The aim of this study was to assess the effect of aluminum on the in vitro activity of acid phosphatases (APases) of four potato clones, Macaca and Dakota Rose (Al-sensitive), and SMIC148-A and Solanum microdontum (Al-tolerant), grown in vitro, in hydroponics or in a greenhouse. The enzyme was assayed in vitro in the presence of 0, 1.85, 3.70, 5.55 and 7.40 mM Al. In plantlets grown in vitro, root APases were inhibited by Al in all clones, while shoot APases were inhibited by Al in S. microdontum and Dakota Rose and increased in Macaca at all Al concentrations. In plantlets grown in hydroponics, root APases increased in Macaca at 1.85 mM Al, whereas decreased at all Al levels in S. microdontum. In greenhouse plantlets, root APases decreased at 7.40 mM Al in S. microdontum and SMIC148-A, and at 3.70, 5.55 and 7.40 mM Al in Dakota Rose. Shoot APases decreased in Macaca and SMIC148-A. Conversely, in Dakota Rose, APases increased at 1.85 and 3.70 mM Al. These results show that the effect of Al toxicity on in vitro APase activity depends not only on Al availability but also on the plant organ, genetic background, and the growth conditions. Therefore, it suggests that acid phosphatases activity assessed in vitro might not be a good parameter to validate the screening for adaptation of potato clones to Al toxicity.

Seeds of pearl millet [Pennisetum glaucum (L). R.Br.] susceptible cv. 7042S were treated with thiamine at 5, 10, 15, 20 and 25 mM concentrations and growth promotion and downy mildew resistance were tested. Seed treatment with 20 mM thiamine resulted in 72 and 70 % disease protection under greenhouse and field conditions, respectively, and enhanced vegetative and reproductive growth parameters. Analysis of lipoxygenase (LOX) activity in inoculated pearl millet seedlings at different time intervals indicated that increased LOX activity was initiated at 3 h after inoculation (hai) and maximum activity was observed at 24 hai. Northern analysis showed that LOX mRNA transcript accumulation was higher in the resistant seedlings (cv. IP18292) than in susceptible seedlings. Thiamine seed treatment induces rapid LOX gene expression and results in significant disease protection against downy mildew disease.

Chilling stress impedes growth, development, and productivity of maize (Zea mays L.). MicroRNAs (miRNAs) play critical roles in plant responses to biotic and abiotic stresses at the post-transcriptional level. Although some miRNAs have been identified in maize, little is known about the miRNAs that accumulate differently in the response to chilling stress. In this paper, we combined Illumina sequencing with Northern blot to identify chilling-responsive miRNAs in maize. Novel miRNAs (36) were predicted and some were validated. Twenty-eight known miRNAs and 24 novel miRNAs were found to be differentially expressed under various chilling (6 ºC) treatment times, and most of them were down-regulated after the chilling treatments. Northern blot and real time quantitative polymerase chain reaction proved that miR408b and miRn138 were up-regulated, miR168a, miR529, miRn120, miRn44, and miRn22 were down-regulated, miR166b, miR396c, and miRn59 undulated under 2, 6, and 12 h of the chilling stress. Analysis agriGO based on the target genes of differentially expressed miRNAs indicates that it might change hydrolase and phosphatase activities, nucleic acid metabolisms, and many cellular components to adapt to the chilling stress.

Plant cell lines represent useful models in plant cell biology. They allow simple analysis of the effects of various factors including modulated gene expression at cellular and subcellular levels. The tobacco BY-2 cell line is a favoured model due to its high proliferation rate, capability of effective synchronization, and accessibility to transformation. A relatively high uniformity of BY-2 cultures allows morphological phenotyping and assessment of growth parameters like mitotic index, viability, or cell density. Here we review already published and newly introduced optimized guidelines to carry out reliable, reproducible and efficient characterization of BY-2 cultures from suggestions of appropriate methods to acquire primary data, proper statistical treatment, and biological interpretation. The presented experimental data demonstrate the extent of natural variability and the effect of initial cell density on various cell culture features. Supportive equations allow to estimate some derived phenotypic parameters like cell cycle duration or fresh biomass of the culture and to determine the size of data sets for reliable documentation of a certain phenotypic change. The optimized protocols and accompanying discussion of weak points of different approaches should serve as practical guide for both beginners and experienced researchers working on BY-2 cells.

