The antioxidative system was studied during the development of pea plants. The reduced glutathione (GSH) content was higher in shoots than in roots, but a greater redox state of glutathione existed in roots compared with shoots, at least after 7 d of growth. The 3-d-old seedlings showed the highest content of oxidised ascorbate (DHA), which correlated with the ascorbate oxidase (AAO) activity. Also, the roots exhibited higher DHA content than shoots, correlated with their higher AAO activity. The activities of antioxidant enzymes were much higher in shoots than in roots. Ascorbate peroxidase (APX) activity decreased during the progression of growth in both shoots and roots, whereas peroxidase (POX) activity strongly increased in roots, reflecting a correlation between POX activity and the enhancement of growth. Catalase activity from shoots reached values nearly 3 or 4-fold higher than in roots. The monodehydroascorbate reductase (MDHAR) activity was higher in young seedlings than in more mature tissues, and in roots a decrease in MDHAR was noticed at the 11^th day. No dehydroascorbate reductase (DHAR) was detected in roots from the pea plants and DHAR values detected in seedlings and in shoots were much lower than those of MDHAR. In shoots, GR decreased with the progression of growth, whereas in roots an increase was seen on the 9^th and 11^th days. Finally, superoxide dismutase (SOD) activity increased in shoots during the progression of growth, but specific SOD activity was higher in roots than in shoots.

Metallothioneins are involved in detoxification of heavy metals. A cDNA encoding type 3 metallothionein (PcMT3) was isolated from the salt stressed leaf cDNA library of Porteresia coarctata (Roxb.) Tateoka (wild rice) that grows well in the heavy metal laden estuarine soils. The PcMT3 cDNA (581 bp) encodes a protein of 64 amino acids. PcMT3 is highly homologous (82 %) to OsMT-I-3a of rice, but is unique from other type 3 plant MTs due to the presence of an additional glycine residue in the C-terminal domain. Analysis of the 5' upstream region of PcMT3 showed the presence of cis-acting elements like the CG box and STRE previously reported to be involved in gene expression under heavy metal stress. Southern analysis suggested the presence of more than one copy of PcMT3-like sequences in the P. coarctata genome. Analysis of genomic clone of PcMT3 revealed the presence of two introns. A comparison of the genomic sequence of PcMT3 with closely similar type 3 MTs from rice and mangrove species revealed conservation in the number and position of introns. Transcript profiling for PcMT3 in P. coarctata leaves in the presence of Cd, Cu and Zn showed an increase in transcript accumulation.

Universal (consensus) primers are those primers that have the ability to amplify the targeted region of DNA across a broad range of individuals in a certain group of organisms. In plants, such universal primers have been designed to target regions in the nuclear, mitochondrial or chloroplast genome. Among these three genomes, the chloroplast genome is the most suited for the design of consensus primers due to the lower rate of evolution and hence conservation of gene order and sequence of the genome among the different plant species compared to the other two genomes. Several molecular studies in plants have developed and used chloroplast-specific universal primers. In this review, I present some examples of the nuclear DNA-specific universal primers and discuss the features of the chloroplast DNA that make it the most suited for the design of such primers. I then refer to all chloroplast-specific primers developed so far and provide some examples of molecular studies and applications that made use of them.

Grape (Vitis vinifera L.) seedlings grown in vitro were treated with either 200 mM NaCl or 350 mM mannitol for 7 d. Both salinity and osmotic stress caused significant increase in electrolyte leakage. From the three commonly occurring free polyamines (PA), only conspicuous accumulation of putrescine was found in the NaCl-treated seedlings. Four PA biosynthetic genes encoding arginine decarboxylase (pVvADC), S-adenosylmethionine decarboxylase (pVvSAMDC), spermidine synthase (pVvSPDS) and spermine synthase (pVvSPMS) were successfully isolated. While induction of pVvADC was observed from the 1^st day of salt treatment, pVvSAMDC and pVvSPMS were induced only at late stage of stress. As for expression levels of genes in the mannitol-treated seedling, either temporary (pVvADC at day 1) or late (pVvSPMS at days 5 and 7) induction was observed.

