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.

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.

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.

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.

GA₃, cyclic AMP as well as 3'-AMP and 5'-AMP induced the formation of floral buds inImpatiens balsamina under strictly non-inductive photoperiods. While photoperiods and treatments with GA₃ or AMPs did not much affect acid phosphatase activity, AMPs increased the activity of alkaline phosphatase both in the stem and the leaves under both photoperiods. The phosphatase activity of the water- and GA₃-treated plants under inductive photoperiods was higher than that of the plants of the respective treatments under non-inductive photoperiods. GA₃ as well as all the three AMPs induced both in the stem and the leaves the formation of new isoenzymes of both these enzymes under both photoperiods.

Three short-day inductive cycles bring about inhibition followed by transitional enhancement of growth, not only in roots and leaves but also in different zones of shoot apical meristem, as shown by measurement of DNA synthesis using³H-thymidine autoradiography. The first inductive cycle resulted in marked inhibition of the cells of the central zone (CZ), rib meristem (RM), and peripheral zone (PZ). Subsequent enhancement of DNA synthesis occurs in RM during the second inductive cycle, but in CZ only in the third cycle. The growth activation in PZ is counteracted by decrease in apical dominance which results in further inhibition of leaf primordia and increases in bud primordia. In plants induced only by one cycle, which later reverse the vegetative pattern of growth and differentiation, increased DNA synthesis in RM and CZ was not observed. The significance of inhibitory and stimulatory processes in particular zones of the shoot apex is discussed considering flower morphogenesis.

Mycoplasma-like organisms (MLO) spread from the infectious grafts intoSolanum laciniatumAit. stock plants relatively slowly. MLO were present in all sprouts ofS. laciniatum four weeks after grafting, but the infected plants remained under glasshouse conditions mostly symptomless and flowered normally and formed fruits like healthy plants. The growth of plants with infectious tomato grafts was identical with the controls but that of plants with infectious tobacco (Nicotiana glaucaGrah.) grafts was expressively stimulated. The first flower symptoms appeared onS. laciniatum plants with tomato grafts after five and half months and on.S. laciniatum plants with tobacco grafts after seven months of graft symbiosis. Electron micrographs of ultrathin sections showed the presence of MLO in sieve tubes of potiols and midribs of the infected but symptomless plants. In the phloem parenchyma cells of the witches' broom diseased plants, highly ordered crystals were occasionally found lying in a microbody surrounded by a membrane. The possible reasons of the disease latency are discussed.

On squash preparations of anthers from pollen fertile and sterile plants of sweet pepper (Capsicum annuum L. cv. Severka) callose envelopes of microsporocytes, stained specifically with resorcin blue, were investigated microscopically. During normal course of microsporogenesis in fertile plants the envelopes remained intact up to the stage of microspore tetrads. Then callose begins to dissolve, and that from individual microspores towards the envelope periphery. In sterile analogues of the same cultivar the callose breakdown occurred precociously, usually in the course of the second, but sometimes as early as the first meiotic division of PMCs. Having completed meiosis sporadic microsporocytes formed microspore tetrads. Most PMCs contained an undivided four-nucleate protoplast rimmed with a narrow or wider unstained zone of dissolved callose. In certain cases more condensed callose septa pointing to the furrows on the surface of the PMC protoplast were well-observable in this lytic zone, as a residuum of normal mechanism of tetradogenesis.

Protein content, total and specific peroxidase activity and isoperoxidase patterns were determined in crude protein preparations from individual parts of field-grown wheat (Triticum aestivum L., cv. Jubilar). Protein content in roots, leaves, and stalks increased at the beginning of ontogenesis and then decreased from 6th, 9th, and 10th development phase (according to Feekes), respectively. Steady increase of the protein content in the ears was observed.
Highest peroxidase activity was found in the roots; it diminished from the onset of ontogenesis till maturity of the plants. In the leaves and stalks a slight decrease of peroxidase activity till the 10th development phase and then an increase till maturity was found. The ears exhibited a gradual increase of peroxidase activity. The course of specific peroxidase activity was found to be very similar to that of total activity.
Isoperoxidase patterns did not change significantly. In the leaves, a decrease of activity of C₄ and C₅ isoperoxidases was recorded. In the stalks, C l isoenzyme emerged at the end of ontogenesis. A gradual increase of A₁ and A₅ isoperoxidase intensity took place both in the leaves and stalks.

