Proteins WCS120 and DHN5 are known as the major cold-inducible dehydrins in wheat and barley plants, respectively. WCS120 and DHN5 relative accumulation increased exponentially along with a growth temperature decline in the range from optimum to cold temperatures. Even at optimum growth temperatures, the most frost-tolerant wheat and barley cultivars can be distinguished from the remaining ones according to dehydrin relative accumulation. The highly tolerant wheat and barley cultivars started accumulating dehydrins at higher growth temperatures and reached higher dehydrin amounts than the less tolerant ones. Statistically significant correlations between lethal temperature for 50 % of the samples (LT50) and dehydrin relative accumulation have been found at all growth temperatures (5, 10, 15 and 20 °C) for WCS120 in wheats and at 5 and 10 °C for DHN5 in barleys. Analogous relationships between dehydrin relative accumulation at different growth temperatures and plant acquired frost tolerance have been proved for wheat WCS120 and barley DHN5.

Aquaporins (AQPs) are proteinaceous channels known to regulate transmembrane water transport, and therefore may be important component of imbibition during osmopriming and germination. To explore the association between AQPs and osmopriming-led enhanced germination performance, we studied the expression patterns of four spinach (Spinacia oleracea) AQP coding genes (SoPIP1;1, SoPIP1;2, SoPIP2;1, and SoδTIP) during osmopriming and subsequent germination under optimal conditions, chilling and drought. All these genes were up-regulated within 2-4 d of priming (phase II-imbibition). We hypothesize such up-regulation to facilitate the pressure potential-driven cell expansion and increase germination potential of primed seeds. Our data during post-priming germination suggest that SoPIP1;1 and SoδTIP were more closely associated with enhanced germination performance. In general, all AQPs were downregulated under chilling and drought. However, under chilling, SoPIP2;1 was expressed at relatively higher level in primed seeds that also exhibited greater chilling tolerance, while SoPIP1;2 and SoδTIP exhibited opposite pattern. Similarly, SoPIP1;1, SoPIP2;1, and SoδTIP exhibited higher expression in primed seeds that also had greater drought tolerance.

The presence of visible multilamellar bodies in the cytoplasm of pollen grains of at least seven species of the family Papaveraceae has led us to study the behaviour of these bodies during pollen-grain ontogeny and in growing pollen tubes of Sarcocapnos pulcherrima C. Morales & R. Garcia germinated in vitro. Our transmission-electron-microscope (TEM) studies in pollen grains show that the multilamellar bodies may be classified as: 1) small, isolated and placed in the region of apertures in the cytoplasm; and 2) large, in clusters and in contact with the active plasmalemma apertures only when tubules are being formed in the apertural intine. Similar types of multilamellar bodies to those observed in the pollen apertures can be seen near the apex of the growing pollen tube (small and isolated) and in contact with the apex plasmalemma (large and clustered). Our results support the hypothesis that the multilamellar bodies are functionally linked to moments when the cytoplasmic membrane is very active. We have also linked the multilamellar bodies to Golgi vesicles as they both react positively to acid-phosphatase (AP) staining and also to the plasmalemma by the thiocarbohydrazide-silver proteinate-staining (TCH-Sp) electron-contrasting technique.

An efficient, rapid, and reproducible plant regeneration protocol was successfully developed for Abrus precatorius L. using mature nodal explants excised from a 5-year-old field grown plant. The highest shoot regeneration frequency (87 %) with maximum number of multiple shoots (15.0) and shoot length (4.8 cm) were recorded on Murashige and Skoog (MS) medium amended with 2.5 μM thidiazuron, 120 mg dm^-3 polyvinylpyrrolidone, and 0.5 μM α-naphthalene acetic acid. The best treatment for maximum root (4.0) induction was half strength MS medium supplemented with 1.5 μM indole-3-butyric acid. The in vitro plantlets with well-developed shoots and roots were successfully transferred into plastic cups with Soilrite and acclimatized in a culture room under photon flux density (PFD) of 150 μmol m^-2 s^-1, thereafter transferred to a greenhouse with PFD of 300 μmol m^-2 s^-1, and finally to a field with 70 % survival rate. During the acclimatization period (0-49 d), leaf chlorophyll and carotenoid content increased whereas malondialdehyde and H₂O₂ content decreased probably due to increasing activities of antioxidant enzymes (catalase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase). Our work suggests that micropropagated plants developed an antioxidant enzymatic protective system to avoid oxidative stress during establishment under ex vitro environment.