Sexual polyploidization has both a theoretical as well as an applied significance. Morphological screening for large pollen grains and shape of pollen produced by the individual, cytological investigation of hybrid progeny, and unbalanced separation of chromosomes at anaphase I in pollen mother cells were used to detect the gametes with somatic chromosome number in Fuchsia. The interspecific hybrids of F. fulgens (sect. Ellobium) × F. magellanica (sect. Quelusia), F. fulgens (sect. Ellobium) × F. splendens (sect. Ellobium), and F. triphylla (sect. Fuchsia) × F. splendens (sect. Ellobium) produced at the University of Auckland, New Zealand, showed both large and normal pollen grains in the same anther indicating the presence of unreduced gametes. Cytological investigation carried out on the hybrid progeny of F. fulgens (diploid, 2n=22, sect. Ellobium) × F. magellanica (tetraploid, 2n=44, sect. Quelusia) and F. triphylla (diploid, sect. Fuchsia) × F. arborescens (diploid, sect. Schufia) revealed unexpected chromosome numbers of 2n=44 and 2n=33, respectively. In general, the hybrids showed low fertility caused by genetically unbalanced gametes resulted from random disjunction of chromosomes at anaphase I. Studies on meiosis together with the presence of different shapes and sizes of pollen grains in Fuchsia proved indirectly that unreduced gametes are the products of first division meiotic nuclear restitution. These unreduced gametes were viable irrespective of pollen shape, their predominance in the hybrids, nuclear DNA amount and species phylogenetic position.

This study investigated guard cells on the adaxial and the abaxial epidermes during Erythrina corallodendron sepal development. On the adaxial epidermis, the morphology of guard cells was highly variable and changes in aperture induced by abscisic acid (ABA) were observed in 9.1 % stomata, while on the abaxial epidermis 86.7 % stomata responded to ABA. On the adaxial epidermis, stomata did not close even when guard cell pressure potential was reduced to zero by plasmolysis, even if fluorescein diacetate revealed that guard cells were alive. It was concluded that guard cells on the adaxial and the abaxial epidermes of sepals sensed environmental conditions differently, maybe due to different guard cell wall elasticity.

Strawberry (Fragaria ananassa Duch.) seedlings were pretreated with hexanoic acid 2-(diethylamino)ethyl ester (DA-6) in concentrations of 0, 10, 20 and 40 mg dm^-3 and then subjected to chilling and rewarming. The effects of applied DA-6 on the generation of reactive oxygen species (O₂ ^-, H₂O₂), lipid peroxidation, proline accumulation and photosynthesis were evaluated. Pretreatment with DA-6 alleviated the inhibition of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities caused by chilling stress thus reducing O₂ ^- and H₂O₂ production and lipid peroxidation in pretreated plants. DA-6 pretreatment also accelerated accumulation of proline and reduce the decrease in proline content after rewarming. DA-6 pretreatment increases maximum quantum yield of photosystem 2 (F_v/F_m), actual photochemical efficiency of photosystem 2 (Φ_PS2), photochemical quenching coefficient (qP) and net photosynthetic rate (P_N) and decreases non-photochemical quenching coefficient (qNP) of the seedlings under chilling stress. DA-6 pretreatment also increased the recovery rate of photosynthesis after rewarming.

