The results of experiments conducted with autumn rye and summer wheat on sandy loam soil at the Institute for Cereal Production of the Martin-Luther University, Halle-Wittenberg (G.D.R.) have revealed that an increase in soil moisture improved the plant water balance, width of stomata, shoot growth, tiller density, leaf area and growth rate. Net assimilation rate, however, decreased with the increase in soil moisture above 50 per cent water holding capacity. Increased soil moisture improved contents of nitrogen, potassium and phosphorus only during early stages of growth, but their uptake was not reduoed at maturity. Air conditioning irrigation proved superior in respect to all above mentioned characteristics, except the uptake of potassium, which decreased with air conditioning irrigation at higher soil moisture relations.

Abscisic acid (ABA) had no significant immediate effect on the activities of Photosystems PS 1 (DPIP/Ascorbate → MV) and PS 2 (H2O → K3[Fe(CN)6]), when added during the activity measurements in a final concentration of 10¯4 M to both freshly prepared chloroplasts from primary leaves ofPhaseolus vulgaris L. and chloroplast preparations preincubated with ABA for 22 h. This incubation also did not induce any significant post-effect on PS activities.

Long-term callus cultures of two barley cultivars have been investigated at the cellular level. One slowly growing, root forming callus of the barley cv. Bulgarische Nackte consists of cells the majority of which contain the diploid chromosome number. Contrarily, a fast growing callus of the cv. Elgina having no regeneration potency at all, is highly polyploid and includes more than two thirds of aneuploid cells. Tn this callus strain, a great number of multinucleate cells has been found. Some problems are discussed with respect to the relationships between growth rate, karyological stability and regeneration capacity in long-term callus cultures of cereals.

Response of epidermal diffusive conductance to simultaneous changes in leaf water potential and photon flux density was studied in primary bean leaves. Values of epidermal conductance corresponding to every photon flux density decreased with decreasing leaf water potential below - 6.9 x 10⁵Pa; slight deorease was followed by a rapid one at water potential ranging from - 8.0 to -10.5 x 10⁵ Pa. In the leaves with water potential lower than -10.5 x 10⁵ Pa neither the saturated photon flux density (1200 [xeinstein m^-2s^-1) induced photoactive stomatal opening.
Negative influence of one factor could be partially compensated by positive influence of the other. These results were in good agreement with the considered mechanism of action of leaf water potential and photon flux density on epidermal conductance.

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.

Gibberellic acid GA₃ (50 ppm) decreases the photosynthetic rate and increases respiration rate of rye leaves (Secale cereale L., cv. Dankowskie Zlote). The effect of GA₃ on transpiration rate is not distinctly marked.

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.

Genotypes on the Belgian national list as well as about 120 genotypes of winter wheat from the world collection were examined for the relationships of their stomatal frequencies in the flag leaf with yield, yield components and other morphological characters. Stomata were in rows, with a higher density in adaxial leaf surface. Cultivars differed significantly in both stomatal density and number of rows of stomata per unit of leaf width. Yield and morphological characters in general showed no significant correlation with stomatal frequencies. Densities in all series examined ranged from 46 to 78 stomata per mm² in the adaxial leaf epidermis and from 32 to 93 in the abaxial one.

Nitrate reductase (NR) induction is enhanced by exogenously supplied sucrose in excised pea roots exposed to both exogenous nitrate and exogenous nitrite. NR synthesis is preferentially supported by sugars transported to the cells at the moment, however NR induction can take place for some time without exogenous sugar influx if roots are saturated with sugars during precultivation. Steady high NR levels are dependent on steady sugar and nitrate influxes. NR induction is low in roots precultivated for 20 h without sucrose although sugar content is still high in them. This suggests that compartmentation of sugars in the cells is of major importance during NR induction. Total nitrate content in roots exposed to nitrate is not influenced by sucrose supplied together with nitrate. Some nitrite is oxidized to nitrate in roots exposed to exogenous nitrite ; we assume that this nitrate is responsible for NR induction. Our results indicate that sugars, besides many indirect effects on NR induction, may also directly influence NR synthesis either as coinducers or as derepressors of NR synthesis. Our results further show that NR is not a product-inducible enzyme.

