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.

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.

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.

ADPglucose pyrophosphorylase level and mechanisms regulating its activity were studied in cucumber plants infected with the cucumber mosaic virus at the stage of chronic infection. Studies carried out with partially purified preparations of the enzyme have shown that there was no substantial difference in the regulatory influence of the ratio 3-PGA/P₁, or in the number of binding sites of the effectors on the enzyme, but that the virus infection reduced the level of the enzyme in the tissues to 74% of the control and the 3-PGA/P₁ ratio to one half which resulted in a further decrease in ADPglucose pyrophosphorylase activity. In crude homogenate prepared from diseased plants, activity of the enzyme was reduced to 42% of the healthy control.
The level of UDPglucose pyrophosphorylase was three times higher in cucumber leaf tissues than the level of ADPglucose pyrophosphorylase which was inhibited by both 3-PGA and P₁. Inhibitory effects of both these effectors were cumulated. The enzyme isolated from healthy plants was inhibited by inorganic phosphate more strongly than the enzyme isolated from diseased plants. UDPglucose pyrophosphorylase activity was increased in crude homogenate of diseased plants to 127% of the healthy control when the level of the enzyme was the same in the tissues of both healthy and diseased plants which was presumably connected with the enhanced rate of sucrose catabolism.

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.

The LpDH and NpDH activities in crown gall tumors incited byAgrobacterium tumefaciens strain C58 were followed in 7 plant species and 100 tumors were assayed in each experimental variant. The NpDH activity was found in 790 out of 800 crown galls observed. The LpDH activity was tested, after induction of tumors withA. tumefaciens strain B6-806 and 37400, in three experimental variants. The LpDH activity was found in 290 out of 300 crown galls. In the small fraction of the LpDH and NpDH negative tumors, the activity was possibly actually present, but it was below the limits of the sensitivity of the detection technique used.

The effects of 6-benzylaminopurine (BAP, 5.10^-5M) treatment of pumpkin cotyledons and their starvation after excision upon polysome/monosome ratio and translational capacity of polysomes in cell-free system were studied. It has been found that starvation causes a progressive polysome degradation. Polysome translation in a wheat germ cell-free proteinsynthesizing system reveals that the translation capacity of polysome preparations decreases with the time after cotyledon excision much more sharply than polysome/monosome ratio. This indicates the starvation damage in elongation steps of protein synthesis. The decrease of postribosomal supernatants activity in the system of poly(U)-directed polyphenylalanine synthesis confirms this conclusion.
BAP treatment brings about a very rapid monosome mobilization into polysomes and activation of cell-free translation of ribosome preparations which is however closely parallel to the polysome percentage in them. That means that during this initial period of BAP action only protein synthesis initiation is under BAP control. The experiments with aurintricarboxylic acid (ATA) support this idea.

Using biospecific chromatography on D-Glc-Separon-fetuin, lectins were isolated from seed albumin complexes of four cultivars ofPhaseolus vulgaris (Veltruská Saxa, Vainica Saavegra, Krupnaya sakharnaya, Olympia) andPhaseolus vulgaris ssp.aborigineus (wild form, considered to be one of the ancestors of cultivated beans). In the lectins isolated the agglutinating activity against human erythrocytes of the A, B, and O groups was estimated, as well as against trypsin-treated and non-treated rabbit erythrocytes. Further analyses involved their mitogenic activity against lymphocytes of murine spleen, their isoelectric points by isoelectric focusing in polyacrylamide gels, and eventually their immunospecific similarity with the lectins of the standard cultivar ofPhaseolus vulgaris, Veltruská Saxa.
The lectins of all taxa were mitogenic, but differed from one another in their agglutinating activity and in the number and isoelectric points of the zones, as revealed by both isoelectric focusing and immunoelectrophoresis. In the case of the cultivar Vainica Saavegra, which is a seggregating population, even the lectins of individual seed groups were different.

The content of endogenous gibberellins was estimated in leaves adjacent to the individual nodes ofBryophyllum crenatum in five ontogenetic periods (July 10, August 12, September 17, October 22, and December 8). Their content decreased from the stem base to the apex when 5 to 7 leaf pairs were developed (July 10 and August 12). Before transition to the generative state when 8 leaf pairs were formed (Sept. 17 and Oct. 22) the content of gibberellins was gradually increased in the apical leaves and decreased in the basal ones. This change resulted in the increasing gradient of leaf gibberellins from the stem base to the apex just before flowering (Dec. 8).
The content of endogenous gibberellins increases during the leaf ontogenesis up to the beginning of its senescence. This trend occurs first in the basal leaves (I -III) where the initial increase is followed by the decline in the gibberellin content. On the other hand gibberellins in leaves derived from the apical nodes (VII-VIII) only gradually increase in the course of leaf ontogenesis.