Viral resistance can be effectively induced in transgenic plants through their silencing machinery. Thus, we designed nine short hairpin RNAs (shRNA) constructs to target nuclear inclusion protein b (NIb), helper component proteinase (HC-Pro), cylindrical inclusion protein (CI) and viral protein genome linked (VPg) genes of Potato virus Y (PVY^N) and Tobacco etch virus (TEV-SD1). The shRNAs were completely complementary to the genes of PVY^N, and contained 1-3 nt mismatches to the genes of TEV-SD1. To study the specificity of gene silencing in shRNA-mediated viral resistance, the constructs were introduced into tobacco plants. The results of viral resistance assay revealed that these nine kinds of transgenic tobacco plants can effectively induce viral resistance against both PVY^N and TEV-SD1, and the shRNA construct targeting the NIb gene showed higher silencing efficiency. Northern blot and short interfering RNA (siRNA) analyses demonstrated that the viral resistance can be attributed to the degradation of the target RNA through the RNA silencing system. Correlation analysis of siRNA sequence characteristics with its activity suggested that the secondary structure stability of the antisense strand did not influence siRNA activity; 1 to 3 nt 5' end of the sense strand caused a significant effect on siRNA activity where the first base such as U was favourable for silencing; the base mismatch between the siRNA and the target gene may be more tolerated in the 5' end.

Isoflavone synthase (IFS; CYP93C) plays a key role in the biosynthesis of phenolic secondary metabolites, isoflavonoids. These compounds, which are well-known for their benefits to human health and plant defence, are produced mostly in legumes. However, more than 200 of them have been described in 59 other plant families without any knowledge of their respective IFS orthologue genes (with the sole exception of sugar beet). In this study, we selected IFS from Pisum sativum L. (CYP93C18) for functional expression. CYP93C18 was isolated, cloned, and introduced into Arabidopsis thaliana. The presence of the gene was shown by Southern blot analysis and its expression in the transgenic Arabidopsis was proven by RT-PCR and Western blots. The functional activity of the heterologous IFS was verified by HPLC-MS analysis of the metabolite levels: the isoflavone genistein and its derivatives tectorigenin and biochanin A were detected in the overexpressing lines. In addition, 35S::CYP93C18::GFP fused proteins were transiently expressed in the leaves of Nicotiana benthamiana and the localization of the GFP signal was observed on the endoplasmic reticulum using confocal microscopy which is consistent with the data from the literature and with our in silico predictions. The putative mode of attachment of IFS to the endoplasmic reticulum membrane is suggested. The undemanding methodology presented in this paper is applicable to the functional analysis of newly-identified isoflavone synthase genes from various species.

This study aimed to investigate the effects of irradiance on plant growth and content of proline and phytohormones during ex vitro acclimatization of micropropagated Ulmus minor plants. In vitro rooted plants were acclimatized to ex vitro conditions in a climate chamber with two irradiances, 200 μmol m^-2 s^-1 (high irradiance, HI) and 100 μmol m^-2 s^-1 (low irradiance, LI) for 40 d. Immediately after the ex vitro transfer, the plants experienced a water deficit [wilting leaves with the reduced relative water content (RWC)], but following the experiment, the recovery of the RWC was more pronounced in the HI treatment. Also, the content of proline, ABA, and JA-Ile were higher in HI treatment. Growth analyses revealed that HI improved growth and biomass production.

