Leaf expiants from vegetative plants of the short-day plantStreptocarpus nobilis (C. B. Clarke) developed flower budsin vitro when cultured in 8 h photoperiods. Tn non-inductive photoperiods only vegetative buds were formed.In vitro photoinduction was demonstrated by giving the expiants short-day (SD) cycles and then transferring them to non-inductive photoperiods for expression of flowering. On medium containing 6-benzylaminopurine (BAP) organogenesis was initiated during the photoinductive treatments. Photoinduction of leaf tissue without adventitious bud development was obtained on medium without BAP. The photoinductive state of the leaf tissue was fairly stable, being expressed after 2-3 weeks in non-inductive photoperiods when adventitious buds were formed. The quantitativein vitro flowering response to the endogenous floral stimuli, resulting from photoinduction, could provide the basis of a bioassay for presumptive flower inducing chemicals.

The rice is important in plant science for its ability to germinate and grow with restricted or without oxygen availability. In this work we have investigated the variation of growth substances when anoxia was imposed to rice seedlings previously grown in air. An increase, in all the organs of a seedling and in particular in the fraction released in the medium, was observed for ABA (abscisic acid), PA (phaseic acid) and DPA (dihydrophaseic acid) quantities.Vice versa a reduction of total IAA (indol-3-ylacetic acid) was observed in seedlings. This was accompanied by its accumulation in roots. IAA was poorly released in aerobic conditions and anoxia has not changed this pattern.

Isolated uninucleate microspores of tomato,Lycopersicon esculentum Mill, were cultured in defined, liquid nutritive media. The microspores developed to haploid embryoids with or without an attached suspensor or into calli with compactly or loosely arranged cells.

Diphenylamine (DPA), 2-hydroxybiphenyl (OHBP) and 9-fluorenone (9-F), known inhibitors of carotenoids (car) synthesis, altered the pattern of incorporation of 2-¹⁴C-mevalonate into car in ripening fruits ofCapsicum annuum. OHBP was the most powerful inhibitor of the whole process of biosynthesis, followed by DPA and 9-F. The most sensitive step was the dehydrogenation of phytofluene. Cyclization of β-carotene and isomerizations yielding the structure of hydroxy-cyclopentane were also affected, although to a lesser extent.

The effect of phosphorus deficiency on acid phosphatase activity in the apical, middle and basal parts of the root of maize plants was followed. The supernatant obtained by centrifuging the homogenate of plant tissue at 1500 ×g was further centrifuged at 18 000 ×g, the sediment being marked as fraction II and the supernatant as fraction III. The results obtained document the fact that acid phosphatase activity of the two fractions of all analyzed root segments was higher in plants cultured in nutrient medium without phosphate than in those containing phosphorus in nutrient medium. In most cases this difference was significant to highly significant. The results of experiments proved unambiguously a higher enzymatic activity in all root segments in fraction III than in fraction II. In fraction III the highest acid phosphatase activity was found in the apical part, in fraction II in the basal part of the root.

The level of gibberellin-like substances was determined in the cotyledons and axis of developing seedlings of dwarf (Little Marvel) and normal (Tall Telephone) cultivars of pea (Pisum sativum L.). The effect of cotyledon removal with GA₃ application on growth was also examined. Greater levels of gibberellin-like substances were observed in the cotyledons of the normal cultivar than the dwarf. This was particularly evident in the cotyledons during the early stages of seedling growth. Subsequently there was a decline in GA levels in the cotyledons. This was coincidental with a rise in GA content in the axis with markedly greater levels in the normal than the dwarf cultivar.
Decotyledonated dwarf and normal plants supplied with GA were much taller than the decotyledonated controls. This observation along with those of the gibberellin levels in the cotyledons and axis, provided circumstantial evidence that there may be translocation of gibberellins from the cotyledons to the axis.

This paper describes the differentiation of karyotypically stable callus strains ofCrepis capillaris (with modal chromosome numbers 7, 8 -11 and ≧ 12, in particular) during 12 years' subculturing on an identical M-S medium with supplements, including 2,4-D (1 mg 1^-1) and adenine (1 mg 1^-1). The possible modes and factors of karyotypic adaptationin vitro are discussed.