Iron availability affects plant growth depending on soil type. Mangroves are characterized by alkaline soils in which the halophytic wild rice relative Porteresia coarctata thrives. Young plants of P. coarctata grew optimally in the presence of 150 mM NaCl in a hydroponic medium and tolerated iron deficiency and salt up to 21 d without showing any symptoms of stress. A homolog of the rice iron deficiency responsive cis-acting element binding factor (IDEF1) that functions at the base of an iron regulated network was isolated and characterized from P. coarctata. PcIDEF1 had a close paralog in P. coarctata genome and its transcript expression was upregulated by both iron deficient conditions and salt treated conditions for up to three weeks. Sub-cellular localization study suggests nuclear targeting PcIDEF1 protein in guard cells and root tissues of tobacco. In vitro assays for metal binding affinity and binding PcIDEF1 to iron deficiency responsive element 1 (IDE1)-like elements in the 5' flanking region of an iron regulated transporter from P. coarctata suggest that PcIDEF1 could potentially sense iron content in a plant cell and regulate expression of iron responsive genes containing IDE1-like elements in their promoter region. This study provides evidence for a possible cross-talk between iron deficiency and salt responses.

The in vitro response of sweet cherry rootstock Gisela 5 (Prunus cerasus × Prunus canescens) to increasing concentrations of NaCl (0, 50, 100 and 150 mM) in the Murashige and Skoog culture medium was studied. Induced salinity reduced growth and chlorophyll content in shoots but had no effect on water content. The increase in malondialdehyde content indicated that salinity induced oxidative stress which was accompanied with the visible symptoms of salt injury in the shoots. Antioxidant enzymes, such as superoxide dismutase, ascorbate peroxidase, peroxidase, catalase, and glutathione reductase were also significantly elevated. Although no change was observed in the Cl concentration, Na concentration of shoots significantly rose and NaCl treatments impaired K, Ca and Mg nutrition and induced imbalance in K:Na and Na:Ca ratios.

Short-time direct and indirect effects of 25 μM Cd on the growth of dicotyledon (Phaseolus coccineus) and monocotyledon (Allium cepa) plants were investigated in the presence of inhibitors of ethylene synthesis, NADPH oxidase, and the octadecanoid pathway. Only 5 min-long action of Cd was enough for inhibition of growth in bean roots, but its recovery time was extended to several days. After 7 h treatment, Cd was significantly accumulated in bean roots, but maximum H₂O₂ accumulation was seen after 1 h. Cd-induced H₂O₂ accumulation decreased especially after addition of ethylene inhibitor silver thiosulphate (STS). Low Cd accumulation and high growth inhibition were observed also in bean leaves and in A. cepa roots. The inhibitors of the octadecanoid pathway greatly weakened the inhibitory effect of Cd in P. coccineus roots, while no significant effect was observed in A. cepa. NADPH oxidase and ethylene blockade reversed (in the case of bean plants and indirectly treated A. cepa plants) or significantly diminished Cd action. Cd-induced growth inhibition of P. coccineus leaves was also alleviated by most inhibitors of the jasmonate pathway and by STS. These results indicate that Cd may have indirect and direct effects on growth processes.

Ascorbic acid (AsA) is naturally occurring compound with antioxidant activity and plays a pivotal role in plant cell adaptation to salinity stress. The objective of this work was to assess the influence of exogenous AsA on the embryogenic callus of indica rice (Oryza sativa L.) cv. MRQ74 cultivated under saline conditions. NaCl (200 mM) decreased callus fresh and dry masses, relative growth rate, and K⁺ and Ca⁺² content, and increased Na⁺ content and Na⁺/K⁺ ratio. Application of AsA (0.5 or 1 mM) alleviated these effects of salinity. Activities of peroxidase, catalase, superoxide dismutase, as well as content of proline increased due to the NaCl treatment, and these parameters were mostly further increased by 0.5 mM AsA. Thus, AsA can increase callus tolerance to NaCl stress.