Photosynthetic rate (P_N) and chlorophyll (Chl) fluorescence induction of source leaves in response to a low sink demand created by girdling the branch (GB) between the root-tuber-system and the leaves were studied in Dahlia pinnata L. cv. Rigolet during the stage of rapid tuber growth in the greenhouse. GB resulted in significantly lower values of P_N, stomatal conductance (g_s), and transpiration rate (E), but in higher leaf temperature (T_l) compared with those of controls. With exception of maximum quantum yield of photosystem 2 (PS 2) photochemistry (F_v/F_m) and maximum ratio of quantum yields of photochemical and concurrent non-photochemical processes in PS 2 (F_v/F₀), no significant differences were observed in Chl fluorescence parameters between girdled and control leaves on days 1 and 2 after GB, indicating no apparent damage in the photosynthetic apparatus. However, longer girdling duration resulted in higher non-photochemical Chl fluorescence quenching (NPQ), but lower F_v/F₀, actual efficiency of energy conversion in PS 2 under steady-state conditions (Φ_PS2), and photochemical quenching coefficient (qP) in comparison with controls from 10:00 to 16:00 or 15:00 on days 4 and 5, respectively, indicating reversible injury in the photosynthetic apparatus.

The effect of increased Cd²⁺ concentrations in the watering solution on citrus physiology was studied by using two citrus genotypes, Cleopatra mandarin and Carrizo citrange. Cadmium content in roots and leaves was tested together with measurements of leaf damage, gas exchange parameters, and hormonal contents. Citrus roots efficiently retained Cd²⁺ avoiding its translocation to the shoots and Cleopatra mandarin translocated less Cd²⁺ than Carrizo. With increasing Cd²⁺ concentration all gas exchange parameters were decreased more in Carrizo than in Cleopatra mandarin. Cd-induced increases in abscisic acid and salicylic acid contents were observed in leaves but not in roots of both genotypes.

Pseudomonas fluorescens was used as a biological control agent against bacterial wilt disease caused by Ralstonia solanacearum. Activities of phenylalanine ammonia lyase (PAL), guaiacol peroxidase (POX), polyphenol oxidase (PPO) and lipoxygenase (LOX) increased in P. fluorescens pretreated tomato seedlings, which were later inoculated with R. solanacearum and activities of PAL, POX, PPO and LOX reached maximum at 12, 9, 15 and 9 h, respectively, after inoculation. Reverse transcription - polymerase chain reaction (RT-PCR) confirmed the maximum induction of all these enzymes in P. fluorescens pretreated seedlings.

Anther-derived pre-embryogenic masses (PEMs) of callus, established via suspension cultures, were encapsulated to form synthetic seeds suitable for cryopreservation. The synchronised suspension culture proliferation necessitated the optimisation of plant growth regulators for different cultivars. The growth phase and density of the culture were also important as well as the exposure of cells to vitrification solution containing 0.75 M sucrose with 0.1 M CaCl₂ and 2.0 % sodium alginate (pH 5.7). Pre-treatment of the encapsulated cells for 2 d with Nitsch and Nitsch (NN) medium containing 0.75 M sucrose solution followed by dehydration for 4 h in a laminar flow box provided maximum cell viability, which varied from 0 to 40 %. The embryo proliferation from the cryopreserved beads involved warming them and then transfer to NN medium containing glutamine (50 mg dm^-3) and activated charcoal (2.5 %). The maximum number of embryos obtained was 31-53 per bead. Subculture into the same medium induced secondary embryogenesis, which was initiated from the meristematic region, radicle, and root cap. Proliferation and maturation of secondary embryos was faster than of primary embryos. No phenotypic variation or abnormal structures compared to the control were observed in the regenerated plantlets.

This article describes the complete microsporogenesis and pollen formation in cassava (Manihot esculenta Crantz) at the various developmental stages (pollen mother cell, meiosis, tetrads, early free spore, mid uninucleate, late uninucleate, binucleate and mature pollen grain). Light microscopy, transmission electron microscopy and confocal laser scanning microscopy were used for the study. Floral bud size and other inflorescence characteristics were correlated with specific stages of the microspore development. This association allows a rapid selection of floral buds with similar microspore developmental stages, useful when a large number of homogeneous cells are needed for analysis and for in vitro induction of androgenesis. This article also compares methods for digestion the exine wall in microspores.