6-benzylaminopurine (BAP), β-indolylbutyric acid (IBA), phenylacetic acid (PAA) and a triazine herbicide (TH) affected the development of vascular bundles both in coleoptiles and the last intemodium below the ear of wheat plants. These substances were applied before the conductive tissues in the organs investigated were fully differentiated, the degree of their effect being dependent not only on the concentration, but also on the developmental stage of the plants and on cultivation conditions. In coleoptiles the area of vascular bundles was increased especially in the dark. In the stalk, BAP, PAA, IBA and IBA + TH increased the area of phloem. BAP also stimulated the activity of parenchymatous cells of xylem. TH had the same effect only on xylem, which became evident by an increase in vascular bundle area, but not in that of phloem. These anatomical aberrations were confirmed by cytological analysis which revealed that the stimulatory effect of the substances investigated consisted in activation both of companion cells of phloem and parenchymatous cells of xylem, whose function is analogous. As a result, both types of cells contained numerous organelles characteristic of meristematic cells, which suggests protein synthesis and an active transport of substances.

The radiotracer technique is described for transport and metabolic studies in latex producing bark. This technique provided further evidence that carbohydrates are supplied to latex vessels as sucrose and that sucrose is readily used for rubber synthesis. Bark treatment with ethylene resulting in latex flow stimulation is shown to activate within a few hours sucrose and water transport into the latex vessels. The available knowledge suggests an implication of an energy-dependent process of proton excretion which could explain the earlier observed ethylene induced alkalization of latex cytosol enhancing invertase and sucrose utilization.
An increase of tapping intensity decreases the level of latex sucrose and changes its distribution pattern in drained bark. There is a clonal difference in the early response to exploitation. Bark excision by conventional tapping inhibits downward sucrose translocation, the inhibition being proportional to the surface of consumed bark above the tapping cut. Seasonal variation in the level of latex sucrose is related to variations in sunshine duration and sucrose concentration rises during the process of refoliation. The results stress the importance of sucrose supply to latex vessels for latex producing potentialities and indicate an association of low sucrose availability in latex vessels with premature latex vessel degeneration and bark dryness.

Treatment of etiolated and excisedCucurbita cotyledons with exogenous cytokinin (benzyladenine) in darkness or light results in a marked stimulation of Rubisco activity, content of enzyme protein, and incorporation of labelled precursors into it, indicating cytokinin-stimulatedde novo synthesis of the enzyme. Cell-free translations of RNA in the wheat germ andE. coli systems show an increase in both large and small subunit mRNA amounts relative to the increase of total RNA under the influence of the phytohormone and light. This increase in the level of translatable RNA is confirmed by RNA hybridization with the Rubisco large subunit gene of spinach. In addition, our results demonstrating additive effects of benzyladenine and light in cotyledon and chloroplast development suggest that the two factors co-act independently in the causal sequence of Rubisco gene expression. The data are discussed in a general view of cytokinin action in gene expression steps.

Two phases of radish ontogenesis (I-when the plant had produced 3 -5 nodes and II-when the plant had produced 8 -10 nodes) were established on the basis of axillary, meristem localization. Flowering of the plants in response to GA treatment depends on the phases in which they were treated and on growth correlations in the apical meristem. The results obtained suggest that the reaction ofRaphanus sativus (LDP) to GA treatment is parallel to that ofChenopodium rubrum (SDP), and that the response of radish plants also depends on changes in growth correlations in the shoot apical meristem at the time of treatment.

Capsicum annuum L. cv. Ramillete fruits grown in the field were covered 60 d after flowering with "white", yellow, red and blue cellophane filters. Two other sets were left in full sunlight and under cover, respectively. After 30 d of treatment, during the ripening period, the contents of individual carotenoids were analyzed.
The red radiation was the most effective to increase the carotenoid biosynthesis, but the green and blue radiations inhibited their production. Either class of filters inhibited the formation of capsanthin, the most important carotenoid in the production of red colour of the maturation, but capsorubin, the other carotenoid responsible for the maturation colour, was more enhanced in the shade and under red radiation. Neither type of radiation was so efficient in increasing the total carotenoids content as the full sun radiation.

