Rhododendron catawbiense cv. Album propagated in vitro were transferred ex vitro and grown in a greenhouse, under long or short days. Under long days, the rhythmic growth led to an acrotonous development. In contrast, under short days, the upper buds were unable to burst, allowing basitony. In both photoperiodic conditions, the apical buds were sampled at different stages of the experiment. Growth capacities of the isolated buds were estimated by measuring their abilities to increase and diversify their non-adenylic nucleotide pool (NTP) after supplying adenosine as a precursor. Under long days, during the growth pause, the apical buds were able to increase and diversify their NTP pool. Under short days, adenosine was used to produce important quantities of ATP, while NTP pool increase became weaker. Nevertheless, during this long growth pause, apical bud tissues retained capacities to increase their NTP pool until the basal shoots developed.

The effect of different hermetic and non-hermetic closure-types (aluminum foil, cotton bung, cotton plug, polypropylene cap and Steristopper) on potato (Solanum tuberosum L.) plantlets growth and chlorophyll contents was studied in three genotypes belonging to different maturity groups. Plantlets grown in culture tubes closed with aluminum foils and polypropylene caps had higher fresh mass and shoot length, but lower chlorophyll contents, higher senescence index and various morphological abnormalities. Non-hermetic closures like cotton plugs and Steristoppers were found optimum for plant growth without any morphological abnormalities. Besides, these plantlets exhibited low senescence index and had higher chlorophyll contents that favour acclimation to ex vitro conditions.

A field study was conducted to evaluate the drought tolerance of three sorghum [Sorghum bicolor (L.) Moench] cultivars, Gadambalia, Arous elRimal and Tabat, and quantify the physiological bases for differences in their drought tolerance. Water stress reduced shoot dry mass of Gadambalia, Arous elRimal and Tabat by 43, 46 and 58 %, respectively. The respective reduction in leaf area of the three cultivars was 28, 54 and 63 %. The reduction in net photosynthetic rate, stomatal conductance and transpiration rate due to water stress was lowest in Gadambalia and highest in Tabat. The leaf water potentials and relative water contents of Gadambalia under wet and dry treatments were similar, while those of Tabat were significantly reduced by water stress. The lowest and highest liquid water flow conductance was displayed by Tabat and Gadambalia, respectively. Drought tolerance in Gadambalia is associated with its smaller leaf area, higher liquid water flow conductance, and ability to maintain high leaf water potential, relative water content, stomatal conductance, transpiration rate and photosynthetic rate under drought stress.

Shoot cultures of Alyssum markgrafii O.E. Shulz, endemic nickel hyperaccumulating species of central Balkan, were established and maintained on Murashige and Skoog medium supplemented with 0.2 mg dm^-3 benzyladenine (BA). Nickel in form of NiCl₂ . 6 H₂O was supplemented at 22 different concentrations ranging from 0.0001 to 15 mM but none of them was lethal to cultures. High Ni²⁺ concentrations (10 mM or more) arrested shoot growth which, upon transfer to Ni-free medium, commenced via axillary bud proliferation. Shoots that developed from axillary buds through the subculture manifested increased tolerance to Ni²⁺ expressed as shoot elongation. Shoot multiplication and dry biomass production decreased with increase of Ni²⁺ in medium. Only the accumulation of Ni²⁺ in tissues increased with Ni²⁺ content of the medium. Apart from shoot cultures, high Ni²⁺ accumulation was registered in undifferentiated callus cultured on medium with 0.5 mg dm^-3 BA and 0.5 mg dm^-3 naphthylacetic acid. Highest content of accumulated Ni was 2.37 μg g^-1 (d.m.) in shoots and 2.65 μg g^-1 (d.m.) in callus, both measured on medium with 15 mM Ni²⁺.

Effects of phosphorus and thiourea application (either alone or in combination) were studied on clusterbean (Cyamopsis tetragonoloba Taub.) plants subjected to water stress by withholding irrigation at pre- and post-flowering stages in pot culture trial. Water stress significantly decreased shoot water potential, relative water content of leaves, net photosynthetic rate, contents of total chlorophyll, starch and soluble proteins as well as nitrate reductase activity at both the growth stages. Application of phosphorus and thiourea or combined application increased most of these parameters. Results revealed synergistic effects of P and thiourea in enhancing net photosynthesis, leaf area, chlorophyll content and nitrogen metabolism leading to significant improvement in plant growth and seed yield under water stress condition.