Dendrobium Sonia 17 calluses were used for co-transformation study using particle bombardment. The bombarded transformed callus tissues were selected using half-strength MS medium containing 25 mg dm^-3 hygromycin. Expression of green fluorescent protein (GFP) was observed in the callus and protocorm-like body (PLBs) tissues survived on the selection medium. The presence of green fluorescence protein (sgfp), hygromycin-B-phosphotransferase (hptII) and β-glucuronidase (uidA) genes in the transformed tissues were verified using PCR, Southern blot and dot blot analyses. Based on the results from PCR and expression of sgfp and uidA genes in the calluses and PLBs survived from hygromycin selection, we reported the co-transformation of sgfp, hptII and uidA genes into Dendrobium Sonia 17. GFP-expressing tissues were also observed in the regenerated transformed plantlets.

In this study, we selected two known pathogen-inducible cis-acting elements, F and E17, to construct synthetic pathogen-inducible promoters for analysis in transformed canola (Brassica napus L.). The synthetic promoter approach was used, which involved the insertion of dimers and combining two cis-acting elements (E17 and F) upstream of the minimal CaMV 35S promoter. Canola plants were transformed by three constructs, pGEE, pGFF, pGFFEE containing synthetic promoters (SP), SP-EE, SP-FF and SP-FFEE, respectively. Analyses of histochemical and fluorometric GUS expression indicated that synthetic promoters responded to fungal elicitors and phytohormone treatments. The SP-FF promoter showed high responses against methyl jasmonate and Sclerotinia sclerotiorum, while SP-EE demonstrated inducibility only in response to salicylic acid and Rhizoctonia solani. The SP-EE promoter similar to SP-FFEE, did not respond to S. sclerotiorum and methyl jasmonate. However, SP-FFEE was highly induced by R. solani elicitors and showed that the level of GUS expression was greater than that by either of E17 or F elements alone. These three synthetic promoters did not activate the expression of the reporter gene in response to cold, heat, UV and wounding.

In this work, the effect of lead on sunflower seedlings with two root system types: primary - formed from embryonic tissues and adventitious - originating from hypocotyl after cutting off primary roots was investigated. The seedlings were subjected to Pb(NO₃)₂ in doses: 0, 0.5, 2.5, 5 and 20 mg(Pb) dm^-3 for a week. Lead accumulation, seedling length and mass as well as selected parameters representative of oxidative damage (malondialdehyde) and protection (superoxide dismutase and glutathione) were used to compare stress response of plants. The comparison showed significant differences between plants with different root systems in almost all the parameters and the plants with adventitious root were more tolerant to lead.

To identify genes that are up and down-regulated by water deficit in sugarcane we used the macroarray methodology and the expression level of 3 575 independent sugarcane cDNAs was measured by hybridization with RNA extracted from plants submitted to mild, moderate and severe water deficit. We identified approximately 1 670 differentially expressed genes from which 62 % were up-regulated by different stress-conditions, whereas many repressed genes were exclusive for each time-point. Analysis of similarity showed that approximately 24 % of the differentially expressed genes shared homology with proteins involved in different processes such as signal transduction, hormone metabolism, photosynthesis, transcription and stress response. Transcripts with no known function accounted for approximately 39 % and those without similarity represented 36 % of the sequences. Five genes analyzed by RT-PCR confirmed the macroarray results.

