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Maize (Zea mays L.) is one of the most widely cultivated crop plants. Unavoidable economic and environmental problems associated with the excessive use of phosphatic fertilizers demands its better management. The solution lies in improving the phosphorus (P) use efficiency to sustain productivity even at low P levels. Untargeted metabolomic profiling of contrasting genotypes provides a snap shot of whole metabolome which differs under specific conditions. This information provides an understanding of the mechanisms underlying tolerance to P stress and the approach for increasing P-use-efficiency. A comparative metabolite-profiling approach based on gas chromatography-mass spectrometry (GC/MS) was applied to investigate the effect of P starvation and its restoration in low-P sensitive (HM-4) and low-P tolerant (PEHM-2) maize genotypes. A comparison of the metabolite profiles of contrasting genotypes in response to P-deficiency revealed distinct differences among low-P sensitive and tolerant genotypes. Another set of these genotypes were grown under P-restoration condition and sampled at different time intervals (3, 5 and 10 days) to investigate if the changes in metabolite profile under P-deficiency was restored. Significant variations in the metabolite pools of these genotypes were observed under P-deficiency which were genotype specific. Out of 180 distinct analytes, 91 were identified. Phosphorus-starvation resulted in accumulation of di- and trisaccharides and metabolites of ammonium metabolism, specifically in leaves, but decreased the levels of phosphate-containing metabolites and organic acids. A sharp increase in the concentrations of glutamine, asparagine, serine and glycine was observed in both shoots and roots under low-P condition. The new insights generated on the maize metabolome in response to P-starvation and restoration would be useful towards improvement of the P-use efficiency in maize.

Plants are able to extract metal(loid) contaminants from the soil or water through their roots and translocate them to harvestable aerial shoots. Of late, this plant potential has been used as a phytotechnology, termed as phytoextraction, for cleaning contaminated sites, and this process has successfully removed elements like As, Cd, Cu, Ni, and Pb, among others. Exploring plants with high metal-accumulation capacity, as well as engineering new hyperaccumulators, is a need of the hour. It is assumed that hyperaccumulators have a >1 shoot:root metal-accumulation ratio, which they achieve by way of (i) overexpression of transport systems for improved sequestration, (ii) tissue-specific protein expression, and (iii) high concentration of metal chelators. Unlike nonhyperaccumulators, the hyperaccumulating species normally bind metal ions to weak oxygen ligands and use strong ligands only for transient binding during transport to storage sites. Adequate understanding of genetics, biochemistry, and molecular biology of metal accumulation is a prelude to developing transgenics with improved phytoremediation capacity. Current research in plant breeding, genomics, and proteomics suggest promising leads to the creation of “remediation” cultivars. Several transporter genes associated with metal uptake, transport, and accumulation have been identified. Efforts are underway to enhance the phytoextraction capacity of relevant species, not only by using chelating agents but also by attempting hybridization, protoplast fusion, as well as genetic engineering through novel gene transfer, overexpression of genes, and (or) reverse gene insertion, to enhance (i) transpiration rate; (ii) uptake, translocation, and metabolism of metals; (iii) activity of enzymes related to rate-limiting steps; and (iv) transformation of accumulated metal to volatile forms, and (or) silencing gene(s) that encode proteases. Genome evolution in hyperaccumulators needs to be understood through a systematic study of ecological and molecular genomics. Sequencing of a complete genome of hyperaccumulators can help in identifying the promising functional noncoding regions in the genome, thus making the experimental analysis more accurate. In addition to the constitutive overexpression of a single gene, simultaneous expression of several genes in specific cellular components has to be focused. Other areas that require expert attention include identification of metal-transporter proteins and the introduction of genes encoding the metal transporters, overexpression of metallothioneins and phytochelatin synthase, and overproduction of nicotianamine and histidine in plants. A comprehensive study of transgenic gene frequency, covering several plant generations growing on polluted as well as nonpolluted soils, may assess the possibility of gene escape into the environment and its transfer to the microorganisms present in the surroundings. This review attempts not only to collect and collate information available on mechanisms of metal accumulation and detoxification in plants and on the factors affecting the tolerance and phytoextraction capacity of plants but also the strategies that have been or can be devised for raising novel plant genotypes with elevated capacity of metal accumulation and toxicity tolerance.

