During the germination, wheat and sorghum plants tolerated salinity up to 10 mM NaCl. Seedling growth and dry matter production remained more or less unchanged up to 10 mM NaCl in case of wheat and up to 5 mM NaCl in case of sorghum. The water content of test plant species exhibited nearly constant values irrespective of the salinity level applied. The proline and carbohydrate content increased with elevating NaCl, while free amino acids content decreased. Irrigating of seedlings with tryptophan had non significant effect at all salinity levels used.

Possibilities of adventitious buds induction on the cotyledons obtained from sterile seedlings ofAbies concolor xAbies grandis hybrid were investigated. The following variables influencing bud induction and their further development were studied: the effect of expiant age, the effect of different growth regulators and their concentrations and duration of their application. The most suitable expiants proved to be the cotyledons of 7 d old seedlings. The most efficient cytokinin was benzylaminopurine (S mg l^-1) in combination with napthaleneacetic acid (0.01 mg l^-1). The most optimal duration of treatment was 17 to 21 d culture of explants on induction medium. Shoot growth was achieved on basal medium to which 14 mg 1^-1 spermidine was added.

Changes in the phenylalanine ammonia-lyase (PAL) activity, accumulation of phenolic acids and ionically-bound peroxidase activity in thein vitro selected embryogenic and nonembryogenicMedicago sativa callus cultures resistant to the filtrate ofFusarium spp. were found. The PAL activity in bothin vitro selected cultures during a 4-week cultivation on a medium with phytotoxins was higher than in the control calli grown on a medium without toxin. The filtrate fromFusarium spp. evoked an increase in the contents of all determined phenolic acids in the selected calli. They occurred predominantly bound as esters. The most pronounced portions in the elevated acids level were of ester-bound p-hydroxybenzoic, vanillic, p-coumaric and ferulic acids. The ionic cell wall-bound peroxidase activity in both selected calli cultivated on a medium with a filtrate was twice as high as the activity determined in the control cultures. The activity of soluble peroxidase was not influenced by challenge with a filtrate. No significant differences were found between thein vitro selected embryogenic and nonembryogenic alfalfa callus cultures in the response to the phytotoxic filtrate.

One-month-old plants of two chickpea (Cicer arietinum L.) cultivars were exposed to salinity of 4 and 8 dS m ^-1 in pots in a greenhouse. The cultivar BG 312 performed better than Pusa 209 in terms of visible injury and dry mass accumulation. Tissue water content of the various plant organs was affected differently by salinity. Expression of Na⁺ and Cl ^- concentrations on a dry mass basis indicated retention of Na⁺ and Cl ^- by roots, thereby keeping the leaves free of ion accumulation, but their expression on a tissue water basis did not indicate Cl ^- retention and showed less Na ^- exclusion. Changes in the apparent exclusion mechanisms resulted from a higher water content in the roots than in the shoots. On a dry mass basis, roots appeared to retain K⁺, but on a tissue water basis stems appeared to act as a reservoir of K⁺; leaves and nodules received K⁺ preferentially. The exclusion mechanisms and their efficiency differ with cultivar and salinity. The expression of ion concentrations on a tissue water basis appears to be more useful then on a dry mass basis in studies of salinity tolerance.

The stomatal density on abaxial epidermis of the second wheat(Triticum aestivum L.) leaf increased step by step from the leaf base to its tip. On adaxial epidermis, this increasing tendency was generally maintained, but close to both the base and the apex two maxima were determined. In the direction perpendicular to leaf length, maximum stomatal density was close to the edges, and minimum one was in the central part of the leaf blade.

The effect of NaCl at sublethal concentration was observed on germinating seeds of salt-sensitive and -resistant rice cultivars with respect to the level of proline regulatory enzymes and the growth of seedlings on different days of early germination period. The two enzymes of proline biosynthesis and catabolism, Δ-pyrroline-5-carboxylate reductase and L-proline dehydrogenase, were taken into consideration to observe the effects of 100 mM NaCl on their activities in both rice cultivars. The activity of Δ-pyrroline-5-carboxylate reductase in salt-resistant cultivar was increased twice after 5 d in 100 mM NaCl. Simultaneously, the activity of L-proline dehydrogenase was decreased significantly. High activities of Δ-pyrroline-5-carboxylate reductase may be regarded as a biological marker for screening the sensitive and resistant cultivars of rice seed under NaCl-salinity.

A comparative study of the isoenzyme patterns of esterase and peroxidase and overall peroxidase activity in stamens of male-sterile (MS) lines of Pearson ms-35 and P ms-35aa and of the respective male-fertile (MF) tomato plants have been conducted. The study has been made at two stages of stamens development - tetrad and pollen. Higher activities of the esterase isoenzymes in the MF stamens than that of MS in both ontogeny stages have been found. The slow moving esterase isoenzymes both of the MF and the MS stamens are the major isoenzymes in the early stage and are connected with tapetum development while the fast moving esterase isoenzymes are connected with pollen formation in the later ontogeny stage. Overall peroxidase levels in the MS stamens were higher than those of MF. The peroxidase patterns of the MS lines are also characterized by the greater number of isoenzymes and also the presence of specific isoenzymes, the contrast between the MF and the MS stamens being more strongly expressed at the later stage of development. A strong similitude between esterase and peroxidase patterns behaviour in both MS lines has been found.

