Showing papers in "Biologia Plantarum in 2009"

Interactions of lichens with heavy metals

Abstract: Recent developments in knowledge about the interactions between lichens and heavy metals at different levels, from populations to cells and from ecology to molecular biology are reviewed. Sources of heavy metals, mechanisms of heavy metal accumulation and detoxification by lichens are discussed. Special emphasis is placed on ultrastructural changes as well as physiological parameters such as membrane integrity, pigment composition, chlorophyll a fluorescence, photosynthesis, respiration, contents of ATP, amino acids, ergosterol, ethylene, non-protein thiols, activity of antioxidant enzymes and expression of stress proteins.

Waterlogging induced oxidative stress and antioxidant activity in pigeonpea genotypes.

Abstract: The objective of this study was to examine the role of antioxidant enzymes in waterlogging tolerance of pigeonpea (Cajanus cajan L. Halls) genotypes ICP 301 (tolerant) and Pusa 207 (susceptible). Waterlogging resulted in visible yellowing and senescence of leaves, decrease in leaf area, dry matter, relative water content and chlorophyll content in leaves, and membrane stability index in roots and leaves. The decline in all parameters was greater in Pusa 207 than ICP 301. Oxidative stress in the form of superoxide radical, hydrogen peroxide and thiobarbituric acid reactive substances (TBARS) contents initially decreased, however at 4 and 6 d of waterlogging it increased over control plants, probably due to activation of DPI-sensitive NADPH-oxidase. Antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, glutathione reductase and catalase also increased under waterlogging. The comparatively greater antioxidant enzyme activities resulting in less oxidative stress in ICP 301 could be one of the factor determining its higher tolerance to flooding as compared to Pusa 207. This study is the first to conclusively prove that waterlogging induced increase in ROS is via NADPH oxidase.

Salt stress effects on growth, pigments, proteins and lipid peroxidation in Salicornia persica and S. europaea

Abstract: The effects of NaCl stress on growth, water status, contents of protein, proline, malondialdehyde (MDA), various sugars and photosynthetic pigments were investigated in seedlings of Salicornia persica and S. europaea grown in vitro. Seeds were germinated under NaCl (0, 100, 200, 300, 400, 500 and 600 mM) on Murashige and Skoog medium for 45 d. The shoot growth of both species increased under low NaCl concentration (100 mM) and then decreased with increasing NaCl concentrations. In contrast to S. persica, root length in S. europaea reduced steadily with an increase in salinity. Proline content in S. persica was higher than in S. europaea at most NaCl concentrations. Proline, reducing saccharide, oligosaccharide and soluble saccharide contents increased under salinity in both species. In contrast, contents of proteins and polysaccharides reduced in both species under salt stress. MDA content remained close to control at moderate NaCl concentrations (100 and 200 mM) and increased at higher salinities. MDA content in S. europaea was significantly higher than S. persica at higher salinities. Salt treatments decreased K+ and P contents in seedlings of both species. Significant reduction in contents of chlorophylls and carotenoids due to NaCl stress was also observed in seedlings of both species. Some differences appeared between S. persica and S. europaea concerning proteins profile. On the basis of the data obtained, S. persica is more salt-tolerant than S. europaea.

Effects of salicylic acid and salinity on apoplastic antioxidant enzymes in two wheat cultivars differing in salt tolerance

