The effect of several nitrogen compounds on the germination of the first seed of each spikelet ofAvena sterilis spp.macrocarpa Mo. was studied on Petri dishes placed in germination chamber. The compounds assayed were ammonium sulphate, ammonium nitrate, urea and calcium nitrate, generally used as fertilizer for cereal crops, as well as a control supplied with water only
The concentration of the assayed compounds were 100, 1000, 2500 and 5000 ppm either at a constant temperature of 15 ° C or at alternated temperatures 5°C and 15 °C, for 16 and 8 h, respectively
Significant increase in the germination percentages occurred when nitrate compounds were used in relation to other compounds and no significant differences were found between the urea, and ammonium sulphate. This increase became significant at 1000 ppm, and therefrom until 5000 ppm germination stabilized. In the case of urea, very high abnormal germination percentages were obtained at 2500 ppm, while the effect turned noxious from 5000 ppm
The use of alternating temperatures significantly increased the germination capacity of the wild oat seeds in the case of urea, ammonium sulphate and ammonium nitrate.
It is found that nitrates are capable of breaking the dormancy ofAvena sterilis spp.macrocarpa Mo. seeds, which according to various authors, is due to an increase of the respiratory activity of the seeds

Axillary meristems of short day plantChenopodium rubrum are localized as caulinar, foliar or axillar. The localization of axillary meristems and axillary buds of 14 day old plants varied in similar pattern as in other plant species so far investigated: after several nodes with foliar axillary meristems the caulinar ones were produced. However, unlike in other species, in C.rubrum a very high percentage of caulinar meristem is produced also on the first node. In this case, like in the case of its later differentiation at higher nodes, the formation of caulinar meristem is confined also to the vegetative state. It was found that the caulinary position coincides with higher responsiveness to photoperiodic induction. The developmental significance of such behaviour is discussed.

Biochemical characteristics (enzyme activities, contents of vitamins, phytohormones, nucleic acids, proteins, saccharides, etc. ) in germinating seeds and developing seedlings are summarized, and the inhibitory and stimulatory actions of these compounds on plant growth and development are discussed.

Respiration rate of foliarPelargonium discs was insensitive to ageing. The addition of BAP or GA₃ to the ageing medium did not produce any effect.
The presence of GA₃ or BAP in the ageing medium induced an increase (27 %) or a decrease (45 %) of the phosphate uptake. The analysis of phosphorylated compound labelling showed that these two hormones decreased³²P incorporation in the non-acid soluble fraction and increased³²P incorporation in the acid soluble organic fraction. GA₃ and BAP had little effect on the distribution of radioactivity between the different acid soluble compounds, but they increased the ATP level.
These results suggest that both GA₃ and BAP increase the basal metabolism, but they seem to act differently on the development of the uptake mechanism during ageing.

There exist two main mechanisms of allelopathy: 1) direct transfer of metabolites between neighbouring plants during their life and 2) accumulation and transformation of bioactive substances in the environment with their subsequent influence on higher plants. The latter mechanism is similar to that causing soil sickness or soil toxicity. Allelochemicals affect all functions of the living system: photosynthesis, respiration, mineral nutrition, transpiration, immunity, and growth. The initial biochemical effect of allelochemicals seems to be on the synthesis of protein mediated by RNA/DNA. Knowledge of the mechanisms of concrete signals during realization of hereditary codes would serve as a powerful tool for the improvement of crop plant development and productivity.

Divisional activity, intrusive growth of the cell wall and loss of fusiform initials have been studied in Holoptelea integrifolia. The dimensional changes in relation to mean length, length frequency, mean width and length variation in relation to fibre length have also been analysed.

Potato root cultures transformed by_pRiA4 T-DNA do not regenerate plants in vitro spontaneously, but regeneration can be induced by a sequence of callogenesis and regeneration media. Both T_l and T_r-DNA were found by Southern blotting. Regenerated transformants showed characteristic morphological deviations in the in_vitro cultures. Plants in the soil showed differences in the inflorescence and tuber development.

Bromegrass cell suspension cultures, varying in frost hardiness, were immersed ìn distilled water and electrical conductivity of the bathing solutions was measured at various intervals after immersion. It was found that tissue frost-hardened by maintenance at 2‡C leaked more electrolytes than the relatively frost-sensitive tissue grown at 20‡C, but that tissue frost-hardened by abscisic add treatment displayed decreased leakage, despite comparable levels of frost-hardiness having been achieved. It is concluded, in contrast with the conclusion of a previous report, that changes in membrane permeability to electrolytes may not be directly related to the capacity of cells to tolerate freezing stress.