Photoperiodic responses of seedlings of long-day plantBrassica campestris L. cv. Ceres were investigated at different ages and varying length of inductive period. It was found that photoperiodie response increased with age. All plants flowered after one inductive cycle beginning with a light-period of 16h, but remained in the vegetative phase when kept under short-days (16h darkness, 8h light).
Both auxins (IAA and NAA) and cytokinins (kinetin and benzyladenine) inhibited flowering when applied to the plumule or via the roots immediately before the inductive photoperiod. This inhibitory effects was confined to bud formation, whereas the rate of leaf initiation remained mostly unchanged. Only high concentrations of growth substances also affected the growth of roots and leaves. These results agree, in general, with the effects of growth substances in the short-day plantChenopodium rubrum.

High accumulation of³²P was observed in the leaves of intact gherkin plants 9 days after their roots had been treated with 0.005% suspension of the systemic fungicide Folcidin 50WP (cypendazole),i.e. 8 days after the roots had been exposed to labelled phosphate. Folcidin also influenced phosphorus metabolism in the plants. High biologic cytokinin-like activity of the fungicide was established when using a callus cytokinin bioassay.

GA₃ as well as SA increase the protein content of the stem and the leaves at 1 day under both 8- and 24-h photoperiods. A new protein band with Rm 0.47 seems to be associated with floral bud initiation as it develops within 1-3 days in the stem as well as in the leaves of plants exposed to inductive treatments regardless of whether the induction is caused by 8-h photoperiods or by treatment with GA₃ of SA under 24-h photoperiods. Another band with Rm 0.23 developed only in the stem of water-as well as GA₃- or SA-treated plants under 8-h photoperiods. It may possibly be associated with extension growth.

Abscisic acid (ABA) was applied in a concentration of 1. 10^-3 M and 1. 10^-4 M to the quantitative SD plantChenopodium rubrum under various light regimes. ABA did not influence flowering in plants under continuous illumination, enhanced flowering in plants subjected to long days and inhibited it in plants induced by short days. It was concluded that ABA can not substitute for inductive treatment but its action may be additive to initial stages of reproductive morphogenesis (enhanced growth rate and branching of the apical meristem) as evoked by long days.

In decapitated pea plants an increased peroxidase activity ocours after the cotyledon excision in cotylars growing in axillas of cotyledons prior to the growth of excised cotylars. It was found that peroxidase plays an important role in this correlation.
Auxin applied on epicotyl stumps inhibited the growth of cotylars and the removal of this inhibition by cytokinin or ethrel was associated with an increased peroxidase activity followed by the growth of cotylars situated in axillas of treated cotyledons.

The investigation of phosphorus absorption by intact plants during a short period has above all confirmed the validity of the results obtained in the foregoing study of the kinetics of absorption by excised roots. Further, the results show the unquestionably important role of mass flow in transporting ions to plant roots, mainly at lower and medium concentrations, that is, from about 0.1 to 10 mM. Under conditions of growth close to the optimum, the supply by means of mass flow can be sufficient even at lower concentrations of phosphorus, such as 1.47 mM KH₂PO₄, or the absorption of phosphorus by plants can be higher than in the case of ions being transported to roots by diffusion. With a higher absorption the phosphorus distribution somewhat changes as well, relatively more of it being accumulated in the roots. 2.4-DNP applied to the nutrient solution at a concentration of 10^-5 M reduces the phosphorus absorption.

Uptake of magnesium was studied by continuous flow technique for 82 days old rice plants in nutrient solution over a range of 0.2 to 1 ppm or 8.2 to 41 µM magnesium concentration. Uptake of magnesium followed a Michaelis-Menten kinetics with a Michaelis constant, K_m of 0.2 × 10^-4M and V_m 156 µg g^-1 h^-1. With increasing flow rate, the rate of magnesium absorption was increased.

IAA-oxidase activity increased in the stem as well as in the leaves of plants treated with GA₃, SA and GA₃ + SA during the early stages under inductive and non-inductive photoperiods, the activity being the highest in GA₃ + SA-treated plants. An isoenzyme of IAA-oxidase with Rm 0.15 developed in the stem as well as in the leaves subsequent to 1 or 2 inductive treatments. As this band persisted till the end of the experiment, it may be associated with the initiation as well as development of floral buds. Another band (Rm 0.30) appears to be associated with the phenol (SA) as it developed in the stem as well as in the leaves of SA- and GA₃ + SA-treated plants under both photoperiods. A band with Rm 0.60 developed in the leaves but not in the stem of GA₃-, SA- and GA₃ + SA-treated plants under both photoperiods.