Calcium is a critical component in a number of plant signal transduction pathways and the calcineurin B-like protein (CBL) family is a unique group of calcium sensors regulating a family of CBL-interacting protein kinases (CIPKs). In this study, two poplar CBL genes, PeCBL6 (GenBank acc. No. DQ907710) and PeCBL10 (GenBank acc. No. DQ899956), were characterized in transgenic Arabidopsis thaliana, particularly with regard to its role in abiotic stress resistance. Expression of the two CBL genes in poplar was induced by cold, drought, or high salinity, but not by abscisic acid (ABA) treatment. In Arabidopsis thaliana, PeCBL6 was found in the nucleus and PeCBL10 in the tonoplast. Transgenic Arabidopsis plants overexpressing PeCBL6 or PeCBL10 showed enhanced tolerance to high salinity, drought and low temperature. These results suggested that PeCBL6 and PeCBL10 may function as positive regulators of salt, drought and temperature responses.

Brassinosteroids are known to protect plants against various abiotic and biotic stresses, however, very limited information is available about the role of progesterone. Therefore the effects of Pseudomonas syringae pv. syringae (P.s.) wild type strain 61, its hrcC mutant, and the saprophytic P. fluorescens (P.f.) strain 55 were investigated in wild type Arabidopsis thaliana cv. Columbia and its rbohF knock-out mutant, with and without progesterone pre-treatment. The reactions of wild type and rbohF mutant Arabidopsis to bacterial inoculations were similar, although 2 h after injection of P.s. a larger increase of electrolyte leakage was measured in wild type than in rbohF knockout mutant leaves. The hrcC mutant caused weak necrotic symptoms and increased leakage in both types of Arabidopsis, although to a much lesser extent than P.s. The P.f. did not induce any visible symptom, but slightly increased the electrolyte leakage in both types of Arabidopsis. Inoculation by all Pseudomonas bacteria led to significant alterations in photosystem 2 efficiency as compared to control plants. Pre-treatment of leaves with progesterone diminished the necrotic symptoms, the electrolyte leakage and improve the efficiency of photosystem 2 caused by Pseudomonas bacteria.

The present study evaluated the effects of 100 and 500 μM arsenate (Na₂HAsO₄) on pigment composition and photosynthesis in Hydrilla verticillata (L.f.) Royle. Arsenic accumulation increased in concentration and duration dependent manner. The maximum accumulation [568 μg(As) g^-1(d.m.)] was observed at 500 μM concentration and 96-h exposure. This concentration led to a significant decline in chlorophyll a content and PS II efficiency during the whole experiment, and in chlorophyll b and carotenoids after 96 h, but no significant changes in photosynthetic pigments were noticed at 100 μM arsenate. Net photosynthetic rate, electron transport rate, and water use efficiency declined whereas transpiration rate increased, and stomatal conductance and photochemical quenching did not show any effect or increased. The content of reactive oxygen species increased and content of reduced ascorbate declined at 500 μM arsenate in comparison to the control.

This study was carried out to better understand the role of salicylic acid (SA) applied before cold stress in the cold tolerance mechanism. Two barley (Hordeum vulgare) cultivars, cold-sensitive (Akhisar) and cold-tolerant (Tokak), were used and 0.1 mM SA was applied to 7-d-old barley seedlings growing under control conditions (20/18 °C). The seedlings were transferred to cold chamber (7/5 °C) at the age 14, 21, and 28 d. After three days, the leaves were harvested to determine the activities of apoplastic antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) and ice nucleation activity and electrophoretic patterns of apoplastic proteins. Cold treatment decreased the activities of all enzymes in cold-sensitive cultivar, however, it increased CAT and POX activities in cold-tolerant cultivar. Exogenous SA increased enzyme activities in both cultivars. Ice nucleation activity increased by cold treatment, especially in 17-d-old seedlings in both cultivars. In addition, SA treatment increased ice nucleation activity in all examined samplings in both cultivars. SA treatment caused accumulation or de novo synthesis of some apoplastic proteins. The results of the present study show that exogenous SA can improve cold tolerance by regulating the activities of apoplastic antioxidative enzymes, ice nucleation activity, and the patterns of apoplastic proteins.

