Nitrogenase activity at periods of differentiation of heterocysts and akinetes was assayed by the acetylene reduction technique. There was no nitrogenase activity in ammoniumgrown, non-heterocystousAnabaena sp.; the activity appeared only after a lag-phase of about 17 - 21 h after the ammonium-grown culture had been transferred to medium free of combined nitrogen. This activity started appearing as the proheterocysts were developing to mature heterocysts. Maximum nitrogenase activity was attained with exponential phase of culture and mature heterocysts. This activity gradually decreased with the differentiation of akinetes. Only insignificant nitrogenase activity was observed in old cultures in which most cells had matured into akinetes.

Application of sodium chloride to crop plants in the culture medium leads to an increase in their endogenous content of free proline. There is a certain concentration of sodium chloride above which the proline content of the plants strongly rises (critical point). A relationship between endogenous sodium and proline contents could be found. In salt-sensitive plants (wheat) the critical point lies below that of salt-tolerant plants (barley). The critical concentration is not changed by certain alterations of the culture medium. The determination of the critical point by means of measurement of the proline concentration served as a basis for the analysis of the salt tolerance of crop plants.

After infection ofNicotiana tabacum cv. Samsun with tobacco mosaic virus (TMV) crude extracts from dark-green spots of upper leaves had a more strongly marked inhibitory effect upon TMV addedin vitro than crude extracts from the surrounding light-green tissue. Likewise, crude extracts from leaves ofNicotiana tabacum cv. Samsun showing recovery after infection with tobacco ringspot virus (TRV) were seen to have a marked inhibitory effect on TMV addedin vitro. The results obtained suggest that virus inhibitors are produced after virus infections not only in hypersensitive hosts but also in systemic hosts. Necrotizing processes are not an indispensable prerequisite of the production of virus-induced virus inhibitors.

The effect of silymarin complex on various types of expiants differing in their nutrition requirements was investigated. The growth of tumorous periwinkle (Catharanthus roseus [L.] G. Don) callus tissue was still identical with the control tissue at the silymarin concentration of 35 mg in 1000 ml of the nutrient medium. However, this silymarin concentration totally inhibited the growth of habituated periwinkle callus tissue; in the presence of 10 mg of silymarin, the growth of this tissue was similar to that of the corresponding tissue grown without silymarin. The growth of tobacco callus tissue (D-strain) requiring for its growth kinetin was reduced by 46.2% at the concentration 10 mg of silymarin in 1000 ml of nutrient medium, but its dry weight was increased by 21% in comparison with the control. Silymarin was most effective on the growth of callus derived from tobacco (Nicotiana glauca Grah:) stem pieces; callogenesis was observed in control tissue in 89.5% cases while in the presence of silymarin (10 mg) only in 48.6%. The primary callus growth was strongly inhibited, too (by 89.9%). The organogenesis onset was never observed on tobacco stem pieces cultured on a nutrient medium with kinetin and IAA in the presence of silymarin. When all types of expiants were transferred from the medium with silymarin on control medium, normal growth appeared very soon and the differences between the experimental and control expiants were smoothed out during two months. These results indicate that the observed changes might be due to the blocking of membrane system permeability leading to an insufficient supply of cells with nutrients and growth substances.

Seedlings of spring barley,Hordeum vulgare L. cv. Mirena, were grown in complete mineral solution (Richter's solution: R) or in solution lacking either phosphorus (R-P) or nitrogen (R-N) at low (LI: 28 W m^-2) or high (HI: 122 W m^-2) irradiance. Plants were kept in controlled environment chamber with 16 h photoperiod and 20 °C/15 °C day/night temperature. The experiment was terminated after 15 days when plants grown under R -N nad HI conditions died. The content of chlorophyll was estimated during the plant growth and content of nitrogen and phosphorus was determined at the end of the experiment. Deficiency of N and P induced higher chlorophyll formation at low irradiance. The efficiency of nitrogen and phosphorus utilization,i.e. ratio of plant dry mass/weight of N and P, respectively, per plant, was higher at HI in all experimental variants. Extremely high value of P utilization was found in plants grown under P-deficiency (850) as compared to the control (80). Understanding of interactions between the irradiance and deficiency of mineral nutrients is necessary for optimization of fertilization and understanding the mechanisms of action of mineral substances on plant structures and functions.