Growth correlations in the shoot apical meristem during transition to flowering were studied in a quantitative long day plant,Brassica campestris L. cv. Ceres, requiring only one long day for floral initiation. During photo-inductive exposure of the plants, an overall increase in cell number could be observed at the shoot apex concomitant with promotion of leaf initiation. Release from apical dominance and decline in relative growth rate of leaf primordia are reported as early effects of photo-induction. With the onset of floral differentiation, production of new leaf primordia had stopped altogether. Maximum increase in RNA concentration could be noticed in axillary meristems following photoperiodic treatment, whereas in vegetative plants the highest RNA concentration was found in leaf primordia. The significance of these changes occurring during transition to flowering is discussed.

Considerable changes in tryptophan synthase aotivity occur during the ontogenesis of pea plants (Pisum sativum L.) in their individual parts. Maximal tryptophan synthase activity is connected with the vigorous growth period of the individual organs and of the entire plant. The content of free serine which is present in excess and is one of the substrates in the reaction catalyzed by tryptophan synthase, also changes, as well as the content of free tryptophan, the product of the reaction. The changes in the contents of these amino acids do not correspond to the variation in tryptophan synthase activity and mainly follow the alterations in the total nitrogen metabolísm. The limiting factor in the biosynthesis ofL-tryptophanin vivo is probably the availability of the aromatic precursor, above all of indole-3-glycerophosphate. The content of bound tryptophan also shifts in the pea plants owing to the enrichment of proteins in older parts of pea plants with this amino acid.

Amaranthus viridis is a quantitative SD plant in which inflorescence primordia are initiated under both 24- and 8-h photoperiods after 12 and 10 days, when 8 and 7 leaves are differentiated, respectively. Photoperiod plays a non-determinate role, whereas the maturity of plants linked with the attainment of minimum leaf number is significant and of primary importance in floral induction. This is further confirmed by the more or less identical nature of changes in the total enzyme activity and isoenzyme patterns of peroxidase, esterase and alkaline and acid phosphatase under the two photoperiods. These changes occur once the minimum vegetative growth has been achieved prior to the reproductive transformation, irrespective of the photoperiod, pointing to the activation of a general common pathway of events leading to floral induction.

In field-grown sugar beet plants (Beta vulgaris L. cv. Dobrovická A), each of66 successive leaves produoed in the course of the vegetation period was different with respect to its photosynthetic capaoity (P_c), life span, duration of leaf area expansion, and longevity after its maximum leaf area (A_max) has developed. The proportionality between the seasonal changes in these characteristics was not the same if the sequential senescence of leaves was taken into account. With aging of individual leaves, P_c increased with the leaf area expansion having attained the peak value between 75% to 100% of A_max The rate of ontogenetic changes in P_c of each leaf was specified by the rate of its growth and development so that even at comparable ages the successive leaves constituted a series of different physiological units.
The seasonal changes in quantum irradiance (PAR) were found to be responsible for differences in the growth characteristics between the successive leaves: Leaf expansion period was related with daily integrals of the incoming PAR (Io), while leaf longevity, after the A_max had been attained, was closely linked with PAR intercepted by the canopy (I). P_c expressed per the total leaf area of the plant was significantly correlated withI, while P_c calculated per unit leaf area of the plant was related toI _o Leaf potential to adapt P_c correspondingly to changes in PAR was greatest during leaf blade expansion; after the leaf had ceased to expand, changes in P_c were independent of differences in leaf irradiance.
The results stress, at least for field conditions, the inadmissibility of the extrapolation of attributes from one leaf to the other ones sequentially senescing on the plant.

The increased activity of GOT (E.C.2.6.1.1.) and GPT (E.C.2.6.1.2.) transaminases in maize seedlings found as a marker of genotype opaque-2, was investigated in extirped sprouts of both genotypes, normal and opaque-2. The enzymatic activity was determined in three maize samples from breeding experiments, each sample consisting of a genotype pair, normal and opaque-2, collected from segregating ears of maize plants in the S₁ generation. The seedlings were aseptically grown for 7 days in two variants of cultivation, intact seedlings and sprouts extirped after 4 days of germination.
In the intact seedlings of genotype opaque-2 an increased activity of GOT and GPT, as compared to the intact normal plants, was observed. The extirpation of the sprouts enhanced GOT and GPT activity in the sprouts of both genotypes. However, in extirped sprouts the GOT and GPT activity was found to be still higher in the genotype opaque-2 as compared with the sprouts of normal genotype. Thus it seems that the increased transaminase activity in the sprouts of genotype opaque-2 is genetically determined. The increase does not result from an induction of enzyme synthesis through the supply of amino acids translocated from the endosperm to the sprouts. The absolute level of transaminases in the different breeding samples is dependent on the parenteral lines, the relative level of GOT and GPT activities is higher in the genotype opaque-2.

