The effect of the growth substances indol-3-ylbutyric acid (IBA), kinetin (Kn) and gibberellic acid (GA3) on the alkaloid content and recovery from the stress induced by removal of roots inNicotiana rustica L. plants have been studied. All treatments, mainly GA₃, overcome the stress more effectively than the controls. The alkaloid content was increased 2.5fold with GA₃. Treatment with Kn also increased the alkaloid content, but only in the absence of roots. In contrast, treatment with IBA slightly reduced the alkaloid content. The results of this investigation indicated that a degradation of stored alkaloids did not occur in spite of the stress.

The effect of macroelements on nitrogen assimilation, level of nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) and content of nitrate nitrogen were studied in 17 day-old pea seedlings. The highest inhibition of NR was found at deficiencies of Mg and Ca while deficiency of K was less effective. The level of GS was decreased only in roots exclusively at deficiency of Mg. On the other hand, the deficiency of Mg and Ca increased the level of GDH. The lowest level of endogenous nitrate was found at deficiency of K. Present results show that assimilation of nitrate by plants was decreased by Mg and Ca deficiency while assimilation of ammonium was not affected.

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.

Ethylene formation by loaves of the central stem zone of the short-day tobacco cv. Maryland Mammoth and long-davNicntiana sylvestris was followed for 40 days during in duction and transition to flowering. In SD tobacco Mammoth, ethylene formation rose between days 0-10, remained unchanged for the next 10 davs, rose slightly between days 20 - 30 and sharply within the last 10 days. The time-course of ethylene formation by the leaves of LD tobacco N.silvestris resembled that of Mammoth, but tho changes were less pronounced, especially at the beginning of the period. Generally, ethylene formation is much higher in SD tobacco Mammoth than in LDN. silvestris.
Ethephon (0.02 %) application during flower induction significantly reduced flowering in SD tobacco Mammoth (by 47.5 %) and also reduced apical meristem length. In N.silvestris ethephon application did not reduce flowering, but most of the treated plants (62.5 %) did not attain the stage of inflorescence. Apical meristem (or inflorescence) and stem length were also reduced. The possible role of ethylene in regulation of transition to flowering is discussed.

Eight to nine months old seedlings of the Cactaceae Gereus validus HAWORTH grown in soil culture were chosen to study day-night cycles of net CO₂ exchange, indicating the stomatal rhythm of crassulacean acid metabolism, CAM, in relation to day-night changes of abscisic-acid levels. Drought stress was imposed by repotting the seedlings in dry sand and keeping them without watering for up to 37-39 days while control plants were watered regularly. Abscisicacid levels were higher in the stressed plants than in the controls and higher in the light period aa compared to the dark period. In the stressed plants abscisic-acid levels increased throughout the light period. Abscisic acid reached particularly high levels in the late afternoon in plants stressed for 37 days. It is conceivable that stomatal closure during the first part of the light period of CAM is elicited by high internal partial pressures of CO₂ built up by decarboxylation of nocturnally stored malic acid. However, the elimination of late-afternoon stomatal opening and the reduction of stomatal opening during the dark period of CAM observed under conditions of drought stress must have other reasons. The analyses of abscisic acid presented allow the conclusion that this stress hormone is involved in stomatal regulation of CAM under such conditions.

The cross B. campestris ssp. japonica x B. oleracea var. botrytis fails due to incompatibility barrier at the stigma. To realize this cross, irradiated compatible pollen (mentor pollen) was used before the incompatible pollination. The presence of mentor pollen stimulated the incompatible pollen to germinate and effect fertilization and seed set. One hybrid was thus obtained. Most of the seeds were inviable. Of the 5 plants raised one was a hybrid and 4 resembled the female parent.

Previous electrophysiological and tracer kinetic studies indicated that the uptake of neutral amino acids took place by means of the proton cotransport mechanism in the leaf tissue of broad bean plants. The present investigations were designed to characterize the origin of the driving force for this process, and the proton pumping activity of leaf cells ofVicia. This activity is known to be revealed when peeled broad been leaf discs, floated on a bathing solution in the light or in darkness acidify the medium.
White light caused the strongest acidification. The presence of K⁺ and Na⁺ in the external solution increased the H⁺ secretion significantly, whereas addition of Ca⁺⁺caused only an insignificant enhancement of proton extrusion. The inhibitors of photosynthetic electron transport DCMTJ (50 μM) and nitrofen (50 μM) eliminated the light-enhanced H⁺ release indicating the dependence on photosynthesis. The involvement of a proton pump was evidenced by the effects of the uneoupler CCCP, the SH reagent HgCl₂ and the ATPase inhibitor orthovanadate. The experimental results support the conclusion that H⁺ extrusion byVicia leaf cells is an active electrogenic process requiring metabolic energy. In the light this energy requirement is suppliedvia photosynthetic electron transport.