In vitro cultures of Azadirachta indica A. Juss. were raised by first culturing the root segments on modified Murashige and Skoog (MS) medium supplemented with 8.88 μM 6-benzylaminopurine (BAP), 9.84 μM N⁶-(2-isopentenyl) adenine (2iP), 5.71 μM indole-3-acetic acid (IAA), 81.43 μM adenine hemisulphate and 2.27 μM putrescine for 2 d followed by their transfer to the same medium except containing one-tenth of the initially used concentrations of BAP, 2iP and IAA. The regenerated shoots sustained proliferation in the basal medium supplemented with 1.11 μM BAP, 1.43 μM IAA and 135.72 μM adenine hemisulphate. The isolated shoots were rooted to produce plantlets in the presence of 2.46 μM indole-3-butyric acid (IBA). The plantlets showed uniform luxuriant growth under field conditions. True-to-type nature of the field-grown root-regenerated plants was ascertained by random amplified polymorphic DNA (RAPD) analysis.

Imaging fluorometry was applied to investigate the tolerance of Japanese honeysuckle (Lonicera japonica Thunb.) of different ploidy levels to heat stress. Seedlings of L. japonica, the diploid cv. Damaohua and the tetraploid cv. Jiufengyihao, were exposed to heat stress of 42 °C for 6 h and a recovery for 10 h. Heat stress significantly decreased maximum photochemical efficiency, electron transport rate, effective quantum yield of photosystem 2, and photochemical quenching of both cultivars, but it decreased the non-photochemical quenching (NPQ) only in the tetraploid. Heat stress increased the content of total soluble sugars, proline, and malondialdehyde in both cultivars while it increased NPQ only in the diploid. Our findings suggest that the tetraploid showed to be more resistance to heat stress than the diploid of L. japonica, which was indicated by different chlorophyll fluorescence imaging techniques and metabolic changes. Moreover, the degree of recovery in the tetraploid was higher than that of the diploid. The tetraploid also possessed thicker epidermis (both upper and lower) and palisade tissue as well as denser pubescence.

Embryogenic and non-embryogenic calli were induced from the Centella asiatica leaf explants on Murashige and Skoog medium supplemented with kinetin and 2,4-dichlorophenophenoxyacetic acid. The extracellular matrix (ECM) layer was seen on the surface of embryogenic cells but not on the non-embryogenic cells. The ECM formed bridges with net-like material between the embryogenic cells. This network like structure was believed to play an important role in plant morphogenesis and can serve as an early structural marker of embryogenic competence in Centella asiatica calli culture.

The effects of the ectopic expression of a barley transcription factor (HvCBF4) under the control of a constitutive (maize Ubi1) or a stress-inducible (Arabidopsis RD29A) promoter in the abiotic stress response in rice (Oryza sativa L.) was investigated. The transformed plants were analyzed both at molecular and physiological level and the AtRD29A::HvCBF4 plants were further analyzed using the GeneChip® rice genome array under control conditions. Only the plants constitutively expressing HvCBF4 have shown increased survival to drought stress, but not to cold or high-salinity. These plants have also shown better photosynthetic capacity, as determined by chlorophyll fluorescence. Plants expressing AtRD29A::HvCBF4 did not show increased survival to any of the stresses applied. However in the GeneChip® microarray, these plants have shown up-regulation of many stress-responsive genes (> 400) as compared to non-transformed plants. Interestingly, RT-PCR analysis revealed not only differential gene expression between roots and shoots, but also between transgenic lines with the different promoters. Our results indicate that different HvCBF4 expression levels resulted in different transcriptomes and drought tolerance. Given that AtRD29A::HvCBF4 plants did not show increased tolerance to any of the imposed stresses, we may conclude that this promoter may be inappropriate for rice transformation aiming for enhanced abiotic stress tolerance.

The effects of temperature (25-45 °C) and pH (7.5-5.5) on photosystem (PS) 2 was studied in spinach (Spinacia oleracea L.) thylakoid membranes using chlorophyll a fluorescence induction kinetics. In high temperature and low pH treated thylakoid membranes a decline in the variable to maximum fluorescence ratio (F_v/F_m) and PS 2 electron transport rate were observed. More stacking in thylakoid membranes, studied by digitonin fractionation method, was observed at low pH, while the degree of unstacking increased under high temperature conditions. We conclude that the change in pH does not significantly affect the donor/acceptor side of PS 2 while high temperature does. Fluorescence emission spectra at 77 K indicated that low pH is associated with energy redistribution between the two photosystems while high temperature induced changes do not involve energy re-distribution. We suggest that both, high temperature and low pH, show an inhibitory effect on PS 2 but their mechanisms of action are different.

