Quanzhen Wang

Model analysing the antioxidant responses of leaves and roots of switchgrass to NaCl-salinity stress

Salinity is a major environmental stress and a substantial constraint on plant production. The objective of this research was to better understand the mechanisms of the antioxidant responses of leaves and roots to NaCl-salinity stress in switchgrass (Panicum virgatum L.). The effects of NaCl-salinity stress (1, 3, 5, 10 and 15gNaCl/kgdrysoil) on lipid peroxidation and antioxidant defences in switchgrass leaves and roots were investigated, and a model analysis was conducted. The results of the correlation analyses indicated that CAT, POD and SOD were more important than APX, GSH and MDA, whereas the model analyses suggested that the latter three biochemical indices were more sensitive than the former three indices to NaCl-salinity in switchgrass. The connective models of APX, GSH, MDA, CAT, SOD and POD between leaves and roots were obtained, respectively. The new models can be used to closely predict the biochemical index values in switchgrass roots or leaves.

Synergistic and Antagonistic Effects of Salinity and pH on Germination in Switchgrass (Panicum virgatum L.)

The effects of salt-alkaline mixed stress on switchgrass were investigated by evaluating seed germination and the proline, malondialdehyde (MDA) and soluble sugar contents in three switchgrass (Panicum virgatum L.) cultivars in order to identify which can be successfully produced on marginal lands affected by salt-alkaline mixed stress. The experimental conditions consisted of four levels of salinity (10, 60, 110 and 160 mM) and four pH levels (7.1, 8.3, 9.5 and 10.7). The effects of salt-alkaline mixed stress with equivalent coupling of the salinity and pH level on the switchgrass were explored via model analyses. Switchgrass was capable of germinating and surviving well in all treatments under low-alkaline pH (pH≤8.3), regardless of the salinity. However, seed germination and seedling growth were sharply reduced at higher pH values in conjunction with salinity. The salinity and pH had synergetic effects on the germination percentage, germination index, plumular length and the soluble sugar and proline contents in switchgrass. However, these two factors exhibited antagonistic effects on the radicular length of switchgrass. The combined effects of salinity and pH and the interactions between them should be considered when evaluating the strength of salt-alkaline mixed stress.

Modeling Analysis on Germination and Seedling Growth Using Ultrasound Seed Pretreatment in Switchgrass

Switchgrass is a perennial C4 plant with great potential as a bioenergy source and, thus, a high demand for establishment from seed. This research investigated the effects of ultrasound treatment on germination and seedling growth in switchgrass. Using an orthogonal matrix design, conditions for the ultrasound pretreatment in switchgrass seed, including sonication time (factor A), sonication temperature (factor B) and ultrasound output power (factor C), were optimized for germinating and stimulating seedling growth (indicated as plumular and radicular lengths) through modeling analysis. The results indicate that sonication temperature (B) was the most effective factor for germination, whereas output power (C) had the largest effect on seedling growth when ultrasound treatment was used. Combined with the analyses of range, variance and models, the final optimal ultrasonic treatment conditions were sonication for 22.5 min at 39.7°C and at an output power of 348 W, which provided the greatest germination percentage and best seedling growth. For this study, the orthogonal matrix design was an efficient method for optimizing the conditions of ultrasound seed treatment on switchgrass. The electrical conductivity of seed leachates in three experimental groups (control, soaked in water only, and ultrasound treatment) was determined to investigate the effects of ultrasound on seeds and eliminate the effect of water in the ultrasound treatments. The results showed that the electrical conductivity of seed leachates during either ultrasound treatment or water bath treatment was significantly higher than that of the control, and that the ultrasound treatment had positive effects on switchgrass seeds.

Antimicrobial and antioxidant activities of Cichorium intybus root extract using orthogonal matrix design.

Solvent, impregnation time, sonication repetitions, and ultrasonic power were important factors in the process of ultrasound-assisted extraction from chicory (Cichorium intybus) root, while there were no studies about optimizing these 4 factors for extract yield, total phenolic content (TPC), antioxidant, antibacterial, and antifungal activity of the extracts using orthogonal matrix design. The present research demonstrated that the solvent composition played a significant role in the improving extract yield, TPC, antioxidant, and antibacterial activities. The other 3 factors had inequable effect on different purposes, ultrasonic power could improve TPC and antioxidant activity, but long time of extraction lowered antioxidant activity. The TPC increased from 22.34 to 27.87 mg GAE (gallic acid equivalents)/100 g (dry extracts) with increasing solvent polarity. The half inhibition concentration (IC(50,) μg/mL) of the radical scavenging activity of the chicory extracts ranged from 281.00 to 983.33 μg/mL. The content of caffeoylquinic acids of root extract, which was extracted by the optimal combination was 0.104%. Several extracts displayed antibacterial activities against Escherichia coli, Staphylococcus aureus, Bacillus thuringiensis, Bacillus subtilis, and Salmonella typhi, while Penicillium sp. and Aspergillus sp. resisted against all the extracts. Combination of 70% ethanol v/v, 24-h impregnation time, 3 sonication rounds, and 300-W ultrasonic input power was found to be the optimal combination for the chicory extract yield, TPC, antioxidant activity, and antibacterial activity.

