Maize (Zea mays L.) is generally considered to be a plant with aerenchyma formation inducible by environmental conditions. In our study, young maize plants, cultivated in various ways in order to minimise the stressing effect of hypoxia, flooding, mechanical impedance or nutrient starvation, were examined for the presence of aerenchyma in their primary roots. The area of aerenchyma in the root cortex was correlated with the root length. Although 12 different maize accessions were used, no plants without aerenchyma were acquired until an ethylene synthesis inhibitor was employed. Using an ACC-synthase inhibitor, it was confirmed that the aerenchyma formation is ethylene-regulated and dependent on irradiance. The presence of TUNEL-positive nuclei and ultrastructural changes in cortical cells suggest a connection between ethylene-dependent aerenchyma formation and programmed cell death. Position of cells with TUNEL-positive nuclei in relation to aerenchyma-channels was described.

We followed the diurnal cycles of isoprenoid emissions from Quercus ilex seedlings under drought and after re-watering. We found that Quercus ilex, generally considered a non-isoprene emitter, also emitted isoprene although at low rates. The emission rates of isoprene reached 0.37 ± 0.02 nmol m^-2 s^-1 in controls, 0.15 ± 0.03 nmol m^-2 s^-1 under drought and 0.35 ± 0.04 nmol m^-2 s^-1 after re-watering, while emission rates of monoterpenes reached 11.0 ± 3.0, 7.0 ± 1.0 and 23.0 ± 5.0 nmol m^-2 s^-1, respectively. Emission rates recovered faster after re-watering than photosynthetic rate and followed diurnal changes in irradiance in controls and under drought, but in leaf temperature after re-watering.

To study the effect of sucrose on the sink-source relationship in in vitro-grown plants, Cistus incanus seedlings and plantlets were grown horizontally in a two-compartment Petri dish (split dish), with the root system in one compartment and the shoot in the other. Shoots and roots were exposed to different sucrose concentrations (0-30 g dm^-3), two irradiance levels (25 and 160 µmol m^-2s^-1) and the presence or absence of a minimum medium containing minerals and vitamins (M medium). Root and shoot biomass of the seedlings was enhanced by an increase in irradiance when the growth medium was not supplemented with sucrose indicating the role of photosynthesis in biomass production. When sucrose was added to either organ growth was enhanced as well. In the presence of sucrose in the root compartment, sucrose applied to the shoot compartment enhanced growth of both organs under low irradiance, while under high irradiance, sucrose had no further additive effect. In the absence of sucrose in the root compartment, the enhancement of root biomass by sucrose added to the shoot compartment was lower under high irradiance than under low irradiance. The response of Cistus plantlets to sucrose and irradiance differed from that of seedlings, probably reflecting a greater susceptibility of the plantlets to sucrose feedback inhibition on photosynthesis and biomass accumulation. The decrease in root and shoot growth when M medium was added to the shoot compartment and the relatively better growth of these organs when the roots were supplied with minerals and the shoot with sucrose, indicate that growth of the two organs in our experimental set-up was regulated by opposing fluxes of C and nutrients.

The lengths of open reading frame (ORF)100 and ORF29-TrnC^GCA, the intronic sequence of rps16 and the transcribed spacer of TrnT^UGU-TrnL^UAA in chloroplast from different lines of cytoplasmic male sterility (CMS) rice were studied using indica types, japonica types and common wild rice as controls. The results show that the lengths of ORF100 and ORF29-TrnC^GCA in CMS lines are similar to those of typical indica. The sequences of the rps16 intron and the TrnT^UGU-TrnL^UAA spacer in sporophyte sterile types (wild-abortive type, Yinshui type and K type) are almost the same, and they also share a molecular marker of GTTGAG at nucleotide positions 220-225 in the rps16 intron. Therefore, it is speculated that the source of these three types is the same. In contrast, a gametophyte sterile type, Yuetai A does not contain such a GTTGAG sequence in the rps16 intron and has a unique G at position 595, which may works as a molecular marker distinguishing the sporophyte sterile type from the gametophyte sterile type. Based on the observation that CMS rice has much lower cytoplasmic polymorphism than indica, japonica and wild rice, it is concluded that CMS rice lack cytoplasm diversity. Therefore, it is important to introduce new sources of cytoplasm into hybrid rice.

