino acids were missing in them. In the exceptional UV absorbing fractions (K_av 0.61-0.75) in spite of their high N-content (10.23%) after hydrolysis practically no amino acid could be detected.

Treflan has the ability to induce polyploidy inAllium cepa root tips. The frequency of polyploidy was reduced after allowing the roots to recover, which indicates that the process of polyploidy is a reversible one, if we apply Treflan for a short time (4 h). As soon as the chemioal is removed from the cells, they go on with their normal way in division. It was found that the concentration 350 × 10^-5 ml Treflan per 100 ml water is an effective concentration in producing polyploidy in the roots ofAllium cepa.
Treflan induced C-tumours in root tips ofAllium cepa. Two types of enlargement were noticed, complete swelling along the majority of root tips and complete swelling with a certain enlargement immediately after 2 mm terminal tips. The histological examination of these zones revealed that swellings were due to cell enlargement both in meristematic and in tumour zones. This conclusion was evidenced by the results obtained from the nucleoplasmic index.

The final length of the root cell is the result of a series of prooesses which represent a transition of the growing cell from its origin up to the completion of its elongation. These processes are associated on the one hand with cell proliferation, or, after the termination of proliferation, with the proceeding DNA synthesis, and with cell elongation on the other. The group of properties characterizing the growth region of the root as a cytologically heterogeneous complex, is at the same time the group of causes which affect the length of root cells. The individual cases documented in the paper point out the fact that the mechanisms regulating growth processes, have a locally limited action, often only within one single cell, and that they are simultaneously subordinated to the regulatory mechanism which controls the growth of the root as an entirety.

Calcium deficiency resulted in a 20% increase in the total content of phenolic compounds in the shoots of 10-day-old wheat plants and in a 10% decrease in the roots compared with the control. Differences in specific activities of the lyases of the shikimate pathway (L-phenylalanine ammonia-lyase, E.C.4.3.1.5, PAL; L-tyrosine ammonia-lyase, TAL) were established between control and Ca-deficient wheat and pumpkin plants. The lyase activities were higher in the shoots of Ca-deficient plants and lower in their roots, compared with the control. Thus, there is a certain correlation between PAL and TAL activities on the one hand and the content of phenolic compounds on the other. The time course of PAL activity during a few first days of growth and the dependence of TAL activity on pH were also investigated.

A field experiment was conducted to study the effects of N doses and row-direction on LAI, light transmission, plant height and dry matter production in the pure and mixed stands of 3 wheat (Triticum aestivum L.) cultivars Moti, Sonalika, and NP 824 differing in plant height. The mixed stands gave more transmitted light and shorter plants than the pure stands but dry matter production was not much affected. Nitrogen application increased the plant height, LAI, and dry matter but decreased the transmitted light. Row direction had no influence on plant height, LAI and dry matter production.

Following a previous biological and serological evidence of tobacco necrosis virus by means of an electron microscope, isometric virus particles of an average size of 26 ± 0.5 nm were found, in ultrathin sections prepared from the tissue of sprouting buds of underground stalks and from that of runners butts with symptoms of mosaic line pattern, as well as from the tissue of the indicator plantChenopodium quinoa.

Cucumber mosaic virus (CMV) isolates obtained from spontaneously infected (1)Chelidonium majus L. and (2)Impatiens parviflora DC. plants growing in the same part of a scree forest in central Bohemia showed differences in ten test plants, but not in further 26 plant species tested and in TIP. Slight quantitative differences between both isolates were obtained in serological tests. Properties of both isolates did not suit precisely any proposed CMV strain classification.

Paracytic, anisocytic, anomocytic, transitional forms, tetracytic, cyclocytic stomata and partly and completely amphicyclic forms are found, often on the same surface, in nine combinations. The most frequent type is paracytic. A few morphological variations in the basic types and eight types of abnormalities in stomata are recorded. The stomatal ontogeny may be mesogenous, mesoperigenous or perigenous. Trichomes are multicellular glandular club-shaped and unicellular eglandular. The taxonomic significance of stomata is indicated.

The effects of some growth regulators on the dark-germinating seeds ofCucumis anguria have been investigated. GA₃, 6-BA and ethrel strongly promoted the germination of seeds kept in white light. GA₃ had no effect in counteracting the far red effect, but did counteract partially the blue light. Ethrel partially counteracted both the far red and blue light effect. No interaction could be found between red light and GA₃ or 6-BA.

The nutational movements performed by the leaves of the "Sensitive plant",Mimosa pudica L., result from periodical turgor variations taking place in the parenchymatous cells of specialized motor organs. The trajectories in the three kinds of leaf motor organs usually show irregular elliptical paths with a period ranging from 10 to 60 min. The morphological analogy of these turgor movements is discussed in relation to nutational movements observed in growing organs.