Molecular hydrogen (H₂) could be a novel signal in phytohormone signaling pathways in response to biotic and abiotic stresses. Here, we employed two wild rice species (Oryza rufipogon Griff. and O. minuta J. Presl) to test this hypothesis using hydrogen-rich water (HW). The expression differences of phytohormone and hydrogenase genes between conventional rice (Oryza sativa L,) and wild rice were determined by real-time quantitative polymerase chain reaction, and the effects of HW on gene expression of wild rice were detected during three growth stages. Expression of hydrogenase genes, synthesis genes, and receptor genes of salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) signalling pathways was higher in six wild rice types than in conventional rice. Hydrogen-rich water up-regulated expression of two hydrogenase genes, SA, JA, and ET receptor genes and synthesis genes in the seedling stage of wild rice. But this positive regulation by HW was less significant in the vegetative and reproductive stages.

Agricultural production worldwide has been severely impacted by cold and freezing stresses. Plant capacity to acclimate to environmental conditions in their immediate vicinity largely control their survival, growth, and productivity. Molecular as well as biochemical mechanisms underpinning plant cold acclimation are very complex and interwoven. The cold-impacted plants try to modulate expression of variety genes controlling cell membrane lipid composition, mitogen-activated protein kinase cascade, total soluble proteins, polyamines, glycinebetaine, proline, reactive oxygen species (ROS) scavengers, cryoprotectants, and a large number of cold responsive factors. To this end, this paper dissects the array of transcriptional factors/genes down- or up-regulated, their identification in different plant species, recognition of cold tolerant/resistant transgenic plants, complexity of the mitogen-activated protein kinase cascade, as well as their cross talk under different stresses and molecular mechanisms. Furthermore, it also comprehensively elucidates physio-biochemical interferences in cold acclimation with a particular emphasis on endogenous content as well as exogenously supplied different types of polyamines, ROS, and osmoprotectants. Overall, low temperature stress tolerance or cold acclimation varies greatly among species depending on the stress intensity and duration and type of plant species.

Desiccation tolerance (DT) is the ability to tolerate dehydration to levels below 0.1 g(H₂O) g^-1(dry mass) and subsequent rehydration without lethal damage. Here, it is proposed that Leucaena leucocephala, a tree species, has potential to be model tolerant species in seed research. Using flow cytometry and transmission electron microscopy, cytological changes related to loss of DT in Leucaena primary roots were followed during germination. Leucaena seeds lost their DT at the end of germination and this coincided with an increase in cellular 4C DNA content. A negative correlation between the 8C DNA content and the capacity of germinating Leucaena seeds to tolerate desiccation was also observed. Apparently, the seeds of Leucaena underwent extra cycles of endoreduplication and accumulated a high content of DNA - an event not previously linked to DT. The ultrastructural damage imposed by drying overcame Leucaena primary root cell resilience and their ability to resume normal growth. Nuclear DNA content may be used as indicator of progress of germination and loss of DT in Leucaena.

In northern China, freezing injury is observed frequently in the rare species Magnolia wufengensis but not in the more common species Magnolia denudata. To investigate the role of the phytohormone abscisic acid (ABA) on frost tolerance in these two species, exogenous ABA was applied to the seedlings and then physiological and biochemical responses were measured during cold acclimation. Shoot growth cessation was stimulated by ABA in M. wufengensis but not in M. denudata. Abscisic acid inhibited shoot growth in M. wufengensis but not in M. denudata. Treatment with ABA stimulated leaf senescence in both species, and this effect was greater in M. denudata. For both species, ABA-treated plants exhibited bud dormancy sooner and had an increased tolerance to freezing, decreased water content and increased accumulation of proline, glucose, and fructose in shoots. These effects were generally greater for M. denudata. Freezing tolerance was significantly correlated with content of water, proline, glucose, and fructose for both species, but freezing tolerance was significantly correlated with raffinose content only in M. wufengensis. We conclude that exogenous ABA could increase cold acclimation and improve cold hardiness of both Magnolia species, although M. denudata was more responsive to ABA than M. wufengensis, which might result from a greater dehydration and accumulation of proline and certain soluble sugars.

