The effects of different nitrogen salts on nitrate reductase activity and protein contents were investigated in three Yugoslav cultivars of wheat. The nitrate salts appeared to be a better form of nitrogen than ammonium in respect of the increase of the nitrate reductase activity and root total protein contents, whereas the treatment with ammonium salt resulted in a comparably higher shoot total protein contents. KNO₃ was the best in respect of the level of nitrate reductase activity. Different concentrations of nitrate and ammonium ions in nutrient solution, showed very similar effects on investigated parameters. NS Rana 2 cultivar had the highest values of nitrate reductase activity and protein contents.

The efficiency ofAgrobacterium-based transformation technique in oilseed rape and cauliflower was influenced by cultivar specificity, donor plant age and explant type. Marked differences in demands for plant hormone contents in the regeneration medium were recorded already among different types of nontransformed explants. The highest regeneration capacity was recorded with stem and leaf segments isolated from one-month-old aseptically grown plants. The regeneration was markedly species-dependent. Regeneration of transformed plants from stem segments and thin layers isolated from field-grown oilseed rape plants (at the most 2% of regenerating explants) and from oilseed rape hypocotyls (0.8% of regenerating explants) and cauliflower (1.2% of explant regenerated transformed shoots) was achieved after disarmedAgrobacterium treatment. Hypersensitive reaction of explants could be prevented by using prolongedin vitro precultivation and delayed application of the selective agent.

Relative competition among various plant parts for N during water stress,i.e. nitrogen distribution index (NDI) was determined in relation to specific nitrogenase activity (SNA) and nodule and soil nitrogen in both indeterminate (H-77-216) and determinate (ICPL-151) types of pigeonpea (Cajanus cajan L.) under greenhouse conditions. Two levels of water stress,i.e. moderate (soil Ψ_w) -0.77 MPa) and severe (soilΨ_w -1.34 MPa) were created by witholding the irrigation at vegetative (40 DAS) and flowering (70 DAS) stages. At vegetative stage under moderate stress the highest NDI was in nodules of cv. H-77-216 and in leaf of cv. ICPL-151. Under severe stress both the cultivars showed negative values of NDI, with maximum loss of N from root and nodules. Cultivar ICPL-151 behaved differently at flowering and vegetative stages. Very high loss of N from different plant parts was seen at flowering under severe stress. All the plant parts showed gain in N during rehydration. Loss and gain in N at both the stages under stress and rehydration respectively, correlated with available N in soil. Specific nitrogenase activity (SNA) and nodule N were maximum at moderate stress and related with NDI values of leaf and nodules.

Changes in the levels of free indol-3-ylacetic acid (IAA) and free cytokinins were determined in the course of dormancy and sprouting period in potato tubers(Solanum tuberosum L., cv. Nevskii) stored at 4 °C. The same analyses were performed in potato tubers after Ethrel application, which prolongs dormancy. No significant changes were found in free IAA level during dormancy followed by a rapid decrease during sprouting. After Ethrel application a significant lower IAA level was found 3 weeks after application, but further on no changes in free IAA level between treated and non-treated tubers were detected. Cytokinin level was relatively low and constant till sprouting and increases then by about 55 %, mainly due to an increase in the level of zeatin riboside and isopentenyladenosine. Ethrel application decreased cytokinin level during dormancy slightly, but postpones the increase coupled with sprouting by about 1 month. Thus, IAA does not seem to have a significant effect on tuber dormancy, while cytokinins are probably necessary for sprouting initiation.

The angiosperm root parasiteCynomorium coccineum and the halophytic hostsLimonium delicatulum andArthrocnemum glaucum were invesrigated under natural conditions in a Mediterranean salt marsh in March 1992. The diurnal transpiration rate of the parasite was low and parallel to the climatic factors. The non-infected plants showed higher transpiration rates than the parasite and its hosts. Compared to the non-infected plants, it is apparent that the perennial herbL. delicatulum is more sensitive to infection since its reduction in the fresh and dry mass was higher than that found inA. glaucum.

Using a membrane potential probe, Oxonol VI, it was possible to demonstrate generation of ATP- and NADH-dependent membrane potential across the plasmalemma, with membrane vesicles derived from parenchyma cells of Jerusalem artichoke tubers(Helianthus tuberosus L.). It was shown that ATP- and NADH-dependent membrane potential generation was higher in dormant material than in non-dormant tissue and that the effects of ATP and NADH on membrane potential generation were additive. ATP-dependent potential generation was sensitive to vanadate, an inhibitor of plasmalemma ATPase activity. The results are discussed in relation to the properties of the different enzymes bound to the plasma membrane, the morphogenetic potentialities of tuber buds and the hypothesis that tuber dormancy could be an extreme case of nutrient deficiency induced by short-distance intercellular relationships.