The activity of an enzyme system decomposing phloridzin was investigated in fruitbearing and nonbearing spurs of apple trees, Landsberger Reinette cv., throughout vegetation. Acetone powder obtained from xylem sap of apple spurs was incubated with phloridzinsubstratum in citric buffer at pH 5.5 for 12, 18 and 24 h at 30 °C. A paper and thin-layer chromatography as well aa a spectrophotometric assay were employed for tentative identification of enzymic degradation products. Phloretic acid (PA), co-factor of IAA-oxidase, as well as phloretin (Pin), and phloroglucinol (PI) were found after the digestion of phloridzin. The chromatographed enzyme reaction products were measured densitometrically. The activity of the enzyme system was estimated by its efficiency in PA production and phloridzin disappearance. Obtained values, expressed in percentages, showed that the enzyme activity in fruitbearing spurs was much higher than in nonbearing ones; 30 and 10% of released PA in July, respectively. Because fruitbearing spurs of the apple tree are possibly additionally supplied with auxin translocated from developing seeds, an adaptive character of the enzyme system producing PA, a known auxin repressor, is suggested.

Hydration level of seeds determines vigour of soybean,Glycine max (L.) Merr. The seeds should contain at least 20% of moisture for a good performance at low temperatures. This hydration level can be reached by pre-sowing exposure of seeds in water saturated atmosphere (WSA). The exposure decreases both visible symptoms of chilling injury and leaching electrolytes during imbibition, and increases both germination and growth of seedlings at 10 to 12 °C. It is concluded that the cell membrane integrity is re-established in a course of the WSA exposure.

Isolated barley embryos were cultivated aseptically in three different complete media. The growth of the primary root of each embryo was measured during four days of cultivation. Embryos were cultivated on three different consistencies of media: on agar plates, on cellulose tissue moistened with the medium and in liquid shaken cultures. The last way of cultivation yielded the highest degree of the growth of roots. Optimum combination of conditions in shaken liquid medium was selected on the basis of systematic study. The growth of roots of isolated embryos under appropriate conditions approaches that of roots of seedlings cultived on moistened blotting paper.

Roots were excised from barley embryos cultivated in the complete liquid nutrient solution and cultivated in the same nutrient solution separately. The excised roots continued their growth but a progressive decrease in the growth rate was observed. There was a considerable short-term drop of the mitotic activity immediately after excision, which was followed by a compensatory increase and then equilibrium was reached 12 h after excision. During the next at least three days, the mitotic index of isolated barley roots varied between 5-6.5%, which is slightly lower than the mitotic index of the root meristems of isolated barley embryos under identical conditions. The mitotic cycle index of isolated barley roots and the size of the root meristem later decreased gradually.

Xylem exudates were collected from 20-day-old maize seedlings grown for 24 h in labelled manganese chloride solution (10 ppm) with or without EDTA (18 mgl^-1).
The distribution of radioactivity on paper ohromatograms of exudates did not show the existence of free Mn. Fractionation of exudate constituents by gel filtration on Sephadex G-26 showed that⁵⁴Mn is associated with three UV (254 nm) -absorbing fractions. Two fractions contain amino acids (M. wt.:≧ 10 000 and ∼ 900). The third fraction (M. wt. ∼ 600) however, appears to be a carrier of a different type, which is practically amino acid free, although it contains 10.23% N (by elementary analysis). The properties of this carrier are discussed. Application of EDTA has favoured the; transport of Mn in xylem sap with fractions of relatively lower molecular weights.

When cultivated in culture solutions salinized with different concentrations (0 to 100 meq I^-1), of either NaCl or Na₂SO₄, the oil producing castor bean, flax and sunflower plants exhibited significant changes in their water relationship parameters (stomatal frequency, rate of transpiration and water content). Although the trend of these changes was nearly the same, their magnitudes depended on the plant treated as well as on the type and level of the salinizing agent. In this respect the values of the stomatal frequency and the rates of transpiration increased significantly with the rise of salinization up to the level 40 meq I^-1. Above this the values of these parameters were generally reduced with the rise of salinization up to the highest level used. In addition a considerable number of stomata in either the lower or upper epidermis was found to be closed at the levels ranging from 60-100 meq l^-1. The water content of leaves of either castor bean or sunflower subjected to low or moderate salinization levels, remained more or less constant, but with a general tendency to decrease at high levels. However, in the case of flax the leaf water content was generally elevated at nearly all salinization levels.

