Following moderate water stress in the cortical cells of theZea mays primary roots, the condensation of the nuclear chromatin, a higher density of free ribosomes and a reduction of polyribosomes, the reduction of mitochondrial cristae, elongation of ER elements, less compact dictyosomes and inhibited production of the Golgi vesicles were observed. Severe water stress would cause more severe structural damage in the cortical cells. The more differentiated cortical cells showed more expressive ultrastructural damage when compared with the meristematic nonvacuolated cells. Similarly, the cells of the peripheral layers of the cortex suffered more from water deficit than the cells of the layers situated closer to the central cylinder.

Following a 24-h exposure to a solution of polyethylene glycol 4 000 of a -12.66 bar osmotic potential the roots of maize ceased growing. The inhibition of growth was conditioned by the inhibition of cell elongation and division. The elongation of cells was substituted by their radial enlargement which took place both in the peripheral and central root parts. The cells either did not divide at all, or sporadic mitoses still occurred in the roots. The meristematic cells treated were highly vacuolized, chromatin condensation being observed in their nuclei. In contrast to growth processes, differentiation was stimulated: the formation of the secondary wall in protoxylem elements occurred at a shorter distance,i.e. 1 500-2 400 µm from the apex, in comparison with 4000-5 000 µm in the control, this evidently being caused not only by the inhibition of growth, but also by the capacity of cells to differentiate more rapidly. The changes induced by a 24-h exposure to water stress were of a reversible nature; however, a 48-h treatment brought about irreversible changes.

In a greenhouse pot oulture experiment, a dinitrogen (N2) fixing - acetylene reduction activity profile was examined in detail as affected by plant age. Total [μmol C2H4 root-1 h-1] and speoifio nitrogenase [nmol C2H4 (mg nodule d. wt.)-1 min-1] activities peaked 63 days after sowing, near the end of flowering. The nitrogenase activities, nodule dry matter accumulation, top dry matter accumulation, and total nitrogen yield in the top dry matter were found to be highly correlated.

The capability of the submergentLemna trisulca L. to utilize various inorganic and organic sources of nitrogen was studied using both non-axenic and axenic cultures. When doubling time for frond production was measured, the nitrogen sources in order of effectiveness were urea, aspartic acid, nitrate, glutamic acid, arginine, ammonium and casein hydrolysate. Nitrite supported a relatively rapid growth rate after an initial lag of 7 days. Other parameters of growth such as fresh or dry weight per frond or ohlorophyll content did not oorrelate well with rate of frond production. Casein hydrolysate and urea were found to elicit a morphology different from that seen in cultures containing the other nitrogen sources. These preferences for source of nitrogen were different than those known for the emergent species ofLemnaceae. The unique value ofL. trisulca as a subject for plant physiological research is discussed. This study also provides a possible explanation for the existence of nutritional niches existing in aquatio ecosystems containing several different species ofLemnaceae.

Calcium deficiency resulted in a 20% increase in the total content of phenolic compounds in the shoots of 10-day-old wheat plants and in a 10% decrease in the roots compared with the control. Differences in specific activities of the lyases of the shikimate pathway (L-phenylalanine ammonia-lyase, E.C.4.3.1.5, PAL; L-tyrosine ammonia-lyase, TAL) were established between control and Ca-deficient wheat and pumpkin plants. The lyase activities were higher in the shoots of Ca-deficient plants and lower in their roots, compared with the control. Thus, there is a certain correlation between PAL and TAL activities on the one hand and the content of phenolic compounds on the other. The time course of PAL activity during a few first days of growth and the dependence of TAL activity on pH were also investigated.

The growth stimulating effect of 5-bromouracil and uracil on two strains of chlorococcal algae has been found in cell colonies grown from single cells, which were inoculated onto an agar medium. Analyses of the effect recorded in the cell cycles after treatment have revealed that the growth stimulating effect required four, or more, cell cycles to become evident. This has been proved by the number of autospores released from the treated cells and by the length of the lag phase after inoculation. The differences between the control and the treated population in some experiments with 5-bromouracil inChlorella and with uracil inScenedesmus obliquus have been visible by the unaided eye, whereas in some other experiments, they have been proved statistically. Growth stimulation has not been found only in a small number of experiments. The inhibition of growth induced by 5-bromouracil has been recorded in one experiment withScenedesmus quadricauda.

