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.

A field experiment was conducted to investigate the effects of presoaking the wheat grains (Triticum aestivum L.) in different levels of salinity (33 or 66 mM) and in growth regulators (indolyl-3-acetic acid, IAA at SO g m^-3, gibberellic acid, GA₃ at 100 g m^-3, or kinetin at 100 g m_-3) on the shoot growth and pigment content of the developing wheat flag leaf. Salinity at 33 or 66 mM led to an insignificant increase in the fresh and dry masses as well as in the shoot diameter and shoot length, but it attenuated the flag leaf area. In the majority of cases, salinity increased the chlorophyll (Chla, Chlb) and carotenoid contents as well as the number of chloroplasts per a mesophyll cell. The growth in the wheat shoot of the saline-treated plants was, in general, stimulated in response to presoaking the grains in kinetin or GA₃. On the other hand, IAA + salinity led to a negligible effect on the growth in the wheat plants particularly at the early stages of growth. The presoaking of grains in NaCl at 33 mM + IAA or 66 mM + kinetin induced a marked increase in the pigment content of the wheat flag leaf particularly at the early stages of growth. The interaction between salinity and phytohormones increased the number of chloroplasts; kinetin was the most effective.

Effects of a short-term pre-irradiation of etiolated wheat seedlings by radiation of various wavelengths and various irradiances on the rates of photophospho-rylation, Hill reaction, and chlorophyll accumulation were studied. The curves, constructed for the dependence of inhibitory effect in different processes on pre-irradiance doses, have a saturation level corresponding to photostationary state of the phytochrome system and a pre-threshold site where the inhibition is absent. For an interpretation of the experimental data we suggest a general model that includes both the threshold concept of Mohr and the presence of an additional control mechanism not sensitive to far-red radiation. According to the model, the phytochrome-controlled biological effect is pro-portional to the time during which the level of active phytochrome is higher than the threshold one and may be analysed according to the inhibition degree. The difference in control by red (RR) and green radiation (GR) pretreatments is attributed to the difference of the phytochrome photoconversion rate under RR and GR.

Pollen of pigeonpea(Cajanus cajan (L.) Millsp.) cultivars H-77-216 and ICPL-151 were cultivatedin vitro at six different temperatures (12, 17, 22, 27, 32, 37 °C). Pollen of cv. H-77-216 started to germinate at 17 °C whereas the pollen of cv. ICPL-151 at 22 °C, the optimal temperatures were 22 and 27 °C, respectively. Pollen germination at different temperatures was found to be positively correlated with the tube length. Per cent pollen bursting increased with rising temperature. The indeterminate cv. H-77-216 showed a wide range of suitable temperatures (17 - 27 °C) for pollen germination while the determinate cv. ICPL-151 had optimum at 27 °C

The effect of methyl jasmonate (JA-Me), applied to mature green tomato fruits cv. Modena, on the content of some fatty acids in ripe fruits was studied. Methyl jasmonate greatly increased content of linolenic acid and in the lesser degree decreased the amount of linoleic acid. The ratio of linolenic acid to linoleic acid content increased 4.5-7.7 times in methyl jasmonate treated samples in comparison to untreated-controls. JA-Me did not affect the contents of lauric, myristic, palmitic, stearic, palmitoleic and oleic acids.

The chlorophyll and protein contents of the flag, second and third leaves gradually decreased during the reproductive development of rice (Oryza sativa L. cv. Rasi) and wheat (Triticum aestivum L. cv. Sonalika) plants, whereas proline accumulation increased up to the grain maturation stage and slightly decreased thereafter. In rice plant, the rate of decrease in chlorophyll and protein and increase in proline level were higher in the flag leaf than in the second leaf. It was opposite in wheat plant. The export of [³²P]-phosphate from leaves to grains gradually increased reaching a maximal stage at the grain development stage, and then declined. The export of this radioisotope was greater in rice than in wheat. Removal of panicle at the anthesis and grainfilling stages delayed leaf senescence of rice plant, while in wheat the ponicle removal at any stage did not have a marked effect on delaying leaf senescence. The contents of chlorophyll and protein of glumes were higher in wheat than in rice. The variation of such source-sink relationship might be one of the possible reasons for the above effect on leaf senescence.

The DNAase II, Mg²⁺ procedure was used to fractionate the seedling chromatin of a heterotic maize hybrid and its parental inbreds FRM017 and FRN28. The hybrid and the more vigorous maize inbred FRN28 have 14 and 11 percent soluble chromatin (euchromatin) respectively, while the less vigorous FRM017 contains 30 percent. The unfractionated chromatin of the hybrid contains less protein than either inbred. The RNA contents of the unfractionated chromatin of the hybrid and of FRN28 are similar and are one-half that of less vigorous FRM017. Hybrid euchromatin contains relatively more protein and RNA than DNA as well as higher proportions of protein and RNA than heterochromatin, unfractionated chromatin, or inbred euchromatin; this suggests a more "efficient" type of activity, as reflected by the low amount of euchromatin and a high proportion of RNA and chromosomal proteins.

The tolerance to iron-deficiency stress and the iron uptake were studied in two Japanese mint(Mentha arvensis L.) cultivars MAS1 and MS77 and their local strain MA2. A considerable reduction of pH of the nutrient medium in MAS1 and MS77 treatments associated with different degree of chlorosis was found. A rapid recovery from chlorosis was found only in MS77 and to some degree in MAS1, but not in the MA2. The results indicated that iron uptake and translocation were inversely related to iron stress tolerance.