The counter-flow of³H-IAA and¹⁴C-ABA was studied in both aeropetal and basipetal arrangement in 11-cm long segments of pea epicotyls. A significant acropetal flow of¹⁴C-ABA was promoted by exogenous application of³H-IAA in the apical part of the segment together with a simultaneous promotion of its elongation growth. In the case of limited basipetal flow of¹⁴C-ABA neither the accumulation of this growth regulator on site of³H-IAA application nor a growth promotion were observed.

During high altitude acclimatization soluble sugar contents were highest in temperateArtemisia species when grown at 550 m and tropicalArtemisia species at 3600 m in the active growth phase. During the senescence in all the species the soluble sugar contents were low in plants grown at 3600 m.
The starch content was low in the leaves of the tropical and sub-temperate species when grown in the alpine zone but in the temperate species a significantly higher amount of starch was observed at 3600 m altitude.
The amount of lignin acids was lower in the tropical and sub-temperate species but higher in the temperate species when these were grown at a higher altitude.

During 6 days of pea seed germination the depletion of legumin with mol. m. 390 000 from protein bodies was observed. SDS-PAGE indicated that the legumin subunits with mol. m. 41 700 and 21 000 were prevailing. Only the former of these, probably corresponding to α-subunit, was degraded rapidly during 6 days of germination.
Water-soluble proteins (albumins) prepared from pea cotyledons were separated by preparative IEF into proteins with pI 7.1, 6.5, 6.0, 5.4, 5.0, and 4.6. During 6 days the components of albumin with pI 7.1, and 6.5 were dramatically depleted. Major fractions with pI 6.5, 6.0, and 5.4 were subjected to SDS-PAGE and their subunit composition was determined. Moreover, albumin of pea cotyledons was resolved into 13 components by SDS-PAGE. Mobilization of albumin began from the degradation of components with higher mol. m. during germination.

The male sterilants exo-3,4-methano-L-proline (MP) and cis-α-(carboxycyclopropyl)glycine (CCPG) were not converted to ethylene, eitherin vitro or in wheat coleoptile segments. Neither of these substances was able to affect IAA- and ACC-induced ethylene biosynthesis in wheat coleoptile segments to such an extent that it could explain their effect ay male sterilants.

A mathematic model of loaf water potential daily dynamics was employed to study the relationship between this characteristic and soil moisture for the speciesQuercus cerris,Acer campestre andCarpinus betulus. It was found that when evaluating the availability of soil water for a plant it is necessary to consider the vapour pressure deficit which remarkably affects the relationship between the soil moisture and leaf water potential. A quantitative description of the dependence between the leaf water potential and soil moisture enabled a physiological interpretation of the limit values of soil moisture - permanent wilting and reduced availability of soil water for the plant - as well as evaluation of the drought resistance of plants.

The capacity of pollen tubes to utilize exogenous uridine during 8 h of cultivation in shaken suspension in a sugar-mineral medium was examined by continuous and pulse labelling with³H-uridine. The increase of uptake with increasing concentration of the nucleoside indicated a saturable transport system with an approximate K_m of 9.4 × 10^-6 M and 12.5 × 10^-6M as determined in 1-h and 6-h cultures, respectively. Maximal uptake took place at the beginning of germination reaching a rate of about 2 nmol h^-1 per 1 mg of dry pollen at 0.1 mM external uridine. The uptake activity decreased with the time of pollen tube growth to less than one third during the 8-h cultivation period. Moreover, the level of radioactivity taken up initially decreased later on during continuous cultivation in the presence of³H-uridine. The uptake took place against a concentration difference and the onset and rate of uridine release depended on its exogenous concentration.
The activity of the nucleoside incorporation into RNA increased during the first 4 h of cultivation, decreasing later on. The proportion of RNA radioactivity in continuously labelled pollen tubes grew steadily during 6 h and reached 2.5% with respect to soluble pool at 0.4 μM uridine. The time course of RNA labelling was independent of uridine concentration within the range of 0.4 μM to 40 μM but this concentration rise resulted in an about fiftyfold increase of the total amount of external uridine incorporated.

This paper deals with the verification of a test of crop seedlings for the determination of the salt tolerance. There is a typical concentration of NaCl in the culture medium above which an enhancement of the free proline content is induced (critical point, critical concentration). The determination of this critical concentration in 19 cultivars of crop plants has proved that plants grown in aride areas (i.e. Hordeum, Triticum durum) have a critical concentration that is by about 50 to 80 mmol l^-1 of NaCl higher than that of plants grown in more humid regions (i.e. Triticum aestivum). The critical concentration is not influenced by pH changes of the external solution. Calcium application leads to an enhancement of tolerance. The different increases of growth and fresh mass of salt sensitive and salt tolerant plants selected by this test system proved the aptitude of the critical concentration in culture medium for proline augmentation as a test parameter.