Abstract: The effects of salicylic acid (SA) and salinity on the activity of apoplastic antioxidant enzymes were studied in the leaves of two wheat (Triticum aestivam L.) cultivars: salt-tolerant (Gerek-79) and salt-sensitive (Bezostaya). The leaves of 10-d-old seedlings grown at nutrient solution with 0 (control), 250 or 500 mM NaCl were sprayed with 0.01 or 0.1 mM SA. Then, the activities of catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) were determined in the fresh leaves obtained from 15-d-old seedlings. The NaCl applications increased CAT and SOD activities in both cultivars, compared to those of untreated control plants. In addition, the NaCl increased POX activity in the salt-tolerant while decreased in the salt-sensitive cultivar. In control plants of the both cultivars, 0.1 mM SA increased CAT activity, while 0.01 mM SA slightly decreased it. SA treatments also stimulated SOD and POX activity in the salt-tolerant cultivar but significantly decreased POX activity and had no effect on SOD activity in the saltsensitive cultivar. Under salinity, the SA treatments significantly inhibited CAT activity, whereas increased POX activity. The increases in POX activity caused by SA were more pronounced in the salt-tolerant than in the salt-sensitive cultivar. SOD activity was increased by 0.01 mM SA in the salt-tolerant while increased by 0.1 mM SA treatment in the salt-sensitive cultivar.

Photosynthetic parameters and leaf water potential of five common bean genotypes under mild water deficit

Abstract: 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.

Cadmium-induced oxidative damage and antioxidant responses in Brassica juncea plants

Abstract: Indian mustard (Brassica juncea L. cv. Vitasso) plants exposed to 10, 30, 50 and 100 µM of Cd for 5 d in hydroponic culture were analysed with reference to the distribution of Cd2+, the accumulation of biomass and antioxidants and antioxidative enzymes in leaves. Cd induced a decrease in plant biomass. The maximum accumulation of Cd occurred in roots followed by stems and leaves. Cd induced a decrease in catalase (CAT) and guiacol peroxidase (GPX) activities but an increase in ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) activities. Enhancement in dehydroascorbate reductase (DHAR) activity was also at 10 µM Cd. Glutathione reductase (GR) activity showed pronounced stimulation after all treatments, but glutathione S-transferase (GST) and glutathione peroxidase (GPOX) activities decreased. The effectiveness of ascorbate-glutathione cycle (AGC) was determined by the ratio of ascorbate to H2O2. This ratio decreased in the Cd-treated leaves which indicated that the cycle was disordered.

Waterlogging induced oxidative stress and antioxidant enzyme activities in pigeon pea

Abstract: An experiment was conducted with two contrasting pigeon pea (Cajanus cajan L.) genotypes, ICPL 84023 (tolerant) and ICP 7035 (susceptible), to study the physiological and molecular basis of waterlogging tolerance in relation to oxidative stress and antioxidant enzyme activities. Waterlogging resulted in visible yellowing and premature senescence of leaves, and greater decline in relative water content, chlorophyll content, and membrane stability index in ICP 7035 than in ICPL 84023. Superoxide radical and hydrogen peroxide contents increased at day 4 and 6 of waterlogging probably due to activation of NADPH-oxidase. O2 ·− production was inhibited, by diphenylene iodonium chloride, a specific inhibitor of NADPH oxidase and expression of NADPH oxidase-mRNA was increased under waterlogging condition in ICPL 84023. ICP 7035 showed higher contents of ROS in control condition and after recovery, however, during waterlogging the O2 ·− production was higher in ICPL 84023. Activities of antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase and catalase increased under waterlogging more in ICPL 84023 than in ICP 7035. Cu/Zn-SOD and APX-mRNA expression in 24-h waterlogged plants showed enhanced expression in ICPL 84023 compared to ICP 7035. The cloning and sequencing of APX gene of tolerant and susceptible genotypes yielded cDNAs of 622 and 623 bp, having 95 % homology with each other and 92 % with the corresponding sequences of Vigna unguiculate APX-gene.