Effects of drought and salt stress on seed germination of three leguminous species

The seeds of Medicago sativa (L.), Astragalus adsurgens (Pall.) and Coronilla varia (L.) were evaluated at germination for tolerance to salt (NaCl) and drought conditions induced by polyethylene glycol (PEG) in an experiment of orthogonal design. The results reveal that the germination percentages of M. sativa and A. adsurgens were much higher than that of C. varia . The radicle and hypocotyl lengths of M. sativa were significantly longer than that of A. adsurgens and C. varia (P<0.05). The effects of PEG (PEG 6000) on the radicle length showed a trend similar to that of NaCl where the radicle length decreased significantly; additionally, the hypocotyl length was inhibited by 10 and 15% PEG and 50 and 100 mM NaCl. The fresh weights of the three species decreased as a result of the combined effects of PEG and NaCl, yet no difference was observed on the dry weights of the early seedlings in comparison with the control and the seed germination of M. sativa was not inhibited by 5% PEG + 50 mM NaCl. This study indicates that the seed germination of the three species was inhibited by PEG and NaCl but there was no inhibitory effect on M. sativa at a low concentration of PEG and NaCl. Key words: Drought and salt stress, germination, leguminous species.

Models analyses for allelopathic effects of chicory at equivalent coupling of nitrogen supply and pH level on F. arundinacea, T. repens and M. sativa.

Alllelopathic potential of chicory was investigated by evaluating its effect on seed germination, soluble sugar, malondialdehyde (MDA) and the chlorophyll content of three target plants species (Festuca arundinacea, Trifolium repens and Medicago sativa). The secretion of allelochemicals was regulated by keeping the donor plant (chicory) separate from the three target plant species and using different pH and nitrogen levels. Leachates from donor pots with different pH levels and nitrogen concentrations continuously irrigated the target pots containing the seedlings. The allelopathic effects of the chicory at equivalent coupling of nitrogen supply and pH level on the three target plants species were explored via models analyses. The results suggested a positive effect of nitrogen supply and pH level on allelochemical secretion from chicory plants. The nitrogen supply and pH level were located at a rectangular area defined by 149 to 168 mg/l nitrogen supply combining 4.95 to 7.0 pH value and point located at nitrogen supply 177 mg/l, pH 6.33 when they were in equivalent coupling effects; whereas the inhibitory effects of equivalent coupling nitrogen supply and pH level were located at rectangular area defined by 125 to 131 mg/l nitrogen supply combining 6.71 to 6.88 pH value and two points respectively located at nitrogen supply 180 mg/l with pH 6.38 and nitrogen supply 166 mg/l with pH 7.59. Aqueous extracts of chicory fleshy roots and leaves accompanied by treatment at different sand pH values and nitrogen concentrations influenced germination, seedling growth, soluble sugar, MDA and chlorophyll of F. arundinacea, T. repens and M. sativa. Additionally, we determined the phenolics contents of root and leaf aqueous extracts, which were 0.104% and 0.044% on average, respectively.

Modelling of seed yield and its components in tall fescue (Festuca arundinacea) based on a large sample

Tall fescue ( Festuca arundinacea Schreb.) is a primary cool-season grass species that is widely used as a cold-season forage and turfgrass throughout the temperate regions of the world. The key seed yield components, namely fertile tillers m -2 (Y 1 ), spikelets fertile tiller -1 (Y 2 ), florets spikelet -1 (Y 3 ), seed number spikelet -1 (Y 4 ), seed weight (Y 5 ), and the seed yield (Z) of tall fescue were determined in field experiments from 2003 to 2005. The experiments produced a large sample for analysis. The correlations among Y 1 to Y 5 and their direct and indirect effects on Z were investigated. All of the direct effects of the Y 1 , Y 3 , Y 4 and Y 5 components on the seed yield were significantly positive. However, the effect of Y 2 was not significant. In decreasing order, the contributions of the five components to seed yield are Y 1 >Y 4 >Y 3 >Y 5 >Y 2 . Y 4 and Y 5 were not significantly correlated with Z. However, the components Y 1 , Y 2 and Y 3 were positively correlated with Z in all the three experimental years and the intercorrelations among the components Y 1 , Y 2 and Y 3 were significant. Ridge regression analysis was used to derive a steady algorithmic model that related Z to the five components; Y 1 to Y 5 . This model can estimate Z precisely from the values of these components. Furthermore, an approach based on the exponents of the algorithmic model could be applied to the selection for high seed yield via direct selection for large Y 2 , Y 3 and Y 5 values in a breeding program for tall fescue. Key words . Modelling, seed yield, components, tall fescue, path and ridge analyses, large sample.