Morphological, physiological, fruit yield and quality related traits were compared between the seed-grown and tissue-cultured plants of tomato (Lycopersicon esculentum Mill.) cv. Red Coat in a greenhouse. No significant differences were observed for any of the traits studied except for the number of leaves and branches, which were higher in the seed-grown plants than in tissue-cultured plants at the later stages of growth. No phenotypic abnormality of the tissue-cultured plants was observed suggesting that genetic fidelity of tissue cultured plants can be maintained if appropriate plant growth regulators are used with fewer member of subcultures in the multiplication medium.

The purpose of this research is micropropagation of Ginkgo biloba L. Apical and nodal meristems removed from plantlets or apical buds from a tree were used as explants. Meristems produced an extensive callus and single or rare multiple shoots on Murashige and Skoog medium with different growth regulators and endosperm extract (En) obtained from mature seeds of the same species. For successful root production it was necessary to transfer the shoots to a rooting medium with En.

The primary phytotoxic effect of aluminum (Al) is confined to the root apex. It is a matter of debate whether the primary injury of Al toxicity is apoplastic or symplastic. This review paper summarizes our current understanding of the spatial and metabolic sites of Al phytotoxicity. At tissue level, the meristematic, distal transition, and apical elongation zones of the root apex are most sensitive to Al. At cellular and molecular level, many cell components are implicated in Al toxicity including DNA in nucleus, numerous cytoplastic compounds, the plasma membrane, and the cell wall. Although it is difficult to distinguish the primary targets from the secondary effects so far, understanding of the target sites of Al toxicity is helpful for elucidating the mechanisms by which Al exerts its deleterious effects on root growth.

This study reports survival and physiological responses of micropropagated Ceratonia siliqua L. cvs. Galhosa and Mulata plants during ex vitro acclimatization under ambient (AC; 330 μmol mol^-1) or elevated (EC; 810 μmol mol^-1) CO₂ concentration and a photosynthetic photon flux density of 125 μmol m^-2 s^-1. CO₂ enrichment during acclimatization did not improve survival rate that was around 80 % for both treatments. Eight weeks after ex vitro transplantation, photosynthetic capacity and apparent quantum yield in acclimatized leaves were higher in comparison with those in in vitro-grown leaves, without any significant difference between CO₂ treatments. Chlorophyll content increased after acclimatization. However, EC led to a decrease in the total amount of chlorophyll in new leaves of both cultivars, compared to those grown at AC. Soluble sugars and starch contents were not markedly affected by growth EC, although starch had significantly increased after transfer to ex vitro conditions. EC induced an increase in the stem elongation and in the effective life of leaves, and a decrease in the number of new leaves.

The aim of this work was to assess the responses of seedlings of five species of Nicotiana genus to red and far red radiation. N. acuminata exhibits positive photoblastic behaviour and germination was completely inhibited under far red and darkness. In N. glauca germination was reduced under far red and darkness, but the other species showed neutral behaviour. The hypocotyl elongation was inhibited in N. glauca and N. tabacum under white and far red radiation. In N. langsdorffii and N. debneyi hypocotyl was elongated under far red radiation. Only in N. acuminata red radiation promote greater hypocotyl elongation than dark condition. On the phylogenetic tree obtained from restriction analysis N. glauca and N. acuminata are grouped in one branch, while the other species, N. langsdorffii, N. debneyi and N. tabacum, are grouped in the other branch cluster. Moreover, the N. debneyi behaviours under different radiation treatments were similar to those of N. tabacum. These two species are allopolyploid members of the genus Nicotiana, as also was confirmed by this study.

Treatment of excised marrow (Cucurbita pepo L., zucchini) cotyledons with methyl ester of jasmonic acid (MeJA) had no effect on their growth in darkness. On the other hand, MeJA induced the synthesis of three polypeptides (69, 60 and 43 kDa) and stimulated the accumulation of other polypeptides (97.4 and 53 kDa). These changes in the polypeptide profile were accompanied by a suppression of total protein and RNA synthesis as well as the activity of nuclear RNA polymerases. In contrast to MeJA, N⁶-benzylaminopurine (BAP) significantly enhanced cotyledon growth and stimulated protein and RNA synthesis. Furthermore, BAP, when applied together with MeJA, was able to counteract some effects of MeJA including the appearance of specific MeJA-induced polypeptide bands.