Carbon dioxide compensation concentration,Г, net photosynthetic rate,Pn, and photorespiration rate,Rl, were measured in young, adult and old primary leaves ofPhaseolus vulgaris L. over a range of photon flux densities using a closed system with IRGA. Irrespective of leaf age,Г decreased rapidly with rising photon flux density up toca. 260 (μmol m^-2 s^-1. From this valueГ did not change with photon flux density under constant temperature, reaching on the average 178, 118 and 239 mg m^-3 in young, adult and old leaves, respectively. Changes with age in curves relatingPn andRl to photon flux density were found.

Relationships between the CO₂ compensation concentration, the slope of CO₂ curves of P_n and the energy of irradiance were studied in adult leaves ofFagus silvatica L. seedlings. A gazometric method of quantitative analysis of air flow, in a closed system, was applied.
P_n and the slope of CO₂ curve of P_n increased with increasing irradiance at constant temperature of the abaxial leaf surface (19 ± 0.5 °C), however, the CO₂ compensation concentration decreased. This physiological characteristic changed relatively slightly at irradiance close to saturation irradiance (235 Wm^-2).

Nitrogen contents were determined in 20 species of "resurrection plants",i.e. plants with leaves which are able to revive from an air-dry state (viz. Boea hygroscopica, Borya nitida, Cheilanthes sieberi, Coleochloa pallidior, C. setifera, Craterostigma plantagineum, Myrothamnus flabellifolia, Oropetium capense, Pellaea calomelanos, P. falcata, P, viridis, Polypodium polypodioides, Ramondia pyrenaica, Selaginella lepidophylla, Sporobolus stapfianus, Talbotia elegans,Tripogon loliiformis, Xerophyta retinervis, X. villosa, X. viscosa), and in three desiccation sensitive species (Eragrostis tenuifolia, Selaginella kraussiana andSporobolus pyramidalis).
In a preponderance of resurrection plants insoluble nitrogen content fell during dehydration of intact plants and soluble non-protein N rose. Both changes were particularly marked in species which lose chlorophyll and thylakoid structure during drying. These trends were usually only partially reversed after 24 h rehydration. Recovery of¹⁴C-leucine incorporation in rehydrating leaves was slow.
Leaves of desiccation sensitive vascular plants tended on the average to lose soluble protein rather than insoluble N during drying, and tended to have higher soluble non-protein N contents than tolerant plants.
However, similarity in the changes in N-contents inXerophyta villosa leaves killed by airdrying compared to leaves surviving air-drying, opposes the view that death was due to excessive loss of protein.

Significant differences in the net photosynthetic rate (P_N) of sevenHevea brasiliensis clones are found. Though much smaller than the internal resistance to carbon dioxide diffusion (r_i), the stomatal resistance to CO₂ diffusion (r_s') shows larger variation among the clones and might largely explain the differences in P_N.

The frequencies of chlorophyll mutants were investigated in anther cultures derived from mutagen-treated plants ofN. tabacum cv. Samsun (haploid level) and in the seed offspring from the same treated plants (diploid level). Comparison of the induced mutation frequencies at the haploid and diploid levels demonstrated that selection existed against the haploid embryoids with induced chlorophyll deficient mutations. The diploid vegetative stage with phenotypic expression of the chlorophyll mutation was more vital than the haploid one. The suitability of anther cultures for studying induced mutagenesis is discussed.

The effect of different growth substances on the development of normal and abnormal stomata are presented. Anomocytic, paracytic, anisocytic and stoma with a single subsidiary cell are observed. Abnormal developments like persistent stomatal cells, degeneration of guard cells, unusual thickening, unequal guard cells, single guard cells and size and shape of the pore are noticed in various growth substances. The growth substances also affect the stomatal frequency, stomatal index, epidermal frequency and size of guard and epidermal cells in both the plants. The highest meristematic activity is found in MOR 100 ppm in brinjal and in GA 25 ppm in tomato. The largest size of stomata is found in COL 25 ppm in brinjal and in MH 50 ppm in tomato. The same growth substance responds differently in the two plants.

Trifluralin was found to induce isodiametric enlargement ofAllium cepa root tip cells in the elongation zone. It enhanced the endogenous oxygen uptake of the excised root tips. The herbicide was found to have no marked effect on the dry weight of the root tips. It is suggested that the herbicide may exert its effect onAllium cepa root tips through its enhancement of ethylene production.

Thein vitro embryoids ofEschscholzia californica do not form normal plantlets in cultures. However, 6-benzylaminopurine and gibberellic acid, when added to the medium, partially alleviate this inhibition. Experiments involving decotylization, and culture of embryoids at different stages, indicated the cardinal role of cotyledons in plumular growth.