A field experiment was conducted to investigate the effects of presoaking the wheat grains (Triticum aestivum L.) in different levels of salinity (33 or 66 mM) and in growth regulators (indolyl-3-acetic acid, IAA at SO g m^-3, gibberellic acid, GA₃ at 100 g m^-3, or kinetin at 100 g m_-3) on the shoot growth and pigment content of the developing wheat flag leaf. Salinity at 33 or 66 mM led to an insignificant increase in the fresh and dry masses as well as in the shoot diameter and shoot length, but it attenuated the flag leaf area. In the majority of cases, salinity increased the chlorophyll (Chla, Chlb) and carotenoid contents as well as the number of chloroplasts per a mesophyll cell. The growth in the wheat shoot of the saline-treated plants was, in general, stimulated in response to presoaking the grains in kinetin or GA₃. On the other hand, IAA + salinity led to a negligible effect on the growth in the wheat plants particularly at the early stages of growth. The presoaking of grains in NaCl at 33 mM + IAA or 66 mM + kinetin induced a marked increase in the pigment content of the wheat flag leaf particularly at the early stages of growth. The interaction between salinity and phytohormones increased the number of chloroplasts; kinetin was the most effective.

Embryogenic callus was initiated from immature zygotic embryos of black pine on medium DCR supplemented with 2 mg 1^-1 2,4-D and 0.5 mg 1^-1 BAP. The diploid number of chromosomes confirmed the origin of callus from zygotic embryos. The callus was white, glossy, mucilaginous and contained somatic embryos consisted of an embryonic region with densely cytoplasmic cells and suspensor region with long vacuolated cells. Although somatic embryos with green cotyledons were recognisable after ABA treatment and subsequent transfer to growth-regulator free media whole plants have not yet been obtained.

Somatic embryogenesis was induced in immature zygotic embryos of pea (Pisum sativum L.), synthetic auxins α-naphthalene acetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram, PIC) being used. Only one (line HM-6) of 46 genotypes tested exhibited good potential for somatic embryogenesis. 2,4-D was found as the best somatic embryo inductor. Three different ways of somatic embryo conversion have been described. Plantlets from individual somatic embryos were micropropagated as somaclones and subsequently rooted. A sterile morphological mutant has been found within a group of fertile plants of T₀-generation. Sufficient amount of T₁-seeds is available for somaclonal variation studies.

The herbicide terbutryn induced up to 11.3 % chromosomal abnormalities in cells undergoing meiosis inVicia faba. The mean number of pods/plant and the mean number of seeds/pod were considerably reduced, but the average seed dry mass was not or was only slightly affected by this herbicide. In C₂ plants chromosomal abnormalities were observed in few but significant numbers of cells.

Chenopodium rubrum L. ecotype 184 is a qualitative short-day plant with critical length of the night of eight hours that must be exceeded in order to flower: Five days after sowing, the plants were exposed to a various number of inductive cycles (14/10 h of däy/night cycle) to test the optimal photoperiodic conditions for flowering. In our experimental conditions the plants flowered with high percentage after more than four received inductive cycles, but there was no flowering below that. The plants grown on the herbicide Norflurazon (photobleached plants) showed different photoperiodic characteristics. There was negligible flowering of photobleached plants in the same experimental conditions as for the green ones.

In a glasshouse experiment, an increase of the number of wheat plants per pot caused the plants to became taller, have more ears and a greater grain yield per pot, while the number of tillers decreased and the straw mass did not change. The N and P contents in straw and N in grain also trended to decrease, while the translocation of these nutrients to the grain increased.
The increase of wild oat plants (Avena sterilis spp.macrocarpa Mo.) per pot, produced a decrease of the growth attributes, grain yield and N accumulation in grain of wheat per pot. Wild oat competition with wheat was higher than the wheat competition with itself. Such competition affected the height, number of tillers and ears, the fertility index of the shoots, the straw and grain mass, and the total accumulation of N, P and K nutrients per wheat plant.

