Phosphate is an effective inhibitor of the phosphohydrolases of wheat embryos (Triticum aestivum L.).In vitro the inhibition was competitive with K₁ = 4.48 × 10^-3 M (1.6 × 10^-3 M P₁, applied as KH₂PO₄).In vivo the inhibition with KH₂PO₄ was relatively low during germination (48 h), but inhibition increased when other P₁-compounds were used. In ungerminated embryos the phosphatase activity comprised three isozymes; the pattern of iaozymes changes during germination, but there was no influence of P₁ in comparison with the control.
Concluding we may state that the activity of phosphohydrolases is regulated by an inhibition mechanism caused by P_i-concentration.

The frequencies of chlorophyll mutants were investigated in anther cultures derived from mutagen-treated plants ofN. tabacum cv. Samsun (haploid level) and in the seed offspring from the same treated plants (diploid level). Comparison of the induced mutation frequencies at the haploid and diploid levels demonstrated that selection existed against the haploid embryoids with induced chlorophyll deficient mutations. The diploid vegetative stage with phenotypic expression of the chlorophyll mutation was more vital than the haploid one. The suitability of anther cultures for studying induced mutagenesis is discussed.

Poly(A)⁺RNA is synthesized during the first hours of pollen germination and is rapidly incorporated into polysomal structures. After a 2-h pulse with uracil-¹⁴C, 42% of the transcribed fraction of polysomal RNA is polyadenylated. Following 4 h of germination the amount of the newly-made poly(A)⁺RNA decreases steadily at the rate of about 14% per h, whereas that of rapidly-labelled poly(A)^-RNA continues to grow. Beginning 1 h of cultivation the ratio of poly(A)^-/poly(A)⁺RNA increases exponentially. Similarly as in non-polyadenylated mRNA the main portion of the synthesized polysomal poly(A)⁺RNA sediments at a rate of 4 to 14 S and its mean size decreases slightly with the time of labelling. RNA isolated from nuclei and cell wall containing pollen tube fraction differed from the polysomal one in higher apeoific radioactivity and the polyadenylated RNA exhibited higher size distribution. The comparison of the results with earlier observations suggests the involvement of poly(A)in mRNA translation in pollen tubes.

3 peaks of DNA synthesis were observed in the barley embryo of seeds, germinating for 49 h in running tap water at 25°C. The first peak, found after 22h, was formed by S-cells in the roots and in the 1st leaf meristem. The second peak (after 34-37h) and third peak (after 46-49 h) represents the S-cells in the roots, apex and 1st, 2nd and 3rd leaf meristems. Application of N-methyl-N-nitrosourea for 3 h at the onset of germination inhibited the rate of DNA synthesis and postponed the peaks of DNA synthesis in individual meristems of the embryo.

Barley seeds were treated for 3 h at 25°C with 240 mM ethyl methanesulphonate (EMS), washed for 18 h, treated with various concentrations of unbuffered sodium azide (pH 6.7-7.3) for 3 h at 25°C, re-dried to 30% water content and either sown immediately or stored at 25°C for 12 days and then sown. The synergistic action of sodium azide post-treatment has been demonstrated only for the EMS-induced M₁ germination reduction, while the EMS-induced M₁ sterility and the yield of M₂ chlorophyll mutants were unaffected. The "storage" recovery from EMS-induced mutagenic effects was insensitive to sodium azide post-treatment. The 12 day-seed storage at 25°C brought about an improvement of M₁ germination, M₁ survival, M₁ fertility and a decrease in the amount of M₂ mutants, regardless of whether sodium azide post-treatment was applied or not.

The synthesis of tRNA was demonstrated in pollen ofNicotiana tabacum L. according to the incorporation of labeled uracil, adenosine and guanosine during 4 h of germination. tRNA was extracted from postribosomal supernatant and purified by polyacrylamide gel electrophoresis. The incorporation of guanosine was about 1.68 times higher than that of adenosine. This finding indicates that the whole tRNA chain is formed in pollen tubes.

The effects of temperature treatments on rice seeds in the early imbibitional phase were studied with respect to changes in germination percentage, seedling growth in terms of root and shoot lengths, water uptake, respiration and hydrolytic enzymes,viz. α-amylase, adenosine triphosphatase (ATPase) and phytase. As compared with the control, the treatment for 30 min at 50 °C caused a variable degree of increase in all these characters and a positive correlation existed between seedling vigour and hydrolase activities. The treatment for 30 min at 60 °C, on the other hand, elicited a retarding influence on these characters. As regards the enzyme activities, the damaging effect of 60 °C could, however, be visualized only after 72 h of germination which was preceded by an enhancement during the early hours.