Higher³²P uptake per plant was found in the healthy resistant (R) alfalfa (Medicago saliva L.) plants when compared with the healthy plants susceptible (S) to the bacterial wilt, following the exposure of the roots of intact plants to the radiophosphate solution. The bacterial infection markedly decreased³²P uptake and radioactivity levels per dry matter in most organs of the R-plants on the day 8 and 14 after inoculation withCorynebacterium insidiosum whereas in the S-plants a decrease in³²P uptake was only found on the day 8.³²P leakage rate from the infected R-plant roots to the nonradioactive nutrient solution was higher than from the healthy ones on the day 8. At the same time³²P content in the organic P fraction was somewhat increased due to the infection in the R-plant roots, whereas³²P content in DNA was decreased. After foliar application,³²P distribution pattern was similar in the tissues of both the S- and the R-plants and was not affected due to the infection in the course of the 3rd week after inoculation. However, the bacterial infection markedly increased³²P translocation from the primary leaf to the rest of the R-plant.

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.

In the roots of 4-day-old pea plants germinated in unsterile soil from Rhizobium-inoculated seeds, a higher level of native IAA was determined than in roots of pea plants germinated in sterile soil from superficially sterilized seeds. The IAA level in plants grown from inoculated seeds increased markedly up to the age of 6 days of the plant, while in plants growing under sterile conditions it did not significantly change during the same period. Between the 6th and 10th days of the age of the plant, a decline in the IAA level was observed in roots of plante growing from inoculated seeds. It was not until after 10 days of age of the plant that the level of IAA in nodulated roots again increased.

Plant growth and seed yield of mung bean were studied in sand culture at different levels of NaCl [0, 50, 100, 150, 200, 250 mM] in the root medium. Results showed that both dry matter yield and seed yield of plants grown for 14 weeks at 50 mM NaCl and 100 mM NaCl were around 60 % and 25 %, respectively of those for plants grown in control solution. Higher concentrations caused wilting and necrosis of leaves. Very effective exclusion of Na and Cl from salt grown mung bean seed was observed with concommitant high accumulation of Na and Cl in the stem. It is speculated that mung bean plant stem may act as a 'sink' for NaCl during the reproductive stage of the plant growth cycle.

Growth and ionic relations were studied in six triticale cultivars of different geographical origins grown in a greenhouse in nutrient solution with or without the addition of 100 mM NaCl. In 21 d old plants of all the six cultivars growth was little affected in the salt treatment, whereas in the subsequent three harvests during vegetative phase (after 31, 38 and 45 d), growth reduction effects of salinity were progressively pronounced. Generally, shoots of all the six cultivars accumulated relatively more K+ as compared to Na+ or Cl-. Differential accumulation of K+, Na+ and Cl- by various cultivars was coupled with variable rates of Na+ and Cl- transport from root to shoot which were - to some extent- related to cultivar differences in growth in saline root media. Chloride content of shoots of the six cultivars was negatively correlated with the relative growth reduction due to salinity at the four harvests.

Wolffia arrhiza (L.) Wimm. was grown axenically in the chemostat under white luminescent light (photon fluence rate 23 ujnol m^-2 s^-1) and phosphate or magnesium limitation (0.075 and 0.01 jxmol 1^-1, respectively). Aliquots (1 g fresh mass) were taken from the continuous cultures and were irradiated for 1 h with either white light (control) or monochromatic blue (453 nm) or red (654 nm) light. The amount of [5^-3H]-uridine incorporated into cytosolic and chloroplastic rRNAs during these exposures was estimated and following results were obtained: In phosphate limited plants rod light considerably reduced and blue light slightly increased label incorporation as compared with the control. Moreover, in red light, chloroplast incorporation is relatively more slowed down than that in the cytosolic compartment (34 % as compared to 59 % of the control). In blue light the enhancement is approximately equal in both compartments. In magnesium limited plants incorporation under both blue and red light is moderately slower as compared with the control. In both cases also the retardation is slightly greater in the chloroplast than in the cytoplasm. The results suggest that rRNA metabolism is controlled by light quality as well as by mineral nutrition.