Cell cycle events in embryo axes of Norway maple (Acer platanoides L.) seeds were studied during dormancy breaking by flow cytometric analyses of the nuclear DNA content and by immunodetection of β-tubulin. Most embryonic nuclei of dry, fully matured seeds were arrested in the G₂ phase of the cell cycle. In addition, the lowest content of β-tubulin was detected in dry, mature seeds. Imbibition in water and cold stratification resulted in a decrease in the number of nuclei in G₂, and a simultaneous increase in β-tubulin content. In germinated seeds the content of β-tubulin was the highest and the number of cells in G₂ was the lowest. Both cell cycle events preceded cell expansion and division and subsequent growth of the radicle through the seed coat. The anatomical investigation has proved that the main reason for decrease in the number of nuclei in G₂ is mitosis, started with seeds germination (radicle protrusion). The activation of the cell cycle and the β-tubulin accumulation were associated with embryo dormancy breaking.

Oat (Avena sativa L.) plants cultured in soil and hydroponic culture were treated with cadmium [0.154 mg g^-1 (dry soil) and 100 μM CdSO₄, respectively] for 21 d and growth rate and various biochemical processes were studied. Applied cadmium reduced plant growth and chlorophyll content. Changes in activity of enzymes involved in C, N and S metabolism and in guaiacol peroxidase activity were observed. In particular, O-acetylserine sulphydrylase (OASS; EC 4.2.99.8) activity was increased by Cd exposure in both growth conditions, probably as a resistance mechanism to cadmium based on the production of phytochelatins. Results show that both field and hydroponic conditions represent suitable systems for investigating Cd effects on plant growth and metabolism.

More than 500 isolates of bacteria were obtained from the aerial part and rhizosphere of sweet pepper (Capsicum annuum L.) plants harvested from different places in the Region of Murcia (Spain). The isolates were purified and assayed in vitro against Phytophthora capsici and Alternaria alternata. Sixty isolates (12 %) produced an inhibition zone against at least one of the pathogens, while ten had a strongly inhibitory effect on both pathogens assayed. Microscopic observation of interactions zone showed cell vacuolisation, hyphae lysis and spilling of cytoplasm content of the pathogens in the culture media. These ten isolates were then chosen for biocontrol of Phytophthora root rot and Alternaria leaf spots of pepper plants in vivo. Four of them denominated HS93, LS234, LS523 and LS674 reduced P. capsici root rot by 80, 51, 49 and 54 %, respectively, and A. alternata leaf spots by 54, 74, 62 and 53 %. HS93 belongs to the genus Bacillus and probably the species subtilis, while LS234, LS523 and LS674 belong to the genus Bacillus and probably the species licheniformis. Dry mass of plants treated with these bacteria was significantly higher than that of non-treated and inoculated plants.

Effects of NaCl on growth in vitro and contents of sugars, free proline and proteins in the seedlings and leaf explants of Nicotiana tabacum cv. Virginia were investigated. The fresh and dry mass of the seedlings decreased under salinity. These growth parameters in leaf explants decreased at 50 mM NaCl and increased up to 150 mM NaCl and then decreased at higher level of salinity. Free proline content in both seedlings and leaf explants increased and polysaccharide content decreased continuously with increasing of NaCl concentration. Reducing sugars, oligosaccharides, soluble sugars and total sugars contents in both seedlings and leaf explants decreased up to 150 mM NaCl and then increased at higher concentrations of NaCl.

Corchorus olitorius plants treated by 5 μg cm^-3 of Cd, Pb, Al or Cu in hydroponic culture accumulated in leaves 190, 150, 350 and 325 μg g^-1(d.m.) of these metals, respectively, after 6 d of exposure. Exposure of Corchorus plants to tested metals resulted in a sharp rise in content of amino acids in leaf tissues, however the magnitude of accumulation was different from one metal to another. Presence of sulphur in the growth medium significantly increased uptake of Cd and Pb and cysteine (cyst) was more effective than K₂SO₄. Similarly, addition of salicylic acid (SA) in the growth medium significantly enhanced the ability of Corchorus plants to accumulate all these metals. Growth of Corchorus plants was significantly reduced by treatment with any of the four metals except Cu and added cyst, K₂SO₄ or SA alleviated the growth retarding effect of metals.