Eleven species of the genusAllium belonging to the sectionCepa, Phyllodolon, Rhizirideum, Melanocrommyum andAlliun ware investigated as to the presence of esterase isoenzymes by means of the gal isoelectric focusing which shows better resolution than polyaorylamide gel electrophoresis. In all examined species twenty six isoenzymes were found. The individual sections are well characterized by esterase isoenzymes revealed by this method, on the other hand, the differences, as shown by the Jaceard index, between the subganera are insignificant. Investigation of seven cultivars ofAllium cepa shows the isolated position of the cultivar Kaštická. These results are in full agreement with those found with use of the polyacrylamide gel electrophoresis and show the usefulness of gel isoelectric focusing for the solution of the chemotaxonomical problems.

Incorporation of [¹⁴C]-glutamate into soluble proteins accounted for about 14% of the total glutamate uptake, while < 1% of the ammo acid carbon was incorporated into chlorophylla. Most of the remaining 85% of the glutamate was retained in low molecular mass pools. High uptake rates appeared to be related to a "shift-up" phenomenon, resulting from the addition of fresh media. Apparent turnover times, estimated from reverse isotope dilution experiments, varied from about 1 to 3.5 h for the soluble proteins and about 3 to 5 h for chlorophyll a. Rapid changes in glutamate to glutamine ratios, resulting from changes in irradiance, suggest that the intermediary metabolism of glutamate is regulated by irradiance.

Callogenesis was induced in mature embryos. The efficiency of induction and the growth of calli were dependent on 2,4-D concentration. No regeneration of buds or shoots was observed in 720 calli studied, but most calli showed intensive root proliferation on the regeneration medium. Most of the root meristem cells maintained diploid chromosome number. Only a low proportion (about 3.5%) of tetraploid cells was found. No other chromosomal changes were observed. Chromosomal variability does not contribute to the inability of calli derived from mature barley embryos to form buds and shoots.

Leaf form and stomatal characteristics play an important part in the strategy of tall fescue (Festuca arundinacea Schreb) to limit water losses. Transpiration rates of artificially rolled leaves measured by potometer at varying wind velocities support this assertion.

The effect of FeSO₄.7H₂O, Fe₂(SO₄)₃.9H₂O, disodium salt of ethylene-diaminotetraacetic acid, dihydrate (EDTA) and N-(2-acetamido) iminodiacetic acid (ADA) and their combinations on the androgenesis was studiedin vitro in tobacco (cv. White Burley) and datura (Datura innoxia Mill.). Simultaneously the reversibility and irreversibility of the morphogenic process leading to the conversion of the pollen embryoid into complete plant was followed.
Complete plants developed in anthers on media with trivalent iron, chelated trivalent iron, chelated bivalent iron, bivalent iron in the presence of ADA and of media with EDTA. The number of androgenic plants in anthers increased in the following order: Fe₃₊ < Fe₃₊ EDTA ≦ ≦ EDTA < Fe²⁺ EDTA. The marked brown colour of cultured anthers was due to the presence of trivalent iron in the medium. The androgenic development was most rapid on the medium containing only trivalent iron, slower on media with chelated iron and slowest on medium with EDTA. The viability of cultures with complete plants decreased in the reverse order. No complete plants grew on media without trivalent iron and without EDTA and on media containing only bivalent iron whereas globular embryoids arose and developed continuously on these media. The anthers reacted in the same way on both complete and minimal media. Isolated embryoids formed complete plants in corresponding variants on complete media only.
The development of pollen embryoids into complete plants was stopped by the transfer of globular and torpedo-shaped embryoids from medium with EDTA to the medium without EDTA. Isolated greenish cotyledonar embryoids continued to grow even on the medium without EDTA.

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.

Nitrate reductase (NR) activity of bothPisum sativum L. cv. Bonneville andTriticum aestivum L. cv. Sonalika seedlings was influenced by the phytochrome system. Short durations of "red" irradiation (R) increased extractable levels of NR whereas subsequent short "far-red" irradiation (FR) partially inhibited the R modulated increases. Qualitatively, a negative correlation existed between thein vitro NR activities andin vivo phytochrome levels inPisum. "Blue" irradiation (B) also increased extractable levels of NR inTriticum. A partial action spectrum study made by exposing excised etiolated leaves ofTriticum and shoot apices ofPisum revealed a maximum increase in extractable NR activities and tissue nitrate level (inTriticum) at 656 nm. A partial action spectrum for the extracted enzyme ofTriticum indicated that at 700 nm the level of activity was increased (as compared to dark controls) more than by R (656 nm), FR (725 nm) or B (425 or 450 nm) irradiation, although all wavelengths used increased NR activity.