Diurnal variations in endogenous IAA levels inFatsia japonica leaves, maintaining constant other external factors such as temperature and relative humidity, were studied. Plants were cultivated in a growth chamber (20 °C, 75 % RH, 16 h photoperiod, 400 µmol m^-2 s^-1 PAR). IAA analyses were carried out by analytical IP-HPLC with on-line spectrofluorimetry. Rhythmic variation of endogenous IAA levels was found. At the onset of the light period the IAA concentration dropped very rapidly from 1070 pmol g^-1 (fr.m.) to 144 pmol g^-1 (fr.m.). This concentration was nearly constant throughout the entire light period. During the subsequent dark period the IAA levels increased again to about 1000 pmol g^-1 (fr.m.) at the end of the dark phase. These results were not confirmed in open field conditions where many other external factors probably influence the endogenous IAA content.

When distantly related plants are crossed, embryos abort on the mother plant. One of the methods used to rescue the embryo is to cultivate the ovulein vitro. When the ovule is precociously detached from the mother plant, survival rate of the embryo is very low. To increase the chance of survival as well as the growth of the embryo, the medium was supplemented by different extracts of plants after either autoclaving or filtering. Autoclaved tomato extract seemed to have no simulating effect in spite of reports from different authors. Filtered coconut milk increased growth and filtered cucumber extract improved survival. Other new extracts had a stimulating action on both growth and survival and are of interest for further study.

The delay in development of winter wheat plants grown under conditions of Ca deficiency manifested itself also in the time curve of ferredoxin-dependent glutamate synthase activity. Up to the stage of the first leaf the activity increased. Thereafter it gradually decreased similarly as under conditions of complete nutrition, but with a shift of about 7 days as compared with plants given complete nutrition. Increased glutamate synthase activity in Ca-deficient plants may be one of the factors leading to a high glutamate level under these conditions.

Sunflower (Helianthus annus L. cv. PSH-7) plants were subjected to different osmotic potentials, using polyethylene glycol-6000 (PEG-6000), after, prior to and during SO₂ fumigation. Total soluble proteins and nitrate reductase activity (NRA) decreased, and free proline content increased with the increasing water stress. These biochemical parameters were more adversely affected in fumigated plants than in non-fumigated ones, when mild water stress was provided prior to and during fumigation. When severe water stress was given prior to and during fumigation, total soluble proteins, NRA and free proline content were nearly the same in fumigated and non-fumigated water-stressed plants; it is because the stomatal closure was observed in water-stressed plants. The leaf water potential decreased with the increasing water stress; however, it was not significantly affected due to SO₂ fumigation.

The chlorophyll and protein contents of the flag, second and third leaves gradually decreased during the reproductive development of rice (Oryza sativa L. cv. Rasi) and wheat (Triticum aestivum L. cv. Sonalika) plants, whereas proline accumulation increased up to the grain maturation stage and slightly decreased thereafter. In rice plant, the rate of decrease in chlorophyll and protein and increase in proline level were higher in the flag leaf than in the second leaf. It was opposite in wheat plant. The export of [³²P]-phosphate from leaves to grains gradually increased reaching a maximal stage at the grain development stage, and then declined. The export of this radioisotope was greater in rice than in wheat. Removal of panicle at the anthesis and grainfilling stages delayed leaf senescence of rice plant, while in wheat the ponicle removal at any stage did not have a marked effect on delaying leaf senescence. The contents of chlorophyll and protein of glumes were higher in wheat than in rice. The variation of such source-sink relationship might be one of the possible reasons for the above effect on leaf senescence.

The primary transformant of spring rapeseed cv. HM-81 contained TL- and TR-DNA of agropine plasmid pRi ofAgrobacterium rhizogenes 15834. The presence of TL-DNA corresponds to visible transformed phenotype in its progeny; the leaves are wrinkled and the plants are shorter than normal plants. R₁ R₂ and R₃ generations have mostly transformed phenotype. The normal phenotype appears in a low frequency in F₁ generation. Autogamised F₁ plants segregate in F₂ transformed and normal phenotype in 3:1 ratio. It is possible to suppose that TL-DNA is present in two differentloci of one pair of homologic chromosomes. The recombination frequency is 12 % (microsporogenesis) or 6 % (microsporogenesis and macrosporogenesis). In some crosses the transformed phenotype has a maternal type of inheritance. Maternal inheritance influences also several growth characteristics,e.g. length of plants and number of seeds/pods.