Two ways were tested to obtain the definitive bacterial decontamination of a clone of hybrid walnut culturedin vitro: treatment of the plantlets with Rifampicin and other antibiotic agents, and culture establishmentvia shoot tip expiants. The former failed whereas the latter led to plantlets truly free of contaminants which could be satisfactory propagated, rooted and weaned

Chloroplast DNA from three barley cultivars and from one lettuce cultivar was prepared from chloroplasts isolated by Conventional differential centrifugation. Barley chloroplast DNA size was sensibly lower (130 kpb) than lettuce chloroplast DNA (150 kpb). Chloroplast DNAs from the three barley cultivars showed similar restriction fragment patterns after digestion with: BamHI, EcoRI or HindIII. The lettuce chloroplast DNA restriction pattern was very different from the barley chloroplast DNA restriction pattern.

Seeds ofPetunia nyctaginifloraJuss. a common ornamental garden plant, were treated with two alkylating agents (methyl methane sulphonate and N-methyl-N'-nitro-N-nitrosoguanidine). Six morphological and seven chlorophyll mutants were isolated from M₂ segregating families. The isolated induced mutants are described and genetically analysed.

The interactive effects of certain phytohormones (GA₃, IAA or kinetin) and drought on plant-water relations and mineral accumulation of the three crop plants; maize, cowpea and broad bean, were studied. Phytohormone applications were capable of counteracting to some extent, the adverse effects of drought on transpiration, stomatal frequency, and leaf area.

A new method of simultaneous measurement of membrane (E_m) and transorgan (E_tr)electric potential in intactChenopodium rubrum plants and changes in E_m and E_tr under various experimental conditions are described. E_m was measured in mesophyll leaf cells, and E_tr in the same plant as a potential difference between a first pair leaf, tip and roots. The two potentials differed distinctly, E_m averaging-156mV and E_tr -5mV. But the,-changes in E_m and E_tr had approximately the same magnitude and time-course after changing light and darkness or KCl concentration in solution flowing around the leaf or during the photoperiodic induetive cycle. In relation to the same electrode connection they had an opposite polarity. The nature of E_tr and its relation to E_m are discussed.
The measurement of E_tr is much more stable and simpler than that of E_m. The similarity of E_m and E_tr time-courses justifies the use of E_tr measurement in electrophysiological studies as a replacement for E_m measurements especially in intact plants.

The uptake of cadmium and its effect on the growth of potato shoot tips grownin vitro were followed in dependence on cadmium concentration in nutrient medium.
Concentration of 10^-6M Cd²⁺did not substantially affect potato plantlet growth dynamics; but the concentration of 10^-3 M Cd²⁺ showed a strong growth inhibitory effect accompanied with increased cadmium accumulation in both root and shoot tissues.

Growth, carbon uptake and carbon utilization in leaves of various growing phase shoots (GPS) on beech trees(Fagus sylvatica L.) growing under different light conditions were compared. The values of photosynthetic capacity (maximum daily net photosynthetic rate, Pn max) were used as comparable parameters.
Daily time and irradiance (I, PhAR), when PN max was attained, were investigated similarly. Statistically significant differences were found in growth, Pn max and SLM (specific leaf mass) between different GPS and within the same stand, as well as within the same GPS and different stands. Pn max and SLM increased in the leaves of GPS I (spring - plagiotropic shoots) on trees from a sun stand from May till September. At the end of the growing season, the spring leaves exhibited, in comparison with the summer ones, intensive senescence, but leaves of the GPS II and III (summer -orthotropic shoots) evidently attained higher values of Px max and SLM at higher I (PhAR).
The correlation of growth, PN max and SLM in relation to environmental conditions, as well as the importance of transport, distribution and utilization of assimilates for annual carbon gain and biomass production are discussed in detail.

The effect of short chain fatty acids on the cellular permeability of embryonic axis inGcer arietinum seeds was studied. Octanoic (OCT) and nonanoic (NON) adds, which reduce both germination and growth of the embryonic axis and raise the inhibitor effects of the supraoptimal temperatures (30‡C), induce a greater ionic efflux into the medium (conductivity). NON reduces glucose (3-0-MG) and K⁺ (⁸⁶Rb) uptake during the germinative process, this action being counteracted by fusicoccin (FC) at optimal (25‡C) and supraoptimal temperatures (30 ‡C). Tonoplast and plasmalemma increase their permeability to the K⁺ efflux when NON is present. Addition of NON+FC gives rise to higher values in the efflux rate, the vacuolar compartment being the most affected. Temperatures around zero (2 ‡C) notably reduce the isotope efflux from cytosol and vacuole. NON acid does not significantly affect the efflux of³H-ABA, suggesting that it does not cause any important changes in the phytohormone compartmentation.