An efficient tissue culture technology has been designed for mass multiplication of Nyctanthes arbor-tristis L. by preculturing nodal explants in thidiazuron (TDZ)-supplemented liquid Murashige and Skoog (MS) media. Direct inoculation of nodal segments on semi-solid MS medium augmented with various concentrations of TDZ (0.1 to 0.9 μM) produced shoots but with low regeneration response and few shoots per explant. Hence, nodal explants were pretreated with greater concentrations of TDZ (5 to 100 μM) in liquid MS media for different durations (4, 8, 12, and 16 days) with the aim of improving shoot regeneration response from cultured explants. After pretreatment, explants were transferred to agar-solidified hormone-free MS medium. Best response in terms of percent regeneration (94%), number of shoots per explant (20.00 ± 1.15), and greatest shoot length (7.23 ± 0.83 cm) were obtained with nodal segments pretreated in75 μM TDZ for 8 days. Similarly, root induction was obtained from pulse-treated microshoots for 24 h with 200 μM indole-3-butyric acid (IBA) followed by their transfer to 1/2 MS medium which produced an average of 5.50 ± 0.92 roots per microshoot. The rooted plantlets were transplanted to soil with 80% success rate.

The present study investigates the role of foliar application of indole acetic acid (IAA) in mitigating the loss caused by salinity stress in terms of plant growth and leaf characteristics in pea plants (Pisum sativum L. cv. Adi). Potted plants were grown on amended soil (75% soil and 25% farmyard manure), and IAA (0, 15, and 30mg l^sup -1^) was applied to 30-day-old plants as foliar spray for 15 days. Three levels of NaCl (0, 50 and 100mM) were then used for salt-stress treatment and pots were watered regularly with 100% field capacity. Two-month-old plants were sampled for recording data on growth measurements, dry mass production, relative water content and leaf characteristics such as pigment concentration, maximum quantum yield of PSII (Fv/Fm), stomatal conductance (gs), net photosynthetic rate (Pn) transpiration rate (E) and water use efficiency (WUE). All these parameters were suppressed under salinity; the effect of salinity was greater on plants receiving no IAA treatment than on those treated with IAA.

The objective of the study was to analyze chemical structure of date palm (Phoenix dactylifera L.) by employing ultimate, proximate and thermo-gravimetric techniques. Samples from different anatomical parts of date palm, namely trunk, frond base, frond midrib, leaflets, coir, fruit stem, date stone, and fruit empty bunches were considered for the experiments. Based on the findings in this work palm leaflet samples gave the highest amount of extractives content (32.9%), followed by date palm stone specimens with 31.5%. Cellulose content values of 32.8% and 47.5% were obtained for date palm stone and palm coir samples, respectively. Overall the hemicellulose contents of all samples were relatively similar to those of typical wood or non-wood lignocellulosic materials with the two exceptions of palm coir and palm leaflets. Both palm coir and palm leaflet specimens had 12.6% and 16.1% hemicellulose content. Volatile matter values of 74.3% and 87.5% were determined for leaflets and fruit empty bunch samples. The ash content of the samples ranged from 1.4% for date stone to 15.2% for palm leaflet samples. The thermal decomposition was completed below a temperature of 500 °C with an exception of those samples taken from palm leaflets. Taken together the data indicate that date palm stone and palm coir revealed could be more viable for renewable energy production than the other specimens considered in this work.