QTLs mapping of physiological traits related to salt tolerance in young rice seedlings

Abstract: Oryza sativa L. F2 population and F2:3 derived from a cross between salt tolerance cv. Tarommahali and salt sensitive cv. Khazar were used in this study. A linkage map based on F2 population was constructed (74 SSR markers on 192 individuals), which covered a total of 1231.50 cM with an average two locus interval of 19.83 cM. Two QTLs related to Na+/K+ ratio were found on chromosome 3 and 6. qDM-3 and qDM-8 (for dry mass of shoot) are major QTLs with very large effects explained 20.90 and 17.72 % of the total phenotypic variance, respectively. Major locus for DM (qDM-3) was bracketed by RM1022 — RM6283 spread over 13.6 cM on chromosome 3. Major part of the variability for standard tolerance ranking (STR) was explained by the qSTR-6 flanked by RM3727 — RM340 on chromosome 6, which exhibited phenotypic variance of 17.25 % and peak likelihood ratio (LR) of 17.51. The length of this QTL is 8.8 cM and identification of any tightly linked markers in this region will serve as a candidate gene for fine-mapping. qSTR-3 overlapped with qNA-3 and qNAK-3. The qSTR-3 may contain a new major gene for salt stress tolerance at seedling stage in rice. Major QTLs identified in this paper, after fine-mapping, could be used for marker assisted selection.

Growth, lipid peroxidation and photosynthesis in two tall fescue cultivars differing in heat tolerance

Abstract: Seedlings (70-d-old) of two tall fescue (Festuca arundinacea Schreb.) genotypes, heat-tolerant Jaguar 3 and heat-sensitive TF 66, were exposed to a high temperature stress of 35/30 °C (day/night) for 20 d and both light-saturated and CO2-saturated leaf stomatal conductance decreased, especially in TF 66. Higher reductions of quantum efficiency, carboxylation efficiency and maximum photochemical efficiency of photosystem 2 in dark adapted leaves (measured as Fv/Fm) occurred in TF 66 than in Jaguar 3. High temperature stress increased photorespiration in the two plants, but more in TF 66. Moreover, high temperature stress also reduced the growth, chlorophyll content and caused cell membrane injuries in the two cultivars, the changes were again more pronounced in TF 66 than in Jaguar 3.

Effects of zinc and soil moisture on photosynthetic rate and chlorophyll fluorescence parameters of maize

Abstract: Effects of zinc [0 and 5.0 mg Zn kg−1 (soil)] on photosynthetic rate (PN), and chlorophyll fluorescence in leaves of maize (Zea mays L.) cv. Zhongdan 9409 seedlings grown under different soil moisture regimes (40–45 % and 70–75 % of soil saturated water content) were studied. Zn application did not enhance maize plant adaptation to drought stress. The relative water content and the water potential of leaves were not affected by Zn treatment. Moreover, The PN of drought-stressed plants was not improved by Zn supply. The increases of plant biomass, stomatal conductance and quantum yield of photosystem 2 due to Zn addition were notable in well-watered plants.

Microarray analysis of Arabidopsis genome response to aluminum stress

Abstract: To better understand the mechanisms involved in aluminum toxicity and tolerance in plants, microarray technology was used to evaluate changes in gene expression in Arabidopsis thaliana under Al stress. With the use of Affymetrix Arabidopsis ATH1 Genechip, a comparison of RNA expression profiles was made between control and Al-treated Arabidopsis seedlings. A total of 256 genes were identified as Al-responsive. Ninety-four genes were shown to be up-regulated and 162 were down-regulated; comprising 1.1 % of the 24 000 Arabidopsis genes. Real-time RT-PCR was used to confirm the microarray data. The analysis showed that a large number of transcription factors and several putative signaling components were up-regulated by aluminum. Chloroplast structural and photosynthetic genes were, in general, down-regulated. A number of previously identified Al-responsive genes, e.g. GST, Auxin-regulated, Peroxidase, and Chitinase, were up-regulated by Al-stress, whereas Wali 3 and Wali 4 were down-regulated. We also identified several up-regulated genes involved in vacuolar signaling, sorting and docking. Three genes were also up-regulated by Al-stress, Ras GTP-binding protein, ABC-cassette binding, and the AtELP1 receptor genes, have previously been documented as responsive to drought and/or oxidative stress and may play important roles the detoxification of Al ions by transportation and storage into root vacuoles. Ultrastructural changes in the roots tips cells of Arabidopsis were evaluated using transmission electron microscopy and energy-dispersive X-ray analysis with scanning electron microscopy and results showed Al accumulation in the root tips of Arabidopsis.