Growth of primary (cv. Wisconsin 38) and long-term (cv. Virginia Bright Italia) tissue cultures obtained fromNicotiana tabacum L. pith was affected by exposure to a single dose of gamma-radiation ranging from 1 to 150 krad. The inhibitory effect was proportional to the applied dose. Changes in the degree of inhibition during the subculture interval were ascertained by quantitative evaluation of the growth response. Primary cultures proved to be several times more radiosensitive than long-term cultures, the capacity to recover from radiation damage of the cultures participating in the resulting manifestation of the effect. The possible reasons for these differences are discussed.

Endogenous growth substances were estimated byAvena coleoptile test in hypocotyls of cuttings ofPhaseolus vulgaris which were treated with Umbelliferone, a coumarin which has been found to have a stimulating effect on rooting. A similar growth promoting zone which corresponded chromatographically to indole-3-acetic acid, was found in both treated and control cuttings. A growth-inhibiting zone detected in control extracts was absent in UM treated cuttings. The results are discussed in relation to Umbelliferone effect on rooting stimulation.

The capability of utilizing 20 amino acids and 2 amides as the sole nitrogen source for growth was studied in two green algae (Chlorophyceae). A comparison was made of the growth rate of algae in a mineral nutrient solution containing nitrate as the nitrogen source, with that in the same solution in which nitrogen in the form of nitrate was substituted by an equivalent nitrogen amount in the form of various amino acids. In addition to this, another series of experiments was carried out in whioh both culture media were supplied with glucose. The results show that both algae utilize a series of amino acids in dependence of their structure (mostly 3-carbon amino acids). The growth rate ofChlorella in the presence of these sources is the same as in nitrate, that ofScenedesmus even much higher. In the cultures containing glucose both algal species exhibit a higher growth rate in the media with the nitrate nitrogen source than in those with amino acids (with the exception of glycine inScenedesmus).

Hydration level of seeds determines vigour of soybean,Glycine max (L.) Merr. The seeds should contain at least 20% of moisture for a good performance at low temperatures. This hydration level can be reached by pre-sowing exposure of seeds in water saturated atmosphere (WSA). The exposure decreases both visible symptoms of chilling injury and leaching electrolytes during imbibition, and increases both germination and growth of seedlings at 10 to 12 °C. It is concluded that the cell membrane integrity is re-established in a course of the WSA exposure.

The specific activity of glucose-6-phosphate dehydrogenase (G-6-PD) in growth zones ofVicia faba roots is increasing with cell maturation and differentiation. Changes in the total activity of G-6-PD are not associated with a change in the number of G-6-PD isoenzymes. Five G-6-PD isoenzymes were found in all root growth zones. Some differences were found in the activity of individual isoenzymes.

Phototropic sensitivity of forest wood seedlings to lateral illumination was proposed as an early assay for distinquishing various ecotypes of woody plants of the same species. Statistical analysis showed that results were significantly influenced by heterogenity of experimental material caused by an interference of phototropic movements and natural oscillations of hypocotyl. Both movements of pine seedlings (Pinus silvestris L.) were registered by phase photography and their mechanism was analyzed. The apical part of growing hypocotyl illuminated from above oscillates in a space spiral with frequency 3.3 h at mean growth rate 0.66 mm h^-1. The mean size of spiral amplitudes is 2.9 mm. The oscillation rhythm is disturbed after the lateral illumination and a phase shift was observed as a result. A new oscillation rhythm with frequency 3.9 h and mean growth rate 0.69 mm h^-1 was stabilized after a period of time equal to one nutation turn. Oscillation amplitudes were increased to 4.3 mm.
In addition to the radiation intensity the appearance of the phototropic response to light pulse is first of all effected by the actual position of the apical part of hypocotyl in the course of endogenous circumnutations. A uniform plant material for the early assay may be obtained by selection of seedlings which are at the beginning of lateral illumination in the same phase of nutation rhythm. Under such conditions the deviations of longitudinal axis of oscillating spirals characterize the actual phototropic curvature.

