Previous electrophysiological and tracer kinetic studies indicated that the uptake of neutral amino acids took place by means of the proton cotransport mechanism in the leaf tissue of broad bean plants. The present investigations were designed to characterize the origin of the driving force for this process, and the proton pumping activity of leaf cells ofVicia. This activity is known to be revealed when peeled broad been leaf discs, floated on a bathing solution in the light or in darkness acidify the medium.
White light caused the strongest acidification. The presence of K⁺ and Na⁺ in the external solution increased the H⁺ secretion significantly, whereas addition of Ca⁺⁺caused only an insignificant enhancement of proton extrusion. The inhibitors of photosynthetic electron transport DCMTJ (50 μM) and nitrofen (50 μM) eliminated the light-enhanced H⁺ release indicating the dependence on photosynthesis. The involvement of a proton pump was evidenced by the effects of the uneoupler CCCP, the SH reagent HgCl₂ and the ATPase inhibitor orthovanadate. The experimental results support the conclusion that H⁺ extrusion byVicia leaf cells is an active electrogenic process requiring metabolic energy. In the light this energy requirement is suppliedvia photosynthetic electron transport.

Euphorbia pulcherrima, an ornamental plant, exhibits severe systemic viral infection. It grows vegetatively during summer and is dormant in winter. During the dormant period the buds on healthy stem cuttings remained dormant or rarely formed cyathia while the buds on virus-infected stem cuttings grew into leafy shoots and never became dormant. Quantitative estimation has revealed that breaking of bud dormancy in virus-infected stem cuttings may be regulated by markedly higher GA-like activity in them throughout the period than in their corresponding healthy stem cuttings.

This work was conducted to study the effects of fertilization with nitrogen (N_aNO₂, NH₄C1 or CO(NH_{2 2}) on NaCl salinized maize and safflower plants. Transpiration rate, stomatal frequency, dry matter and pigment contents were reduced under salinity. However under salinization-fertilization treatments, these parameters were generally raised. The carbohydrate contents exhibited variable results, in dependence on the plant type tested as well as on the treatment applied. The nitrogen contents of variously treated plants were raised except in the case of safflower plants salinized with only NaCl.

Daughter cells of the chlorococcal algaScenedesmus quadricauda incubated under photosynthesizing conditions in a phosphate-free medium accomplished one cell cycle but divided into a lower number of daughter cells compared to the control. RNA synthesis was restricted early in the cell cycle while protein synthesis was retarded as compared to the control only at the end of the cycle. The number of DNA replication rounds (and consequently the number of divisions) was reduced in proportion to the lower content of RNA per cell.
Daughter cells produced by phosphorus-starved mother cells and grown further in a phosphorus free medium performed no net RNA, DNA and protein synthesis within the period corresponding to the duration of control cell cycle an o were unable to develop. They accumulated, however, about half the amount of starch found in normally developed mother cells. In a complete medium, the phosphorus-starved daughter cells resumed macromolecular syntheses with a lag of about 5 h. Thereafter, their development and reproductive processes were comparable to those in a healthy population. A similar course of recovery was obtained with starved daughter cells exposed to light in phosphorus-free medium for the period corresponding to one cell cycle. Thanks to the large amount of starch accumulated in these cells, they were able to run through an entire cell cycle in the dark after being supplied with phosphorus. The first response to phosphorus withdrawal from the nutrient medium was the restriction of RNA synthesis. This occurred in spite of the fact that phosphorus reserves in the cell were still abundant, which suggests an intimate link between the supply of exogenous phosphorus to the cell and RNA synthesis.

The dynamics of changes in the content of four groups of phenolic substances was investigated during the growth cycle of the cell suspension culture ofNicotiana tábacum by means of fractionation. The relative contents of free phenolic acids, their esters, phenolic glycosides, and phenole acids non-extractable with methanol changed in dependence on the growth phase of the culture. A sharp increase, especially in the content of ester- and glycoside-bound phenolics and to a lesser extent also of phenolics belonging to the other two groups, occurred at the end of the lag phase. Then, after a temporary decrease at the early linear phase, the level of phenolics in the three fractions representing bound forms considerably increased again at the late linear and early stationary phases. The synthesized phenolic substances were partially released from the cells into the cultivation medium, which contained 15 to 30 % of the total content of the phenolics in the culture at different phases of the growth cycle. Likely causes of these changes are discussed.