Enhanced chilling tolerance in Zoysia matrella by pre-treatment with salicylic acid, calcium chloride, hydrogen peroxide or 6-benzylaminopurine

Abstract: Following leaf application of salicylic acid (SA), calcium chloride, hydrogen peroxide and 6-benzylaminopurine (BA), Manila grass (Zoysia matrella) plants were exposed to day/night temperature of 7/2 °C for 120 h in a growth chamber. The lower content of malondialdehyde (MDA) and H2O2 and higher activities of ascorbate peroxidase (APX), guaiacol peroxidase (POD) and catalase (CAT) during exposure to low temperature in pre-treated plants in comparison with control plants demonstrated that these compounds improved the chilling tolerance of Manila grass.

Response of maize genotypes to salinity stress in relation to osmolytes and metal-ions contents, oxidative stress and antioxidant enzymes activity.

Abstract: Effect of long term soil salinity (control-S0 and three levels S1 to S3) was studied in two maize (Zea mays L.) genotypes, PEHM 3 (comparatively tolerant) and Navjot (susceptible) at vegetative and anthesis stages during summer-rainy season. Salinity stress decreased relative water content (RWC), chlorophyll (Chl) and carotenoid (Car) contents, membrane stability index (MSI), potassium and calcium contents, and increased the contents of superoxide radical (O2 ·−), hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS), proline, glycinebetaine, total soluble sugars, and sodium, and Na+/K+ and Na+/Ca2+ ratios in both the genotypes. Contents of zinc, copper, manganese and iron increased up to S2. Though under S0 PEHM 3 had higher content of all the metals, Navjot recorded higher content of Zn at all salinity levels and contents of all metal ions at S2 and S3. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) increased upto S2 in both the genotypes, and upto S3 in PEHM 3 at the two stages. Salinity induced decrease in RWC, Chl, Car, MSI, K+ and Ca2+ was significantly greater in Navjot, which also recorded higher Na+ content and Na+/K+ and Na+/Ca2+ ratios than PEHM-3. PEHM-3 recorded higher contents of proline, glycine-betaine, total soluble sugars, K+, Ca2+, activity of SOD, APX, CAT, GR, and comparatively lower O2 ·−, H2O2 and TBARS contents compared to Navjot.

Development and evaluation of microsatellite markers in Phoenix dactylifera L. and their transferability to other Phoenix species

Abstract: Forty one simple sequence repeats were isolated from two microsatellite enriched libraries of date palm (Phoenix dactylifera L.). After screening, 17 selected microsatellite loci were characterized and evaluated on a set of 31 cultivars and clones from Algerian and Californian germplasm. All primer pairs produced an amplification product of the expected size and detected high polymorphism among the analysed samples. These nuclear simple sequence repeat (SSR) markers are expected to be a very effective tool for evaluating genetic diversity in date palm germplasm. Acrosstaxa amplification showed the usefulness of most SSR markers in 14 other species across the genus Phoenix.

Stomatal and non-stomatal limitations to photosynthesis in field-grown grapevine cultivars

Abstract: Diurnal changes of photosynthesis in the leaves of grapevine (Vitis vinifera × V. labrusca) cultivars Campbell Early and Kyoho grown in the field were compared with respect to gas exchanges and actual quantum yield of photosystem 2 (ΦPS2) in late May. Net photosynthetic rate (PN) of the two cultivars rapidly increased in the morning, saturated at photosynthetic photon flux density (PPFD) from 1200 to 1500 µmol m−2 s−1 between 10:00 and 12:00 and slowly decreased after midday. Maximum PN was 13.7 and 12.5 µmol m−2 s−1 in Campbell Early and Kyoho, respectively. The stomatal conductance (gs) and transpiration rate changed in parallel with PN, indicating that PN was greatly affected by gs. However, the decrease in PN after midday under saturating PPFD was also associated with the observed depression of ΦPS2 at high PPFD. The substantial increase in the leaf to air vapour pressure deficit after midday might also contribute to decline of gs and PN.