A simple maceration procedure for cell suspension preparation from white poplar tissue culture has been devised which makes it possible to count cell number from microphotographs reliably. The results obtained are suitable for quantitative evaluation of cell proliferation tissue growth.

The association between latex RNA and latex production was examined using MAK column chromatography techniques. In young untapped trees the introduction of tapping or the treatment of bark with growth regulators resulted in an increase of RNA level and of rRNA/tRNA ratio in the latex. In regularly tapped trees an increase in rRNA but not in tRNA was brought about by increasing the tapping frequency. Treatment with growth regulators had the same effect but essentially only through the related enhancement of latex export from latex vessels. During latex flow, the highest RNA level was registered in latex fractions originating from the most heavily drained areas of bark. Using³²P labeling, evidence was obtained that the export of latex results in an enhancement of rRNA migration into the inner latex containing space of the vessels. This is considered as the reason of the generally observed association of high RNA level and of high rRNA/tRNA ratio with high latex yield. It is proposed that in controlling the RNA level and RNA proportions in the latex an important role is played by changes in turgor pressure associated with the loss of latex which may influence the export of RNA from the nucleus through related induction of pressure disequilibrium between the nucleoplasm and the latex cytoplasm.

Groundnut (Arachis hypogaea L.) plants were grown for 55 days in dilute nutrient solution at varying concentration of potassium. Data are recorded for the rate of uptake of potassium, magnesium and growth response. Over the concentration range studied, the rate of absorption of potassium followed Michaelis-Menten kinetics with a Michaelis constant (K_m) of 0.06×10^-3M. Identical response curves were observed for either total growth or total uptake. Maximum yield was obtained at a concentration of about 200 μM potassium. Increasing concentrations of potassium depressed the uptake of magnesium.

The flow of the nutrient solution stimulates significantly the growth of maize plants and enhances the absorption of nitrogen, potassium, and phosphorus. Especially the content of phosphorus in the shoots and in the roots is significantly increased, but its incorporation into organic compounds is considerably decreased. The plants grown, in flowing nutrient solutions have an altered distribution of iron with a higher amount of it remaining in the roots. In the shoots there is an increase in the P/Fe ratio, the ratio between ions changes in all parts of the plants in disfavour of N, K, and Fe, the production of dry matter is higher and the synthesis of chlorophyll is inhibited.

Third internodes or whole stems of 7-days old etiolated pea plants were extracted and the content of gibberellin-like substances and inhibitors has been determined. Extracts were found to contain four or five different gibberellin-like substances, some of which are chromatographically similar to GA₃. The content of gibberellins has been high in young internodes and decreased along with the internodes elongation. Brief red light irradiation brings about quantitative changes in gibberellin content, depending also on the length of internodes. The extracts contain acidic and neutral inhibitors which interfere with the response to GA₃. The content of the inhibitors does not seem to be affected by the ageing of internodes or by the light treatment.

The time courses of the synthesis of diamine oxidase in pea plants grown for 14 days either in the light or in the dark are similar with the highest increase in activity occurring in the cotyledons and in the shoots during the first 6 to 8 days. Plants grown in the dark showed a 2- to 3-fold higher enzyme activity than plants grown in the light. Pea diamine oxidase could bein vivo efficiently inhibited by substrate analogues 1,4-diamino-2-butanone and 1,5-diamino-3-pentanone. The first compound inhibited proportionally to its concentration the growth of etiolated pea plants, but its instability makes an unequivocal interpretation of the results difficult. On the other hand, 1,5-diamino-3-pentanone a stable and more efficient diamine oxidase inhibitor depressed the growth of pea seedlings only at concentrations as high as 5 mM and 10 mM, at which the growth of cress seedlings not containing diamine oxidase was also strongly depressed. The results obtained indicate that tryptamine oxidation catalyzed by diamine oxidase is not involved in the main metabolic pathway leading from tryptophan to indoleacetate in pea plants.