Four different markers [random amplified polymorphic DNA (RAPD), inter simple sequence repeat (ISSR), amplified fragment length polymorphism (AFLP), and selective amplified microsatellite polymorphism length (SAMPL)] were applied for evaluating somaclonal variation of micropropagated genotypes of stone pine (Pinus pinea L.). The total number of primers tested was 130, with 223 combinations assayed. A high number of them amplified successfully (178), representing 79.82 % of the total, and the average number of amplified fragments ranged from 2.47 (ISSR) to 65.76 (SAMPL). Based on internal controls, no problem of reproducibility was detected. Almost no somaclonal variation was detected within the clones. Of the tested markers, ISSR, AFLP, and SAMPL showed monomorphic amplification profiles, with only RAPD markers showing some interclonal variation.

The role of glutathione (GSH) in the adaptation of wild type Arabidopsis thaliana plants to Cd stress was investigated. The nutrient solution (control or containing 50 or 100 μM Cd) was supplemented with buthionine sulfoximine (BSO; 50, 100, 500 μM, to decrease the GSH content in plants) or GSH (50, 100, 500 μM, to increase its content in plants) in order to find how GSH content could regulate Cd stress responses. BSO application did not influence plant biomass, while exogenous GSH (especially 500 μM) reduced root biomass. BSO (500μM) in combination with Cd (100 μM) increased Cd toxicity on root growth (by over 50 %), most probably due to reduced GSH content and phytochelatin (PC) accumulation (by over 96 %). On the other hand, combination of exogenous GSH (500 μM) with Cd (100 μM) was also more toxic to plants than Cd alone despite a significant increase in GSH and PC accumulation (up to 2.7 fold in the roots). This fact could indicate that the natural content of endogenous GSH in wild type A. thaliana plants is sufficient for Cd-tolerance. A decrease in this GSH content led to decreased Cd-tolerance of the plants but an increase in GSH content did not enhance Cd-tolerance, and it showed even toxic effect on the plants.

The effects of different growth conditions (ventilated and closed vessels, medium with 0, 15 and 30 g dm^-3 sucrose) during proliferation of donor quince (Cydonia oblonga Mill.) shoots (stage I) on net photosynthetic rate and soluble sugars content were evaluated. In order to assess the influence of these physiological parameters on morphogenesis, leaf explants harvested from donor shoots were induced to form somatic embryos and adventitious roots under ventilated and closed Petri dishes (stage II). Natural ventilation and low sucrose contents (0-15 g dm^-3) promoted the photosynthetic rate of quince shoots whereas biomass accumulation was the highest in those shoots cultured with 30 g dm^-3 sucrose in both vessel types and 15 g dm^-3 sucrose under natural ventilation. Increasing sucrose content in the medium induced greater accumulation of sucrose in leaf tissues of donor shoots. The content of reducing sugars was higher than that of sucrose, and it appeared to be higher in shoots cultured under natural ventilation compared to those in closed vessels. Somatic embryogenesis and root regeneration were influenced by stage I and II treatments. A significant correlation between sucrose content in the leaves of donor shoots and the number of somatic embryos regenerated was found, suggesting that identification of biochemical and physiological characteristics of donor shoots associated with increased regeneration ability might be helpful for improving morphogenesis in plant tissue culture.