Five independent tobacco regenerant clones obtained after transformation withAgrobdcterium rhizogenes strain TR101 (four clones of the T phenotype, clone 5 a mixture of plants of the T and T' phenotypes) and untransformed plants cultivatedin vitro were gradually acclimated to the atmosphere and transferred to the soil substrate in pots. During 28 d after transplanting the increase of the leaf area was in T phenotype plants greater than in untransformed plants, but 14 d later no significant differences were observed between T phenotype and untransformed plants in leaf area and dry matter. T'phenotype plants, however, had significantly lower values in all growth parameters than T phenotype and control plants. Abaxial net photosynthetic CO₂ uptake (PN) was in both T (clones 1-4) and T' plants significantly lower than that in control and clone 5T plants. Nevertheless, due to the relatively higher adaxial PN in T plants, the total PN through both leaf surfaces was significantly lower only in clone 4 and clone 5' plants. The tendency to higher transpiration rates (E) in clones 1 - 4 in comparison with the control resulted in significant differences in water use efficiency (W.U.E.). Relatively higher E in T plants of clones 1 - 4 was connected most probably with their more developed root system (greater root dry-matter) than in untransformed plants, because no influence of the differences in stornata density on E was found.

The size of the spring barley root system was studied on the basis of its electric capacity in plants grown in nutrient solutions either lacking or containing nitrogen in the form of nitrate or ammonium.
Root electric capacity changed in dependence on nutrition from Day 12 after emergence, when F values increased in the root systems of plants exposed to nitrate and ammonium salts. In plants grown in H₂O, the values of electric capacity statistically significantly decreased on Days 15 to 17, in plants grown in PK solution lacking nitrogen on Day 20.
Root electric capacity of plants grown in full nutrient solution gradually increased on Day 18 after emergence. Then a marked increase in root electric capacity values followed with no statistically significant differences between NH₄ ⁺ and NO₃ ^- nutrition. Nitrate nutrition of barley plants only resulted in an increased root to shoot mass ratio.

The effect of the glucoainolate sinigrin applied at concentrations from 5×10^-6 to 5 × 10^-3 g cm^-3 on the infectivity of two isolates of turnip mosaic virus (TuMV) was studied. A statistically highly significant linear correlation relationship was found between the concentration of sinigrin added to the sap prepared from infectious plants ofPetunia hybrida hort. Vilm. cv. Lavina and the infectivity of the virus, expressed in the number of local necrotic lesions onNicotiana tabacum L. cv. Samsun leaves. Sinigrin caused a statistically significant decrease in the virus infectivity already at a concentration of 5 × 10^-5 g cm^-3. This virocidal effect of sinigrin was not dependent on the virus isolate applied and was not influenced by the host plantsP. hybrida andNicotiana glutinosa L. A statistically highly significant decrease in the virus infectivity was also caused by sinigrin applied at a concentration of 5 × 10^-3 g cm^-3 in the sap from infectiousSinapis alba L. andBrassica nigra (L.) Koch plants, in which case its enzymic degradation to allyl isothiocyanate was observed. When these plants were homogenized in 0.5 M phosphate buffer pH 8.5, no statistically significant decrease in the infectivity of the virus was observed. Purified virus preparations in 0.5 M phosphate buffer pH 7.5 were not affected by sinigrin applied at the concentration of 5 × 10^-3 g cm^-3. The significance of the content of glucosinolates in the pathophysiology of theBrassicaceae and in their resistance to viruses and other pathogens is discussed.

Certain cultivars ofMalus growing at Geneva, New York, USA, begin growth and bloom 2 -3 weeks later than commercial cultivars of apple. Our research suggests that these late bloomers bloom late because they have a very high chilling requirement for bud burst. The chilling requirement interacts with the heat requirement for bud burst in such a way as to result in delayed bud burst and bloom. Abscisic acid (ABA) decreases in the terminal buds of both early and late bloomers during the chilling period, but it decreases more rapidly in the early bloomers. It has not been determined if ABA plays a role in controlling bloom date.