Chenopodium rubrum L. ecotype 184 is a qualitative short-day plant with critical length of the night of eight hours that must be exceeded in order to flower: Five days after sowing, the plants were exposed to a various number of inductive cycles (14/10 h of däy/night cycle) to test the optimal photoperiodic conditions for flowering. In our experimental conditions the plants flowered with high percentage after more than four received inductive cycles, but there was no flowering below that. The plants grown on the herbicide Norflurazon (photobleached plants) showed different photoperiodic characteristics. There was negligible flowering of photobleached plants in the same experimental conditions as for the green ones.

Fruit setting and development in a monoecious cucurbit,Momordica charantia L. could be regulated by the external application of gibberellin (GA₃) and ethrel. Both GA₃ and ethrel in lower concentrations promoted female flower production as well as fruit setting and development. Both growth regulators improved the quality of theMomordica fruit by increasing length, breath and biomass of the fruits as well as by increasing the content of total sugar of the fruit.

A screening of leaves of 25 taxa of angiosperms was made for their volatile toxicity against damping-off fungi. The volatile substances fromHyptis suaveolens andOcimum canum were toxic againstPythium aphanidermatum, P. debaryanum andRhizoctonia solani. The fungitoxicity of the leaves persisted for 15 d of storage. The volatile substances from the leaves ofO. canum were thermostable, while those fromH. suaveolens were thermolabile. The essential oils exhibited strong potency against the pathogens tested, non-phytotoxic nature to the host plants and superiority over commonly used synthetic fungicidesAgrosan G.N. andCaptan. The findings indicate the possibility to use these essential oils as potential natural fungicides in management of damping-off pathogens.

Two types of esterases, nonspecific esterase and cholin esterase have been distinguished in germinating pollen grains and in pollen tubes ofVicia faba using cytochemical methods. The localization of each of them was different. In the hydrated non-germinating pollen grain the nonspecific esterase was present in the cytoplasm and in the intine. The cholinesterase was localized mainly in the sexine and on the outside of the plasma membrane. A particularly large agglomeration of this enzyme was found in the aperture. During germination both types of extracellular esterases were released into the medium. In the pollen tube the activity of the enzymes studied was connected with the wall of its tip. The localization of both types of esterases in the germinating pollen grain and the growing tube were independent of actinomycin D. Cycloheximid prevented the cholinesterase localization at the pollen tube tip.

Microtubule-like structures were observed in mesophyll cell chloroplasts during the ontogeny of the second leaf of wheat cultured in full nutrient solution as well as under nitrogen deficiency.

The effect of CdCl₂ in a concentration range 0.01-10.0 g m^-3 on the growth ofChlorella vulgaris under synchronous cultivation conditions was determined. The general biological activity, the growth multiplication factor, the cell size and shape and intracellular arrangement showed disturbances of synchronization that depended on Cd²⁺ concentration. The highest inhibition of all mentioned parameters was observed when Cd²⁺ was administered after the second hour of synchronous cultivation, whereas the administration after 6 or 8 h did not induce any significant effect.

Effects of iso-osmotic levels of salts (NaCl, CaCl₂, Na₂SO₄) and PEG-6000 on the activity of hydrolytic and nitrogen assimilatory enzymes in pea embryo axis and coty ledon were studied. The activity of nitrate reductase and nitrite reductase in embryo axis and cotyledon and the activity of protease and α-amylase in cotyledon decreased with decreasing medium osmotic potential as compared to control at all the stages of seedling growth. The activity of protease and amylase increases with increasing levels of stress in embryo axis. Sodium chloride induced, stress had more deleterious effects on the activity of nitrate reductase, nitrite reductase and αamylase followed by other salts and PEG-6000. On the other hand, CaCl₂ induced salt stress was more depressive for protease activity. The maximum increase in the activity of protease and amylase was observed in embryo axis at higher concentration of salts and PEG-6000.

The examination of thermoosmosis in the maize primary root tissue has shown that under the rising temperature gradient (gradT) all flows are declining, which continue also under the gradT levelling between compartments. The permeability coefficients are declining similarly as flows. The reflection coefficient during the rising gradT declines, but it rises during the gradT levelling between compartments. These phenomena depend on the plant age and concentration of the bathing solution.

Gibberellic acid (GA₃) generally increased the contents of chlorophyll but not carotenoid in bothChlamydomonas reinhardii andAnacystis nidulans grown under continuous irradiation. The photosynthetic oxygen evolution of the algae was also affected by GA₃ except for the high (100 μM) concentration of GA₃.