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.

Mechanical scarification of seeds ofPhaseolus mungo L. resulted in 100 per cent gormination in comparison to 90 per cent dormant control. Seeds treated with concentrated sulphuric acid for 8 min led to 85 per cent germination. Heat treatment at 70 °C for 24 h exhibited 75 per cent gormination, while boiled water treatment for 7 min caused 65 per cent germination.

Nine categories (a-i) of seeds inIpomoea pes-tigridis showed diverse germination responses at desiccating high temperatures (65 °C). These nine "generative ecotypes" have assured the persistance of their race by producing sets of seeds suitable for a set of temperature conditions in the Indian desert, where high desiccation of seeds is a major natural controlling factor.

During the germination of fenugreek (Trigonella foenum graecum L.) sulfhydryl groups rapidly declined in cotyledon and seedling axis, while peroxidase activity increased. Studies on purified isoenzymes showed that GSH was oxidized by the isoenzymes and was accomplished in presence of cofactors, Mn²⁺ and DCP along with H₂O₂ (0.01 mM). This reaction was found to be peroxidatic in nature. The oxidation was inhibited by catechol but was enhanced by malic acid.

Fusarium solani (76%),Phyllosticta phaseolina (12%) andAspergillus flavus (10%) were isolated from bean(Phaseolus vulgaris) seeds showing lesions. Out of these the first two caused 30 per cent and 20 per cent seed rotting respectively after artificial seed inoculations. When inoculum was added into the soil before sowing the seed, 35 per cent and 10 per cent pre-emergence rot ocurred and there was 35 per cent and 15 per cent post-emergence blight when soil with healthy seedlings was inoculated withF. solani andP. phaseolina respectively.F. solani caused similar lesions on bean seeds when inoculated after an injury.F. oxysporum was isolated from the roots of dried bean plants showing necrosis.

As an extension of earlier studies performed in our laboratory on enzyme localization on tissue level, the distribution of starch was examined in seedling root tips of peaPisum sativum L., broad beanFaba vulgarisMoench., maizeZea mays L., lupinLupinus albus L., and pumpkinCucurbita maximaDuch., and in tips of adventive roots of onionAllium cepa L. by means of the alcian blue /JJK procedure applied to paraffin sections. In pea, some genetic (various cultivars) and eco-physiological (different harvests, various localities, diverse way of germination, uneven seedling age, unequal stage of cell growth) factors were studied concerning the present problem. In all these cases the starch localization pattern remains constant though the amounts of starch vary in particular cell complexes. From the evaluation of the starch localization at the level of the beginning cell growth in particular species and from comparison of the findings in different species it follows that starch localization and histogenesis patterns are different. This supports the view that the two phenomena are caused or controlled by uneven factors.

A study was made on certain problems connected with the application of methods of stigmatal and placental pollinationin vitro in the snapdragon.
Germinable pollen without microbial contamination could be obtained only from the flowers which were left, after surface sterilization, on the stem till the dehiscence of anthers. The germination of pollen, and especially the growth of pollen tubes was better in a 0.3 M lactose solution with 10^-3 per cent H₃BO₃ than in usual sucrose media.
The seedsin vitro could be obtained only after normal pollination and the successive artificial cultivation of the entire pistil (the method of stigmatal pollinationin vitro). The seeds did not differ either in their morphology or in their size from those developed under natural conditions, they were viable and without dormancy.
Though the pollinated pistils were cultivated in the medium without growth substances, callus formation from uncovered ovules and placenta was observed in some cases. A dependence was revealed of the proliferation on pollination and on the cultivar employed.
When using the method of placental pollinationin vitro we failed to obtain seeds. The main difficulty in the use of this method seems to consist in the fact that pollen tubes are not capable of growing from the surface of ovules and placenta into the micropyle.

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.

Kinetin (KIN) and benzyladenine (BA) stimulate to different extent the germination of apple embryos isolated from dormant seeds or seeds submitted to stratification. KIN is much more active in the replacement of light requirement in apple embryos germination. Both cytokinins decrease the photosensitivity of embryos isolated from the seeds stratified less than one month, but only BA accelerates the appearance of the second photosensitivity maximum, normally occuring on the 70th day of stratification. Both cytokinins stimulate the activity of acid phosphatase between the 30th and 50th day of apple seed stratification. The stimulation between the 50th day and the end of stratification is exerted only by KIN.
These differences allow to discuss the specificity of action of particular cytokinins during the after-ripening and germination of apple embryos.

