A pot culture experiment was performed to evaluate salt tolerance potential ofSesbania aculeata Poir. The plant can tolerate salinity levels up to electrical conductivity (ECe), 10 mS cm^-1 and at 15 mS cm^-1 thero is about 40% reduction in dry matter production. The analysis of inorganic constituents in different plant parts revealed that the plant has the capacity to regulate sodium uptake under saline conditions and chloride uptake always exceeded that of sodium. The potassium: sodium ratio is also maintained at a fairly constant level in leaflets while it is reduced in leaf rachis, stem and roots. Salt stress caused accumulation of calcium and magnesium in all plant parts. A considerable decline in phosphorus uptake was observed due to salinity. Iron was found to be accumulated more in salt stressed roots only. Nitrogen accumulated in both roots and leaves while considerable proline accumulation was observed in leaves of salt stressed plants. The amount of soluble sugars was increased in roots and leaves due to salt stress, while starch content of roots decreased. Those changes induced by salinity are discussed in relation to salt tolerance capacity of the plant.

Nitrate concentration required for maximal extractable level of nitrate reductase (NR) inWolffia varies with the conditions prior to the nitrate treatment. Maximal enzyme activity is obtained at 2 mM nitrate concentration with asparagine grown plants and at 15 mM with nitrate grown. Both the level of enzyme activity and nitrate uptake by the tissue are increased by irradiation. The radiant energy induced increase in enzyme activity is not due to photosynthetic activity alone. An effect of radiant energy at the membrane level is sug gested. The extracted enzyme, which is labile, is protected and activated by NADH at 0 °C.

Considerable changes in the activities of phosphoenolpyruvate carboxylase and ribulosebisphosphate carboxylase were found inNicotiana tabacum cv. Sarasun plants infected with TMV. Ribulosebisphosphate carboxylase is inhibited at the time of maximum TMV reproduction, but its decreased activity is at the same time partly compensated by phosphoenol-pyruvate carboxylase in the shoots of infected plants. The pattern of activity of this enzyme nearly exactly reflects the pattern of reproduction of the tobacco mosaic virus.

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.

Three different treatments by calcium (10²M), namely seed treatment, foliar spraying and their combination were applied on field-grown rice (Oryza sativa L. cv. Ratna) under both water stressed and non-stressed conditions in the course of plant development. The relative water content and leaf water potential decreased with increase in age of stressed and non-stressed plants. Pretreatment of seeds with Ca improved the water status of the plants most prominently at the vegetative stage but the effect gradually faded away with plant development. The foliar spraying by Ca was more effective in improving the water status of the plants at the reproductive stage. The combined Ca treatment significantly improved water status of the plants both at the vegetative and reproductive stages. The contents of chlorophyll and protein decreased and the activities of protease and RNase increased in the course of plant development in both non-stressed and even more in stressed plants. Ca treatments of seeds or plants or their combination inhibited the decline in chlorophyll and protein contents and the rising trends of protease and RNase activities, the combined treatment being most effective. During plant development free proline content increased significantly more in water stressed plants. In non-stressed plants there was a marked increase in the free proline content at the mature fruit stage. Ca treatment inhibited the rise of free proline in stressed plants. A significant reduction in yield components and yield of the crop in water stressed plants was increased by Ca treatment.

Seedlings of spring barley,Hordeum vulgare L. cv. Mirena, were grown in a controlled environment chamber at high (HI: 122 Wm^-2) and low (LI: 28 Wm^-2) irradiance in the complete Richter's nutrient solution (R) or in solution lacking either phosphorus (R -P) or nitrogen (R -N). The experiment was terminated 15 days after sowing when plants (R-N) at HI ceased to grow. At that time the dry mass of one plant was 449.8 mg, 145.7 mg and 116.8mg at HI and 203.4 mg, 110.1 mg and 91.0 at LI for R, (R-P) and (R-N), respectively. Deficiency of P and especially N reduced the size of loaf area more under HI than under LI conditions. Specific dry mass of leaves was the highest in R-N plants. The values of relative growth rate and assimilation rate are presented. Interaction of the effects of deficiency of mineral nutrients and irradiance during cultivation should be analyzed in further experiments for determination of optimum conditions for utilization of mineral nutrients.