A number of markers characterizing the quantitative anatomical structure of the blade of the first and the third leaf were measured in young plants of eight cultivars of spring barley,Hordeum vulgare L.
The number of vascular bundles was in significant negative correlation with the mean distance between two adjoining bundles (r = -0.8) and also with their area in the cross section (r =-0.82). The proportion of the thickness of the epldermis in the thickness of the leaf and the proportion of the volume of the epldermis in the total volume of the leaf was in the order of 0.25 to 0.30. The proportion of the volume of the photosynthetic tissues in the total volume of the first (or the third) leaf fluctuated from 0.51 (0.53) to 0.58 (0.63). The thickness of the leaf blade and the thickness of the particular leaf tissues and their relative voluminal proportion significantly differed in the basal (B), middle (M), and aplcal (A) parts. No significant correlations were found between the values of the parameters of the first and the third leaf. Significant differences between genotypes concern most of the measured characters. No tendency to unequivocal changes between older and new genotypes could be inferred from the results obtained.
The results are discussed with regard to the necessity of a quantitative description of anatomical structures for the elucidation of physiological processes.

The influence of blue, red and white light and gibberellic acid (GA₃) on gibberellin-like activity in tissue extracts of leaves, stems and roots was investigated during growth of pea seedlings (Pisum salivum L. cv. Bördi). Higher GA-like activity was found in leaves and stems of pea plants that were growing in blue light than in those under red or white light. Patterns of change of activity were different in leaves, stems and roots, and in GA₃-treated plants.

The content of endogenous cytokinin-like substances and the release of ethylene were determined in leaves of different insertion of sunflower plants during their ontogeny. The content of cytokinin-like substances was highest in the leaves on the middle part of the stem (that is in leaves just before full expansion), with a decrease occurring both towards the base and the apex of the stem, when followed at four growth phases (vegetative plants, plants with inflorescence diameter up to 0.5 cm, plants with inflorescence diameter up to 3 cm, and plants in flower). Changes in the content of cytokinin-like substances during the ontogeny of the leaf also corresponded to this pattern. Data obtained with the leaf at the third node from the basis of the stem showed that the level of cytokinin-like substances first sharply increased, and then after reaching maximal value (at the time when leaf blade area reached approximately 70 % of the final value) slowly and continuously decreased.
The highest amount of ethylene released from the leaves was recorded in basal leaves and then also in apical leaves, whereas the leaves with the largest blade area situated at the central part of the stem released the lowest amount of ethylene. This pattern was repeatedly found at all four selected growth phases of sunflower plants.

A histochemical method for the determination of IAA-oxidase has been used in sections of various aerial parts of winter wheat plants. High IAA-oxidase activity was localized in the cell walls of sclerenchyma near the periphery of the stem, in the vascular bundle sheath of sclerenchyma and in xylem, both in the stem and in the leaf. The cell wall-bound IAA-oxidase activity therefore appeared in lignifying tissues. The staining was very weak or absent in the cell walls of parenchyma tissues and phloem. The positive reaction of the cytosol at the bulbous ends of guard cells and in the leaf primordia is presumed to be due to cytosolic IAA-oxidase. These results are discussed in relation to peroxidase localization and to our previousin vitro studies.

The carbon balances of whole, 21-d old French bean plants (Phaseolus vulgaris L.) grown in standard nutrient solution (1K) and its modifications without (OK) or surplus (2K) potassium were calculated from the daily photosynthetic carbon inputs of individual leaves, and the daily respiratory carbon losses by individual leaves, stalks and petioles, and roots. Under the three K concentrations, maximum net photosynthetic rates (P_n) were found in the 2nd or in the 3rd trifoliate leaves, maximum respiratory rates (R_d) in the youngest, 4th trifoliate leaves; the P_n/R_d ratio decreased with leaf age. In all leaves of 2K plants, leaf dry masses and thicknesses, P_n, P_n/P_d ratios, and stomatal and intracellular conductances were lower than in OK and IK plants. Daily whole-plant net carbon gain was highest in IK plants, whereas in OK and 2K plants it was 98.0 and 81.3 % of IK, respectively. Similar values were found in the parameters of growth analysis, namely in net assimilation rates and relative growth rates.
No differences were found in water potential (Ψ _w ) or water saturation deficit (W_sat) in the OK, 1K and 2K plants sufficiently supplied with water or during wilting and resaturation. The decrease in Ψ_w to -0.97 MPa was associated with a 19.9 %, 31.4 % and 23.4 % decrease in P_n of OK, 1K and 2K plants, respectively, but no effect on R_d was found. In the three variants, the short-time effect of mild water stress was fully reversible.

