Iron deficiency induced decrease in the rate of whole electron transport chain in chloroplasts of pea (Pisum sativum L.). Such reduction was mainly due to the loss of photosystem (PS) 2 activity. The same result was obtained when the ratio of variable to maximum chlorophyll fluorescence (F_v/F_m) was evaluated. The loss in PS 2 activity was primarily due to a loss of 33, 23 and 17 kDa polypeptides. In contrast, iron deficiency induced the synthesis of 28 and 29 kDa polypeptides.

A greenhouse experiment was conducted to investigate whether small differences in UV-B irradiance would lead to changes in competition between cocksfoot (Dactylis glomerata L. cv. Athos) and white clover (Trifolium repens L. cv. Mervi). Plants were grown in greenhouses covered with different thicknesses of UV-transmittant plexi (3 and 5 mm) resulting in 82 % and 88 % of ambient UV-B radiation. Aboveground biomass was harvested at 4-week intervals and the vertical distribution of biomass, leaf thickness and specific leaf area were determined. Tillering, stubble and root biomass and crop height were also measured. There was only one significant effect: at 88 % of ambient UV-B radiation a larger fraction of the biomass was present in the lower layers and a smaller fraction was present in the upper layers.

The effect of N-(2-chloro-4-pyridyl)-N'-phenylurea (4PU-30) on the growth and content of endogenous cytokinins of adenine type in tobacco (Nicotiana tabacum L.) callus was investigated. Biomass accumulation in calli grown on Murashige and Skoog (MS) medium with 4PU-30 was higher than that on MS medium with kinetin. The obvious presence of isopentenyladenine type cytokinins and traces of zeatin type cytokinins supposes modification in the endogenous cytokinin metabolism of the tobacco callus grown on 4PU-30.

NaCl salt stress induced changes in growth and enzyme activities in blackgram (Phaseolus mungo L.) seeds during germination were studied. A decrease in germination percentage, root length, shoot length, and fresh mass was noticed with an increase in NaCl concentration. With the increase in NaCl concentration and duration of stress proline content increased and catalase (CAT), peroxidase (POX) and polyphenol oxidase (PPO) activities decreased.

The changes in soluble proteins associated with adventitious root formation in hypocotyls of radiata pine (Pinus radiata D. Don) were studied using one- and two-dimensional polyacrylamide gel electrophoresis. Protein content decreased during the first day after root excision, and kept decreasing till the end of the time course under non-rooting conditions, i.e., on medium without growth regulators, with indole-3-butyric acid (IBA) + kinetin, or with kinetic alone. During adventitious root initiation in response to IBA, however, the protein content began to increase from day 1 to its maximum at day 7, coinciding with the early stage of root initiation. A comparative analysis of protein changes by two-dimensional polyacrylamide gel electrophoresis showed 16 proteins that were probably associated with root initiation and development.

Mitochondria isolated from root tissue of maize plants grown on a modified Knop solution containing 10.9 mM nitrate ± 7.2 mM ammonium were purified on the discontinuous Percoll density gradient with polyvinylpyrrolidone (PVP) added. The presence of PVP allowed separation of several mitochondrial fractions of a different density. Contrary to mitochondria isolated from plants grown in the presence of nitrate alone, revealing only two fractions, the mitochondria from NH₄⁺/NO₃^--plants were distributed in four fractions. Total amount of mitochondria, as well as specific activities of some nitrogen metabolism enzymes and tricarboxylic acid (TCA) cycle enzymes of all mitochondrial fractions, and respiratory activities of two lower density fractions isolated from plants grown on mixed nitrogen were higher in comparison to mitochondria from nitrate-grown plants.

The behaviour of myrtle (Myrtus communis L.) plantlets during the last phase of in vitro culture before transplanting was studied. Myrtle plants were sampled from Mediterranean shrubland vegetation. In vitro growth of myrtle microcuttings was evaluated during the rooting phase using 500 cm³ containers fitted with two different types of closures. The number of gas exchanges and time in which aerated and closed vessels lose half of their gas content were calculated. Both types of vessel closure allowed photosynthetic activity in myrtle cultures even though the higher aeration rate induced higher net photosynthetic rate (P_N) during all the culture. In vitro morphogenetic and rooting of myrtle microcuttings were affected by the different environment conditions inside the culture vessels: plantlet growth and root formation of myrtle explants increased in aerated vessels in comparison with closed ones. The well developed root system, the higher P_N and dry mass accumulation during the pre-acclimatization phase in aerated vessels induced a better ability to face the transplant stress.