Variations in water content, relative water content (RWC), pressure potential and intracellular pH (pH) had been studied as factors of bud growth in rose plantlets grown in vitro for micropropagation. During the phase of healing, pressure potential and pH, were high enough to allow bud growth. During the following growth phase only buds of the lower part of the stem were able to grow. The growth ability of these buds and the growth inhibition of the others, associated with ΔpH, were retained during the last three days of culture, when dry matter content and RWC were the lowest. The results also showed a tight link between pH, and pressure potential. This may enable to distinguish different stages of plantlet development in vitro.

Two classes of phosphonopeptides, those containing P-terminal 9-aminofluoren-9-ylphos-phonic acid and those of dialkyl 9-aminofluoren-9-ylphosphine oxides, influence plant growth according to different mechanisms. The effect of these compounds on the growth of several bacterial species, including the photosynthetic bacteriumRhodospirillum rubrum, as well as on the activity of photosystems 1 and 2 in isolatedPisum sativum andSpirodela oligorrhiza chloroplasts was studied. The peptides of free, unblocked 9-aminofluoren-9-ylphosphonic acid acted in a morphactin-like manner, whereas those of dialkyl 9-aminofluoren-9-ylphosphine oxides influenced photosynthesis indirectly.

The contents of NADP⁺, NADPH, changes in the activity of glucose-6-phosphate dehydrogenase and some questions relating to its regulation in leaf tissues of tobacco plants infected with PVY were studied. The content of NADP⁺ and the total sum of pyridine nucleotides decreased after inoculation to 15 % and 30 %, respectively, whereas the content of NADPH increased up to the threefold control value. The contents of NADP⁺, NADPH and Σ(NADPH + NADP⁺) linearly correlated with the reproduction curve of PVY. The value of the reduction charge RC and the value of the ratio NADPH/NADP⁺ sharply increased after inoculation up to tenfold and eighteenfold values, respectively, of the healthy control.
The activity of glucose-6-phosphate dehydrogenase was markedly increased in virus-infected tissues during the entire experimental period both in crude homogenate and after its partial purification when compared with the values found in healthy control plants. The time courses of the activity curves of both crude and partially purified enzymes were coincident and correlated with the reproduction curve of PVY. The results indicate the involvement of coarse regulation of the activity of the enzyme by its content without the involvement of fine regulation by the ratio NADPH/NADP⁺ and RC.

The copy number of genes encoding 5S ribosomal RNA has been found to be constant in Petunia hybrida plants regenerated from protoplast and leaf disc-derived callus cultures. However, in one somaclone a heritable change in the length of the major 5S rDNA repeat has arisen. Despite the constant copy number of 5S rRNA genes, that of the 18S-25S rRNA genes is found to very by at least ten-fold. The relevance of these findings to ribosomal RNA gene variability and to somaclonal variation is discussed.

The ribulose 1,5-bisphosphate activity and its relative content in pea (Pisum sativum L., cv. Bordi) seedlings grown either under white or red light were investigated. Plants grown under red light had a lower ribulose 1,5- bisphosphate carboxylase (RuBPCO) activity as compared to plants grown under white light, if expressed on a fresh mass. These activities were very similar under both lights, as calculated on protein basis, although the relative content of RuBPCO was higher in the red one. The activity of RuBPCO under red light corresponds to the lower rate of net photosynthesis. The results are discussed in respect to possible presence of RuBPCO inhibitor in pea plants growth under red light.

Seven day- and six week-old alfalfa (Medicago sativa L.) plants, susceptible and resistant to bacterial wilt, were inoculated withCorynebacterium michiganense pv.insidiosum (McCulloch) Dye & Kemp. Leakage of solutes absorbing UV light from leaf discs into distilled water was investigated. The bacterial infection did not affect solute leakage rate from unifoliate and trifoliate leaves of either susceptible or resistant plants at an early stage of the disease. This may indicate that cell membrane integrity in alfalfa leaf tissues was not impaired.

Resistance of transformed and non-transformed spring oilseed rape cv. HM-81 to the infection with cauliflower mosaic virus (CaMV), turnip yellow mosaic virus (TYMV) and turnip mosaic virus (TuMV) was studied, to determine the influence of transformation on susceptibility of plants to viruses. For experiments the non-segregating R 1 generation of primary transformant HM-81-JZ and control plants of cv. HM-81 were used. The primary transformant was obtained by inoculation of stems withAgrobacterium rhizogenes 15834. All transformed plants of R 1 generation had typically "transformed" phenotype. No significant differences were revealed in the resistance of both transformed and non-transformed plants to each virus, as proved by qualitative and quantitative ELISA and visual evaluation of symptoms. Transformed plants infected with turnip yellow mosaic virus showed significantly lower reduction of green mass yield than non-transformed. In the case of CaMV and TuMV infection reduction of yield of transformed and non-transformed plants was almost the same.