In vitro regeneration from leaf, cotyledon and hypocotyl explants of six cultivars belonging to three species of Capsicum was achieved by direct organogenesis. The cultivar Umorok showed the best response while Meiteimorok, Haomorok, Mashingkha and Uchithi showed intermediate response and the cultivar Chiengpi was the least responsive. Leaf and cotyledon explants regenerated more shoots than hypocotyl explants and the maximum number of shoots were produced on Murashige and Skoog (1962) medium containing 8.8 µM 6-benzylaminopurine (BAP) with 11.4 µM indole-3-acetic acid (IAA). Elongation of shoot buds derived from different explants was achieved on medium containing 2.8 µM IAA and the elongated shoots were rooted on medium containing 2.8 or 5.7 µM IAA and 2.4 or 4.9 µM indole-3-butyric acid (IBA). Four-week old rooted plantlets were hardened and transplanted to the soil. The plantlets showed 90 % survival during transplantation.

Effects of exogenous salicylic acid (SA) on plant growth, contents of Na, K, Ca and Mg, activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR) and catalase (CAT), and contents of ascorbate and glutathione were investigated in tomato (Lycopersicon esculentum L.) plants treated with 100 mM NaCl. NaCl treatment significantly increased H₂O₂ content and lipid peroxidation indicated by accumulation of thiobarbituric acid reactive substances (TBARS). A foliar spray of 1 mM SA significantly decreased lipid peroxidation caused by NaCl and improved the plant growth. This alleviation of NaCl toxicity by SA was related to decreases in Na contents, increases in K and Mg contents in shoots and roots, and increases in the activities of SOD, CAT, GPX and DHAR and the contents of ascorbate and glutathione.

Two vacuolar green fluorescent proteins (GFP) were stably inserted in Nicotiana tabacum and Nicotiana benthamiana genome, with unexpected difficulties, and compared with A. thaliana cv. Wassilewskaja transgenic plants expressing the same constructs. GFP fluorescence was strong in all tissues of A. thaliana but it was barely visible in Nicotiana. Confocal microscopy analysis revealed a variable distribution of the marker in those cells where GFP fluorescence was visible. The role of light dependent proteases was the variable pointing out more inter-species diversity. GFPs degradation was much higher in Nicotiana spp. than in A. thaliana. The version of GFP used appeared not to be a good vacuolar marker for Nicotiana differentiated tissues, although it can efficiently label vacuoles in protoplasts or calli. Nevertheless the sensitivity of the reporter protein can be used as an indicator of hidden characteristics of the plant vacuoles, revealing differences otherwise invisible. One of the markers in our system, GFP-Chi, evidenced a clear morphological difference in the vacuolar system of guard cells of the three species.

Carnation plantlets (Dianthus caryophyllus L.) cultured in vitro often develop morphological and physiological anomalies, a phenomenon called hyperhydricity, which impairs their survival ex vitro. When the agar concentration of the growth medium was increased (from 0 to 12 g dm^-3), thereby reducing water availability, the hyperhydricity of those adventitious shoots regenerated from carnation petals decreased. This was accompanied by a progressive fall in the water content of shoots (94.9 to 91.4 %), fresh mass (from 57.2 to 1.8 mg), number of leaf parenchyma cell layers (from 9.3 to 7.7), and the size of these cells (from 968 to 254 µm²). However, the number of regenerated shoots also decreased (17.7 in 2 g dm^-3 agar to 4.3 in 12 g dm^-3). Similarly, in ventilated tubes, which exhibit a lower relative humidity than tightly closed tubes, shoot organogenesis diminished up to 28 %, in tandem with shoot water content. Thus, relative humidity and water availability in culture vessels do not only influence shoot hyperhydricity in carnations, but also greatly affect adventitious shoot organogenesis.

Biological control of wilt of egg plant (Solanum melongena L.) caused by Fusarium solani was made with the application of five Trichoderma species, T. harzianum, T. viride, T. lignorum, T. hamatum and T. reesei. The effect of volatile and non-volatile antibiotics of Trichoderma origin on growth inhibition of the wilt pathogen was studied. T. harzianum showed maximum growth inhibition (86.44 %) of the pathogen through mycoparasitism. The non-volatiles produced by the Trichoderma species exhibited 100 % growth inhibition of the pathogen under in vitro condition. Production of siderophores and fungal cell wall degrading enzymes, chitinase and β-1,3-glucanase were found. Treatments with two most efficient Trichoderma species, T. harzianum and T. viride resulted in the decreasing population of Fusarium solani in soil thereby deterring disease incidence in field condition.