Secretion of organic acids (OAs) by roots has been suggested to be an important mechanism of Al resistance in many species. In Stylosanthes, the participation of OAs in the mechanism of Al resistance is poorly understood. We aimed to study the production and secretion of OAs by two Brazilian Stylosanthes species with different Al resistance. Stylosanthes capitata and S. guianensis were treated with Al at different concentrations in 0.5 mM CaCl₂ (pH 4.0), and then root elongation, Al and OA content, OA secretion into the external solution, and the activity of citrate synthase (CS) were measured. Al-induced secretion of citric acid was also evaluated in the presence of protein synthesis and anion channel inhibitors. S. guianensis accumulated lower amounts of Al in its roots and displayed less inhibition of root elongation compared to S. capitata. Citric and malic acids were the most abundant OAs in the roots, and their content decreased with the Al treatment, except for citric acid in S. guianensis. Citric acid was the only OA secreted into the nutrient solution by the Al-treated plants of both species, but more by S. guianensis. Citrase synthase activity decreased in S. capitata but increased in S. guianensis with the Al treatment, and it may have a crucial role in the maintenance of citric acid content in the roots of S. guianensis. The use of anion channel and protein synthesis inhibitors reveal that anion channels were likely involved in the secretion of citric acid, and channel protein transcription was up-regulated by exposure to Al in Stylosanthes.

Leaf anatomy and irradiance-dependent leaf transmittance changes serving as irradiance acclimation mechanisms in leaves were studied in two ecologically contrasting Tradescantia species, a shade plant T. fluminensis Vell. and a sun plant T. sillamontana Matuda, grown at different irradiances. A dramatic increase in leaf thickness (2 to 4-fold) under a high growth irradiance (800 μmol m^-2 s^-1) compared with a low growth irradiance (60 μmol m^-2 s^-1), achieved mainly by expansion of the epidermis, was recorded in both species. The effect took place on the background of modest changes in mesophyll thickness (1.8-fold in T. fluminensis and 1.15-fold in T. sillamontana) and chloroplast size (0.8-fold in T. fluminensis and an insignificant change in T. sillamontana). Mesophyll structure and growth irradiance response did not seem to facilitate significantly light-dependent chloroplast (avoidance) movement in these species. Nevertheless, an exceptionally large (2 to 4-fold) irradiance-induced increase in light transmittance attributable to chloroplast avoidance movement was revealed. This increase by far exceeded that in other higher plants according to available literature. The magnitude of the irradiance-dependent transmittance changes positively correlated both with the rate of photosystem II recovery and with the extent of xanthophyll deepoxidation in the leaves. This was opposite to a negative correlation observed between the same parameters in different plant species. We hypothesize that, at the evolutionary timescale, chloroplast avoidance movement might adjust independently from other photoprotective mechanisms, e.g., non-photochemical quenching, whereas, on the ontogenetic timescale, adjustment of these mechanisms inevitably follows the same trend.

Catechin is associated with several functions in animal and plant systems, with little information available regarding its role in plant growth. Low concentrations of catechin (50 and 100 μM) were found to enhance length of primary and lateral roots, number of lateral roots, fresh and dry masses of shoots and roots, leaf area, water potential of leaf and root tissues, the number of vascular bundles in the inflorescence, and leaf thickness in Arabidopsis thaliana ecotype Col-0. A significant increase in net photosynthetic rate, stomatal conductance and concentration of indole-3-acetic acid was also observed in catechin treated plants.

Crop plants are regularly exposed to an array of abiotic and biotic stresses, among them drought stress is a major environmental factor that shows adverse effects on plant growth and productivity. Because of this these factors are considered as hazardous for crop production. Drought stress elicits a plethora of responses in plants resulting in strict amendments in physiological, biochemical, and molecular processes. Photosynthesis is the most fundamental physiological process affected by drought due to a reduction in the CO₂ assimilation rate and disruption of primary photosynthetic reactions and pigments. Drought also expedites the generation of reactive oxygen species (ROS), triggering a cascade of antioxidative defense mechanisms, and affects many other metabolic processes as well as affecting gene expression. Details of the drought stress-induced changes, particularly in crop plants, are discussed in this review, with the major points: 1) leaf water potentials and water use efficiency in plants under drought stress; 2) increased production of ROS under drought leading to oxidative stress in plants and the role of ROS as signaling molecules; 3) molecular responses that lead to the enhanced expression of stress-inducible genes; 4) the decrease in photosynthesis leading to the decreased amount of assimilates, growth, and yield; 5) the antioxidant defense mechanisms comprising of enzymatic and non-enzymatic antioxidants and the other protective mechanisms; 6) progress made in identifying the drought stress tolerance mechanisms; 7) the production of transgenic crop plants with enhanced tolerance to drought stress.