Intact maize seedlings were examined for the uptake and leakage of labelled sulphate and phosphate anions affected by temperature. Control plants, grown at 25 °C were compared from the aspects of uptake capacity and leakage with plants incubated in nutrient solutions cooled to 15 °C and 5 °C, respectively. Short time intervals as well as 1-7 d exposure to cooling were used. Already after 1 h exposure at 5 °C and 5 h cooling at 15 °C and at 5 °C, considerable changes were manifested in anion uptake and leakage.
The uptake of³²P declined more than that of³⁵S. So, after a 30 min uptake interval the uptake of³⁵S decreased at 15 °C to 49.84% and at 5 °C to 6.05% comparing with the uptake at 25 °C, while the uptake of³²P declined to 28.64% at 15 °C and to 4.45% at 5 °C. The leakage of both anions was the highest at 25 °C in absolute rates, but relatively most of the uptaken³⁵S and³²P was released at 5 °C. Longer exposure to a chilling temperature of 5 °C (1-7 days) resulted in two patterns of sulphate and phosphate uptake.

Uptake of potassium by rice plants at different stages of growth can be described by a biphasic isotherm in the range of 5 × 10^-5 M and is probably mediated bya multiphasic mechanism in the plasmalemma.

White mustard (Sinapis alba L.) plants, susceptible to 2,4-D, and scentless mayweed (Tripleurospermum maritimum L.) plants, resistant to 2,4-D, markedly differ in the distribution and metabolism of 2,4-D. When 2,4-D-¹⁴C was applied onto the leaf, radioactivity was found in mustard after 8 days in the entire plant, whereas in scentless mayweed radioactivity occurred mainly in the leaf onto which it was applied and in another one or two leaves, with the roots showing only traces of radioactivity. The two plant species differed both in the character and in the number and amount of metabolites detected in aqueous and ether fractions. The metabolite with R_f 0.63 -0.65, soluble in ethylether (39% of the total radioactivity applied), and that with R_f 0.35 -0.36 (23% of the total radioactivity) were present exclusively in the roots of scentless mayweed plants. The R_f values established indicate that the former metabolite may be a conjugate with the amino acids alanine and valine and the latter a hydroxylated derivate of 2,4-D. In the shoots of both plants, 2,4-D-¹⁴C was metabolized to identical metabolites with R_f 0.59 -0.61, which occurred in mustard plants only in trace amounts. Free 2,4-D-¹⁴C occurred in the shoots of both plants and in considerable amounts also in mustard roots; it could not be demonstrated in the roots of scentless mayweed. The two species did not differ in the uptake rate or in the amount of absorbed 2,4-D-¹⁴C.

In intact, decapitated and decapitated indole-3-acetic acid (IAA) treated pea seedlings the translocation of benzyl-8-^l4C-adenin (¹⁴C-BA) from the roots was studied with regard to the release of lateral buds from apex-induced inhibition. In intact plants (controls) a substantial part of the activity was found in the apical part of the epicotyl. Decapitation resulted in the initiation of growth of lateral buds. As early as 24 h after decapitation and application of¹⁴C-BA a significantly higher activity was found in growing lateral buds (cotylars) of decapitated plants than in inhibited ones of intact or IAA-treated decapitated plants. The accumulation of¹⁴C-activity in stump tops of decapitated plants treated with IAA was associated with the thickening growth.

The study was concerned with the effects of irradiation of the sodium humate on its biological activity, which was assessed by the elongation of the hypocotyl and root in young plants of lettuce (Lactuca sativa L. cv. Rapid and cv. Smaragd) growing in the solution of the tested preparation. It was found that its stimulative action on hypocotyl and root elongation in lettuce was changed due to irradiation. However, the degree was dependent on concentration; stimulation mostly decreased, only at some higher concentrations did it increase. Further, experiments showed that there was some interaction between the irradiation of the humate and the cultivar used for testing, but none between the irradiation and the light exposure of plants during the test. The response of the experimental plants to the concentration of the humate depends on the light exposure.

Stimulation of flower formation was ohserved in the female plants ofCannabis sativa raised from seeds treated with gamma rays. These plants produced seeds, of smaller size. One of 195 plants formed sterile hermaphrodite flowers with reduced female structures and increased number of anthers.

Shoots have been produced in the explants from flower head receptacles cultured on BDS medium with BAP and/or NAA. The shoots produced could be regenerated to form the whole plants and transplanted into soil. No morphological or cytological variations were observed in mature plants. The histological analysis of adventive bud formation is presented. The importance of this method for clonal propagation ofAllium porrum plants is discussed.