This work tests the hypothesis that sclerophylls (i.e. hard-leaved species) would be less efficient than malacophylls (i.e. soft-leaved species) in terms of water transport through the stem as well as within the leaf blade. Mean leaf surface area (A_L), leaf specific mass (LSM) as well as shoot (K_WL), stem (K_SL) and leaf (K_LL) hydraulic conductances were measured in eight Mediterranean evergreen sclerophylls and eight temperate deciduous malacophylls. No difference was observed between the two groups in terms of K_LL and of the contribution of leaves to the overall shoot hydraulic resistance. Leaves represented in all cases 48 to 90 % of the shoot hydraulic resistance, suggesting that the sclerophyllous habitus does not per se lead to low efficiency in water transport within the leaf blade. A weak negative relationship (r² = 0.252) appeared to exist between K_SL and LSM. This might provide an explanation for the lower growth rates of sclerophylls with respect to malacophylls.

Triglochin maritima had only 40 % germination in distilled water, but germination was substantially enhanced when seeds were exposed to ethephon, fusicoccin, proline, kinetin, and thiourea. Also, the effect of low salinity on germination was alleviated by fusicoccin, kinetin, nitrate and thiourea, whereas, the reduction in germination at high salinity was partially countered by ethephon, kinetin, thiourea and nitrate.

rRNA was labelled with RNase-gold complexes applied to ultrathin Lowicryl sections of excised Cucurbita pepo L. (zucchini) cotyledons grown in darkness. Benzylaminopurine-caused stimulation of cotyledon growth decreases the density of ribosomes in palisade cells despite stimulating rRNA synthesis. Abscisic acid inhibits RNA synthesis and transport, but does not visibly affect the number of pre-existing ribosomes in retarded growth cells. The amount of rRNA in the cells of 24 h treated cotyledons is rather consequence of the growth rate than its leading factor.

Rapid method of in vitro multiplication of date palm was developed. Shoot tips were cultured on Murashige and Skoog (MS) medium supplemented with 2 mg dm^-3 dimethylaminopurine (2iP) + 1 mg dm^-3 naphthalene acetic acid (NAA). Shoot buds were proliferated from white nodular cultures on hormone free medium. Shoot bud proliferation strongly enhanced when cultured on MS-medium contained 3 mg dm^-3 2iP + 0.5 mg dm^-3 NAA. Culturing on full-strength MS medium showed higher multiplication rate compared with half-strength MS medium. Among four concentrations of sucrose used, 30 g dm^-3 speeded up the bud proliferation more than 10, 20 and 40 g dm^-3. However, the largest shoot buds were observed with 40 g dm^-3 sucrose. Solidification of culture media by 1.75 g dm^-3Phytagel showed the highest proliferation rate, but the largest buds were observed with 1 g dm^-3Phytagel.

Two successive cycles of mature embryo-derived callus culture separated by one cycle of sexual reproduction of R₀ regenerated plants were performed using two rice (Oryza sativa L.) cultivars in order to gain information upon the nature of somaclonal variation in this species. Plants regenerated after one cycle of tissue culture exhibited higher variability and lower performances than those of initial cultivar. A second cycle performed using R₁ embryos as explants showed that the cellular component of salt resistance in terms of growth and regenerating abilities selected during the first cycle could be transmitted to the progenies. The extent and the nature of somaclonal variation depended on the identity of R₀ mother plant and culture conditions, somaclonal variation being strongly reduced in some families obtained from salt-treated calli.

Seed proteins of eleven species of Brassicaceae were investigated by polyacrylamide gel electrophoresis. In total 50 different bands were identified. Some of the bands are characteristic and represent constant markers of each species, which allow the unequivocal identification of their electrophoregram. The obtained data have been treated numerically using the cluster analysis method of unweighed pair group (UPGMA). The electrophoregram gives support to the idea that the tribe Sisymbrieae is an unnatural group and suggests its merge with the tribe Brassiceae. On the other hand the distinct position of Zilla spinosa in the dendrograms supports the traditional treatment of this taxon as a monotypic subtribe Zillinae.