The influence of cold acclimation on antioxidative enzymes and antioxidants in sensitive and tolerant barley cultivars

Abstract: In order to better understand the role of cold acclimation in alleviating freezing injury, two barley cultivars with different cold tolerance, i.e. a sensitive cv. Chumai 1 and a tolerant cv. Mo 103, were used. The freezing treatment increased leaf soluble protein content more in the tolerant cultivar than in the sensitive one. Cold acclimation increased H2O2 content of the two cultivars during freezing treatment, especially in Mo 103. Glutathione and ascorbate contents during freezing and recovery were significantly higher in cold-acclimated plants than in non-acclimated ones. Activities of peroxidase, ascorbate peroxidase and glutathione reductase were also higher in cold-acclimated plants than non-acclimated plants during freezing treatment. However, there was no significant difference between cold-acclimated plants and the control plants in catalase activity. It may be assumed that cold acclimation induced H2O2 production, which in turn enhanced activities of antioxidative enzymes and synthesis of antioxidants, resulting in alleviation of oxidative stress caused by freezing.

Agrobacterium-mediated genetic transformation of plants: The role of host

Abstract: Agrobacterium-mediated genetic transformation is the most widely used technology to obtain overexpression of recombinant proteins in plants. Molecular events that occur within Agrobacterium during interactions with host plants have been studied extensively, and now we have a reasonable understanding the key factors involved in the regulation of T-DNA nuclear import and genomic integration. By contrast, very little is known about the events that take place in the host cells during genetic transformation by Agrobacterium. Here, we describe the plant-related factors including genotype, genes, proteins, competency of target tissues and phenolic compounds that participate in Agrobacterium-mediated genetic transformation and discuss their possible roles in this process. Because Agrobacterium probably adapts existing cellular processes for its life cycle, identifying the processes in host cells during Agrobacterium infection might contribute to better understanding of basic biological processes as cell communication, intracellular transport and DNA repair and recombination as well as to expanding the host range of Agrobacterium as a genetic engineering tool.

Aerenchyma formation in maize roots

Abstract: 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

In vitro organogenesis and antioxidant enzymes activity in Acanthophyllum sordidum

Abstract: The effect of various hormonal combinations on callus formation and regeneration of shoot and root from leaf derived callus of Acanthophyllum sordidum Bunge ex Boiss. has been studied. Proteins and activity of antioxidant enzymes were also evaluated during shoot and root organogenesis from callus. Calli were induced from leaf explants excised from 30-d-old seedlings grown on Murashige and Skoog medium containing 4.52 µM 2,4-dichlorophenoxyacetic acid + 4.65 µM kinetin. Maximum growth of calli and the most efficient regeneration of shoots and roots occurred with 2.69 µM 1-naphthalene acetic acid (NAA), 2.69 µM NAA + 4.54 µM thidiazuron and 2.46 µM indole-3-butyric acid. Protein content decreased in calli and increased significantly during regeneration of shoots from callus. Superoxide dismutase activity decreased in calli comparing to that of seedlings, then increased in regenerated shoots and roots. High catalase activity was detected in seedlings and regenerated shoots, whereas high peroxidase activity was observed in calli and regenerated roots.