In only one cultivar out of 1200 investigated cultivars ofPhaseolus vulgaris L. could we find an extreme change in the pattern of reserve proteins on the cathodic side: one of the proteins, called protein I, is completely absent in the cultivar 'Krupnaya sakharnaya' and is replaced on the same site by another protein,i.e. a protein completely different in its immunochemical specificity. The case is of interest from both the phylogenetic and systematic viewpoints and deserves further attention.

The paper deals with the effect of some factors on the set of mature seeds in artificially pollinated excised placentae cultivatedin vitro.
It was revealed that both the degree and the variability of the seed set depend on the age of the experimental flowers. The best results were achieved using placentae excised from the flowers collected 1 to 3 days after anthesis.
The technique of pollination which consists in applying pollen onto a certain site of the placenta was substantially more successful than dusting pollen over the entire placenta surface or sowing pollen on the nutrient medium in close proximity to placentae.
It was confirmed that casein hydrolysate at a concentration of 500 μg ml^-1 nutrient medium favourably affected the seed formationin vitro.
The seed set resulting fromin vitro fertilization does not depend upon whether, during, a fourweek cultivation, the cultures are kept in the dark or in diffused daylight.

The seeds ofFraxinus excelsior L. were stratified at 17-20 °C (warm stratification), at 4-6 °C (cold stratification) and at alternating temperature (warm - cold stratification). The seeds subjected to warm stratification only, remained dormant. The seeds stratified only at 4-6 °C germinated gradually during a long period of time. The seeds subjected to warm - cold stratification, however, germinated with great intensity within a relatively short period of time.
GA₃ was shown to stimulate the growth of embryos markedly, and its effect on the germination of seeds depended on the temperature of stratification. GA₃ applied during the cold stratification accelerated the removal of dormancy by shortening the period of stratification and by influencing the germination of seeds. The results obtained indicate a similarity between the effect of temperature 17-20 °C during the warm stratification and that of gibberellic acid. Both those factors applied separately affect favourably after-ripening of the embryos and accelerate the germination of seeds.

Trypsin and chymotrypsin inhibiting activities were detected in a "crude inhibitor" fraction of a lipid free cashew nut (Anacardium occidentale L.) meal. Both activities were shown to be heat resistant and not affected by pepsin at pH 3.0. Molecular weight distribution of tho trypsin inhibiting activity is similar to the known range of molecular weights for trypsin inhibitors of plant origin.
A "crude extract" of the cashew nut meal was shown to contain strong L-leucine-p-nitro-anilide and moderately strong α-N-benzoyl-DL-arginine-p-nitroanilide hydrolyzing activities. This last activity was strongly inhibited by the "crude inhibitor" fraction shown to contain trypsin and chymotrypsin inhibiting activities. The presence of this endogenous inhibitor-endo-peptidase system seems to indicate that the protein proteinase inhibitors of plant origin could be involved in the control of protein mobilization in the seed.

According to plant age at induction and rate of initial growth ABA leads either to stimulation or inhibition of growth and flowering in youngChenopodium rubrum plants. This differential effect is linked with the morphogenetic potential of the plants at the time of ABA application. Different modes of germination and cultivation of the plants prior to floral induction affect growth and photoperiodic sensitivity of the plants which may also explain differences in the effect of ABA.

A strain of tobaoco mosaic virus(TMVbs) isolated fromPlantago major L. is not seed-borne with this plant species; however, plantain seeds and the mucilage on their surface also contain the virus. The mucilage shows a very low infectivity; the visoous mucilage inhibits infeotion in rubbed leaves both in a mixture with the virus and if applied before (but not after) the inoculation of the virus. Polysaccharides and hexuronic acids were detected in the great plantain seed mucilage. A mixture of mucilage and viras stored at room temperature showed s low infectivity until 33 days, but the infectivity increased oonspicuously on the 40th day, apparently simultaneously with the decay of mucilage. Polysaccharides are suggested as being responsible for the inhibition. They affect the inoculated leaf but not the virus, as ascertained by eleotron mioroscopy and serology. The seed mucilage being an important factor in the spread of plantain seeds may act as a vehicle of the virus as well.