Productivity of Indian mustard ( Brassica juncea L. Czern. and Coss.) is markedly reduced by salt stress. To develop salt tolerance in this important oilseed crop is a need of the hour. This study, based on analysis of growth parameters and antioxidant profile of fourteen Indian mustard genotypes treated with 50, 100, 150 and 200 mM of sodium chloride, was performed to identify the salt-sensitive and salt-tolerant genotypes. Salinity stress inhibited biomass accumulation and reduced the protein and chlorophyll contents in a dose-dependent manner. The reduction was the highest in genotype Pusa Agrani and lowest in CS-54, depicting their contrasting sensitivity to salt stress. Salt treatments triggered a concentration-dependent overproduction of reactive-oxygen species and a concurrent upregulation of the expression of different antioxidants. Genotype CS-54 showed the least damage and maintained a high antioxidant level with almost each salt treatment, exhibiting its competence to withstand the damage provoked by salinity stress. Genotype Pusa Agrani, on the contrary, depicted a salt-sensitive nature by way of its very high lipid peroxidation and low intensity of antioxidants. These two genotypes were further investigated through gel-based proteomic approach, which resulted in the identification and quantification of 42 salinity-responsive proteins related to different metabolic modifications. Molecular processes, including photosynthesis, redox homeostasis, nitrogen metabolism, ATP synthesis, protein synthesis and degradation, signal transduction and respiratory pathways, have exhibited significant changes. The identified stress-responsive proteins could pave the way to develop salt tolerance in Indian mustard plant, thus sustaining its productivity under salinity.

Non-woody biomass species have high-energy potentials, which could be used for bioenergy production. Invasive species are species spreading into areas, where they are not native, consequently causing environmental and economic problems. Therefore, the present study evaluated the proximate, ultimate, chemical, and fuel characteristics of wood and charcoal of three invasive non-forest tree species in Saudi Arabia: Calotropis procera , Rhazya stricta , and Phragmites australis , which were compared with the wood of Acacia tortilis , a preferable local fuelwood. All these data were discussed to investigate the possibility of using the invasive plants for energy production. The thermal behavior of wood was analyzed using thermo-gravimetric and derivative thermo-gravimetric methods. Overall, compared with the wood of A. tortilis , the woods of R. stricta and P. australis are suitable for energy production. The charcoal produced from P. australis emitted less nitrogen (N) oxide than that of R. stricta.

Impacts of increasing environmental stresses (such as drought) on crop productivity can be sustainably minimized by optimizing mineral nutrients (such as sulfur, S). This study, based on a pot-culture experiment conducted in greenhouse condition, investigates S-mediated influence of drought stress (imposed at pre-flowering, flowering and pod-filling stages) on growth, photosynthesis and tolerance of mungbean (Vigna radiata L.) plants. Drought stress alone hampered photosynthesis functions, enhanced oxidative stress [measured in terms of H2O2; lipid peroxidation (LPO); electrolyte leakage (EL)] and decreased the pools of cellular redox buffers (namely ascorbate (AsA); glutathione (GSH)], and the overall plant growth (measured as leaf area and plant dry mass), maximally at flowering stage, followed by pre-flowering and pod-filling stages. Contrarily, S-supplementation to drought-affected plants (particularly at flowering stage) improved the growth- and photosynthesis-related parameters considerably. This may be ascribed to S-induced enhancements in the pools of reduced AsA and GSH, which jointly manage the balance between the production and scavenging of H2O2 and stabilize cell membrane by decreasing LPO and EL. It is inferred that alleviation of drought-caused oxidative stress depends largely on the status of AsA and GSH via S-application to drought-stressed V. radiata at an appropriate stage of plant growth, when this nutrient is maximally or efficiently utilized.

Considering the improvement of acacia species growth in arid and semi-arid environment, a pot experiment was conducted to evaluate the role of arbuscular mycorrhizal fungi (AMF); Funneliformis mosseae (syn. Glomus mosseae), Rhizophagus intraradices (syn. Glomus intraradices) and Claroideoglomus etunicatum (syn. Glomus etunicatum) on growth and drought tolerance of Acacia seyal Del. seedlings under drought cycles (7, 14, 21 and 28 days). AMF-inoculated seedlings showed a clear colonisation percentage (36–68%). AMF treatment significantly improved seedlings shoot and root growth under all drought cycles compared to non-AMF control seedlings. Moreover, AMF treatment enhanced seedlings drought resistance by increasing root surface area (root length increased by 483.76% and root tips number increased by 1 463.94% under 28 days of drought cycle), there was a strong linear relation between proline accumulation, AMF and drought stress (proline content decreased in treated seedlings by 31.3% and 14.3% and increased by 97.5% and 80.4% in untreated seedlings under drought cycles of 21 and 28 days, respectively). In conclusion, the AMF inoculation improved growth and enhanced drought tolerance of A. seyal seedlings and can be used as a natural biostimulator for acacias seedlings establishment in arid areas.