Sex-related differences in the responses of plants to CO₂ enrichment are still rarely studied. In this study, we examined the effects of elevated atmospheric CO₂ (720 μmol mol^-1) on the activities of polyphenoloxidases (PPOs) and guaiacol peroxidases (PODs) in male and female plants of two ecologically divergent willow species Salix repens and S. phylicifolia. We detected that females invested more in PPO-based defence than did males, whose PPO activity decreased as a result of CO₂ enrichment. Moreover, we found that the inherently slow-growing S. repens had markedly higher POD activity than did the more rapid-growing S. phylicifolia. The PODs of these two species also differed in their biochemical properties.

A new ethylene response factor (ERF), GmERF6, was isolated from soybean. Protein sequence alignment of GmERF6 revealed an AP2/ERF domain, two putative nuclear localization signals (NLSs) and an ERF-associated amphiphilic repression (EAR) motif. Real-time quantitative PCR analysis revealed that the expression of GmERF6 was differentially induced in soybean seedlings by drought, salt, cold, salicylic acid, ethylene, abscisic acid and methyl jasmonate. Transient expression experiments demonstrated that GmERF6 functions as a transcriptional repressor to downregulate the transcriptional levels of the reporter gene and repress the activated ability of other transcriptional activator. Transgenic Arabidopsis lines constitutively expressing GmERF6 showed an increased tolerance to drought compared to wild-type plants.

Wood ontogeny patterns were determined during the ex vitro acclimatization period in micropropagated plantlets of hybrid poplar clones T-14 [Populus tremula × (Populus × canescens)] and T-50 [(Populus × canescens) × Populus tremula]. The temporal course of developmental changes in the woody tissue was characterized on a weekly basis starting from the day of transfer to the ex vitro environment until full acclimatization was achieved on day 28. In vitro rooted plantlets had already initiated lignification of secondary xylem cells. The greatest increase in the amount of woody tissue was observed on days 21 and 28. At the end of the acclimatization period, T-14 plantlets contained on average 41.4 % of secondary xylem tissue compared to 30.3 % found in T-50 plantlets. During the course of acclimatization, both clones displayed identical patterns of vessel lumen size distribution from small vessel lumen area to large vessel lumen area. This pattern differs from the characteristic diffuse-porous pattern of approximately evensized vessel lumen area distribution typical of mature wood. At the end of acclimatization, the differences in vessel lumen area and relative conductivity between the clones were negligible. Development of secondary xylem tissue during ex vitro acclimatization promotes the establishment of vigorous regenerants with stems that show increased bending strength and stiffness.

Grafting is an important cultivation method and recent research on the mechanism of interactions between rootstock nad scion is focused on the long-distance transport of mRNA and small RNAs in the phloem. Among these transportable molecules, NACP gene coding NAM, ATAF1/2, CUC2 (NAC) domain protein might be involved in apical meristem development. Here, we report the transport of NACP mRNA between Chinese pear (Pyrus bretschneideri) cv. Yali (scion) and the wild Pyrus betulaefolia Bunge (rootstock). Our results indicated that NACP mRNA can be transported in both directions from the 3^rd to 10^th day after micro-grafting. It can also be transported to the shoot apex 30 to 70 cm away from graft-union in 2-year-old grafted trees. For further investigation, transgenic tobaccos with 35S: P. betulaefolia-NACP construct were grafted on wild-type tobaccos (Nicotiana tabacum L. cv. Samsun). The sustainable transport of Pyrus-NACP mRNA through the graft-union occurred from the 15^th day after grafting.