Various types of meiotic anomalies in Mi generation such as multivalents, fragments, bridges, mioronuclei, polyads and in particular the multispindle formation, were observed after seed X-ray irradiation inCapsicum annuum L. As the dose increased there was a gradual increase in the number of aberrations.

A study was made concerning the effect of the analogues of nucleic acid components upon the seed set inPapaver somniferum L. For the experiments flowers one day after anthesis were used, as the pollination taking place at this flower age had previously been found to be most efficient for the seed set. The solutions of analogues in a 10 per cent sucrose were applied by injecting them into the ovaries three hours prior to pollination. Damage to the ovary by the injection reduces the seed set by about two thirds.
In comparison with control flowers, into which only a sucrose solution was injected, 5-bromouracil at a concentration of 5.2×10^-4 M increases the seed set by about 70 per cent. Uracil brings about the same degree of promotion. The same concentration of 5-bromodeoxyuridine has no significant effect on the seed set. When applied simultaneously with uracil it suppresses its stimulating effect completely. The equimolar mixture of uracil and bromouracil did not cause any significant increase in the number of seeds in the capsules, either.

1. Ethyl methanesulphonate (BMS)-treated barley seeds stored at 30 % water content for 1 - 4 weeks are capable of recovering from the mutagen induced injury. The level and speed of the recovery depends on the EMS dose and storage period. Seeds treated with extremely severe EMS doses reducing the% of germination to 5 - 10 % cannot recover from the induced injury. 2. Due to a 1 to 6 weeks storage of EMS-treated seeds with 20 % water content the amount of induced injury increases in dependence on the applied EMS dose and storage period. Doses of EMS, reducing the seedling height in the M₁ generation to 90 - 95 % of the control reveal no storage after-effects. 3. Storage of X-ray exposed seeds at 20 % or 30 % water content did not result in any significant changes in the yield of induced genetic damage.

CCC in either absence or presence of salinity slightly and irregularly affected the shoot dry weight, but consistently increased the seed cotton yield. The extent of such positive effect upon yield tended to be larger in the presence rather than in the absence of salinity when using CCC as a seed-soaking medium alone, but the reverse if applied as a spray after seed-soaking.

In the course of cold stratification ofAcer pseudoplatanus L. fruits a statistically significant alternation occurs in their seeds of a rise and fall in the level of endogenous growth regulators. In the initial weeks the inhibitory effect slightly declines, or, on the contrary, the stimulatory effect slightly increases; in the middle phase of stratification a marked increase in inhibitions and reduction of stimulations appears, and towards the end of stratification the stimulatory effect of isolated substances in the individual biotests rises again, or their inhibition effect is decreased. No direct dependence was found between the decrease of the degree of dormancy and the drop of inhibitor, or increase of promotor levels. However, a certain analogy was observed between the time course of fluctuations in the level of growth regulators and the germination energy of the seeds investigated. An enhancement of the growth activity of the substances isolated (e.g. those of a gibberellin-like nature) in the last weeks of stratification can already be considered as the result of the release of fruits from dormancy.

The exposure of maize plants to drought led in most cases to a decrease in both the total and free water percentages, but to an increase in cell sap concentration, bound water percentage and bound water/free water ratio, comparing with the case of normal water supply. The employment of any of the studied treatments at either the normal or low soil moisture levels led throughout the period of time preceding the milky stage to a decrease in the free water percentage in maize leaves, but to the reverse effect with respect to both the bound water percentage and the bound water/free water ratio. The determinations of water fractions in leaves (free, bound water % and the ratio between them) before or at the tasseling stage appeared to be more reliable, compared with osmotic pressure determinations, as indication for the effective use of a given treatment in increasing the drought resistance of maize plants.

The high M₁ sterility is the factor limiting the increase of the mutation frequency after treatment with nitrosamides like N-methyl-N'-nitro-N-nitrosoguanidine, N-methyl-N-nitrosourea, N-methyl-N-nitrosourethane and N-ethyl-N-nitrosourethane, whereas for ethylvinylnitrosamine-treatment the limiting factor is the toxic action on the M₁ seed germination. The decrease of mutation frequency at high dimethylnitrosamine doses is explained by the inhibition of enzymes or enzyme-like system which hydroxylate nitrosaminesin vivo and thus enable the production of a mutagenic alkylating intermediate. The increase of mutation frequency after treatment with X-rays is limited both by the decreased M₁ survival and M₁ fertility.