The three plant types ofAmaranthus namely,A. caudatus f.albiflorus, A. caudatus f.caudatus andA. tricolor var.tristis are qualitative short day plants with critical photoperiods 16.0, 15.5 and 15.0 h, respectively. Gibberellins A₃, A₄₊₇ and A₁₃ affect extension growth, leaf differentiation and floral induction differently. Thus, in all the three plant types ofAmaranthus, whereas, GA₃ and G₄₊₇ enhanced extension growth, GA₁₃ was completely ineffective under both, 24- and 8-h photoperiods. None of the three gibberellins could affect the leaf differentiation. In all the three plant types, flowering was promoted by GA₁₃ and not by other gibberellins tried. GA₁₃ caused promotion was manifested in two manners, firstly by lowering the critical dark period requirement in each inductive cycle, and secondly by shortening the total period taken for the initiation of inflorescence primordia under inductive photoperiods. The floral induction by gibberellins inAmaranthus is contrary to the gibberellin-anthesin concept of Chailakhyan. It is suggested that gibberellins other than GA₃ may be playing an important role in floral morphogenesis of short day plants.

Both chlorcholinchloride and ethrel are used as growth retardants in cereal cultivation. Wheat seedlings were cultivated in nutrient solutions containing 10^-3M CCC, CEPA or 5 × 10^-4M CCC and CEPA, respectively. The epidermis of full-grown primary leaves was analysed.
CCC relatively equally decreases the length of leaves and long epidermal cells, whereas CEPA mainly inhibits cell division. Leaf growth is always a little more inhibited than the number of stomata and trichomes is reduced by CCC or CEPA. This results in an increased frequency of stomata and trichomes by about 14 to 16 per cent. This means that retardants can strongly influence the length of leaves and the length or number of long epidermal cells but, due to the mechanism of programmed determination, the frequency of stomata and trichomes is kept constant within relatively narrow limits. Furthermore it can be concluded that long epidermal cells function as pace-makers in the growth of leaves of monocotyledonous plants.

Roots were excised from barley embryos cultivated in the complete liquid nutrient solution and cultivated in the same nutrient solution separately. The excised roots continued their growth but a progressive decrease in the growth rate was observed. There was a considerable short-term drop of the mitotic activity immediately after excision, which was followed by a compensatory increase and then equilibrium was reached 12 h after excision. During the next at least three days, the mitotic index of isolated barley roots varied between 5-6.5%, which is slightly lower than the mitotic index of the root meristems of isolated barley embryos under identical conditions. The mitotic cycle index of isolated barley roots and the size of the root meristem later decreased gradually.

Growth regulators, indole-3-acetic acid (IAA), gibberellic acid (GA₃), and kinetin (KIN), were used in different concentrations to stimulate the initiation and further development of the fruiting bodies of the fungusLentinus tigrinus. Vegetative mycelium of the fungus was cultivated on cellulose cylinders soaked with a synthetic nutrient solution or with a 3% malt extract. When the mycelium covered the surface of the cylinders, further cultivation was carried out in graduated concentrations of the growth regulators mentioned above. The number of developed fruiting bodies showed that the optimum IAA and GA₃ concentrations were in both media 300 p.p.m. The optimum concentration of kinetin was 400 p.p.m.
The individual growth regulators influenced characteristically also the shape of the fruiting bodies and changed in them the natural level of endogenous growth regulators. The addition of IAA into the medium raised the level of endogenous auxins in the cap. The presence of gibberellic acid and of kinetic in the medium resulted in an increase in the level of these regulators in the fruiting bodies.

Anatomical aspects were studied of starch deposition in primary explants of stem pith of marrow-stem kale. During cultivation on semisolid media containing glucose and growth substances starch is accumulated in the inner part of the explant but absent on its periphery. The starch localization pattern formed within originally quite homogeneous tissue seems to be caused both by gradients of substances absorbed from culture medium and by physiological gradients manifested in the explanted tissue. Strange enlarged grains were abundant in cells with high starch content.