We studied changes in physiological parameters of whole leaves and in antioxidant protection of chloroplasts during ageing and senescence of tobacco (Nicotiana tabacum L. cv. Samsun NN) leaves with enhanced cytokinin oxidase/dehydrogenase activity (CKX) or without it (WT). Old leaves of CKX plants maintained higher pigment content and photosystem 2 activity compared to WT leaves of the same age. Chloroplasts of old CKX plants showed better antioxidant capacity represented by higher superoxide dismutase, dehydroascorbate reductase and glutathione reductase activities.

Na⁺ accumulation was investigated in the roots of 11-d-old cowpea [Vigna unguiculata (L.) Walp.] plants. The relative contribution of different membrane transporters on Na⁺ uptake was estimated by applying Ca²⁺, K⁺, NH₄ ⁺, and pharmacological inhibitors. Na⁺ accumulation into the root symplast was decreased by half in the presence of 1 mM Ca²⁺ and it was almost abolished by 100 mM K⁺. The inhibitory effect of external NH⁴⁺ on Na⁺ accumulation was more pronounced in the roots of NH₄ ⁺-free growing plants. Na⁺ accumulation was reduced about 73 % by 0.1 mM flufenamate and it was almost blocked by 2 mM quinine. In addition, 20 mM tetraethylammonium and 1.0 mM Cs⁺ decreased Na⁺ accumulation by 28 and 30 %, respectively. These results evidenced that low-affinity Na⁺ uptake by cowpea roots depends on Ca²⁺-sensitive and Ca²⁺-insensitive pathways. The Ca²⁺-sensitive pathway is probably mediated by nonselective cation channels and the Ca²⁺-insensitive one may involve K⁺ channels and to a lesser extent NH₄ ⁺-sensitive K⁺ transporters.

The relative water content (RWC), cell membrane integrity, protein pattern and the expression of late embryogenesis abundant proteins (LEA; group 1, 2, 3 and 4) under different levels of salt stress (0, 1.0, 1.5 and 2.0 % NaCl) were investigated in mulberry (Morus alba L.) cultivars (S1 and ATP) with contrasting salt tolerance. RWC and membrane integrity decreased with increase in NaCl concentration more in cv. ATP than in cv. S1. SDS-PAGE protein profile of mulberry leaves after the NaCl treatments showed a significant increase in 35, 41, 45 and 70 kDa proteins and significant decrease in 14.3, 18, 23, 28, 30, 42, 47 and 65 kDa proteins. Exposure of plants to NaCl resulted in higher accumulation of LEA proteins in S1 than ATP. The maximum content of LEA (group 3 and 4) was detected in S1 at 2.0 % NaCl, which correlates with its salt tolerance.

The leaf water potential, gas exchange and chlorophyll fluorescence were evaluated in five common bean (Phaseolus vulgaris) genotypes A222, A320, BAT477, Carioca and Ouro Negro subjected to moderate water deficit. At the maximum water deficit (10 d of water withholding), the leaf water potential of genotypes A320 and A222 was higher (-0.35 and -0.50 MPa) when compared to the other genotypes (-0.67 to -0.77 MPa). The stomatal conductance and net photosynthetic rate were significantly reduced in all genotypes due to the water deficit. The greater reduction in stomatal conductance of A320 under drought resulted in high intrinsic water use efficiency. Mild water deficit affected the photochemical apparatus in bean genotypes probably by down-regulation since plants did not show photoinhibition. The photochemical apparatus of A222 and A320 genotypes was more sensitive to drought stress, showing reduced apparent electron transport even after the recovery of plant water status. On the other hand, even after 10 d of water withholding, the maximum efficiency of photosystem 2 was not affected, what suggest efficiency of the photoprotection mechanisms.