Experiments were performed to evaluate the capacity of quince (Cydonia oblonga Mill.) leaves to regenerate somatic embryos and shoots and/or roots simultaneously. Leaves, treated for 2 d in liquid medium containing 2.5 mg dm^-3 2,4-dichlorophenoxyacetic acid were cultured for 0, 3, 6, 9, 12, 15, 18, 21 d on a gelled medium supplemented with 1 mg dm^-3 kinetin (Kin) and 0.1 mg dm^-3 naphthalenacetic acid (NAA) and were transferred to a medium either without growth regulator (GR-) or containing 0.6 mg dm^-3 6-benzylaminopurine (BA) + 0.2 mg dm^-3 gibberellic acid (GA₃) + 0.06 mg dm^-3 indole-3-butyric acid (IBA) (GR+). Leaves producing somatic embryos (SEs) only, or adventitious roots (Rs) only, or SEs+Rs simultaneously, were detected on GR- culture medium; on GR+ medium, leaves producing adventitious shoots (Ss) only, SEs+Ss or SEs+Rs+Ss simultaneously, also appeared. Leaves producing both Ss+Rs were never detected. Proportions among the various types of regenerating leaves varied according to both the length of Kin+NAA treatment and the presence or absence of GR in the transfer medium. The greatest variations, both on GR- and on GR+, took place within the first 9 d of culturing on Kin+NAA. After this period, no further substantial differences in the trend of each type of regenerating leaf were observed. The length of the treatment with Kin+NAA also modified the proportions between the different types of morphogenic structures.

Shoot buds were induced directly on either side of midrib from adaxial surface of immature leaf explants in Stevia rebaudiana Bertoni five weeks after culturing in Murashige and Skoog's nutrient medium supplemented with 8.88 µM of N ⁶-benzylaminopurine and kinetin ranging from 4.65 to 6.98 µM. Immature leaves of 0.6 to 1 cm were found to produce best response (93 %) with a highest number of 4.93 shoot buds per explant. For elongation of regenerated shoot buds, MS medium supplemented with 30 g dm^-3 sucrose and indole-3-butyric acid (IBA) ranging from 4.92 to 7.38 µM were found most suitable. The medium was further modified to suit bioreactor cultivation of regenerated shoots wherein the use of two-fold MS salts and 60 g dm^-3 sucrose resulted in a high biomass yield of 50.68 g dm^-3 (m/v) accounting for about 590 micro-cuttings in three weeks. Best rooting of micro-cuttings occurred in half strength MS medium supplemented with IBA ranging from 4.92 to 7.38 µM, 15 g dm^-3 sucrose and gelled with 0.8 % agar. Rooted plants were successfully established in substrate containing sand, Vermicompost and garden soil in equal proportions and grown in greenhouse. This is the first report on direct shoot regeneration from Stevia leaves.

Three constructs harbouring novel Bacillus thuringiensis genes (Cry1C, Cry2A, Cry9C) and bar gene were transformed into four upland cotton cultivars, Ekangmian10, Emian22, Coker201 and YZ1 via Agrobacterium-mediated transformation. With the bar gene as a selectable marker, about 84.8 % of resistant calli have been confirmed positive by polymerase chain reaction (PCR) tests, and totally 50 transgenic plants were regenerated. The insertions were verified by means of Southern blotting. Bioassay showed 80 % of the transgenic plantlets generated resistance to both herbicide and insect. We optimized conditions for improving the transformation efficiency. A modified in vitro shoot-tip grafting technique was introduced to help entire transplantation. This result showed that bar gene can replace antibiotic marker genes (ex. npt II gene) used in cotton transformation.

Salinity reduced mung bean (Vigna radiata Wilczek) radicle and root elongation, delayed and inhibited hypocotyl elongation and mobilization of reserves from the cotyledons to the embryo axis. Fresh and dry masses and water content of the embryo axes were reduced. Under salinity, a net leakage of K to the media increased with time and increasing NaCl concentrations. Sugars present in the cotyledons of seeds were of primary importance for growth of the embryo axis upto 18 h after sowing whereas breakdown of starch by amylase contributed later, the contribution being delayed and reduced with increasing NaCl concentration. Even when amylase activity in the cotyledons was progressively reduced with increasing NaCl concentration, the increasing contents of soluble sugars in the cotyledons indicated that sugars were not limiting for mung bean seedling growth under salinity.

Calcium chloride (0.3 or 10 mM) was applied to the growth medium before, together with, or after sodium chloride application, and the effect of the timing of Ca application on the alleviation of salt stress was investigated. Seedlings of maize, tall fescue, and reed canarygrass were grown in medium with 0 and 200 mM NaCl for 5 d. Regardless of the plant species the maximum alleviation of NaCl stress was achieved when CaCl₂ and NaCl coexisted in the growth medium. The effects of Ca application were connected with the decrease in the Na content in the plant roots and shoots and increased ATPase activity in the roots.