Red light (660 nm) break which cancels the floral inductive effect of the dark period brought about a transitional rise in the level of free IAA in the shoot ofChenopodium rubrum. The higher content of IAA was then found in treated plants at the beginning of the following photoperiod, too. The red light treatment did not change the phase of endogenous rhythm fluctuations of free IAA.

The content of bound proline sharply increased in proteins of different organs of young plants of winter rape and winter wheat exposed for 72 h to temperatures from 0 to 2 °C while it decreased only in root tips of wheat plants. Free proline which at 20 °C occurs in all plant organs only in trace amounts, accumulated considerably after 72 h exposure to low temperatures in the above-ground organs and only slightly in the roots. Free proline did not accumulate during the first 24 h at 0 to 2 °C in detached leaves of winter wheat but it was incorporated into newly synthetized proteins in which proline content increased after 6 h incubation to its maximum ( + 11.75% in comparison to control); the content of free glutamate sharply decreased during the first 6 h of incubation and the accumulation of bound glutamate was belated in comparison to that of bound proline. Sucrose infiltrated into detached leaves of winter wheat strongly stimulated proline incorporation into proteins at low temperatures, but it did not influence glutamate incorporation. The results suggest that the main reason for thede novo proline biosynthesis during the first six hours of hardening of the plants is the synthesis of proteins rich in proline; free proline accumulates later predominantly in the above-ground organs as a surplus. The above-ground organs are dehydrated in the course of the hardening process approximately to the same extent both in the light and in the dark, but proline content increases much less in the dark than in tho light.

Uptake of phosphate ions by 1 mm segments of isolated maize root cortex layers was studied. Cortex segments (from roots of 8 days old maize plants) absorb phosphate ions from 1 mM KH₂PO₄ in 0.2 mM CaSCO₄ at the average rate of 34.3 ±3.2 μg P_i g^-1 (fr. m.) h^-1,i.e. 0.35± 0.02 μmol P_i g^-1 (fr. m.) h^-1. Phosphate uptake considerably increases after a certain period of "augmentation",i.e. washing in aerated 0.2 mM CaSO₄. This increase is completely blocked by the presence of 10 μg ml^-1 cycloheximide.
The relation of uptake rate to phosphate concentration in the medium was shown to have 3 phases in the concentration range of 0.02 - 40 mM. Transition points were found between 0.8-1 mM and 10-20 mM. Following K_m and V_max values were found: K_m[mM] : 0.37 - 3.82 - 27.67 V_max[μg P_i g^-1 (fr. m.) h^-1] : 3.33 - 39.40 - 66.67
We have found no sharp pH optimum for phosphate uptake. It proceeds at almost constant rate till pH 6.0 and then the uptake rate drops with increasing pH. At low phosphate concentrations (1 mM) the lowest uptake rate was found at 5 and 13 °C, while the uptake is higher at 5 °C than at 13 °C at phosphate concentrations higher than 1 mM. At these concentrations uptake rate at 35 °C is lower than at 25 °C.
Phosphate uptake considerably decreased in anaerobic conditions. DNP and iodoacetate (0.1 mM) completely blocked phosphate uptake from 1 mM KH₂PO₄, while uptake from 5 and 10 mM KH₂PO₄ was left unaffected by these substances. The inhibitors of active - SH groups NEM and PCMB inhibited phosphate uptake: 10^-3 M NEM by 81.6%, 10⁴ M NEM by 42% and 10^-4 M PCMB by 42%.

Stem tips ofSpinacia oleracea were isolated and grown in sterile culture, with Sandoz 9789 added to the medium. Although the herbicide provoked a complete loss of all chloroplast pigments, developed shoots were able to flower, in response to long days; in short days flowering was inducible by adding gibberellins. Sandoz 9789 decreased the elongation of stems by up to 30%; the percentage of flowering plants in culture was also decreased. However, among those plants that flowered, the majority were male, so that Sandoz 9789 produced a shift of the sex ratio toward maleness.