Long-term (30 d) effects of 100, 200, 300, and 400 mM NaCl on photosystem 2 (PS 2)-mediated electron transport activity and content of D1 protein in the thylakoid membranes of chrysanthemum (Dendranthema grandiflorum) cultured in vitro at low irradiance 20 µmol(photon) m^-2 s^-1 were investigated. 100 mM NaCl increased contents of chlorophylls (Chl) a and b, carotenoids (Car; xanthophylls + carotenes), and the ratio of Chl a/b, and Car/Chl a+b. However, further increase in NaCl concentration led to the significant reduction in the contents of Chl a, and Chl b, and increase in the ratio of Chl a/b and Car/Chl a+b. NaCl treatment decreased the PS 2-mediated electron transport activity and contents of various thylakoid membrane polypeptides including D1 protein.

In vitro organogenesis of Citrus volkameriana and C. aurantium was studied considering three explant types: epicotyl segment, internodal segment, and hypocotyl segment with attached cotyledon fragment. The explants were cultured in medium according to Grosser and Gmitter (EME) supplemented with 0, 0.5, 1.0, 1.5, and 2.0 mg dm^{- 3} 6-benzyl-aminopurine (BAP), incubated firstly in darkness for 4 weeks, and then transferred to 16-h photoperiod for 2 weeks. Comparing epicotyl and internodal segments, a higher percentage of responsive explants and a higher number of shoots per explant were obtained with epicotyl segments, regardless of the BAP concentration. For C. volkameriana the highest percentage of responsive epicotyl segments (42 %) was obtained in EME with 1.0 mg dm^-3 BAP, while for C. aurantium (59 %) in EME with 0.5 mg dm^-3 BAP. The organogenesis efficiency was the best with the use of the hypocotyl segment with attached cotyledon fragment (77 % for C. volkameriana and to 75 % for C. aurantium). With this explant the morphogenesis occurred only in the hypocotyl region. The in vitro organogenesis was characterized by histological analyses showing that the morphogenic process started in the cambium region near the explant cut end.

Cuttings of Populus kangdingensis and Populus cathayana, originating from high and low altitudes in the eastern Himalaya, respectively, were examined during one growing season in a greenhouse to determine their responses to drought stress (soil moisture decreased from 100 to 55 or 25 % field capacity). Compared to control plants grown under 100 % field capacity, those poplars grown under 55 and 25 % field capacity possessed lower increases in height and stem diameter, and higher contents of soluble sugars, free proline, malondialdehyde (MDA) and hydrogen peroxide, and higher activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR). Compared with P. cathayana with greater leaf area, P. kangdingensis with greater root/shoot ratio exhibited lower MDA and H₂O₂ contents, higher soluble sugar and free proline contents, and higher activities of CAT, SOD, POD, APX and GR. These results suggested that P. kangdingensis was more drought tolerant than P. cathayana.

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.

MADS-box genes are known to be important for the development of flowers. Two MADS-box genes (MCAG2 and MCAG6) were isolated from the bitter gourd (Momordica charantia) female bud based on the MADS-box conserved sequences. The complete cDNA sequences of MCAG2 and MCAG6 encode a 231 and a 247 amino acid protein, respectively. Sequence comparison and phylogenetic analysis showed that MCAG2 and MCAG6 had high identities of amino acid with AG-like and AGL6-like genes, respectively. The alignment of the deduced amino acid sequence of AGL6-like genes revealed that there were two highly conserved regions in the C-terminus, which were designated AGL6 motif I and AGL6 motif II. Phylogeny reconstructions suggested that AGL6-like genes were divided into three major clades. RT-PCR analysis of the MCAG2 and MCAG6 genes showed that they were both expressed in floral organs at different levels. However, MCAG6 was also expressed highly in shoot apex. Quantitative real-time reverse transcriptase-polymerase chain reaction analysis indicated that the expression of MCAG2 was detected at high levels in carpel, whereas MCAG6 was detected at high levels in shoot apex. The gene expression patterns suggest that MCAG2 and MCAG6 have a role in regulating bitter gourd floral development.

The effect of cadmium on growth and contents of glutathione (GSH) and phytochelatins (PCs) were investigated in roots and leaves of tomato plants (Lycopersicon esculentum Mill. cv. 63/5 F1). The accumulation of Cd increased with external Cd concentrations and was considerably higher in roots than in leaves. Dry mass production decreased under Cd treatment especially in leaves. In both roots and leaves, exposure to Cd caused an appreciable decline in GSH contents and increase in PCs synthesis proportional to Cd concentrations in the growth medium. At the same Cd concentration, PCs production was higher in roots than in leaves. The implication of glutathione in PC synthesis was strongly suggested by the use of buthionine sulfoximine (BSO). The major fraction of Cd accumulated by tomato roots was in the form of a Cd-PCs complex.