In addition to the primary seminal primordium, the so-called secondary seminal root primordia are also initiated in a barley embryo. The primary root primordium is developmentally most advanced. It is formed by root meristem covered with the root cap, and by a histologically determined region with completed cell division. On germination, the restoration of growth processes begins in this non-meristematic region of root primordium by cell elongation, with the exception of the zone adjacent to the scutellar node, the cells of which do not elongate but continue differentiating. In the root primordia initiated later, the zone with completed cell division is relatively shorter, in the youngest primordia the non-meristematic cells may be lacking. The root meristem is reactivated after the primary root primordium has broken through the sheath-like coleorrhiza and emerges from the caryopsis as the primary root. The character of root meristem indicates a reduced water content at the embryonic development of root primordium. With progressing growth the root apex becomes thinner, the meristematic region becomes longer, and the differences in the extent of cell division between individual cell types increase. - The primary root base is formed of cells pre-existing in the seminal root primordium. Upon desiccation of caryopsis in maturation, and subsequent quiescent period, their development was temporarily broken, proceeding with the onset of germination. The length of this postembryonically non-dividing basal zone is different in individual cell types. The column of central metaxylem characteristic of the smallest number of cell cycles, has, under the given conditions, a mean length of about 22 mm, whereas the pericycle, as the tissue with most prolonged cell division, has a mean length of about 6 mm. In the seminal root primordia initiated later the non-dividing areas are relatively shorter. The basal region of seminal roots thus differs in its ontogenesis from the increase which is formed "de novo" by the action of root meristem upon seed germination.

The occurrence of browning in protoplast cultures ofCyamopsis tetragonoloba completely inhibited the growth of protoplast derived colonies. Of the various additives employed to counteract the problem of browning and subsequent necrosis, polyvinylpolypyrrolidone (PVPP) was found most effective. Simultaneous addition of polyvinylpyrrolidone (PVP) to the protoplast culture medium accentuated the effect of PVPP and also improved the frequency of protoplast division.

In the protonema ofFunaria hygrometrica, predetermined cells run through a period of sensitivity to cytokinins, as part of the morphogenetic system with respect to bud formation. The cytokinin sensitivity is highest immediately after the formation of cells in question. The cells can react if enough hormone is present during the sensitive phase. Kinetin is cleaved very rapidly and at an increasing rate. Most probably the concerned enzyme ("kinetin oxidase") is induced by kinetin. Therefore, cells formed after the beginning of the treatment do not respond by forming buds.

The level of endogenous gibberellin-like and cytokinin-like substances was estimated in the plumule and the root of 2-to 3-day-old intact pea seedlings, in the plumule of seedlings from which the radicle was cut off, and in the root of seedlings from which the plumule was removed.
An increase in the level of gibberellin-like substances and a decrease in the level of cytokininlike substances in the plumule as a consequence of radicle amputation were observed within 48 h. Plumule amputation resulted in a decreased level of both gibberellin-like and cytokinin-like substances in the root in the same period.

Ethylene induces the flower formation and stimulates the flower-bud development of some bulbous plants exposed to the gas when the apex is in the vegetative state. For iris bulbs cv. Ideal maximum responses have been found after exposure to 5 ppm for 8 h; lower concentrations, shorter exposure periods and, depending on seasonal conditions, low temperatures during gas treatment, gave intermediate responses. The effects are opposite to the ethylene induced flower-bud blasting which occurs when bulbous plants are exposed to the gas after completion of the flower formation.
Dry storage of the bulbs in atmospheres containing 5% CO₂ reduces the temperature-enhanced flower formation, suggesting a possible effect of endogenous ethylene.