Phenolic acids were separated into three fractions and determined by HPLC inMedicago sativa callus culture at the age of two, three and four weeks. The contents of free and especially of predominating ester-bound phenolic acids decreased with callus age to approx. 80 % while the content of phenolic acids nonextractable by methanol increased byca. 90 %. The proportion of benzoic acid derivatives rose from 15 to 21 % within four weeks. The determined difference in the contents of phenolic acids in the upper and lower parts of callus diminished with age. The content of bound forms was higher in the lower part regardless of the callus age. The content of free acids in two weeks old callus was half as high as in the upper part.

UsingNicotiana tabacum L. plantlets cultivatedin vitro as a model system it was proved that osmotic adjustment may be caused by a decrease in water potential of substrate as well as by a decrease in air humidity.

Plant growth and seed yield of mung bean were studied in sand culture at different levels of NaCl [0, 50, 100, 150, 200, 250 mM] in the root medium. Results showed that both dry matter yield and seed yield of plants grown for 14 weeks at 50 mM NaCl and 100 mM NaCl were around 60 % and 25 %, respectively of those for plants grown in control solution. Higher concentrations caused wilting and necrosis of leaves. Very effective exclusion of Na and Cl from salt grown mung bean seed was observed with concommitant high accumulation of Na and Cl in the stem. It is speculated that mung bean plant stem may act as a 'sink' for NaCl during the reproductive stage of the plant growth cycle.

In 42-chromosome - triticales, chromosome pairing was extremely erratic with very low frequency (60-63 %) of regular bivalents per pollen mother cell. The frequency of univalents was very low or nil in the wheat and rye parents.

The absorptivity of the leaves at all the wavelengths decreased whereas the reflectivity and transmissivity increased when an alpine perennial herb, Selinum vaginatum was grown at lower (550 m) elevation. The lower elevation climate modified leaves to absorb comparatively less near-infrared radiation as compared to that under natural habitat. The lower altitude habitat had a positive effect on infinite reflectance and a negative effect on absorption and scattering coefficients of the leaves. Based on the scattering and absorption coefficients for upper and lower leaf surfaces, the 'sieve' and 'detour' effect factors were estimated. These factors indicate that while 'sieve-effect' increases the 'detour-effect' decreases when this plant is grown at lower elevation. This explains lower light absorption (PAR) in this plant when grown at lower elevation. For survival under the habitat with high thermal load the leaves of this alpine herb could maintain lower temperature by way of reduced absorption in near-infrared radiation region which probably is accomplished by lower water contents and thickness of leaves at lower elevation.

The cotyledons of yellow lupin seeds contain 15.4 mg of the albumins, water soluble proteins, per 100 mg of dry matter. These proteins were resolved by SDS gel electrophoresis into 13 polypeptides with relative molecular mass, Mr, between 16 000 and 84 000. Isoelectrofocusing analyses of the albumins showed that they were composed of six components with isoelectric points between 4.1 and 5.5. These results have indicated that the albumins are acid proteins and exhibited molecular and charge heterogeneity.

The glycollate metabolism of wheat (Triticum vulgare Vill. cv. Sonalika) and rice (Oryza sativa L. ev. Jaya) leaves was studied during senescence by estimating the endogenous levels of glycollate and hydrogen peroxide (H₂O₂) and the activities of glycollate oxidase and catalase. In comparison with light incubation the incubation of excised leaves in the dark caused a decline in the glycollate content and in the activities of glycollate oxidase and catalase, and an increase in the H₂O₂ content, more marked in the leaves of rice than in the leaves of wheat. Glycollate oxidase activity gradually decreased with incubation time, and glycollate metabolism decreased during senescence. The glycollate oxidase in particular and glycollate metabolism of rice were more sensitive to incubation time than those of wheat. Kinetin increased the glycollate oxidase activity and glycollate metabolism during senescence, while ethrel (2-chloroethylpho-sphonic acid) and ABA (abscisic acid) reduced these activities in both plant species.