The influence of artificial wounding on biosynthesis of flavonoids and hydroxycinnamic acids was studied in bilberry leaves using two separate wounding experiments. In the first experiment bilberry leaves were wounded by cutting. The expression of the first gene from flavonoid pathway, chalcone synthase (CHS) and a wound induced pathogenesis related PR-10 gene was analysed from samples collected immediately and after 3, 6, 24 h and 4 d from the wounding treatment. In the second experiment annual shoots were removed. Proanthocyanidins, flavonol glycosides and hydroxycinnamic acids were quantified in leaf samples after 0-5 d (experiment 1) and 5 weeks (experiment 2) from the treatment. In the first experiment, no change was observed in the expression of CHS whereas increase in expression of PR-10 gene was detected after 6 h of wounding treatment. In both experiments, the contents of flavonol glycosides and hydroxycinnamic acids were not influenced by the wounding treatment and the contents of proanthocyanidins were decreased.

The nucleolar vacuole formation in soybean root meristematic cells from seedlings grown 3 d at temperature 25 °C (control), 3 d at temperature 25 °C and then transferred to 10 °C (chilling) for 4 d, and after recovery for 1.5, 3, 6, 12 and 24 h at 25 °C were observed on semi-thin sections. Simultaneously, autoradiographic studies with ³H-uridine on squashed preparations were carried out. During recovery of plants, the number of vacuolated nucleoli increased gradually from 24 % after 1.5 h up to 40 % after 24 h, while in the control there were 18 % of nucleoli with vacuoles and after 4-d chilling only 5 %. Labelling of cells during 20-min incubation in ³H-uridine and during 80-min post-incubation in non-radioactive medium was increased in recovered plants in comparison with the control and chilled plants. The conclusion has been drawn that nucleolar vacuoles in soybean plants are formed as a result of migration of granular component accumulated in nucleolus during 4-d chilling.

The in vitro response of sweet cherry (Prunus cerasus × P. canescens) rootstock Gisela 5 to increasing water deficit in the culture medium was studied. Water stress induced by the incorporation of 1, 2 and 4 % polyethylene glycol (PEG-8000) into the Murashige and Skoog medium was applied for 6 weeks. PEG-induced water stress reduced shoot dry mass, length, water content and relative chlorophyll content. Water stress also induced leaf necrosis without causing loss of viability in the explants. The increase in malondialdehyde content indicated oxidative stress. The activities of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POX) and glutathione reductase (GR) were also significantly elevated. The concentrations of K, Ca, Fe and Mn of shoots were decreased.

The effect of different oxygen availability on the nitrate reductase (NR, EC 1.6.6.1) activity in cucumber roots was studied. NR activity measured in the presence of Mg²⁺ (actual NR activity) as well as activity measured with EDTA (maximum NR activity) increased distinctly after 30 min of root incubation in a medium flushed with N₂ (anaerobic conditions). In contrast, aeration of roots (aerobic conditions) decreased both enzyme activities. Such inactivation of NR was rapidly reversed after transferring the roots to anaerobic conditions. An air-induced decrease of the actual enzyme activity was prevented by staurosporin, a protein kinase inhibitor; whereas microcistin LR, an inhibitor of protein phosphatases, completely eliminated the reactivation of NR actual activity under limited oxygen availability. An increase of the NR actual activity in roots incubated in a nitrogen-flushed buffer was correlated with a lower content of ATP in root tissues. These data suggest that reversible protein phosphorylation is involved in the regulation of NR activity under limited oxygen. On the other hand, feeding roots with inhibitors of protein kinases as well as phosphatases did not affect the maximal activity of NR indicating that other modification(s) of enzyme activity could also function in cucumber roots. Since the changes in the expression level of gene encoding nitrate reductase (CsNR) under different oxygen availability were not correlated with the enzyme activity, the transcription level of oxygen action was excluded. On the other hand, it was demonstrated that oxygen-induced alteration of NR was dependent on the ratio of oxidized/reduced pyridine nucleotides in tissues. In aerobic conditions, when maximal NR activity was inhibited, a drop of the NAD(P)H level was also observed. These data point to hysteretic modifications of NR protein induced by NAD(P)H as the target of reversible and rapid changes in maximal enzyme activity under different oxygen availability.