The activity of L-tryptophan synthase (TS, E.C.4.2.1.20) was comparedin vivo in seedlings of plants high in L-tryptophan (L-trp) (pea and kohlrabi) and low in this amino acid (maize). In maize the TS was studied both in the normal and in the opaque-2 genotype that forms an endosperm richer in essential amino acids. The activity of TS was determined on the basis of the increase in radioactivity of the chromatographically purified L-trp-¹⁴C, synthetized after vacuum infiltration of L-serine-¹⁴C-(U) and ineubation for 24 h. As regards the TS activity in seedlings, maize is comparable to pea and kohlrabi; in contrast to this TS is less active in pea seedlings, which can be attributed to the presence of TS inhibitor (CHEN and BOLL 1969). In ripening maize kernels and leaves adjacent to the ear the TS activity is about 20 times lower than in seedlings. The differences in the activity of TS in the genotypes of maize could not be detected, even at the period of seed ripening. Therefore the differences in L-trp content in the investigated plants cannot be explained by a differing activity of TS. TS is probably not the determining regulator of L-trp level in plants, its activity is relatively high even in plants low in L-trp.

The biosynthesis of L-tryptophan (L-trp) from anthranilic acid-¹⁴C (AA-¹⁴C) in. undamaged organs of the seedlings of kohlrabi and pea, with high L-trp content and ma ze plants, with low L-trp content was compared. As for maize the experiments were carried oiut with normal and opaque-2 phenotypes, both with the seedlings and with the ripening kernels. AA-¹⁴C is metabolized in the plants to L-trp pool (i.e. free and bound L-trp, and secondary metabolites) and to glycosyl esters of AA (i.e. to simple glucosyl ester in pea and kohlrabi and more complex glycosides in maize). In maize seedlings L-trp-¹⁴C is synthesized relatively less. (40% in the 1st and 2nd leaf and 33% in the 3rd leaf of the total radioactivity of the incorporated AA-¹⁴C is transferred into the L-trp-¹⁴C pool after 24 h) than in kohlrabi (52% in the hypocotyl and 85% in the cotyledons) and in pea (58% in the 1st and the 2nd internode and 85% in the 3rd and the 4th internode). Thede novo formation of L-trp-¹⁴C is stoped earlier in maize (after 5 h) than in kohlrabi (after 15 h). The level of free L-trp-¹⁴C is relatively low ill maize (15% and 13% of the total radioactivity of the incorporated AA-¹⁴C is converted to free L-trp-¹⁴C and remains in this form after 24 h) in comparison with kohlrabi (31% and 60%) and pea (30% and 49%). In spite of this the formation of L-trp-¹⁴C from AA-¹⁴C is sufficient in maize to incorporate L-trp both into the proteins and into a secondary metabolite that is not yet defined. At the period of seedlings the incorporation in maize of L-trp into the proteins (11% and 10% of the activity of the incorporated AA-¹⁴C) is comparable with that in kohlrabi (11% and 17%), and it is maximum in pea (29% and 36%). Maize, at the stage of germination, thus forms proteins rich in L-trp. The formation of free L-trp is approximately ten times lower in ripening kernels and in the leaves adjacent to the ear and it further decreases in the course of the ripening of the kernels. Although the activity of the biosynthesis of the AA-¹⁴C → L-trp-¹⁴C pathway is relatively lower in maize than in kohlrabi and pea, this pathway is most responsible for the differences in the content of L-trp in these plants.
Neither amitrol nor histidine affected the biosynthesis of L-trp in kohlrabi; the interaction of the biosynthetic pathways of L-trp and histidine known in microorganisms is thus not important in a higher plant.

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.

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.

A new undescribed yellows-type disease ofGypsophila paniculata L. was found. Since a stunted growth is the predominant symptom the disease has been termed stunting. Electron micrographs of ultrathin sections revealed numerous mycoplasma-like organisms in diseased phloem tissues. Attempts to maintain the diseasedGypsophila plants for further investigation of this disease failed for the present in spite of all applied modifications in nutrient media.