Pollen embryos of Brassica juncea (L.) Czern., obtained through anther culture, were examined histologically and histochemically to find explanation for their inability to germinate normally like a zygotic embryo. Most of the embryos lacked a distinct plumule or both plumule and radicle. Anotherabnormal feature of these embryos was the degeneration of cells in the hypocotyl and radicle, whichoccurred either through lysis or cell shrinkage. Reserve food material was mainly in the form of proteinbodies and starch grains. Unlike the zygotic embryos, the pollen embryos lacked lipids. It is concluded thatthe inability of the pollen embryos to germinate normally is due to their structural abnormalities andphysiological immaturity.

A method of cultivation and effectiveness of different light sources and light regimes in photoperiodic induction of flowering in non-rosette long-day plantChenopodium murale L. ecotype 197 are described. Under the described conditions of cultivation 5 days, of continuous light produced by incandescent bulbs (TESLA 74 3x40 W, red 4.9 μWcm-²nn-¹, far-red 7.4 μWcn-2nm-¹, blue 0.25 μW cm-²nn-¹) induced flowering in the majority of plants.

From nine different plant species grown at 1500 cm³ m^-3 CO₂ five responded with a significant increase in stomatal numbers per mm² as compared with plants grown under normal air conditions. Within a collection of twelve french bean cultivars remarkable cultivar differences with regard to the CO₂ enhancement effect on stomatal numbers was found.

In triticale and its parental species, the application of a root osmotic stress induced either a transient increase or an immediate decrease in transpiration rate. The response of wheat (Trticum dicoccum farrum) proved to depend on relative humidity of air. In rye (Secale cerealecv. Petkus) and triticale (T. 300) the effect of NaCl stress was less expressive, than the effect of PEG.

The hypothesis that allelochemicals released from members of the Florida scrub community deter the invasion of fire-prone sandhill grasses was investigated. Constituents of the endemic scrub members, Ceratiola ericoides, Conradina canescens and Calamintha ashei, were examined for their phytotoxic activity. Effects of the plant natural products on the germination and radicle growth of lettuce (Lactuca sativa), as well as little bluestem (Schizachyrium scoparium) and green sprangletop (Leptochloa dubia), two native grasses of the Florida sandhill community, were tested.
The data suggest that ursolic acid and other natural detergents which are released from a source plant enhance the solubilization of allelopathic lipids via micellization. In general, natural surfactants seem to play a significant role in the water transport of lipophilic phytotoxins to target seeds or seedlings.

Germinated seeds ofVicia faba were continuously irradiated at low dose rate of gamma rays (0.05 Gy h-¹) up to a total accumulated dose of 2 Gy. The FPG (fluorescence plus Giemsa) technique of differential chromatid staining was used to monitor the frequency of sister chromatid exchanges (SCEs) in irradiated root tip meristem cells. The results of the experiments have demonstrated that SCE frequency is raised by continuous gamma irradiation only in plant cells containing BrdU in the chromosomal DNA. No effect concerning SCE formation was recorded at continuous irradiation of meristematic cells of Vicia faba with native, i. e. BrdU-nonsubstituted, DNA. In contrast to SCEs, a significant increase was found in the yield of chromosomal aberrations in all variants of irradiation.

Electrophysiological processes were investigated in the reception organ of photoperiodism, cotyledons and first leaves, in a model short-day plantChenopodium rubrum L. (selection 374) within the dark inductive cycle for flowering. Membrane potential (E_m) was measured in cotyledon and first leaf mesophyll of intact plants. The E_m time-course was fairly similar during inductive dark or postinductive light period or in non-inductive continuous light and had a character of irregular oscillations. The most distinct oscillations were found during the postinductive light period. Changes in light régime at the beginning (light off) and the end of inductive dark period (light on) triggered marked transient E_m changes having a character of damped oscillations. Cortical root cells in intact plants did not react to switching light and darkness. Changes in E_m in reception organs during the inductive cycle could not be correlated with the formation and transport of floral stimulus or with reaching the induced state. Thus, the electrophysiological nature of floral stimulus has not been confirmed.