Two dimensional polyacrylamide gel electrophoresis (2D-PAGE) was used to identify differentially expressed proteins in wild-type (DP 5690) and fiberless (SL 1-7-1) cotton ovules. One protein, designated V2 was unique to ovules of the fiber producing DP 5690 line. The protein was purified from 2D-PAGE of 4 d post anthesis DP 5690 ovules and partially sequenced. The short amino acid sequence was nearly identical to the deduced amino acid sequence for cotton phenylcoumaran benzylic ether reductase (PCBER) protein. A consensus sequence was assembled from ESTs encoding cotton PCBER genes, primers were designed, and a full length gene was amplified from plasmid DNA from a 72 h etiolated cotton cotyledon library. The polymerase chain reaction generated a 950 bp product with unique EcoRI (5') and (3') KpnI restriction sites for directional insertion into the expression vector pPICZA. Nucleotide sequencing was performed, and the full length coding region was 924 bp encoding a protein of 308 amino acids. The molecular mass and pI measured (2D PAGE) were similar to the theoretical protein.

Agrobacterium tumefaciens strain EHA105 carrying a binary vector pCAMBIA2301, which contains a neomycin phosphotransferase gene (nptII) and a β-glucuronidase (GUS) gene (uidA) interrupted with an intron, was used for transformation of Vigna mungo cotyledonary node explants. Various factors such as preculture and wounding of explants, manipulations in inoculation and co-cultivation conditions were found to play a significant role in influencing tissue competence, Agrobacterium virulence and compatibility of both, for achieving the maximum transformation frequencies. The stable transformation with 4.31 % efficiency was achieved using the optimized conditions. The transformed green shoots that were selected and rooted on medium containing kanamycin and tested positive for nptII gene by polymerase chain reaction were established in soil to collect seeds. GUS activity was detected in leaves, roots, pollen grains and T₁ seedlings. Southern analysis of T₀ plants showed the integration of nptII into the plant genome.

The role of irradiance on the activity of antioxidant enzymes: superoxide dismutase (SOD) and catalase (CAT) was examined in the leaves of Pisum sativum L. plants grown under low (LL) or high (HL) irradiance (PPFD 50 or 600 µmol m^-2 s^-1) and exposed after detachment to 5 mM Pb (NO₃)₂ for 24 h. The activities of both enzymes increased in response to LL compared with HL and no effect of Pb ions was observed. Photosystem (PS) 1 and PS 2 activities were also investigated in chloroplasts isolated from these leaves. LL lowered PS 1 electron transport rate and changes in photochemical activity of PS 1 induced by Pb²⁺ were visible only in the chloroplasts isolated from leaves of LL grown plants. PS 2 activity was influenced similarly by Pb ions at both PPFD. This study demonstrates that leaves of HL grown plants were less sensitive to lead toxicity than those from LL grown plants. Changes in electron transport rates were the main factors responsible for the generation of reactive oxygen species in the chloroplasts and as a consequence, in induction of antioxidant enzymes.

Heat caused reduction in membrane protein thiol content, increased accumulation of thiobarbituric acid reactive substances and reduced germination rate and early growth in germinating Amaranthus lividus seeds. Imposition of heat stress during early germination also causes accumulation of reactive oxygen species like superoxide and hydrogen peroxide while activities of antioxidative enzymes catalase, ascorbate peroxidase, and glutathione reductase decreased. Calcium chelator (EGTA), calcium channel blocker (LaCl₃) and calmodulin inhibitor (trifluroperazine) aggravated these effects. Added calcium reversed the effect of heat, implying that protection against heat induced oxidative damage and improvement of germination requires calcium and calmodulin during the recovery phase of post-germination events in Amaranthus lividus.