Acid-soluble phosphate esters were determined in extracts of plant material after a 24 h exposure of the roots of intact alfalfa plants to nutrient media labelled with³²P_i. Similar phosphate ester patterns were found in 2-, 3-, 8-, and 9-week-old plants with the exception of Gra-P which could be detected only in shoot extracts. However, phosphate ester levels differed in the shoots and roots. Whereas Fru-P₂, Glc-6-P, Fru-6-P, and adenine nucleotides were more abundant in the shoots, Grn-P and P-choline levels were higher in the roots. Certain differences in the levels of P-esters were also recorded between plants susceptible and resistant to bacterial wilt.

The possible implication of ethylene on the growth regulation of etiolated lupin hypocotyls was investigated. Excised hypocotyl sections from actively growing seedlings produced ethylene at a rate of 3 nmol h^-1 g^-1 min^-1. The rate of ethylene production was increased about 7 times when sections were treated with 10 mM 1-aminocyclopropane-1-carboxylic acid (ACC). Measurement of endogenous ACC showed that 95 % of total ACC (64.2 nmol g^-1 min^-1) corresponded to conjugated ACC.
Treatments to intact seedlings with the ethylene precursor ACC, and the ethylene generating compound, 2-chloroethyl phosphonic acid (ethephon) during the cell elongation phase of the hypocotyl (from 7 to 21 dage), modified the cell growth of the organ. ACC (1 or 5 mM) or low concentrations of ethephon (0.66 mM) produced a transient decrease in the growth rate without modifying the final length of the hypocotyls. Higher concentrations of ethephon reduced the final length; the younger the seedlings were, the greater the reduction. Simultaneously to inhibition of cell elongation, ethephon produced stimulation of the radial expansion of cells in pith and cortex.
The growth inhibition period, which lasted for 2 days after the treatments, was followed by another period in which the growth rate of treated plants surpassed that of the control. In both cases differences were observed along the hypocotyls due to the different growth status of the cells. It is suggested that the sensitivity to ethylene and the metabolism of ethylene depend on the growth status of the cells.

CAM-like photosynthesis was found in the isoetid aquatic plantsLittorella uniflora andIsoetes lacustris, but not in the isoetid speciesLobelia dortmanna or in the elodeidElodea canadensis. Of the taxa studied, the first three are known to utilize sediment-borne CO₂, whereasElodea is dependent on bicarbonate.

21-day old plants ofChenopodium rubrum L. ecotype 374 were used. Organ relationships in the shoots were investigated by³²P distribution, which indicated different organ correlations in plants grown in continuous light and in plants treated with flower-inducing and non-inducing dark periods. Dark periods were associated with a low³²P distribution in young leaves and a high one in axillary buds. In the following light period the high³²P distribution in axillary buds continued whereas the³²P distribution in the leaves on the main axis increased and was similar to that in plants grown in continuous light. The high³²P distribution in axillary buds was brought about by both, flower-inducing and non-inducing dark treatments. Decapitation resulted in a high³²P distribution in buds, in continuous light an increased³²P distribution was also found in leaves. These effects were not fully cancelled by IAA application.
The results are discussed with respect to an assumption that decrease of apical dominance represents a step in a sequence of events leading to flowering.