Drought stress enhances the production of superoxide radical (O₂ ^._) and superoxide dismutase catalyses dismutation of it to H₂O₂ and O₂, and hence provides a first line of defense against oxidative stress. Over-expression of a cytosolic copper-zinc superoxide dismutase, cloned from Potentilla atrosanguinea (PaSOD), in potato (Solanum tuberosum ssp. tuberosum L. cv. Kufri Sutlej) resulted in enhanced net photosynthetic rates (P_N) and stomatal conductance (g_s) compared to that in the wild type (WT) plants under control (irrigated) as well as drought stress conditions. Drought stress declined leaf water potential, P_N, g_s, photosystem II activity, and chlorophyll content, but increased proline and O₂ ^._ content more in WT than transgenic potato plants (SS5). The significantly higher SOD activity in SS5 coincided well with lower O₂ ^._ content suggesting its role in maintaining higher g_s and P_N in transgenic potato plants.

Soil salinity is a major abiotic stress and salt overly sensitive (SOS) pathway plays an important role in imparting tolerance to salinity by reinstating cellular ionic equilibrium. Salt overly sensitive 1 (SOS1) gene of SOS pathway has been implicated in increasing salt tolerance in plants. In this study, a 734 bp fragment of SOS1 promoter (SbUSOS1) was isolated from a halophyte Salicornia brachiata Roxb. In silico analysis of SbUSOS1 predicted several cis-acting regulatory elements such as DOF motif, GT elements, ABRE-like sequence, and root specific motifs. Functional validation of SbUSOS1 into tobacco stems and leaves using the GUS reporter gene showed that this promoter is induced by salt stress (250 mM NaCl) but not by ABA (500 μM) and cold (4 °C) stresses. This study indicated that SbUSOS1 was functional with predicted cis-acting elements that could be responsible for its salt-inducible nature. It can be used for the development of salt stress tolerant transgenic plants.

The effects of paclobutrazol (PBZ) on the ex vitro transfer efficiency of in vitro grown Dendrobium nobile seedlings were investigated. The survival percentage was increased by 41.6 % with 0.8 mg dm^-3 PBZ treatment compared to controls. The PBZ-treated D. nobile plants were shorter than control plants. Morphological and anatomical analyses showed that root diameter, especially at the root apex, became larger after treatment with PBZ which is consistent with the increases in cortical cell sizes and row numbers. In addition, the first observations of thickened velamen of the PBZ-treated seedling were made in the present study. The activities of cellulase and indole acetic acid oxidase increased in PBZ-treated plantlets, whereas that of cell wall-associated peroxidase declined compared to controls. The content of endogenous gibberellic acid and iso-pentenyladenosine of root tips changed little by PBZ but that of indole-3-acetic acid decreased by 53 %. These results indicated that PBZ could improve the transfer efficiency of D. nobile from in vitro culture to pots due to its effects on root development.

The rice OsMyb4 gene, which encodes a Myb transcription factor (TF), improves the stress tolerance/resistance when expressed in both monocotyledonous and dicotyledonous transgenic plants. In this study, a phylogenetic analysis showed the existence of putative OsMyb4 homologues in monocot and dicot species. In particular, the analysis revealed that OsMyb4 belongs to a small rice gene subfamily conserved among monocots. The expression analyses of the OsMyb4-like genes in rice, wheat, and Arabidopsis indicated that these genes are involved in the response to dehydration, cold, and wounding. Moreover, the in silico analysis of the 5' upstream regions of the Osmyb4-like genes highlighted that the positions of some cis-elements involved in the stress response were conserved among the putative promoters, especially between OsMyb4 and its putative paralog Os02g41510. Finally, our transient expression assays in tobacco protoplasts demonstrated that OsMyb4 is able to repress the activity of both its own promoter and the Os02g41510 promoter by acting on the same binding site. A compensatory mechanism of auto-regulation is consistent with the well-known complexity of the OsMyb4-activated pathway, and this mechanism could regulate the transcription of other genes belonging to the family.

Two cultivars of winter wheat (Triticum aestivum L.) differing in their drought tolerance (KTC86211 and ND7532) were subjected to a progressive soil water stress and recovery at four developmental stages. Dehydrins with molecular masses of 45 and 37 kDa were constitutively accumulated during all stages in both genotypes. The 28 kDa dehydrin accumulated exclusively at seedling stage in both genotypes. The 49 and 40 kDa dehydrins accumulated at both tillering and jointing stages but showed a genotype-specific pattern. The content of most dehydrins increased with decreased soil moisture and then decreased during recovery. These results suggest that accumulation pattern of dehydrins during water stress was related to the genotype and developmental stage.