Pigeon pea cultivars AL 15 (early-) and T₂₁ (late-maturing) were compared for dry matter accumulation in fruit parts pod wall (PW), seed coats (SC) and seed at various seed developmental stages. Significant water loss and dry matter accumulation in the fruit parts commenced much earlier in cv. AL 15 as compared with cv. T₂₁. The pod wall accumulated starch, reducing sugars and N-substances up to 21 and 28 days after anthesis (DAA) in cultivars AL 15 and T₂₁, respectively, which was later distributed to the seed. Growth of pod wall and seed was sequential, not concurrent, as the pod wall lost significant dry matter when the seeds within them reached their maximum dry matter. The fruit parts of cv. AL 15 accumulated more photosynthates than cv. T₂₁ at all comparable stages.

Flours prepared from seeds of two non-agglutinating and one agglutinating cultivar ofPhaseolus vulgaris ssp.vulgaris (tested against human A, B, O, and rabbit erythrocytes) were stored in a refrigerator for eight months. Extracts from aliquot portions of these flours were prepared in one-month intervals, their agglutinating activity was tested against rabbit erythrocytes, and their immunoelectrophoretic patterns and protein contents were determined. Agglutinating activity occurred during storage in ageing flours of originally non-agglutinating cultivars and a typical lectin zone which was absent in extracts of freshly prepared flours appeared in their immunoelectrophoretic patterns. This newly formed agglutinating activity in some cases again disappeared during further storage.

The influence of IAA in two concentrations (10^-8M and 10^-5M) on relations between growth, water absorption and cation uptake and accumulation was tested.IAA in a higher concentration retarded growth remarkably. First of all, potassium uptake and water absorption were significantly decreased while the uptake of divalent cations was affected later and less remarkably. 10^-8 M IAA accelerated the growth rate slightly together with acceleration of water absorption and cation uptake.

Under strictly non-inductive photoperiods (24-h photoperiods) floral buds were initiated on plants receiving 25 treatments with Reso (resorcinol) or 8 treatments with GA₃ (gibberellic acid) or GA₃ + Reso, while water treated control plants did not flower at all. Although a single treatment of plants with GA₃ or GA₃ + Reso is not adequate to cause induction under LD conditions, its effect is added to the sub-threshold induction caused by one SD (short day: 8-h photoperiod) cycle. The initiation of floral buds was hastened with an increasing number of SD cycles accompanying respective number of treatments, the effect of GA₃ alone or together with Reso being more pronounced than that of Reso alone. GA₃ increased the number of floral buds more than Reso, the number being the highest in plants receiving the respective number of treatments with the combination GA₃ + Reso under both inductive as well as non-inductive photoperiods.

A rapid method is presented for the determination of ribonuclease activity in coloured extracts from citrus leaves. At the same time, the influence exercised by several precipitating reagents and the storage time at 4 °c on the activity of the enzymatic system are studied. In addition the enzyme stability against heat is studied.

As the dynamics of changes in phytohormones may be involved in photoperiodic regulation of the rates of growth and flowering, fluctuation of cytokinins was followed in long-day and short-day tobacco. Zeatin (Z) and zeatin riboside (ZR) were identified in leaves and roots using a GC-MSC system. In plants of the long-day tobaccoNicotiana silvestris increasing the number of long-day inductive for flowering (10, 20, 30, 40 LD) resulted in a rise in ZR activity. Half the plants reached a reproductive stage on the 40th day of induction. In short-day Mam moth tobacco plants, short-day floral induction (10, 20, 30, 40 SD) caused similar but less marked changes in ZR.

The clone SJ ofSpirodela polyrhiza (L.) Schleiden forms turions under various nutritive conditions. As compared to 1500 μmol 1^-1 phosphate (P+), growth and frond yield of mixotropic cultures decreased, when 60 μol 1^-1 phosphate (P-) were available. By contrast, P-conditions increased the number, individual size, dry matter content, and total turion yield (mg turions per ml of the nutrient medium) of P-turions as compared to P+ ones. Germination behaviour of P-turions is characterized by fairly low zero levels in the controls, and by low heterogeneity in individual size as well as in the response patterns concerning the influence of light and/or phytoactive substances. P-turions from youngSpirodela cultures are extremely dormant. However, they undergo an after-ripening process if kept inside ageing cultures.