IAA oxidase, catalase and peroxidase activities of seedlings (the first day of radicle emergence) or organs of young plants (the fifth day of radicle emergence) germinated in NaCl media (0, 25, 50, 100 or 150 mM) were measured. Three species with successively lower thresholds of salinity sensitivity were measured: tomato, radish and red cabbage. NaCl sensitivity of the above enzymes was also analysed in extracts from control seedlings or plants incubated in media with different NaCl concentrations. No relation was found between enzyme activities and protein levels or Na contents of young plants; on the contrary, a good relation was observed between enzyme activity and Na contents of seedlings. Oxidase activities have similar NaCl sensitivity in the three seedlings. Comparing the enzyme activity and sensitivity with NaCl tolerance of the species, the consequences of the oxidase activities in young plants germinated in NaCl media are discussed.

DNA-dependent RNA polymerase II (nucleosidetriphosphate: RNA nucleotidyltransferase, EC 2.7.7.6.) from duckweed Wolffia arrhiza (L.) HORKEL ex WIMMER was partially purified by polyethylenimine precipitation and DEAE cellulose ion exchange chromatography. Whole plants were irradiated with red light pulses. After a dark period of 2 to 12 h there is no effect of light pretreatment on the total or specific activity of the purified enzyme.

A cabbage variety with particularly strongly developed leaves and extremely shortened stems (tight heads) was treated during the first year of its development with growth retardants (CCC and CEPA, Ethephon) at different concentrations. A 4-fold treatment with CCC, CEPA or a mixture of both proved to be most effective Leaf growth was inhibited by this treatment (head mass decreased) but stem growth increased. Only in treated plants the bud of the stem apex could break through the leaf sheath and develop generative stem. The results are discussed as examples of correlative relations between leaf and stem growth.

Transpiration rate, leaf area, the content of nitrogen and saccharides decreased with the decrease in soil moisture content from 90 % to 30 % of full field capacity. Stomatal frequency, fresh and dry matter and the chlorophyll and carotenoid contents of lupine or safflower remained more or less unaffected. After spraying with the antitranspirant (PMA) the saccharide contents were raised. As concern the lipids content and the contents of Ca, Mg and P, treated plants exhibited variable response to both drought stress and spraying with various PMA concentrations.

Changes in ribosephosphate isomerase and ribosephosphate pyrophosphokinase activities occurring in tobacco leaf tissues infected with the potato virus Y (PVY) were studied at the stage of acute infection. The results obtained have shown that during the entire experimental period the activities of both enzymes were at the end of a dark phase much higher in virus-infected tissues compared with the values found in healthy control plants. The courses of the activity curves of both enzymes were consistent and correlated with the reproduction curve of PVY. The results obtained suggest a direct involvement of both enzymes inde novo biosynthesis of the virus RNAvia the oxidative pentose phosphate pathway.

D,L-indol-3-yllactie acid was applied at concentrations 0.2 - 20 mg 1^-1 (10^-6-10^-4M) to the roots of 3-d-old intact maize seedlings grown in the dark and in the light. By day 3 after application, ILA at lower concentrations (0.2-1 mg l^-1) caused slight increase in the mass of etiolated plants, mainly roots. Shoot and root length was not increased. ILA at concentrations equal to, or greater than, 2 mg 1^-1 reduced the length of the main roots and from 10 mg 1^-1 on also the length of the shoots. In contrast, root mass was decreased by higher ILA concentrations to a lesser extent than shoot mass. The response to ILA application of etiolated seedlings differed from that of the seedlings grown in the light only at 20 mg 1^-1. The inhibitory effect was more pronounced in the case of quickly growing etiolated plants.

In vitro culture was established from shoot tips ofDigitalis lanata cotyledonous plants. The propagated plant material was rooted, transplanted into soil and grown under field conditions. Lanatoside C content was determined in a total of 20 clones and statistically evaluated by means of variance analysis of unequal-sized samples.In vitro clonal propagation ofD. lanata was found not to affect lanatoside C content. Drug level was dependent on a plant genotype.