Wolffia arrhiza (L.) Wimm. was grown axenically in the chemostat under white luminescent light (photon fluence rate 23 ujnol m^-2 s^-1) and phosphate or magnesium limitation (0.075 and 0.01 jxmol 1^-1, respectively). Aliquots (1 g fresh mass) were taken from the continuous cultures and were irradiated for 1 h with either white light (control) or monochromatic blue (453 nm) or red (654 nm) light. The amount of [5^-3H]-uridine incorporated into cytosolic and chloroplastic rRNAs during these exposures was estimated and following results were obtained: In phosphate limited plants rod light considerably reduced and blue light slightly increased label incorporation as compared with the control. Moreover, in red light, chloroplast incorporation is relatively more slowed down than that in the cytosolic compartment (34 % as compared to 59 % of the control). In blue light the enhancement is approximately equal in both compartments. In magnesium limited plants incorporation under both blue and red light is moderately slower as compared with the control. In both cases also the retardation is slightly greater in the chloroplast than in the cytoplasm. The results suggest that rRNA metabolism is controlled by light quality as well as by mineral nutrition.

Ten centimeter long stem cuttings of sweet potato (Ipomoea batatas L. cv. Georgia Jet) with intact apex and leaves were cultured in distilled water as well as in varying concentrations of abscisic acid (ABA) in open top chambers at 364, 438 and 666 cm³ m{-3}CO₂. Low concentration of ABA promoted rooting and elongation of roots at 364 cm₃ m{-3} CO₂ while rooting was suppressed at enriched levels of CO₂. However, biomass production in shoots and roots was higher in 666 than in 364 cm³ m^-3 CO₂.

A reduction in abscisic acid (ABA) content was not a pre-requisite for the breaking of dormancy of vegetative lateral buds of both field-grown trees and shoots of willow (Salix viminalis L.) maintained in controlled conditions. Similar variations in bud ABA levels were observed whether the shoots were stored in a warm (22 ± 1 °C) or cold (6 ± 0.5 °C) environment. Following transfer to a growth room the ABA content of chilled buds declined more rapidly than did that of non-chilled buds.

In the roots of 4-day-old pea plants germinated in unsterile soil from Rhizobium-inoculated seeds, a higher level of native IAA was determined than in roots of pea plants germinated in sterile soil from superficially sterilized seeds. The IAA level in plants grown from inoculated seeds increased markedly up to the age of 6 days of the plant, while in plants growing under sterile conditions it did not significantly change during the same period. Between the 6th and 10th days of the age of the plant, a decline in the IAA level was observed in roots of plante growing from inoculated seeds. It was not until after 10 days of age of the plant that the level of IAA in nodulated roots again increased.

The structure of the cells was studied in two strains of grapevine calli (Vitis riparia ×V. labrusca). These callus cultures contained only highly vacuolised cells. The pattern of division in these slightly cytosolic cells was described. In both callus strains caryological instability has been found.

Seasonal changes in leaf water potential (Φ) and leaf conductance (g₁) were determined in almond trees under different irrigation regimes. The development of water stress in the rainfed treatment induced a specific seasonal dynamics of Φ values and an important reduction in g₁ values. A decrease in g₁ values occurred independently of the irrigation treatment through the growing season. No statistically significant differences were obtained in g₁ values within the drip irrigated treatments.

Daughter cells of the chlorococcal algaScenedesmus quadricauda were incubated under photosynthesizing conditions in a sulphur-free medium. The course of the cell cycle under these conditions was changed in daughter cells which differed in their stage of development. In absence of sulphur, advanced daughter cells with two nuclei and 2 or 4 genomes passed a cycle identical with that of control in sulphur containing medium. Each cell yielded eight binuclear daughter cells. With less advanced daughter cells (one nucleus and 1 or 2 genomes) restriction of RNA synthesis occurred near to the end of the cell cycle and protein synthesis ceased two hours later (practically at the time of the protoplast fission). The last round of DNA replication found in the control culture was not initiated in sulphur-starved culture and uninuclear daughter cells with one genome were released.
If the daughter cells coming from the starved populations were kept further in the sulphur-free medium, macromolecular syntheses were dramatically restricted. Only photosynthesis continued to produce starch at a similar rate as in normally grown cells. Thus, a very large amount of starch accumulated. Supported by these reserves, starved cells refed with sulphur passed an entire cell cycle in the dark and divided into eight daughter cells. In sulphur-supplied cells, both in the dark and in light, RNA, protein and DNA synthesis started without any delay in a similar way as in the control culture. Competition for sulphur reserves occurred between the growth and division processes; the former were preferred in the light and the latter in the dark.