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.

The growth of root, hypocotyl and cotyledons was measured in apple seedlings cultured for nine days from embryos isolated from seeds after various periods of after-ripening. Greening of the cotyledons was taken into account and the chlorophyll content determined as well.
Embryonal dormancy results in anomalies already appearing in the early stage of development. They are manifested by differentiated greening and uneven growth of cotyledons, as well as by hypotrophy of root or hypocotyl. The frequency of those anomalies in the population decreases during the removal of dormancy, and therefore it may be accepted as the criterion of its depth.

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.

Irradiation with X-rays and gamma rays reduced the speed of germination of seeds of jute cultivars,viz., JRO 632, JRO 620, Sudan Green ofCorchorus olitorius and JRC 212, Fanduk, D 154 ofC. capsularis. Though the first phase of germination(i.e. seed variability) remained apparently unaffected, the second phase (i.e. the sprouting ability) and the third phase(i.e. the attainment of autotrophic status) were found to be the best indicators of radiation injury and provided dependable data for the assessment of radiosensitivity.
The jute cultivars have not shown accountable intervarietal differences in radiosensitivity in respect of LD 50 and LD 100 for the second and the third phases of germination.

Excised tomato cotyledonswere subjected to mannitol induced water stress solutions for three days. Extracts of proteins and the enzyme peroxidase were made and separated with polyacrylamide gel electrophoresis. The water stress injury caused increases in bigger protein molecules but decreases in smaller protein molecules. The small fastest moving peroxidase isozyme was almost completely eliminated. Applications of growth regulators to the stress solutions indicated that the protein and peroxidase changes could be explained on the basis of reduction in endogenous cytokinin activities by the water stress.

Carbohydrate requirement for the growth of the cells and accumulation of polyphenols in culturedCassia fistula L. andDatura metel L. tissues were examined. Superiority of suerose over other carbohydrates was observed both for the growth of the cells and for the maximum production of phenolic compounds; and its availability was found to be a limiting factor for the synthesis of phenolic compounds.
Progressive changes in the pattern of peroxidase and phenylalanine ammonia-lyase (PAL) activities were followed and the relationship between the development of the enzyme activities and synthesis of polyphenols was further examined. The significance of peroxidase and PAL in the regulation of phenolic production is discussed in the light of recent findings.

The elongation of primary roots of pedunculated oak (Quercus robur L.), which is associated with nutation oscillations, was registered by a time lapse cinematography. The following characteristics were expressed graphically: relative growth rate [mm h-¹], frequency [rev. h-¹] and amplitudes [mm] of nutation oscillations, their direction and location of nutation curvatures. The growth-oscillation mechanism is interpreted as a part of the geocontrol system of the root and was evaluated on the basis of its physiological efficiency. Comparison of nutation periods showed that the control system of pedunculated oak is three times more and two times less efficient than that of pea and maize, respectively. Comparison of the oscillation amplitudes of growing roots gives similar results.