Randomly amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) markers were applied to assess the genetic stability of micropropagated olive (Olea europaea L. cv. Maurino) plants regenerated by axillary buds. Initial olive explants, isolated from one donor tree, were multiplied on Murashige and Skoog medium for 12 repeated subcultures. A total of 40 RAPD and 10 ISSR markers resulted in 301 distinct and reproducible band classes showing homogeneous RAPD and ISSR patterns. The amplification products revealed genetic stability among the micropropagated plants and between them and the donor plant. The results demonstrate the genetic stability of nine year old mature micropropagated olive plants cultured in field, and corroborated the fact that axillary multiplication is the safest mode for multiplication of true to type plants.

The influence of freezing on phospholipase D (PLD) was studied in Chorispora bungeana Fisch. & C.A. Mey., which is a naturally cold-tolerant species. During the freezing treatment (-4 °C), PLD activities in both microsomal and mitochondrial membranes increased at day 3, remained at a high level at day 6 and then declined to a moderate level. The RT-PCR analyses showed that PLD activity partially corresponded to the CbPLD gene transcript level. The freezing treatment resulted in increases in the K _m and V _max for microsomal and mitochondrial PLD, respectively. Freezing injury, as measured by electrolyte leakage and malondialdehyde content, peaked at day 6 and then gradually decreased. Alleviation of freezing injury was related to a decreased content of membrane-associated Ca²⁺. We suggest that the specific mechanism of cold resistance of C. bungeana is linked with PLD.

Cytokinins have been implicated in delaying leaf senescence. We previously generated transgenic cotton (Gossypium hirsutum L.) plants that harbor the Agrobacterium isopentenyl transferase gene (ipt) directed by a proteinase gene promoter. Here, we report that mRNAs were isolated from ipt cotton leaves and azygous leaves and were subsequently sequenced using Illumina Solexa technology. The sequence tags were searched against the TIGR database and the related gene expression profiles were compared resulting in the identification of 1 218 differentially expressed genes (DEGs): 719 up-regulated and 499 down-regulated. Analyzing the DEGs in the ipt cotton leaves showed that these genes belonged to four pathways: flavone biosynthesis, arginine and proline metabolism, glyoxylate and dicarboxylate metabolism, and RNA degradation. These pathways increased the activities of antioxidants, inhibited the effect of ethylene, and prevented degradation of macromolecules during senescence. The expression patterns of 17 genes were evaluated by real-time PCR and results were in agreement with the patterns of sequencing analysis. The identification of the DEGs may help us to understand a role of cytokinins in leaf senescence.

Peanut plants exposed to water stress induced by polyethylene glycol (PEG) accumulated abscisic acid (ABA) and hydrogen peroxide (H₂O₂), the increase being significant at 12 and 24 h after addition, respectively. To address the question whether the increase in H₂O₂ production was related to ABA accumulation, the peanut leaves were pretreated with ABA biosynthesis inhibitor (sodium tungstate) and then exposed to water stress. Under these conditions, a decrease of ABA and H₂O₂ content were found after 12 h. The addition of 100 μM ABA restored H₂O₂ content reaching values similar to those under water stress at 12 h. We concluded that ABA accumulation is the first signal that triggers the H₂O₂ generation in peanut during first 12 h but its subsequent production is partially ABA-independent.