Light was required for induction of nitrate reductase (NR, E.C. 1.6.6.1) in intact cotyledons of 2-day old seedlings ofLactuca sativa L. Molybdate strongly enhanced efficiency of induction. Benzyladenine (BA), gibberellin, and succinic acid-2,2-dimethylhydrazide reduced the enzyme activity. BA thrice enhanced incorporation of labelled leucine to the protein fraction. (2-chloroethyl)trimethylammonium chloride did not affect NR activity and markedly inhibited greening and protein synthesis. KNO₃ stimulated protein synthesis as well as growth of the cotyledons.

The participation of the genotype and of organ specifity effect in the quality of morphogenetic response (callogenesis, bud and root formation) of primary maize explants has been investigated. The presence of synthetic auxins - especially 2,4-D at 1 to 5 mg 1^-1 conc. - in cultivation medium was essential for both callus formation and continuous growth of tissue and suspension cultures. Anatomic structure of callus cultures is permanently heterogeneous, their growth is ensured by the action of meristems of the type found in root tips, and by repeated callogenesis from malformed roots. Adventive buds and plants could be regenerated only from cultures of embryonal origin (of one line). The presence or absence of the endosperm gene "opaque" did not influence callogenesis intensity in cultures of isolated embryos; however the morphogenetic response was clearly "line specific".

The alga occurring in rice fields grew in nitrogen-free medium and fixed Ca. 1.5 rng nitrogen per 50 ml of culture in 30 to 35 d of incubation period.

InOrobanche aegyptiaca PEES. (Orobanchaceae) the mature seed is tiny and contains a subglobose embryo which is not differentiated into radicle, hypocotyl, plumule, and cotyledons. In aseptic seed cultures on medium TB supplemented with yeast extract or coconut milk, both roots and shoot originated from the morphological radicular pole of the embryo (monopolar pattern). The bipolar mode of seedling formation, that is a shoot originating from the plumular pole and roots from the radicular pole, ensued on the basal medium THS and on TB supplemented with certain concentrations of IAA, kinetin, GA3, or strigol.

On the roots of the unchilled apple seedlings treated with morphactin many deformed adventitious shoots were formed, whereas when the roots were dipped in the mixture of morphactin and NAA more adventitious roots were produced than when only NAA was used. The growth of these lateral roots was greatly inhibited. Similar interaction of NAA with morphactin in the development of roots was obtained when the chilled seedlings were treated with these growth regulators before the buds developed. The sections of the roots from all the treatments were made and the anatomy studied.

This work is a study on the presence of free and bound (mainly proteins) amino acids at the levels of both the individual plants and the producers of a phryganic ecosystem. Therefore the amount of free and bound amino acids (both quantitatively and qualitatively) is determined during two seasons. As far as the producers (green plants) at the ecosystem level are concerned, the amount of free and bound amino acids was determined for both the above ground (stems, leaves) and the below ground (roots) parts during an annual period. On the basis of the above mentioned measurements it was found that, in a year, 17 and 4 g.m~²of bound and free amino acids are produced, respectively. A percentage of about 50% of this quantity remains in the plants, as their annual growth, and the rest returns to the soil because of the litter and root turnover. The model of their flow in the ecosystem was formed considering also data from plant physiology.

The effects of foliar application of morphactin (0, 10, 50 and 100 ppm) onPennisetum typhoides (cv. HB3) have been studied under different soil moisture conditions (0.3, 3 and 9 x 10Pa tension). Morphactin application reduced the plant height, increased the tillering and leaf number of the main shoot and adversely affected the growth characters associated with the grain production. The overall performance of plants was not improved by morphactin treatment under low moisture regime and it did not impart any efficiency of water use for grain production. Findings on the phosphorus and potassium levels of the shoot tissue suggested a possibility of its interference in the nutrient uptake process.