In the natural monsoon environment, the leaves of Bala and Jaya cultivars experienced more than 10 per cent LWD for about 8 and 6 1/2 h in the diurnal cycle, respectively. The maximum LWD of around 14 per cent occurred between 14.30 to 15.30 at the time of minimum relative humidity (EH) and maximum air temperature (Ta). On the other hand, under controlled environment conditions, LWD values of both the cultivars remained below 10 per cent in the entire diurnal cycle. There was a close relationship between LWD and Ta (r = 0.90 for Bala and 0.91 for Jaya) as well as RH (r = -0.95 for Bala and -0.85 for Jaya). The results suggested that RWC values obtained on an interval of 30 min were not enough to observe more than the general trend as a complete recovery of stress achieved within 25 min of rewatering the stressed leaves. Calculations indicated that the determination of LWD with the techniques using excised leaf are likely to incur error as rice leaf may loose water at a rate of 0.3 MPa min^-1.

The degree of tolerance of two crown gall tumors and leaf calli ofArabidopsis thaliana to BUdR was compared. The nopaline producing teratoma tumor tolerated BUdR in concentration as high as 2.10^-4 M. The tolerance of octopine producing unorganized crown gall tumor to BUdR was lower, but both exceeded significantly the degree of tolerance to BUdR of untransformedA. thaliana calli, where 10^-5 M BUdR already show some inhibitory effect on the growth rate.

The effects ofo-, m- andp-hydroxyphenylacetic acids on total peroxidase activity and isoperoxidase patterns of wheat coleoptile sections were studied.o-andm-HOPA reduced the total peroxidase activity whilep-HOPA increased it. Electrophoresis in polyacrylamide gel revealed thato- andm-HOPA diminish the intensity of some anodic and cathodic bands, but thatp-HOPA increases anodic and reduces cathodic isoperoxidases. These results may explain the apparently paradoxical positive effects ofp-HOPA on both growth and total peroxidase activity.

Extracts of small amounts of inflorescence material (3 lingular flowers, 3 tubular flowers, 1 receptacle with involucral bracts), obtained withn-hexane, were analysed by gas-liquid chromatography using a capillary column. The presence of terpenoids was demonstrated and differences in composition between extracts from different inflorescence parts were found.

α-N-Benzoyl-DL-arginine-p-nitroanilide (BAPA) hydrolytic enzyme was partially purified from cotyledons of mature dry seeds ofVigna unguiculata (L.) Walp, cv. Seridó. Extracts of a finely ground meal ofVigna seeds were obtained with 0.02 M phosphate buffer (KH₂PO₄/ /Na₂HPO₄) pH 7.6. A protein fraction was obtained from the extracts by ammonium sulfate precipitation (25 to 50% saturation). This protein fraction was subjected to chromatography on DEAE-cellulose. A separated fraction of the cellulose column presented one main component and two minor bands as seen on polyacrylamide gels. The main component of the separated fraction gave a positive reaction with BAPA and acetyl-DL-phenylalanine-β-naphthyl ester (APNE). This fraction shows a molecular mass of 60 000 by gel filtration on Sephadex G-100, pH 7.6.
The BAPA-ase activity was stable at pH values of 7.0 to 9.0 and no decrease in activity was observed by heating at 40 °C up to 40 min. The activity was not affected by PMSF, EDTA, cysteine,p- CMB, and IAC but was inhibited by NEM and strongly inhibited by TLCK.
Leucine-p-nitroanilide (LPA) hydrolytic enzyme properties were also determined. This activity was inhibited by PMSF,p- CMB, and NEM.

Coumarin-caused stimulation of rooting of cuttings ofImpatiens balsamina L. is associated with an increase in the endogenous contents of carbohydrates, total phenols and proteins. Peroxidase, IAA oxidase and polyphenol oxidase activities also increased in coumarin treated cuttings at the time of cell division preceding primordia formation (6-12 h after treatment). Coumarin effect on rooting as well as on related biochemical changes resembles the effect of auxins in some ways.

An investigation has been carried out to find out in what compounds carbon is radially transported from stele to the cortex and to study sucrose metabolism in the root. These tissues were fed with¹⁴C-sucrose either directly or through the mesocotyle. In the latter case, the bulk of radioactivity, both in the stele and cortex, was concentrated in sucrose rather than in mono saccharides. This corresponds to the radial transport of carbon from stele to cortex predominantly in the form of sucrose. In the case of a direct exposure of stele and cortex,¹⁴C-sucrose was utilized for respiration, amino acid biosynthesis, and accumulation of carbon in the form of glucose. The hydrolysis of sucrose to the monosaccharides and subsequent utilization of the latter in respiration was more intensive in the stele. In the cortex, the sucrose carbon was more actively used for amino acid synthesis, owing to a high concentration of nitrate reductase, glutamate dehydrogenase and glutamine synthetase. It was concluded that the cortex is the main issue zone providing nitrogen assimilation in the root.