Three isolates of strawberry mottle agent (SMA) from strawberry plants were regularly maintained and multiplied by mechanical inoculation onChenopodium quinoa plants showing mosaic and mottle symptoms. The use of 5 mM borate buffer pH 8.6 or tap water pH 6.6-7.9 with 4 % (m/v) charcoal for homogenization resulted usually in 100 % infection. The total of 2090 plants were infected from 2264 inoculated ones under the same conditions. The infectivity of SMA isolates in crude sap ofC. quinoa was retained from 48 h to 72 h at 20 °C. The dilution end points of SMA isolates were 10^-3 while the inactivation temperatures were between 50 and 55 °C. The infectivity of SMA isolates in frozen leaves ofC. quinoa was detected still after six months.
Purification procedure of SMA is based on using low molar 25 mM borate buffer pH 8.3 with cysteine hydrochloride, DIECA and Tween 20 for homogenization of infectedC. quinoa leaves, polyethyleneglycol precipitation, clarification with octanol, low and high speed centrifugation and sucrose density-gradient centrifugation. Partially purified preparations are highly infectious, causing mosaic, mottling and tip necrosis ofC. quinoa plants. The agent could not be completely separated from host proteins and it could not be concentrated to a high extent. Isometric virus-like particles 14-16 nm were observed in partially purified preparations.

The influence of increasing concentrations of copper, zinc, lead, nickel, chromium and cadmium on 14-day-old seedlings of wheat (Triticum aestivum L. cv. Vergina) was studied. Plants were grown in 1/10 strength Rorison's nutrient solution with increasing concentrations of each of the metals added separately. The toxicity of metals depressed shoot growth but the most evident symptoms were on roots. The concentration of each metal which caused inhibition of root growth was chosen to study the influence of metals on isoperoxidases of wheat shoots. The concentrations employed did not alter the number of peroxidase bands but almost in all cases enhanced the intensities of bands of pH 4.0-4.2 and 5.0-5.4, while they decreased the intensities of bands of pH 4.2-4.6 and 5.4-6.5.
The similar effects of the different heavy metals employed may suggest similarity in metal action on wheat isoperoxidases. The increased intensities of peroxidase bands may be considered as an indication of enhanced senescence caused by the heavy metal treatments.
Generally, our results suggest that the heavy metals employed have caused complex changes on the multiple forms of peroxidases.

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.

Correlations within a shoot ofChenopodium rubrum L. ecotype 374 grown under continuous light or photoperiodic flower induction were studied using surgical treatments. Removal of a single pair of shoot organs had a variety of effects depending on position: significant changes in the number of leaf pair on the main axis or in axillary buds and in the height of shoot apices; or no effect on the parameters scored. Flowering was not affected by any of the treatments carried out. Decapitation brought about a significant increase in the number of leaf pairs in axillary buds and flowering was inhibited in 8- and 9-d old plants. Flowering was not affected in 21-d old plants. The role of shoot organ correlations, especially that of apical dominance, in regulation of flowering inC.rubrum is discussed.

The activity of acetylcholinesterase (AChE) isolated from coleoptiles of etiolated oat seedlings is strongly inhibited by neostigmine and less so by eserine. The optimum of the enzyme activity occurs at pH 7.2 and a temperature of + 36 °C. The enzyme Michaelis constant is 280 μM. Choline within the range of concentration from 0.001 to 10 mM does not affect the enzyme activity. Calcium ions at 5 mM concentration cause inhibition, while magnesium and manganese ions do not affect the enzyme activity.
AChE isolated from oat seedlings differs in a number of properties from AChE occurring in the tissues of other plants.

Twenty six winter wheat cultivars representing early maturing (Em), medium early maturing (Mm), and late maturing (Lm) cultivar groups were grown in the field for two growing seasons. The dates at which plants reached the double ridge (DR) and terminal spikelet (TS) stages were determined using anatomical analysis of shoot apices. Thereafter the dates of anthesis (AN) and full maturity (MA) were recorded. The length of the time spans between subsequent developmental stages was then expressed both chronologically (number of days, d) and in terms of thermal time (degree day, °C d) which was calculated with the basal temperature equalling to zero. The results obtained confirmed the suitability of the utilization of degree days for the description of the time course of plant development, because the great differences in the time between subsequent developmental stages recorded between the two growing seasons when expressed in terms of numbers of days markedly diminished when expressed in terms of degree days. For example the period DR-MA expressed in number of days amounted in the year 1986 only to 87 % when related to the number of days recorded in the year 1985, whereas the corresponding value expressed in terms of degree days amounted to 98 %. The utilization of degree days is especially suitable for the AN-MA period (956 and 937 degree days in the years 1985 and 1986, respectively) within which temperature is the main factor determining the rate of plant development. Further analyses of the effects of basal temperatures, vernalization, and daylength appear to be necessary for a better understanding of the length of the period to the DR stage and differences among groups of cultivars and among different cultivars.