Determination of genetic stability of long-term micropropagated plantlets of Platanus acerifolia using ISSR markers

Abstract: Inter-simple sequence repeat (ISSR) markers were used to assess the genetic stability of long-term micropropagated plantlets of London plane tree (Platanus acerifolia Willd.). Twenty micropropagated plantlets were chosen from a clonal collection of shoots that originated from a single mother shoot. This clonal collection had been maintained under in vitro culture conditions for at least 8 years, as achieved by axillary branch multiplication. Out of 38 ISSR primers screened, 16 primers were found to produce clear reproducible bands resulting in a total of 103 distinct bands with an average of 6.44 scorable bands per primer. Of these 103 bands, 86 were monomorphic across all 20 of the plants tested and 17 showed polymorphisms (16.5 % polymorphism). Based on the ISSR band data, similarity indices between the plantlets ranged from 0.92 to 1.00. These similarity indices were used to construct an UPGMA dendrogram and demonstrated that all 20 micropropagated plants grouped together in one major cluster with a similarity level of 91 %. A total of 1771 scorable bands were obtained from the full combination of primers and plantlets and only 51 (2.88 %) were polymorphic across the plantlets which indicates that this micropropagated line of P. acerifolia is genetically stable.

Defence responses of chilli fruits to Colletotrichum capsici and Alternaria alternata

Abstract: The induction of defence compounds and enzymes involved in the phenylpropanoid pathway were studied in the ripe and green chilli fruits inoculated with Colletotrichum capsici and Alternaria alternata. Total phenols and the activity of phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO) and catalase (CAT) increased in the inoculated ripe and green chilli fruits compared to the corresponding healthy fruits. Total phenols and the activities of the enzymes were at the maximum 2–3 d after inoculation and thereafter declined sharply in ripe chilli fruits, whereas slowly in green chilli fruits. In comparison with ripe chilli fruits, green chilli fruits were more resistant as they showed higher accumulation of total phenols and also higher activities of enzymes.

Responses to drought stress in two poplar species originating from different altitudes

Abstract: 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.

Physiological responses of Lupinus luteus to different copper concentrations

Abstract: Yellow lupin (Lupinus luteus L.) plants were grown in hydroponic solution for 15 d under different copper concentrations (0.1, 0.5, 1.0, 10, 25 and 50 µM). With increasing Cu concentration total biomass was not affected, leaf area slightly decreased, while chlorophyll content decreased considerably. Cu content increased significantly both in roots and in leaves, but the contents of other ions were only slightly affected at the highest Cu concentration (Mn content decreased both in roots and in leaves, P content decreased only in leaves and Zn content increased in roots). Superoxide dismutase (SOD) activity increased up to day 7 after copper application. Peroxidase (GPOD) and polyphenol oxidase (PPO) activities also increased, while catalase (CAT) activity remained constant.

Pre-treatment with H2O2 induces salt tolerance in Barley seedlings

Abstract: Barley seedlings were pre-treated with 1 and 5 µM H2O2 for 2 d and then supplied with water or 150 mM NaCl for 4 and 7 d. Exogenous H2O2 alone had no effect on the proline, malondialdehyde (MDA) and H2O2 contents, decreased catalase (CAT) activity and had no effect on peroxidase (POX) activity. Three new superoxide dismutase (SOD) isoenzymes appeared in the leaves as a result of 1 µM H2O2 treatment. NaCl enhanced CAT and POX activity. SOD activity and isoenzyme patterns were changed due to H2O2 pre-treatment, NaCl stress and leaf ageing. In pre-treated seedlings the rate of 14CO2 fixation was higher and MDA, H2O2 and proline contents were lower in comparison to the seedlings subjected directly to NaCl stress. Cl− content in the leaves 4 and 7 d after NaCl supply increased considerably, but less in pre-treated plants. It was suggested that H2O2 metabolism is involved as a signal in the processes of barley salt tolerance.