Immature and mature zygotic embryos were used as source of explants for induction of somatic embryogenesis in Araucaria angustifolia. Embryogenic cultures (EC) were only obtained from immature zygotic embryos. Basic medium, carbon source, and genotype showed a significant influence on the formation of stage I somatic embryos (SE). When EC were submitted to maturation conditions, SE continued their individual development until stage II, but mature embryos were not obtained. Proteins secreted by embryogenic cultures were, to a certain degree, genotype specific and included an extracellular class IV chitinase and β-1-3-glucanase.

Phosphoenolpyruvate carboxylase (EC 4.1.1.31, PEPC) in the three crassulacean acid metabolism (CAM) plants: Kalanchoë pinnata, K. daigremontiana and Ananas comosus (pineapple) undergoes regulatory phosphorylation during the dark period. We cloned PEPC kinase gene from two CAM Kalanchoë species using conventional RT-PCR approach. The PEPC kinase transcripts comprise only a protein kinase catalytic domain, encoding 272-276 amino acids with predicted M_r of 30.6-31.0 kDa. The expression of PEPC kinase gene in the Kalanchoë species was abundant at the beginning of dark phase, but that in pineapple cross-hybridized with Kalanchoë PEPC kinase probes was abundant at the end of dark phase. The PEPC kinase was encoded by a small gene family containing at least two members in each species. Treatment of detached leaves with the protein synthesis inhibitors cycloheximide and puromycin blocked the nocturnal appearance of PEPC kinase activity and maintained PEPC in the dephosphorylated state in the three CAM species. The calcium/calmodulin antagonist W7 blocked the apparent phosphorylation state of PEPC in pineapple, but not in Kalanchoë species. Furthermore, the transcript abundance of PEPC kinase matched the apparent in vivo phosphorylation state of PEPC in the Kalanchoë species, but unmatched that in the pineapple. These results implicated that the phosphorylation state of PEPC in Kalanchoë species is largely controlled by PEPC kinase transcript abundance, while that in pineapple may be controlled by both PEPC kinase transcript abundance and Ca²⁺-dependent protein kinase (CDPK).

Trigonelline (TRG) is known as a compatible solute in response to stress as well as a cell cycle regulator, and is more concentrated in legumes than other non-legume dicots. Four Glycine max L. genotypes (Essex, ExF 67, Forrest and Stressland) were used to examine TRG concentration in seeds and seedlings exposed to 30 or 100 mM NaCl, and to determine the association of TRG concentrations in seedlings with seedling growth. Seed germination across genotypes was inhibited by elevated salinity (71-91 %) in ExF 67 and Forrest and by accelerated aging (77-92 %) in Forrest. Length of seedlings in most genotypes stressed with NaCl apparently decreased. The TRG content in mature seeds of four genotypes was 44.4-74.6 µg g^-1(d.m.). TRG content significantly increased during early young seedling development, but remained or significantly reduced in some genotypes stressed with NaCl.

To investigate the molecular mechanisms of Al toxicity, cross-species cDNA array approach was employed to identify expressed sequence tags (ESTs) regulated by Al stress in root tips of Al-tolerant maize (Zea mays) genotype Cat100-6 and Al-sensitive genotype S1587-17. Due to the high degree of conservation observed between sugarcane and maize, we have analyzed the expression profiling of maize genes using 2 304 sugarcane (ESTs) obtained from different libraries. We have identified 85 ESTs in Al stressed maize root tips with significantly altered expression. Among the up-regulated ESTs, we have found genes encoding previously identified proteins induced by Al stress, such as phenyl ammonia-lyase, chitinase, Bowman-Birk proteinase inhibitor, and wali7. In addition, several novel genes up-and downregulated by Al stress were identified in both genotypes.

The influences of cefotaxime and carbenicillin on regeneration potential of wheat (Triticum aestivum L.) mature embryos were investigated. Filter-sterilized cefotaxime enhanced regeneration capacity although it did not affect the average number of shoots per explant. The highest regeneration capacity of 55.4 % was obtained on regeneration medium supplemented with 100 mg dm^-3 cefotaxime. Filter-sterilized carbenicillin did not stimulate plant regeneration. However, higher concentration (100 mg dm^-3) accelerated callus browning and inhibited the following regeneration. Autoclaved antibiotics at all tested concentrations showed detrimental effects on callus morphogenesis and plant regeneration.