To determine the allelopathic potential of root exudate from early developmental stage of rice (Oryza sativa L), 6-d-old seedlings of eight cultivars were grown with 3-d-old alfalfa (Medicago sativa L.), cress (Lepidium sativum L.) or lettuce (Lactuca sativa L.) seedlings in Petri dishes under controlled condition. All rice cultivars (cv. Norin 8, Kamenoo, Nipponbare, Kinuhikari, Koshihikari, Sasanishiki, Yukihikari and Hinohikari) inhibited growth of roots, shoots and fresh mass of alfalfa, cress and lettuce seedlings. Effectiveness of cv. Koshihikari was the greatest and more than 60% inhibition was recorded in all bioassays, followed by that of cv. Norin 8 of which effectiveness was more than 40%.

Several Czech and foreign hop mericlones were tested in vitro for efficiency of green callus formation and plant regeneration from internodal or nodal explants. Modified MS media gelled either with agar, starch or a mixture of potato starch and Gelrite, supplemented with different concentrations of either glucose or maltose, were investigated. Two mericlones of Czech hop (Osvald 72 no. 5216 and Sládek no. 6908) were studied in more details because of their different regeneration capacities. The HPLC analysis of medium sugar concentrations after the explant cultivation has revealed slow uptake of sugar from the medium. Presence of glucose at concentration of 45 g dm^-3 in agar medium resulted in a decreased number of nodes compared to the control with 30 g dm^-3 of glucose. The use of a mixture of potato starch plus Gelrite instead of routinely used agar and decreasing the medium glucose concentration to 15 g dm^-3 proved to be most efficient for multiplication rate. The use of this medium results in lower cost of micropropagation of healthy hop cultures without exhibition of vitrification.

A series of experiments were conducted to characterize the water stress-induced changes in the activities of RuBP carboxylase (RuBPCO) and sucrose phosphate synthase (SPS), photosystem 2 activity, and contents of chlorophylls, carotenoids, starch, sucrose, amino acids, free proline, proteins and nucleic acids in mulberry (Morus alba L. cv. K-2) leaves. Water stress progressively reduced the activities of RuBPCO and SPS in the leaf extracts, the chlorophyll content, and PS2 activity in isolated chloroplasts. Plants exposed to drought showed lower content of starch and sucrose but higher total sugar content than control plants. While the soluble protein content decreased under water stress, the amino acid content increased. Proline accumulation (2.5-fold) was noticed in stressed leaves. A reduction in the contents of DNA and RNA was observed. Reduced nitrogen content was associated with the reduction in nitrate reductase activity. SDS-PAGE protein profile showed few additional proteins (78 and 92 kDa) in the water stressed plants compared to control plants.

Study on the effect of elevated CO₂ concentration on leaf structure of Brassica juncea L. cv. Bio-141 (95) under moisture stress revealed, that CO₂ elevated to 600 μmol mol^-1 increased the length of epidermal cel and length of palisade parenchyma cells, and induced larger chloroplasts and more oval shaped starch granules in comparison with plants grown at ambient CO₂ concentration. This increase in structural sink size helped in check feedback inhibition by excessive photoassimilate which was subsequently used to compensate the adverse moisture stress effect in B. juncea leaves.

The ultrastructure of tomato leaf disks treated with a biostimulator (0.01 mg dm^-3 BB6, brassinosteroid analogue from Cuba), and subjected to high temperature (40 °C for 1.5 h) was studied. High temperature stress caused the appearance of granules in the nucleus, nucleolus and cytoplasm. In chloroplasts and in mitochondria the internal membrane system was disorganised and in chloroplasts some starch granules were detected. These symptoms were more marked in the cells treated with BB6. The influence of BB6 on the ultrastructure of leaf cells was apparent also before being subjected to heat stress.

The changes in endopeptidase activity in different parts of germinating triticale cv. Malno were investigated. Haemoglobin, gliadin, azocasein and azoalbumin were used as substrates. During the first day of germination the activity of haemoglobin hydrolyzing endopeptidases predominated while after the second day, mainly in the endosperm, a rapid increase in endopeptidases activity preferring gliadin hydrolysis was observed. In all the investigated tissues azocaseinolytic activities increased with the successive days of germination. Similar changes were observed using azoalbumin with one exception: in the embryo axis this activity decreased with the progression of germination. Separation of endopeptidases on the DEAE Sepharose CL-6B reveals three activity peaks in extract from dry seeds and four peaks in extract from 3 d germinated seeds. The obtained peaks differed in substrate specificity and in sensitivities to class-specific inhibitors.

