The capacity of pollen tubes to utilize exogenous uridine during 8 h of cultivation in shaken suspension in a sugar-mineral medium was examined by continuous and pulse labelling with³H-uridine. The increase of uptake with increasing concentration of the nucleoside indicated a saturable transport system with an approximate K_m of 9.4 × 10^-6 M and 12.5 × 10^-6M as determined in 1-h and 6-h cultures, respectively. Maximal uptake took place at the beginning of germination reaching a rate of about 2 nmol h^-1 per 1 mg of dry pollen at 0.1 mM external uridine. The uptake activity decreased with the time of pollen tube growth to less than one third during the 8-h cultivation period. Moreover, the level of radioactivity taken up initially decreased later on during continuous cultivation in the presence of³H-uridine. The uptake took place against a concentration difference and the onset and rate of uridine release depended on its exogenous concentration.
The activity of the nucleoside incorporation into RNA increased during the first 4 h of cultivation, decreasing later on. The proportion of RNA radioactivity in continuously labelled pollen tubes grew steadily during 6 h and reached 2.5% with respect to soluble pool at 0.4 μM uridine. The time course of RNA labelling was independent of uridine concentration within the range of 0.4 μM to 40 μM but this concentration rise resulted in an about fiftyfold increase of the total amount of external uridine incorporated.

InAnacystis nidulans uptake and efflux kinetics of fluoresceine were studied. It could be concluded that the distribution of fluoresceine depends on the pH_c of the cells. The comparison of different fluoresceine accumulation levels and flux equilibria allows conclusions regarding changes of the pH_c.

Chlorosis induced with a supraoptimum dose of phosphorus in nutrient solution (69 mg P l^-1) was reverted by spraying of leaves of chlorotio maize plants (Zea mays L.) with FeEDTA. Biomass formation, chlorophyll and iron content were decreased in the above-ground parts of plants grown under chlorosis-inducing conditions. Spraying always decreased content of inorganic phosphorus (P_i/Fe ratio was significantly changed), increased chlorophyll content in old plants and stimulated dry mass formation at supraoptimum phosphorus doses. FeEDTA application improved phosphate utilization (portion of phosphate in organic bonds was increased). This may be the basis of chlorosis-reverting effect of FeEDTA.

The results of different photoperiodic treatments preventing flowering and representing the control vegetative treatments in the studies of floral induction and differentiation were studied inChenopodium rubrum seedlings. A fully vegetative growth pattern of the meristem was maintained only in continuous light or after a photoperiodic treatment which consisted in a 15 min light break of the 8 h dark periods which themselves are a threshold for flowering inChenopodium. Light breaks applied to 10 h and longer dark periods did not prevent the changes resembling the early events of transition to flowering. Disappearance of zonal pattern, stimulation of apical growth, precocious initiation of leaf primordia and weakening of apical dominance have been observed. Flower formation did not follow.

The rooting response to exogenous auxin of cuttings in a juvenile phase of growth from plants ofCastanea sativa Mill. was determined and simultaneously the rooting potential of the water extracts was evaluated in presence of IAA by a bean rooting test. The level of the extractable rooting promoters was high in the cuttings which exhibited the highest percentage of rooting. An inhibition of the effect of IAA on rooting was detected in the cuttings which showed the lowest rooting response, the histogram differing not much from that of the adult plant. The results indicate that in chestnut the juvenile condition, easy rooting, is associated with high levels of endogenous rooting promoters.

Nitrate depletion from the media by intact corn seedlings grown under solution culture was measured over a period of time. Two methods were assessed to differentiate corn genotypes for nitrate uptake ability: (1) Nitrate uptake per day per plant basis. (2) Nitrate uptake per day per gram root dry matter basis. The former method was found to be superior as it gave significant and positive correlations with dry matter, nitrate, and reduced nitrogen accumulation in stem, leaf and roots. Nitrate uptake was found to vary with plant age. Root mass and efficiency of roots appear to contribute to the total nitrate uptake ability of the genotype. Corn genotypes studied exhibited marked differences in nitrate uptake ability.

To induce mutation in tomatillo (Physalis ixocarpa Brot.) commonly grown for its fruit value, seeds were treated with three alkylating agents (dimethyl sulphate, diethyl sulphate and methyl ethane sulphonate) and gamma rays. Seven viable and five chlorophyll mutant types were screened both from M₁ and M₂ generations. The isolated mutant lines are described and evaluated with reference to their beneficial value.

Using polyacryl amide gel electrophoresis isoenzyme patterns were studied of α- and β-glucosidase, α- and β-galactosidase, α-fucosidase, β-glucosaminidase, β-glucuronidase, α-man-nosidase and β-xylosidase in whole root tips, in particular growth zones and in the cortex and central cylinder of broad bean and maize. Though considerable differences even in number and position of isoenzymes were found in particular cases in both objects, no general conclusion could be reached. The mentioned differences are not obligatory and have been observed both between zones of division and elongation and between zones of elongation and maturation. This fact is hard to understand on the basis of proteosynthetic processes involved in proliferative and postproliferative cell growth.