Supply of KNO₃, NH₄Cl or NH₄NO₃ to the maize seedlings increased total chlorophyll and carotenoids (over zero nitrogen control) amounts per fresh matter unit of the primary leaves. The increase was most apparent when the pigment level in control plants started declining,i.e. between days 14 and 16. Supply of inorganic nitrogen increased pigment synthesis in excised leaf segments from dark grown seedlings, although the increase during a 24 h incubation was not as high as with either glycine or glutamine. Salicylic acid at 0.01 to 1 mM concentration increased and at 10 mM lowered the pigment biosynthesis. The increase at lower concentrations of salicylic acid was unaffected by KNO₃ but it was suppressed by NH₄Cl. When 12-day seedlings were transferred to the dark, total chlorophyll and carotenoids declined appreciably, but the supply of inorganic nitrogen protected them from decline to same extent. Thus inorganic nitrogen, especially the nitrate, is more important in protecting from degradation of chlorophyll and carotenoids than in increasing their biosyntheses.

Nitrate reductase level in leaves of pea plants is higher than in roots despite of the lower content of endogenous nitrate. Addition of ammonium ions to nutrient solution containing nitrate decreases nitrate reductase level in leaves estimatedin vivo while its level estimatedin vitro is increased.
Glutamine synthetase (GS) level in roots decreases during short (24 and 48 h) and long (14 d) term cultivation of seedlings in solutions containing ammonium ions. This decrease occurs in leaves only after the long term influence of ammonium ions. Level of this enzyme is higher in plants grown in the presence of nitrogen (ammonium and nitrate) as compared to those grown without the nitrogen.
Level of glutamate dehydrogenase in roots is increased after both short and long term cultivation of plants in the presence of ammonium ions.

The changes in cell division rate were studied in different components of the shoot apex ofChenopodium rubrum during short-day photoperiodic induction and after the inductive treatments. Induced and vegetative apices were compared. Accumulation of metaphases by colchicine treatment was used to compare the mean cell cycle duration in different components of the apex. A direct method of evaluating the increase in cell number obtained by anticlinal or periclinal divisions was applied if the corresponding components of induced and non-induced apices had to be compared. The short-day treatment prolonged the cell cycle more in the peripheral zone than in the central zone and still more in the leaf primordia. The importance of changing growth relations for floral transition was shown particularly if the induced plants were compared with the vegetative control with interrupted dark periods. Induced plants transferred to continuous light showed further changes in the rates of cell division. The cell cycle was shortened more in the central zone than in the peripheral zone,i.e. there was a further shift in growth relations within the apical dome. The cell cycle in the leaf and bud primordia was also shortened if compared with the vegetative control, the acceleration being stronger in the bud primordia. There was a subsequent retardation in cell division in the leaf primordia formed during and after the inductive treatment if the plants were fully induced. An inhibition of the oldest bud primordia was observed in fully induced apices, as well.

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.

Spring barley cv. Spartan was cultivated in a complete and nitrogen lacking Richter's solution. In other experimental variants the nitrogen was omitted after six days of cultivation in the complete nutrient solution or the nitrogen lacking solution was replaced with the complete solution after the same period of time. Anatomy of the second leaf blade was quantitatively analyzed after 12 days of cultivation. Continuous nitrogen deficiency resulted in thinning of the blade, reduction of the cross-section areas of the blade, vascular bundles and sclerenchyma region. The most sensitive reaction to the nitrogen deficiency was that of assimilation parenchyma. The values of characters of the other two investigated variants were between the control and permanent nitrogen lacking variant.

Chlorosis induced with a supraoptimum dose of phosphorus in nutrient solution (69 mg P l^-1) was reverted by spraying of leaves of chlorotio maize plants (Zea mays L.) with FeEDTA. Biomass formation, chlorophyll and iron content were decreased in the above-ground parts of plants grown under chlorosis-inducing conditions. Spraying always decreased content of inorganic phosphorus (P_i/Fe ratio was significantly changed), increased chlorophyll content in old plants and stimulated dry mass formation at supraoptimum phosphorus doses. FeEDTA application improved phosphate utilization (portion of phosphate in organic bonds was increased). This may be the basis of chlorosis-reverting effect of FeEDTA.

Polyethylene glycol (PEG-4000) solution in concentration from 7.5 to 200 g 1-¹ rapidly induced water stress of the desirable level in primary leaves of bean plants. At the same water saturation deficit, however, the water potential as well as the osmotic potential were considerably lower in leaves of PEG - treated plants than those in leaves of plants naturally wilting due to a gradual decrease in substrate moisture.