The analysis of growth and movements of seedling organs of kidney bean (Phaseolus vulgaris L.) provides a pattern of periodic phases of activity and relaxation. The existence of a central organ which would control the phase relationships, is not anticipated in the integrity of the plant. The cyclic activity of individual organs shows itself by growth associated with oscillation movements. One and the same organ may simultaneously accomplish oscillatory movements with a diurnal and ultradiurnal frequency. These rhythms originate during the organ development; the first pair of kidney bean leaves at first executes oscillation movements with a diurnal frequency and only after it is fully developed it exhibits a diurnal cycle with the photophil phase upwards and the scotophil downwards, the oscillations with an ultradiurnal oycle being maintained. The movements of the two leaves are synchronous, but there occur short sections with a desynchronous cycle. Simultaneously with these oscillations, in which the leaf petiole takes part, the adult leaf performs oscillatory movements perpendicular to the longitudinal leaf axis, the so-called side swings, controlled by periodical changes of the joint attaching the leaf blade. Their frequency is practically identical with that of the ultradiurnal cycle. Thus the periodic growth activity of the kidney bean results in growth oscillations passing in the diurnal cycle with a frequency of 0.043 rev.h^-1, their ascending and descending phases consisting of periodical ultradiurnal oscillations in cycles of 0.73-0.59 rev.h^-1. The epicotyl growth shows a similar pattern: into the basic diurnal nutation cycle with a frequency of 0.042 rev.h^-1 ultradiurnal oscillation cycles are incorporated having a similar frequency to that revealed in leaves (0.69-0.64 rev.h^-1). The diurnal oscillatory cycles belong to a system established on the basis of periodicity of day and night and other geophysical cycles. The ultradiurnal rhythmic oscillations are presumed to be an expression of the geocontrol system of root and shoot growth direction and orientation of the organ in space. The shape of their trajectories in bean leaves is contradictory to this; they are not spatial helices, as the kybernetic model would presuppose, but have a vertical, upwards and downwards course in one plane. Since these oscillatory movements with an ultradiurnal cycle cease after petiole excision from the stem and after shoot apex amputation, one may presume that they are coupled with the low-frequency oscillatory system of the epicotyl.

Effect of water stress at -1, -3, and -5xl0⁵Pa osmotic potential on some properties of acid phosphatase has been studied in two wheat cultivars. Acid phosphatase from S-308 cultivar, which is less drought resistant than C-306, was less susceptible under varying conditions of pH and temperature treatments.

The growth of callus tissue cultures and the infectivity of twenty fiveSolanum laciniatum Ait. plants and of sixteenNicotiana tabacum L. cv. Samsun plants were investigated. The plants were obtained from callus tissue cultures derived from stem pieces of the respective plants infected with a mycoplasma-like organism (MLO) evoking potato witches' broom. The tissues were cultivated on synthetic nutrient medium with kinetin and IAA. Allde novo obtainedS. laciniatum plants were healthy. On the contrary twelve of the sixteen reconstituted tobacco plants showed MLO presence.
Summarizing these and previous results, the authors suppose that the most important factor influencing MLO persistence in callus tissues cultivated on the applied nutrient medium may be the callus growth rate and the organogenesis set. Both these conditions are determined by the metabolism of the investigated plant species.

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.

Application of hydroxyurea to intact seeds ofAgrostemma githago as well asVaccaria pyramidata causes a strong inhibition of radicular³H-thymidine incorporation into DNA, but germination rate is only insignificantly reduced. The seedling development, however, is strongly affected. Consequently, DNA synthesis is not a prerequisite for the radicle protrusion.

A study was made on the mitotic cycle times in meristematic cells of Vicia faba root tips and on the relationship between their duration and the position of a certain cell in the column of proliferating cells. For the demonstration of the sequence and duration of mitotic oycles a single-column model was used. The results of experiments show that the great variability in the duration of mitotic cycles (from 12 to l20 h)is the result of a different program of the apical meristem cells. The long duration of the cycle of initials corresponds to the sum of cycle times of their descendants.

Various herbicides are applied on seventeen-day-old cucumber seedlings growing in a nutrient solution.
After 1 and 3 days, acid and alkaline pyrophosphatase activities are measured in the leaves and the roots of seedlings treated with lethale dosis of atrazine, chlortoluron, ioxynil, MCPA, dicamba, alachlor. The same enzymes are determined after 5 h in seedlings on which previously paraquat and DNOC were pulverised. In the leaves, acid pyrophosphatase activity is stimulated by almost all the herbicides, especially by ioxynil, paraquat and DNOC while alkaline pyrophosphatase remains similar to the controls. The alkaline and acid pyrophosphatase activity in the roots is either unchanged or stimulated or inhibited without any correlation with the various modes of action of the herbicides.