Using differential staining of cell walls the anatomy of microsporogenesis was investigated on cross-sections of anthers of fertile plants of the sweet pepperCapsicum annuum L. cv. Severka, as well as of its sterile analogues. The lignin-like staining as observed in the microsporocyte primary walls of fertile plants disappears with their getting independent in the course of meiosis. On the contrary, in sterile plants the stain increases in intensity, the thick-walled microsporocytes usually form a continuous block up to the period of tetradogenesis, and so far as microspores originate, they are not dissociated outwards. Moreover, in sterile anthers the external tapetum is usually not differentiated.

Fertilizer induced improvement of growth and yield of wheat (Triticum aestivum L. cv. Kalyan Sona), under salinity stress, was associated with an increase in the concentrations of nitrogen, phosphorus and potassium and a decrease in the level of chloride in the tissue. The concentration of chloride in grains was also reduced under high fertility as compared to low fertility condition. Results reveal that under both normal and saline conditions, nutritional improvement leads to higher chlorophyll concentration and increased efficiency of enzymes like nitrate reductase, ATPase, alkaline pyrophosphatase and amylase in the leaves. This imparts importance to fertilizer application under saline conditions.

Barium chloride at 0.1 mM concentration inhibited elongation of mungbean (Phaseolus aureus) roots more strongly than elongation of hypocotyls. Root growth was completely inhibited at 80 mM and there was no germination at 100 mM. Respiration rates which were directly proportional to seedling vigour declined at varying degrees at the growth-inhibitory concentrations of BaCl₂. Barium retarded senescence in isolated leaf discs ofCephalandra indica by maintaining the chlorophyll level in darkness. The carotenes were similarly protected from degradation by Ba in darkness whereas xanthophylls were retained both in darkness and light. Ba also protected anthocyanin pigments in the staminode discs ofCanna indica flowers and reduced to a variable extent the leakage of betacyanin pigment fromBeta vulgaris root discs caused by various membrane active chemicals. Applied either alone or in combination with IAA, Ba inhibited cell enlargement in wheat (Triticum aestivum) coleoptile sections. Barium-induced inhibition of lettuce (Lactuca sativa) hypocotyl elongation was largely overcome by GA₃.

The effect of high concentrations of the simplest polyphenols on extension growth of maize (Zea mays L.) shoot ooleoptile segments, lettuce (Lactuca sativa L.) roots, and on radish (Raphanus sativus L.) seed germination, was studied. Quinone formation in the process of plant incubation in polyphenol solutions was proved. The data obtained are presumably explained by the important part that is played by the quinoid products of phenol oxidation in the ability ofo- andp-biatomic phenols to inhibit growth.

Chlorflurenol (morphactin) EMD 7301 W (60, 120 and 240 mg I^-1) when applied at five to seven leaf and 10-12 leaf stage induced hermaphrodite flowers in the inflorescences ofRicinus communis. The hermaphrodite flowers were mostly apical in position unlike the apical female flower in the control. With an increase in the time gap between sowing and emergence of the inflorescence there was a reduction of the female structures in the hermaphrodite flowers. The last formed inflorescences had an apical male flower in place of a female. The largest number of inflorescences with an apical male or hermaphrodite flower were produced with 60 mg 1^-1 applied at five to seven leaf stage. The hermaphrodite flowers failed to set fruits.

Preparations of total DNA isolated from algal cells ofChlamydomonas geitleri were characterized by routine methods (UV-spectra, thermal denaturation, sedimentation analysis, centrifugation in CsCl density gradients). In this way, the fundamental physicochemical characteristics, undetermined for this alga up to now, have been attained.
The comparison of the characteristics of the preparations of DNA showed that during isolation it was more convenient to prefer procedures that use the lysis of cells. A mechanical disintegration may sometimes lead to the degradation of the macromolecules of DNA.
The ascertained characteristics of DNA in the alga under study are compared here with the corresponding values of DNA known for the most widely studied volvocal algaChlamydomonas reinhardii as well as for other species of green algae. The greatest difference between the two species comparcd was in the contents of bases G + C. The determined values inChlamydomonas geitleri from 43.4 to 45.4 mol.% are much lower than the values known inChlamydomonas reinhardii (about 65.5 mol.%) or those published for some volvocal algae (60 to 68 mol.%).

The adaptation of Marmur's method, suitable for DNA isolation from plant cell culture, is described.

The effect of nystatin on the fresh-water algaHydrodictyon reticulatum was studied by estimating the electrical resistance of both the membranes and the intracellular fluid. The outflow of potassium ions into the external medium, occurring after addition of nystatin, was determined by flame photometry.
Values of ohmic resistance of membranes treated with nystatin ranged from 0.33 to 1.51 kΩcm², the control values being 8.03-16.73 kΩcm². Values of the resistance of intracellular fluid in nystatin-treated cells lay in the range of 3.21-7.13 kΩcm, those of control cells being 1.10 to 1.91 kΩcm.
The concentration of potassium ions in the external medium increased from 1.35 mM to 4.3 mM after addition of nystatin.