The rooting response to exogenous auxin of cuttings in a juvenile phase of growth from plants ofCastanea sativa Mill. was determined and simultaneously the rooting potential of the water extracts was evaluated in presence of IAA by a bean rooting test. The level of the extractable rooting promoters was high in the cuttings which exhibited the highest percentage of rooting. An inhibition of the effect of IAA on rooting was detected in the cuttings which showed the lowest rooting response, the histogram differing not much from that of the adult plant. The results indicate that in chestnut the juvenile condition, easy rooting, is associated with high levels of endogenous rooting promoters.

Using differential staining of cell walls the anatomy of microsporogenesis was investigated on cross-sections of anthers of fertile plants of the sweet pepperCapsicum annuum L. cv. Severka, as well as of its sterile analogues. The lignin-like staining as observed in the microsporocyte primary walls of fertile plants disappears with their getting independent in the course of meiosis. On the contrary, in sterile plants the stain increases in intensity, the thick-walled microsporocytes usually form a continuous block up to the period of tetradogenesis, and so far as microspores originate, they are not dissociated outwards. Moreover, in sterile anthers the external tapetum is usually not differentiated.

The water potential and the osmotic potential in plants which dominate Greek phryganic ecosystems (Phlomis fruticosa, Sarcopoterium spinosum, Gistus sp.) were measured from April to Nowember. Water potential decreased considerably reaching a minimum in September. Higher values of osmotic potential than that of water potential were found during dry period (i.e. negative values of pressure potential). This interesting fact was confirmed by artificial desiccation.

Crystal-containing organelles in cells of virus infected plants lying at chloroplasts and mitochondria are identical with single membrane-bound microbodies containing crystals of catalase described in healthy plants. Massive complex inclusions caused by turnip mosaic virus very frequently contain the same microbodies with crystal inclusions; that phenomenon may be related to some pathophysiological changes of virus infected plants. Comparable proteinaceous crystals, but not lying within microbodies limited by a membrane, may also be found in cytoplasm of infected cells. These crystals are sometimes surrounded by a substance resembling the microbody matrix. Disintegrated cytoplasm of virus infected cells may also contain the same crystals lying free in "empty spaces". Cytopathological effects responsible for this phenomenon and possible artifacts as well are discussed.

The translocation of¹⁴C-ABA from roots into other parts of the plant was followed in intact and decapitated pea seedlings. In intact plants ABA from roots was translocated above all into the apical part of epicotyl. In decapitated plants the regulative ability of intact apex can be partly simulated by exogenous IAA. The growth of lateral buds occurring after decapitation was associated with an intensive flow of¹⁴C-ABA from roots into released lateral buds as late as 72 h after decapitation,i.e. in the stage of intensive elongation growth of buds.

Starch was determined by means of IKI reaction in shoot apices ofChenopodium rubrum plants induced to flowering by two short days and in non-induced plants. Small starch grains were already observed in the meristematic cells at an age of four days after sowing. Larger grains were found in the subapical region of the apex. Heterogeneity increases during further growth of the plants in induced, as well as in non-induced vegetative plants. Starch disappears from the cells potentially giving rise to axillary buds, while the number and size of starch grains increase in cells from which leaf primordia will be formed. This metabolic specifity of leaf and bud primordia is preserved during morphological differentiation and applies to vegetative, as well as to prefloral apices of photoperiodically induced plants. The amount of starch in the different regions of the apex is linked rather with organogenesis than with the quantitative growth in the apex.

Acid-soluble chromosomal proteins were extracted from purified nuclei, isolated from 3 - 4 h, 12 -14 h and 24 -26 h maize embryos, as well as from nuclei isolated from meris-tematic, elongating and differentiated cells, from 2 and 3-day-oldZea mays seedlings primary roots.
Using polyacrylamide gel electrophoresis (urea-acetic acid in the cylindrical gels and slab-SDS-electrophoresis), it was established that germination and root cell differentiation induced changes in some nuclear acid-soluble chromosomal proteins, especially in histone H1.
The results of proteins belonging to the high-mobility group proteins (HMG) and some other acid-soluble proteins with unknown nature for the plants, based on the electrophoretic mobility, were discussed.