Several studies have been performed to elucidate the role of brassinosteroids (BRs) in plant growth and development. However, information on the role of BR signaling in nutrient uptake is limited. This study explores the relationship between BRs and ammonium transporter 1 (AMT1) expression in Arabidopsis roots. We found that BR treatment reduced the expression of AMT1 genes and that a BR receptor BRI1 mutant bri1-5 reversed its BR-repressed expression. Furthermore, the BR signaling transcription factor, BES1, regulates AMT1 expression in roots. NH₄ ⁺-mediated repression of AMT1;1, AMT1;2, and AMT1;3 was suppressed in a gain-of-function BES1 mutant (bes1-D). This mutant was more sensitive to methyl-ammonium and contained a higher ammonium content compared to wild-type plants. However, BES1 failed to bind E-box elements present in the promoter region of the AMT1 genes. Furthermore, NH₄ ⁺-mediated glutamine synthetase (GS) and glutamine oxoglutarate aminotransferase (GOGAT) gene expressions were partially inhibited, and GS activity was slightly lower in the bes1-D mutant relative to that observed in wild-type En2 roots. NH₄ ⁺-mediated AMT1 suppressions are known to be caused by N-metabolites rather than NH₄ ⁺ itself, and glutamine application inhibited AMT1 expression in both En2 and bes1-D indicating that BES1 activation inhibited NH₄ ⁺-mediated GS/GOGAT induction, which might in turn inhibit AMT1 repression. In conclusion, the present study demonstrates that BR regulated nitrogen uptake and assimilation via the BR signaling pathway.

Gamma-aminobutyric acid (GABA) is a non-protein amino acid that accumulates in a number of plant species under various environmental stresses. In this paper, the ability of applied GABA for the alleviation of NaCl stress was investigated in view of growth parameters, gas exchange, photosynthetic pigments, chlorophyll fluorescence, activities of antioxidant enzymes, malondialdehyde (MDA) content, and electrolyte conductivity (REC) in wheat seedlings. Germination rate and shoot dry mass decreased with an increasing NaCl concentration and this decrease was less pronounced when 0.5 mM GABA was applied. In the NaCl-treated seedlings, exogenous GABA partially enhanced photosynthetic capacity and antioxidant enzyme activities and decreased MDA content and REC. Therefore, GABA reduced the impact of salinity on the wheat seedlings.

We identified a Populus nigra auxin-regulated gene involved in organ size (PnARGOS)-LIKE, encoding one organ size related protein in black poplar. It is homologous to AtARGOS and AtARGOS-LIKE genes of Arabidopsis thaliana. ABRE-like, G-box, GATA and I-box motifs were discovered in the promoter region of the poplar ARGOS-LIKE gene. In wild type aspen (Populus tremula) plants, an ortholog of the PnARGOS-LIKE gene (PtrARGOS-LIKE) was noticeably expressed in actively dividing and expanding young leaves and calli, whereas its mRNA content increased in response to exogenous 6-benzylaminopurine, 1-naphthaleneacetic acid, and 24-epibrassinolide. Expression of the PtrARGOS-LIKE gene was reduced under a salinity treatment. In addition, we generated transgenic tobacco and aspen plants with an up-regulated expression of the PnARGOS-LIKE gene. A constitutive expression of the gene contributed to an increase in size of stems and leaves of the transgenic tobacco plants. In the transgenic aspen, a constitutive expression of the PnARGOS-LIKE gene promoted an increase in the frequency of leaf initiations and in leaf length and area. The size of transgenic tobacco and aspen leaves increased due to the enlargement of individual cells. The results show the significance of the PnARGOS-LIKE gene for control of leaf initiation and organ growth by cell expansion in poplar.