RNA synthesis as measured by the incorporation of tritiated uridine into trichloroacetic acid insoluble material was studied in the leaf protoplasts of cv. Kennebec and its parthenogenically derived dihaploid. Protoplasts of cv. Kennebec incorporated tritiated uridine at a greater rate and accumulated more than twice the amount of radioactive materials than did the dihaploid over a 6-h incubation period. Poly(A)⁺RNA, isolated from the total RNA of the tetraploid and of the dihaploid, by oligo(dT)-cellulose column chromatography, was present in amounts of 11.3 and 5.2 % respectively. The tetraploid synthesized 4.8 times the amount of poly(A)⁺RNA that was synthesized by the dihaploid.

Plants of peanut (Arachis hypogaea L.) were subjected to 7-d and 14-d waterlogging and sprayed with 10 and 100 mg 1^-1 of gibberellic acid (GA₃). Waterlogging decreased the leaf area (A), net photosynthetic rate (P_n), chlorophyll content (Chi) and temporarily the leaf water potential (Ψ_w) and increased stomatal diffusive resistance (r_s) of both leaf surfaces. Application of GA₃ increased A and P_n and significantly decreased the r_s of both leaf surfaces but did not affect Ψ_w or Chl. Thus GA₃ partially alleviated the effects of waterlogging on A, r_s and P_n.

Salinity inhibited growth, and affected the contents of chlorophylls, carotenoids, saccharides, amino acids, proteins, DNA and RNA in broad bean plants. Foliar application of NaH₂PO₄ and NaNO₃ greatly ameliorated the adverse effects of NaCI. This counteraction was associated with an increase in contents of saccharides, proteins, DNA and RNA.

Tobacco cv. White Burley was transformed with disarmed expression vector pCB1314 containing dimeric cDNA of potato spindle tuber viroid (PSTV, severe strain) in plus orientation regulated from the mannopine promoter. Amount of PSTV specific (-) and (+) sequences and PSTV circular forms was measured in transformed tobacco stock and compared with PSTV content in untransformed tomato and tobacco grafts. It follows from the results that lower rate of accumulation of PSTV in tobacco as compared with tomato is due to less intensive viroid transportation through the cytoplasm and/or cell to cell moverment, whereas both, viroid replication and processing showed comparable characteristics in tomato and tobacco with respect to accumulation of minus and plus strands and circular forms in infected tissues. Despite of accumulation of viroid in comparable amount in both transformed tobacco and infected tomato, no expression of any morphological symptom of disease was observed in transgenic tobacco.

Thein vivo ¹⁴CO₂ fixation assay and xylem sap analysis showed that inSesbania rostrata the transport of fixed nitrogen from stem nodules was in the amide form. The majority of nitrogen was transported as asparagine. The close relationship between nodule phosphoenolpyruvate carboxylase and nitrogenase activities suggested that nodule CO₂ fixation contributed directly to nitrogen assimilation in stem nodules ofS. rostrata.

Monogalactosyl diacylglycerol (MGDG), digalactosyl diacylglycerol (DGDG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and sulfoquinovosyl diacylglycerol (SQDG) are the most abundant lipid classes present in both the autotrophically and heterotrophically grownChlamydomonas reinhardtii. However, phosphatidylcholine (PC) and diacylglycerol (N,N,N-trimethyl)-homoserine (DGTS) were absent in both alga types. The polyne index B was higher in heterotrophic than photoautotrophic algae, but the unsaturation index was higher in photoautotrophic algae PI, PE and DGDG. The proportion of linolenic acid decreased under heterotrophy with compensatory increases in hexadecadienoic (16 : 3), oleic (18 : 1) and linoleic (18 : 3) acids.

The current-response method was used to characterize effect of oxygen deficiency on functional state of membranes along the roots of wheat seedlings. The results show apical parts of older roots being most affected by hypoxia, while the youngest roots behaved as effectively adapted.

Decrease in soil water potential during vegetative and flowering stages of two cultivars of pipeon pea (Cajanus cajari) caused higher decrease in relative water content in cv. ICPL-151 than in cv. H-77-216. Both cultivars showed partial recovery during rehydration. Cv. H-77-216 also accumulated more proline and carbohydrates during stress and showed better drought tolerance than cv. ICPL-151.