When distantly related plants are crossed, embryos abort on the mother plant. One of the methods used to rescue the embryo is to cultivate the ovulein vitro. When the ovule is precociously detached from the mother plant, survival rate of the embryo is very low. To increase the chance of survival as well as the growth of the embryo, the medium was supplemented by different extracts of plants after either autoclaving or filtering. Autoclaved tomato extract seemed to have no simulating effect in spite of reports from different authors. Filtered coconut milk increased growth and filtered cucumber extract improved survival. Other new extracts had a stimulating action on both growth and survival and are of interest for further study.

The mechanical stimulation of the sensitive internal lower part of Berberis vulgaris stamen resulted in its rapid bending. In the present study we have examined the influence of external Ca²⁺ concentration on stamen movement. The external Ca²⁺ reduced the extent of the response and the effect was dependent on Ca²⁺ concentration and duration of the treatment. Addition of calcium ionophore A 23187 to the medium reduced the response and the effect was dependent on the external Ca²⁺ concetration. This result might suggest an increase in Ca²⁺ level in cytosol. The inhibitory effect of higher Ca²⁺ concentration on stamen bending was cancelled by Ca²⁺-chelating agents. Ca²⁺-channel blockers prevented the stamen response in higher external Ca²⁺ concentration with different effectiveness. In these conditions, during 4-h experiments, La³⁺, verapamil and nifedipine gave ability of stamen movement at about 85 %, 58 % and 10 %, respectively. An energy-dependent Ca²⁺ efflux was confirmed in experiments by using vanadate, a non-specific ATPase inhibitor. The lack of inhibition of stamen bending after application of calmodulin antagonists suggests that it might not be directly involved in regulation of the response. The inhibitory effect of higher Ca²⁺ concentration on stamen movement might result from: (a) the binding with cell wall materials, (b) changes of structure of cytoplasm and metabolic activity and (c) influence on transport processes.

Embryogenic callus was initiated from immature zygotic embryos of black pine on medium DCR supplemented with 2 mg 1^-1 2,4-D and 0.5 mg 1^-1 BAP. The diploid number of chromosomes confirmed the origin of callus from zygotic embryos. The callus was white, glossy, mucilaginous and contained somatic embryos consisted of an embryonic region with densely cytoplasmic cells and suspensor region with long vacuolated cells. Although somatic embryos with green cotyledons were recognisable after ABA treatment and subsequent transfer to growth-regulator free media whole plants have not yet been obtained.

The physiological response ofScenedesmus obliquus to salinity (NaCl concentration of 40, 80, 120, 60 and 200 mM) for 7 d (long-term experiments) or 2 h (short-term experiments) was followed. Cell number, dry matter and the content of photosynthetic pigments decreased with the rise of NaCl concentration. However, the photosynthetic O₂ evolution mostly increased with the increase of NaCl concentration up to 80 mM, and respiration (dark O₂ uptake) was markedly promoted. Photosynthesis/respiration ratio went in concomitance with the cell number, dry matter or chlorophyll content. Contents of soluble saccharides and soluble proteins increased with the rise of salinization, while the content of insoluble and total saccharides or proteins decreased. Proline content increased greatly with salinization, whereas of other free amino acids were mostly reduced, especially at higher salinities. Similarly, the lipoid contents of salinizedScenedesmus obliquus were obviously higher than those of the control cultures.

The effects of chlorpromazine and calmidazolium on rapid IAA- and GA₃-induced changes in growth rate of etiolated pea stems were measured. During the initial period of up to 160 min after hormone application, the responses to both IAA and GA₃ were seen to be biphasic, showing two acceleration peaks. Chlorpromazine or calmidazolium applied simultaneously with the hormones blocked the first IAA-induced acceleration peak, but did not affect the second one. In contrast, the first GA₃-induced peak was not prevented by chlorpromazine or calmidazolium, while the second one was completely abolished. The results support the concept that the active calmodulin-calcium complex may be an essential component of hormone-controlled stem elongation. They also point to differential mechanisms of IAA and GA₃ actions.

Trans-resveratrol (4,3',5'-trishydroxystilbene) was identified in grapevine leaves with vein necrosis disease symptoms. The compound accumulates from 10 to 60 μg^-1 (fresh mass) in infected leaves.

Differentiation of Acerpseudoplatanus L. cells into tracheary elements (TE) and an increase in the number of TE inHaplopappus gracilis (Nutt.) A. Gray calli were observed after pulse-treatment of the cultures grown in glass tubes with indole-3-acetic acid (IAA) solutions. The effect was enhanced if the treatment was repeated in three subsequent days. The manner of IAA application which caused a wave-like pattern of IAA flow through the callus culture appeared to be more important than the IAA concentration. Induction of differentiation of A.pseudoplatanus cells and an increase in the number of TE inH. gracilis callus did not occur when the calli were grown on agar media supplemented with increased concentrations of IAA.

Ultrastructure of chloroplasts in leaf mesophyll cells of triazine resistant and triazine sensitiveAmaranthus retroflexus L. plants was evaluated stereologically. The most striking difference between both types of the chloroplasts was a small volume of starch inclusions in triazine resistant plants.

Agrobacterium tumefaciens binary vectors carrying kanamycin resistance gene and either C58 T-DNA gene 4 for cytokinin synthesis or genes 1 and 2 for auxin synthesis were constructed and used for transformation of a short-day tobacco Maryland Mammoth. Kanamycin resistant plants were regenerated from a small fraction of transformed tissue and the presence of T-DNA in their genome was verified by Southern blotting. The level of endogenous cytokinin in plants transgenic for gene 4 and the level of endogenous IAA in those transgenic for genes 1 and 2 increased by more than 100 %. A number of morphological characteristics distinguish them from untransformed controls.