A cDNA encoding an ERE-binding protein (EgAP2-1) was isolated from the oil palm fruit mesocarp treated with ethylene using yeast one-hybrid assay. EgAP2-1 belongs to the AP2 subfamily of the APETALA2/ethylene-responsive factor (AP2/ERF) proteins and contains two highly conserved AP2/EREBP DNA-binding domains (DNA-BD). Sequence comparison of EgAP2-1 with other AP2 proteins revealed high conservation of the two AP2/EREBP domains and linker region among these proteins. Its protein was localized to the nucleus of onion epidermis cells and showed ERE-specific binding, transcriptional activation, and transactivation properties in yeast and in vitro. Its mRNA was highly expressed in oil palm mesocarp with elevated levels in ripening fruits but not in leaves and roots. EgAP2-1 was induced in mesocarp in response to ethylene and abscisic acid but not other hormonal stimuli, including methyl jasmonate and salicylic acid, and abiotic stresses including drought, cold, and high-salinity. Our results demonstrate a link between the regulation of EgAP2-1 expression and ethylene- and/or ABA-coordinated control of the fruit ripening and suggest a regulatory role for EgAP2-1 during fruit ripening and development in oil palm.

The gas exchange of the upper fully expanded leaf of the root parasite Striga hermonthica and of its host Sorghum bicolor was measured under wet and dry conditions to identify the mechanisms of the devastating effects of the parasite on its hosts under drought. The short-term water stress severely reduced photosynthetic rate in infected sorghum, but less in S. hermonthica. Soil water stress did not affect leaf respiration rate in either S. hermonthica or infected sorghum. This suggests that under dry conditions both infected sorghum and S. hermonthica decreased autotrophic carbon gain. The transpiration rate of S. hermonthica, a major driving force for assimilate uptake from the host, was higher and less affected by water stress than that of infected sorghum. Stomatal density on the abaxial surfaces of the leaves was higher in S. hermonthica than in sorghum. Both S. hermonthica infection and water stress decreased stomatal conductance of the sorghum leaves. S. hermonthica, irrespective of soil water status, had greater stomatal aperture on the adaxial and abaxial surfaces of its leaves than infected sorghum. These results indicate that the higher transpiration rate of S. hermonthica even under water stress, achieved through higher stomatal density on the abaxial surfaces of the leaves and greater stomatal aperture on both surfaces of the leaves, may induce the maintenance of water and solute transfers from the host to the parasite leading to severe damage to the host under drought.

A segregating population from the cross between drought sensitive (Variant-2) and drought tolerant (Cham-6) genotypes was made to identify molecular markers linked to wheat (Triticum aestivum L.) flag leaf senescence under water-stress. From 38 random amplified polymorphic DNA (RAPD) primers, 25 inter-simple sequence repeat (ISSR) primers and 46 simple sequence repeat (SRR) primers, tested for polymorphism among parental genotypes and F2 population. Quantitative trait locus (QTL) for flag leaf senescence was associated with 1 RAPD marker (Pr9), 4 ISSR markers (Pr8, AD5, AD2 and AD3), and 1 SSR marker (Xgwm382) and explained 44, 50, 35, 31, 22 and 73 % phenotypic variation, respectively. The genetic distance between flag leaf senescence gene and Pr9 was 10.0 cM (LOD score 22.9). The markers Pr8, AD5, AD2 and AD3 had genetic distances of 10.5, 14.6, 15.6 and 18.1 cM, respectively (LOD scores 22.6, 17.8, 17.5 and 14.6). The genetic distance between Xgwm382 was 3.9 cM (LOD score 33.8). Therefore, the RAPD, ISSR and SSR markers linked to the QTL for the drought-induced flag leaf senescence can be further used in breeding for drought tolerance in wheat.

We have compared the influence of two aromatic cytokinin derivatives, N ⁶-benzyladenine (BA) and meta-topolin (mT), on the in vitro multiplication and senescence of wych elm (Ulmus glabra Huds.). After 3 months of cultivation, the micropropagation rate was higher (approx. six times more shoots developed) on Murashige and Skoog (MS) medium supplemented with mT than on MS supplemented with BA. Quantification of 50 endogenous cytokinins, using a recently developed UPLC-ESI(+)-MS/MS method, showed significant differences in the cytokinin metabolites (especially different glucosides) in explants cultivated on media supplemented with BA or mT. Differences in efficiency of photosystem II was also detected.