Two soybean (Glycine max (L.) Merr.) cultivars, Tachiyutaka and Dare, were grown in pots at 30 and 70 % relative humidity (RH) and treated with 0 (control), 40 (moderate), 80 and 120 (severe) mM NaCl for 3 weeks. Increasing RH enhanced growth of salt sensitive cultivar, Tachiyutaka, but had no effect on salt tolerant cultivar, Dare, under control and moderate saline conditions. Both cultivars benefited from elevated humidity under severe saline conditions. Cultivar Tachiyutaka had poorer ability for controlling translocation of Na⁺ to the leaves, lower Na⁺ exclusion ability in the roots, and lower root activity under NaCl treatment, compared with cv. Dare. The increased growth of cv. Tachiyutaka at high RH was consistent with decreased Na⁺ accumulation in the leaves, increased stomatal conductance and root activity, while the unchanged growth of cv. Dare was consistent with similar Na⁺ accumulation in the leaves, and the decreased root activity.

Gas exchange in Gossypium hirsutum L. cv. H-777 as affected by water deficit and growth regulators (IAA, GA₃, BAP, ABA, ethrel) was examined. Sixty days after sowing, growth regulators in concentration 50 µM were applied as foliar spray and irrigation was withheld to get desired (moderate and severe) water deficit. All the parameters were measured on the third leaf from the top between 10:00 and 11:00. Net photosynthetic rate (P_N), transpiration rate (E), stomatal conductance (g_s), carboxylation efficiency (CE), and water potential (ψ_w) decreased significantly with the increasing water stress, however, water use efficiency (WUE) was unaffected. Foliar spray with IAA, GA₃ and BAP partially counteracted the effect of water deficit on the above parameters except ψ_w, which became more negative. ABA and up to some extent ethrel increased WUE and maintained higher ψ_w, however, caused further decrease in P_N, E, and g_s.

Leaf discs from vegetative plants greatly increase their phenolic content when cultivated in vitro. Under long days the values remained constant, and were higher when compared with short days cultures. Under short days total phenolics decreased after 10 d, corresponding to the induction and expression of in vitro flowering. The effect of photoperiod and chlorogenic acid (0.01 mM) on leaf discs cultured from induced and non-induced plants, were analyzed regarding the neo-formation of roots, as well as vegetative and flower buds. Chlorogenic acid enhances the regeneration of roots in all treatments tested, with the highest stimulation on induced leaf discs cultivated in short days. The flowering was not affected by chlorogenic acid, but an inhibitory effect was observed on the neo-formation of vegetative buds in non-induced explants maintained in short days. Vegetative buds were reduced by 50% in flower-induced leaf discs cultivated under short days.

The root cell walls of the resistant cultivars of the date palm were more resistant to the action of the cell wall-degrading enzymes (CWDE) of Fusarium oxysporum f. sp. albedinis than those of the susceptible cultivars. Date palm roots contain four cell wall-bound phenolics identified as p-hydroxybenzoic acid, p-coumaric acid, ferulic acid and sinapic acid. The contents of p-coumaric acid and ferulic acid in the resistant cultivars (IKL, SLY, BSTN) were about 2 times higher than those in the susceptible cultivars (BFG, JHL, BSK). The contents of p-hydroxybenzoic acid and sinapic acid in the resistant cultivars were 8.4 and 4.5 times, respectively, higher than those in the susceptible cultivars. The lignin contents in roots of the resistant cultivars were 1.8 times higher than those of the susceptible cultivars. The cell wall-bound phenols accumulated particularly in resistant cultivars reduced strongly the mycelial growth and the CWDE production in vitro.

Trichloroacetic acid (TCA) belongs to secondary atmospheric pollutants affecting the forest health. Distribution of [1,2-¹⁴C]TCA-residues and TCA biodegradation were investigated in 4-year-old nursery-grown trees of Norway spruce [Picea abies (L.) Karst.] in the whole plant/soil system. Radioactivity was monitored in needles, wood, roots and soil as well as in the air. During two weeks of exposure TCA was continuously degraded, especially in the soil. Estimates of radioactivity balance showed loss of radioactivity into the atmosphere in the form of ¹⁴CO₂; unincorporated [1,2-¹⁴C]TCA, chloroform, carbon monoxide and methane were not detected at all. TCA degradation to CO₂ was indicated also in the spruce needles. Moreover, it was found that soil litter contained [1,2-¹⁴C]TCA unavailable to microorganisms.