The Agrobacterium-mediated transformation was done in rice (Oryza sativa L. var. indica) cv. HKR126 and elite cross-bred cv. Pusa Basmati1 (PB1), using strain LBA4404 containing pCAMBIA1300 cloned with gene cassettes; potato proteinase inhibitor and Bacillus thuringiensis endotoxin (plasmid JDW53) or mannitol-1-phosphate dehydrogenase (plasmid RKJ108). Co-cultivation with scutellar-calli derived from mature seeds showed stable and highly efficient transformation. In cvs. HKR126 and PB1, 35 % and 41 % of hygromycin resistant calli were obtained. The transformation efficiency in PB1 (22.0 %) was much higher than in HKR126 (12.5 %). Similarly, PB1 had higher plant regeneration efficiency than HKR126. The shoots regenerated per callus were, 3-4 in HKR126 and 5-6 in PB1. The transformation efficiency with pRKJ108 (18.6 %) was higher than pJDW53 (15.9 %). Polymerase chain reaction (PCR) analysis showed the presence of transgenes in regenerated transgenic plants of both cultivars.

The review summarizes the level of current knowledge of impacts of vernalization and photoperiod on the induction and maintenance of frost tolerance (FrT) in wheat and barley. The phenomenon of vernalization is briefly described and the major vernalization (VRN) loci are characterised. Vernalization requirement and the three major growth habits of Triticeae (facultative, winter and spring) are defined on the basis of the two-locus VRN-2/VRN-1 epistatic model. Major photoperiodically regulated genes, which influence the transition to flowering, are characterised and their interactions with VRN genes are briefly discussed. The phenomenon of induction of FrT during the process of cold acclimation (CA) is described and the major cold-induced Cor/Lea genes are listed. Important regulatory mechanisms, i.e., CBF pathway, controlling the expression of Cor/Lea genes under cold, are discussed. The major loci affecting the development of FrT in Triticeae, the Fr loci, are characterised. In conclusion, current progress in this research field is summarized and new questions arising in the area are formulated.

The daily dynamics of CO₂ concentration in the culture vessels and the photoautotrophic or photomixotrophic growth capacity of apple (Malus pumila hybrid MM 106 paradisiaca× Northern Spy) cultures were studied. The photoautotrophic cultures were grown on a sugar-free growth medium and submitted (0S+CO₂) or not (0S-CO₂) to periodic injections of exogenous CO₂. The photomixotrophic cultures were grown in the presence of 30 g dm^-3 sucrose, with (30S+CO₂) or without (30S-CO₂) CO₂ enrichment. The photosynthetic photon flux density applied was of 210 ± 5 μmol m^-2s^-1. In the 0S-CO₂ treatment, CO₂ showed rather uniform and narrow light-dark fluctuations throughout the culturing cycle. In the 30S-CO₂ treatment, the daily ratio between CO₂ produced during the dark period and that uptaken during the following light period, was almost always above 1 with the only exception of a few days (from the 5^th to the 9^th day) when the amount of photosynthesised CO₂ was equal to or higher than that produced during dark respiration. The 0S+CO₂ cultures needed to be enriched all days with exogenous CO₂ to avoid periods of gas deficiency while in 30S+CO₂ the CO₂ injected the first culturing day was uptaken over 5 d; thereafter, daily injections were necessary. Culture fresh and dry mass, number of newly formed shoots and number of nodes per shoot in 0S+CO₂ treatment did not statistically differ from the values obtained with 30S-CO₂. The highest growth was observed in 30S+CO₂ treatment. The increase in culture fresh mass due to 1 μmol of CO₂ added to the culture vessels was 1.54 and 1.36 mg for 30S and 0S respectively, while in terms of dry mass the increase was about 2.5 times higher in the sugar-enriched treatment. CO₂ enrichment accounted for 77.3 % and 21.2 % of the final fresh mass in 0S+CO₂ and 30S+CO₂, respectively.

Senescence is a genetically regulated process that involves decomposition of cellular structures and distribution of the products of this degradation to other plant parts. Reactions involving reactive oxygen species are the intrinsic features of these processes and their role in senescence is suggested. The malfunction of protection against destruction induced by reactive oxygen species could be the starting point of senescence. This article reviews biochemical changes during senescence in relation to reactive oxygen species and changes in antioxidant protection.