The study was conducted to investigate the physiological effects of exogenous NO on potherb mustard (Brassica juncea Coss.) seedlings under salt stress. The plants were grown in Hogland nutrient solution for 15 d and treated with 150 mM NaCl, NO donor sodium nitropruside (SNP) and NO scavenger methylene blue (MB-1) for 4 d. The NaCl stress increased superoxide dismutase, peroxidase and ascorbate peroxidase activities and malondialdehyde (MDA) and free proline contents, and decreased soluble protein content. However, the application of exogenous NO limited the production of MDA and free proline, while markedly promoted SOD, POD and APX activity.

We isolated and characterized eleven polymorphic microsatellite loci for Aegiphila sellowiana an outcrossing pioneer tree species that is frequently used in reforestation programs of tropical riparian forests in Brazil. A total of 38 alleles were detected across a sample of 45 individuals of A. sellowiana, with an average number of 3.45 alleles per locus. The average polymorphic information content (PIC) was 0.430 and the observed (H_O) and expected (H_E) heterozygosity values varied from 0.156 to 1.000 and 0.145 to 0.730, respectively. Eight loci exhibited significant deviation from Hardy-Weinberg equilibrium (P ≤ 0.001) and 32 pair combinations of loci showed significant linkage disequilibrium (P ≤ 0.001). All 11 primers were tested for cross amplification in 12 species belonging to the family Lamiaceae and 5 species belonging to the related family Verbenaceae. The sequence and diversity information obtained using these microsatellites and their cross-transferability to other species of Lamiaceae as well as Verbenaceae will increase our understanding of genetic structures and species relationships within Aegiphyla and other genera of these families.

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.

Plants are subjected to several abiotic stresses that adversely affect growth, metabolism and yield. The dynamic research in plant genetics complemented by genome sequencing has opened up avenues to address multiple problems caused by abiotic stresses. Though many drought-induced genes have been phytoengineered in a wide range of plants, the drought signal transduction pathways, and the alteration of plant sensing and signaling systems to adverse environments still remain an intriguing subject for comprehensive investigation. To impart enhanced drought tolerance in plants, a thorough perception of physiological, biochemical and gene regulatory networks is essential. Recent functional genomics tools have facilitated the progress in our understanding of stress signaling and of the linked molecular regulatory networks. This has revealed several stress-inducible genes and various transcription and signaling factors that regulate the drought stress-inducible systems. Translational genomics of these drought specific genes using model plants have provided encouraging outcomes, but the in-depth knowledge of the specific roles of various metabolites in plant stress tolerance will lead to evolvement of strategies for the phytoengineering of drought tolerance in plants in future.

Four mutants induced by ethylmethane sulphonate (N22-H-dgl56, N22-H-dgl101, N22-H-dgl162 and N22-H-dgl219) with conspicuous dark green leaves were identified in the drought and heat-tolerant rice cultivar Nagina22 (N22), when screened under prolonged drought and heat conditions in field. During dark-induced senescence, these mutants maintained higher chlorophyll and carotenoid contents, and photochemical efficiency of photosystem 2 in comparison with N22. Following heat treatment, these mutants accumulated less reactive oxygen species (assayed by histochemical staining for H₂O₂ and superoxide radicals) and maintained higher chlorophyll content than N22.

The paper reports the in vitro cultivation of two commercial lines and 23 wild populations (with 10, 20 and 30 chromosomes) of Brachypodium distachyon. Callus induction was assayed on Murashige and Skoog medium containing 1 mg dm^-3 2,4-dichlorophenoxyacetic acid (2,4-D) with 30 g dm^-3 of sucrose (MSs) or maltose (MSm). No significant differences were seen between the two media with respect to callus induction. Calli were transferred to MSm medium without 2,4-D but containing 0.1 mg dm^-3 of 6-benzylaminopurine for plant regeneration. The plant regeneration response was very variable depending on the original induction medium, although no overall preference for one or the other medium was seen. The three main culture stages (callus induction, plant regeneration, and green plantlets formation) are probably differently controlled in the plants with different chromosome numbers. This supports the idea that the three cytotypes of Brachypodium cultured actually belong to different species.