We study apical dominance in Alstroemeria, a plant with an architecture very different from the model species used in research on apical dominance. The standard explant was a rhizome with a tip and two vertically growing shoots from which the larger part had been excised leaving ca. 1 cm stem. The axillary buds that resumed growth were located at this 1-cm stem just above the rhizome. They were released by removal of the rhizome tip and the shoot tips. Replacement of excised tips by lanolin with indole-3-butyric acid (IBA) restored apical dominance. The auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA) and N-1-napthylphthalamic acid (NPA) reduced apical dominance. 6-Benzylaminopurine (BAP) enhanced axillary bud outgrowth but the highest concentrations (> 9 μM) caused fasciation. Thidiazuron (TDZ) did not show improvement relative to BAP. Even though the architecture of Alstroemeria and the model species are very different, their hormonal mechanisms in apical dominance are for the greater part very similar.

We isolated and characterized a novel Ran GTPase homologous gene, FaRan from tall fescue (Festuca arundinacea Schreb.). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis indicated that FaRan is broadly expressed in old mature leaves, young leaves, plumules, stems, infloresence meristems, but at different levels. Transcript of FaRan is higher in young meristems than in old ones. Ectopic expression of FaRan resulted in increased number of axillary buds and reduced apical dominance in transgenic Arabidopsis plants. These results suggest that FaRan in F. arundinacea may be involved in the initiation of meristem and subsequent growth as well as development. In addition, it also suggests that FaRan can be used potentially to improve turfgrass quality.

The photosynthetic and growth characteristics of Mosla hangchowensis, an endangered species and M. dianthera, a weed, were compared under three irradiances (PPFD) similar to shaded forest understory, forest edge and open land. Both species grown at lower PPFD had lower PPFD-saturated photosynthetic rate (P_max), saturation PPFD, compensation PPFD, apparent quantum yield, total mass and root/shoot ratio and higher specific leaf area, leaf area ratio and height ratio. At the same PPFD treatment, however, specific leaf area and leaf area ratio of M. hangchowensis were higher than those of M. dianthera, other above parameters were lower than those of M. dianthera. Water use efficiency did not differ between M. hangchowensis and M. dianthera, but it reached its maximum at 70 % of full PPFD. These results suggested the optimum habitat of M. hangchowensis is the forest edge.

Differences in Cd accumulation and Cd tolerance between Thlaspi arvense ecotype Aigues Vives (AV) from a commercial grower in South France and ecotype Jena collected in the polluted urban area of Jena (Germany) were reported here. Ecotype Jena exhibited considerable Cd-tolerance. Shoot and root masses were unaffected and root elongation was even enhanced by exposure to 50 μM Cd. In contrast, growth of ecotype AV was severely affected by this Cd treatment. Ecotype Jena was much more efficient in excluding Cd from both roots and shoots than ecotype AV. Despite the efficient restriction of Cd transport from roots to shoots in Jena, this ecotype maintained high root to shoot transport of Zn and Fe under Cd exposure. Cd supply strongly decreased the activities of antioxidant enzymes in AV, while in the Cd resistant Jena these activities either remained unaffected (SOD, APX) or were increased (CAT) by Cd supply. In conclusion, naturally selected Cd-tolerance in Thlaspi arvense is due to efficient Cd exclusion. The mechanisms underlying exclusion of Cd from the shoots seem Cd-specific yet they did not affect the homeostasis of Fe and Zn in the shoots.

This communication examines the role of small heat shock proteins (sHsps) targeted to mitochondria (Mt) and endoplasmic reticulum (ER) in tomato plants (Lycopersicon esculentum Mill.) under heat stress. Genetic response of transgenic and wild type plants varied under optimum, moderately elevated and elevated temperature. In optimum temperature higher biomass was recorded in wild type than the transgenic lines, whereas in moderately elevated temperature biomass increased in Mt-sHsp line. Also, net photosynthetic rate (P_N) increased in Mt-sHsp line in both the elevated temperatures, though higher in moderately elevated. Cell membrane stability (CMS) improved in all the lines after exposure to elevated temperatures, but always remained higher in transgenic lines. Transgenic lines expressed sHsps in different temperature regimes in both vegetative and reproductive parts, while wild type expressed such proteins only after 1 h of heat shock.