Total nonstructural saccharides (TNS) content in young plant ofAlopecurus pratensis was always above 4% of dry matter even at several types of stress treatment (nitrogen deficiency, low irradiance). TNS content was in negative correlation with concentration of total nitrogen in all cases. Positive correlation was found between the TNS content in plants and relative increase in their root growth rate.

Restriction fragment analysis of the chloroplast gene psbA was carried out in twelveAbies species native to Asia, Europe and North America using the four restriction enzymes. The pair of Asiatic representatives ofA. koreana andA. veitchii differed profoundly not only from each other but also with respect to the European and Northamerican species. The variation observed within the last mentioned groups of firs was mainly due to the different restriction profiles of the gene inA. alba andA. nordmanniana species of the former region as well as owing to its heterogenous nature in all the four species from North America. The RFLP data presented to far only partially correlate with the taxonomic status and hybridological relationships of the species concerned.

Introduction of the gene for cytokinin synthesis into potato genome lead to a manifold increase in the level of cytokinins (zeatin, zeatin riboside, isbpentenyl-adenine, isopentenyladenosine) in plantlets grownin vitro.The increasing cytokinin level was associated with increasing tendency to teratoma formation, to decreasing leaf net photosynthetic rate and to increasing dark and light respiration rates and CO₂ compensation concentration. During plantlet (or teratoma) ontogeny, net photosynthetic rate increased simultaneously with the decrease in cytokinin level. High level of endogenous cytokinins was associated also with lower photochemical activities of both photosystems in isolated chloroplasts.

Growthof Atriplex amnicola P.G. Wilson was not affected by different levels (10, 100, and 200 mM) of NaCI. Na concentrations in roots and shoots increased significantly at higher levels of NaCI. K/Na ratios in plant parts were higher compared to those in the external solutions, indicating selectivity for K over Na. P uptake, as determined using³²P, was not affected by increasing NaCl in the root medium.

Somatic embryos were induced from immature cotyledons and immature embryonal axis ofArachis hypogaea L. on L-6 basal medium supplemented with NAA, picloram or 2,4-D at 5-50 mg 1^-1. Immature embryonal axis produced a higher number of somatic embryos in comparison with immature cotyledons. The highest number of responding cultures was produced on medium supplemented with NAA (50 mg 1^-1), while the highest average number of somatic embryos per culture was produced on medium with 2,4-D (10 or 20 mg 1^-1) and picloram (30 mg 1^-1) from cotyledons. The somatic embryos developed into plants on basal medium supplemented with activated charcoal and about 100 plants were successfully transferred to the field.

Eight major pathogenesis related (PR) proteins were found in a soluble extract of cucumber mosaic virus (CMV) infectedCapsicum annuum leaves. None of them was present in the soluble extract of sham-inoculated controls. The proteins were detected by two-dimensional polyacrylamide gel electrophoresis using (2D-PAGE)PhastSystem, native-PAGE in the first dimension and SDS-PAGE in the second. Two major acidic PR-proteins were identified on the basis of their relative molecular mass (M_r), PR1 of 15.3 kD and PR2 of 29 kD. Six proteins were basic and were identified as PRla of 15.9 kD, PRlb of 15.0 kD, PRlc of 15.9 kD, PR2 of 27.0 kD, PR3 of 36.3 kD and PR4 of 48.8 kD.

A culture system was developed which allows continuous production of adventitious buds. Segments of seedlings germinated on media supplemented with different growth regulator combinations were used as explants. Cultivation was carried out in two phases, which alternate permanently: (I) without and (II) with growth regulators. Thus it was possible to establish meristematic tissue cultures from 5-10% of the seedlings tested. They have produced buds now for over 3 years with multiplication rates of about 1.5 within 5-6 weeks.

In barley genotype susceptible toErysiphe graminis f. sp.hordei 1,3-β-glucan synthase activity in whole leaf extracts was higher in comparison with healthy plants. A positive correlation was found between the activity of 1,3-β-glucan synthase and the degree of barley resistance. On the contrary, the 1,3-β-D-glucanase activity in whole leaves was negatively correlated to host plant resistance. This phenomen is evident only in the early phase of plant pathogen interaction. However, in epidermal cells the 1,3-glucanase activity was not significantly changed after attack and the 1,3-glucan synthase activity was practically zero. Chitinase activity in inoculated leaves and epidermis was higher than in healthy ones, but no unambigous correlation was found between the enzyme activity and host resistance.