Water deficit-induced oxidative stress and the activation of antioxidant enzymes in white clover leaves

Abstract: The objective of this study was to determine the development of the antioxidant enzymes induced by drought stress in white clover (Trifolium repens L.) leaves. Water stress was imposed during 28 d by decreasing the daily irrigation. Leaf water potential (Φw) gradually decreased from −0.46 to −2.33 MPa. For the first 7 d, dry mass (DM), H2O2 and lipid peroxidation were not significantly affected by water deficit. From 14 d of treatment, water stress decreased dry mass and increased content of reactive oxygen species (O2·− and H2O2) and oxidative stress (malondialdehyde content). The ascorbate peroxidase (APOD) was activated most rapidly, already during the first week of water stress, but then its activity slowly decreased. Activation of superoxide dismutase (SOD) and catalase (CAT) by water deficit continued during the 14 d (Φw ≥ −1.65 MPa) and then their activities remain on the similar level. The activity of guaiacol-peroxidase (GPOD) increased mostly under progressive water stress and was correlated with increase in lipid peroxidation and growth restriction.

The effect of yeast extract and methyl jasmonate on rosmarinic acid accumulation in Coleus blumei hairy roots

Abstract: The leaves of axenically grown Coleus blumei were inoculated with Agrobacterium rhizogenes strain A4 and hairy root were established. PCR and Southern hybridization analysis confirmed transgenic nature of hairy root clones. Cultures of normal roots, induced by α-naphthaleneacetic acid on leaf explants, and hairy roots were evaluated for growth and rosmarinic acid content. Significantly better growth and up to 2.8 higher amount of rosmarinic acid was detected by HPLC analysis in hairy root clones. Methyl jasmonate stimulated rosmarinic acid accumulation in 6 out of 11 tested clones, while yeast extract induced RA accumulation in two and diminished it in 5 out of 11 tested hairy root clones.

Increase in isoprene and monoterpene emissions after re-watering of droughted Quercus ilex seedlings

Abstract: 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.

Multiple hormone analysis indicates involvement of jasmonate signalling in the early defence of potato to potato virus YNTN

Abstract: The involvement of plant hormones in the very early response of plants to virus infection was studied in potato plants (Solanum tuberosum L.) infected with potato virus YNTN (PVYNTN). Endogenous plant hormones and compounds mediating a stress response (JA-jasmonic acid, OPDA-12-oxo phytodienoic acid, SA-salicylic acid, IAA-indole-3-acetic acid, ABA-abscisic acid) were simultaneously quantified in susceptible cv. Desiree and resistant cv. Sante, one and three hours after inoculation. Of the hormones analysed, only the contents of endogenous JA and its precursor OPDA changed in a way that could be clearly connected with the early resistant response. In comparison to susceptible cultivar, a much more pronounced increase of JA was detected in virus-inoculated leaves of resistant cultivar at both time points. The same trend of changes was also observed with OPDA. However, there were no significant changes of JA and its precursor in upper intact systemic leaves and roots, at either time point. These findings implicate the jasmonate signalling pathway in a very early local but not systemic resistant defence of potato to PVYNTN.

Role of phytohormones and nitrogen in somatic embryogenesis induction in cell culture derived from leaflets of Azadirachta indica

Abstract: A protocol for somatic embryogenesis in Azadirachta indica A Juss. has been standardized using in vivo leaflets. Experiments were carried out to examine the effect of various auxins, cytokinins, sucrose, inorganic and organic salts on subsequent somatic embryo induction and maturation. Embryogenic calli were induced on Murashige and Skoog (MS) medium supplemented with 1.5 mg dm−3 kinetin and 1.5 mg dm−3 indole-3-acetic acid and subsequently all the stages of somatic embryo development (globular, cordate, torpedo and cotyledonary) were observed. Maturation of these embryos was accomplished with the same growth regulators after three subcultures. The histological study of somatic embryos showed resembles to zygotic embryos. The matured somatic embryos were transferred onto half strength MS-medium devoid of growth regulators for their germination (82 %). Plantlets were acclimatized in the field with a survival rate of 80–83.5 %.