The changes in activities of soluble and cell wall-bound peroxidases and lignin contents in juglone-stressed soybean (Glycine max) seedlings and their relationships with root growth were investigated. Soybean seedlings (3-d-old) were cultivated in nutrient solution supplemented with 0.5 to 25 μM juglone for 24 h. Length and dry mass of roots decreased after 5 to 25 μM juglone treatments. Low juglone concentrations (≤ 1 μM) increased soluble peroxidase activity, while high concentrations (≥ 10 μM) inhibited activities of soluble and cell wall-bound peroxidases. Juglone (≤ 1 μM) did not affect lignin content but highly increased lignification after 5 to 25 μM treatments. Results indicate that lignification may be an important step in root growth reduction of juglone-stressed soybean.

cDNA-AFLP fingerprinting was used to identify genes with modulated expression during germination in common bean (Phaseolus vulgaris L.). The analysis was performed on the embryo axes. Nine time points covering the whole germination were considered and 800 transcript-derived fragments (PvTDFs) were scored. Among them, 80 % showed no changes during germination. The 97 PvTDFs showing differential expressions during germination were sequenced along with 14 constant transcripts that were randomly chosen. The expression of seven variable PvTDFs was confirmed by real-time RT-PCR. We observed that 92 % of the transcript changes, including 35 % of appearing mRNAs, took place before radicule protrusion, 0-17 h after imbibition (HAI). A major shift in gene expression was observed between 9 and 14 HAI, suggesting a key moment of cell re-programming. Sequence homologies were found for 52 % of the sequenced PvTDFs. The identified transcripts encode proteins belonging to several functional groups including transcription factors, proteins involved in storage compound hydrolysis, cell elongation or oxidative stress protection.

The growth of kiwifruit explants was affected by boron (B) and methionine (Meth) in the culture medium. The longest shoots, the greatest number of shoots and the highest amount of fresh mass per explant were produced in Murashige and Skoog medium with 2 mM B and 2 μM Meth. Furthermore, by increasing B concentration in the culture medium from 0 to 2 mM, an increased rate of shoot proliferation was observed for the various Meth concentrations employed.

In Pinus peuce zygotic embryo culture grown on Gresshoff and Doy (1972; GD) basal medium, 2.22 μM benzyladenine (BA) was superior in promoting adventitious bud induction during 4 weeks comparing to kinetin or BA + kinetin. Shoot elongation was achieved on half-strength GD medium devoid of plant growth regulators and containing activated charcoal. Pulse treatment with 1 mM indole-3-butyric acid (IBA) for 2 h, followed by transfer to half-strength GD medium, produced the most efficient rooting. Rooted shoots were transplanted to the greenhouse and plantlets continued to grow and developed into phenotypically normal plants. Up to 10 plants per explant can be obtained within 36 weeks from culture initiation.

Lettuce plants were treated with gibberellic acid (GA₃) and uniconazole (UZ; a gibberellin synthesis inhibitor) to investigate the influence of GA₃ on cell division frequency in the shoot apical meristem (SAM) during stem elongation and flower initiation in lettuce (Lactuca sativa) grown in a greenhouse. GA₃ (0.1 mM) was sprayed on the surface of outer leaves and uniconazole solution (0.86 mM) was applied to the soil. GA₃ increased cell division frequency in the peripheral zone and the rib meristem of shoot apices, and this was associated with the stimulation of stem elongation. UZ treatment decreased cell division frequency in the peripheral zone, rib meristem and subapical pith, and this was associated with restricted stem elongation. Treatment with UZ and GA₃ together induced minor stem elongation. Flower induction occurred 3 d earlier in the GA₃ and UZ+GA₃ treatments than in the control, while the UZ treatment delayed flower initiation for more than 9 d relative to the control.

Plants of Miscanthus sinensis (cv. Giganteus) were grown in hydroponics for three months in nutrient solution with 0, 2.2, 4.4 and 6.6 μM CdNO₃. Growth parameters, catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities were analysed in leaves and roots collected after 1-and 3-month exposure. Dry biomass of all miscanthus organs was affected by Cd concentration both after 1-and 3-month exposure. No visible symptoms of Cd toxicity were observed in shoots and rhizomes of plants grown in presence of Cd. In contrast, roots became shorter and thicker and the whole root system more dense and compact already after one month of treatment with 6.6 μM Cd. The lower Cd concentration increased the enzymes activities after 3 months in leaves and only after 1-month in roots, while a decrease in activity was observed at higher Cd concentrations.