Genhua Niu

Stress response and tolerance of Zea mays to CeO2 nanoparticles: Cross talk among H2O2, heat shock protein, and lipid peroxidation

The rapid development of nanotechnology will inevitably release nanoparticles (NPs) into the environment with unidentified consequences. In addition, the potential toxicity of CeO(2) NPs to plants and the possible transfer into the food chain are still unknown. Corn plants (Zea mays) were germinated and grown in soil treated with CeO(2) NPs at 400 or 800 mg/kg. Stress-related parameters, such as H(2)O(2), catalase (CAT), and ascorbate peroxidase (APX) activity, heat shock protein 70 (HSP70), lipid peroxidation, cell death, and leaf gas exchange were analyzed at 10, 15, and 20 days post-germination. Confocal laser scanning microscopy was used to image H(2)O(2) distribution in corn leaves. Results showed that the CeO(2) NP treatments increased accumulation of H(2)O(2), up to day 15, in phloem, xylem, bundle sheath cells and epidermal cells of shoots. The CAT and APX activities were also increased in the corn shoot, concomitant with the H(2)O(2) levels. Both 400 and 800 mg/kg CeO(2) NPs triggered the up-regulation of the HSP70 in roots, indicating a systemic stress response. None of the CeO(2) NPs increased the level of thiobarbituric acid reacting substances, indicating that no lipid peroxidation occurred. CeO(2) NPs, at both concentrations, did not induce ion leakage in either roots or shoots, suggesting that membrane integrity was not compromised. Leaf net photosynthetic rate, transpiration, and stomatal conductance were not affected by CeO(2) NPs. Our results suggest that the CAT, APX, and HSP70 might help the plants defend against CeO(2) NP-induced oxidative injury and survive NP exposure.

Development and application of photoautotrophic micropropagation plant system

Research has revealed that most chlorophyllous explants/plants in vitro have the ability to grow photoautotrophically (without sugar in the culture medium), and that the low or negative net photosynthetic rate of plants in vitro is not due to poor photosynthetic ability, but to the low CO2 concentration in the air-tight culture vessel during the photoperiod. Moreover, numerous studies have been conducted on improving the in vitro environment and investigating its effects on growth and development of cultures/plantlets on nearly 50 species since the concept of photoautotrophic micropropagation was developed more than two decades ago. These studies indicate that the photoautotrophic growth in vitro of many plant species can be significantly promoted by increasing the CO2 concentration and light intensity in the vessel, by decreasing the relative humidity in the vessel, and by using a fibrous or porous supporting material with high air porosity instead of gelling agents such as agar. This paper reviews the development and characteristics of photoautotrophic micropropagation systems and the effects of environmental conditions on the growth and development of the plantlets. The commercial applications and the perspective of photoautotrophic micropropagation systems are discussed.

Monitoring the environmental effects of CeO2 and ZnO nanoparticles through the life cycle of corn (Zea mays) plants and in situ μ-XRF mapping of nutrients in kernels

Information about changes in physiological and agronomic parameters through the life cycle of plants exposed to engineered nanoparticles (NPs) is scarce. In this study, corn (Zea mays) plants were cultivated to full maturity in soil amended with either nCeO2 or nZnO at 0, 400, and 800 mg/kg. Gas exchange was monitored every 10 days, and at harvest, bioaccumulation of Ce and Zn in tissues was determined by ICP-OES/MS. The effects of NPs exposure on nutrient concentration and distribution in ears were also evaluated by ICP-OES and μ-XRF. Results showed that nCeO2 at both concentrations did not impact gas exchange in leaves at any growth stage, while nZnO at 800 mg/kg reduced net photosynthesis by 12%, stomatal conductance by 15%, and relative chlorophyll content by 10% at day 20. Yield was reduced by 38% with nCeO2 and by 49% with nZnO. Importantly, μ-XRF mapping showed that nCeO2 changed the allocation of calcium in kernels, compared to controls. In nCeO2 treated plants, Cu, K, Mn, and Zn were mainly localized at the insertion of kernels into cobs, but Ca and Fe were distributed in other parts of the kernels. Results showed that nCeO2 and nZnO reduced corn yield and altered quality of corn.

Responses of Jatropha curcas to Salt and Drought Stresses

Two greenhouse experiments were conducted to quantify growth responses of Jatropha curcas to a range of salt and drought stresses. Typical symptoms of salinity stress such as leaf edge yellowing were observed in all elevated salinity treatments and the degree of the foliar salt damage increased with the salinity of irrigation water. Total dry weight (DW) of Jatropha plants was reduced by 30%, 30%, and 50%, respectively, when irrigated with saline solutions at electrical conductivity of 3.0, 6.0, and 9.0 dS m − 1 compared to that in the control. Leaf Na + concentration was much higher than that observed in most glycophytes. Leaf Cl − concentrations were also high. In the drought stress experiment, plants were irrigated daily with nutrient solution at 100%, 70%, 50%, or 30% daily water use (DWU). Deficit irrigation reduced plant growth and leaf development. The DW of leaves, roots, and total were reduced in the 70%, 50%, and 30% DWU compared to the 100% DWU control treatment. In summary, salinity stress and deficit irrigation significantly reduced the growth and leaf development of greenhouse-grown Jatropha plants.

Soil organic matter influences cerium translocation and physiological processes in kidney bean plants exposed to cerium oxide nanoparticles.

Soil organic matter plays a major role in determining the fate of the engineered nanomaterials (ENMs) in the soil matrix and effects on the residing plants. In this study, kidney bean plants were grown in soils varying in organic matter content and amended with 0-500mg/kg cerium oxide nanoparticles (nano-CeO2) under greenhouse condition. After 52days of exposure, cerium accumulation in tissues, plant growth and physiological parameters including photosynthetic pigments (chlorophylls and carotenoids), net photosynthesis rate, transpiration rate, and stomatal conductance were recorded. Additionally, catalase and ascorbate peroxidase activities were measured to evaluate oxidative stress in the tissues. The translocation factor of cerium in the nano-CeO2 exposed plants grown in organic matter enriched soil (OMES) was twice as the plants grown in low organic matter soil (LOMS). Although the leaf cover area increased by 65-111% with increasing nano-CeO2 concentration in LOMS, the effect on the physiological processes were inconsequential. In OMES leaves, exposure to 62.5-250mg/kg nano-CeO2 led to an enhancement in the transpiration rate and stomatal conductance, but to a simultaneous decrease in carotenoid contents by 25-28%. Chlorophyll a in the OMES leaves also decreased by 27 and 18% on exposure to 125 and 250mg/kg nano-CeO2. In addition, catalase activity increased in LOMS stems, and ascorbate peroxidase increased in OMES leaves of nano-CeO2 exposed plants, with respect to control. Thus, this study provides clear evidence that the properties of the complex soil matrix play decisive roles in determining the fate, bioavailability, and biological transport of ENMs in the environment.

Growth and Physiological Responses of Maize and Sorghum Genotypes to Salt Stress

The growth and physiological responses of four maize inbred lines (CUBA1, B73, B5C2, and BR1) and four sorghum hybrids (SS304, NK7829, Sordan 79, and KS585) to salinity were determined. Fifteen days after sowing, seedlings were irrigated with nutrient solution (control) at electrical conductivity (EC) of 1.5 dS m−1 or saline solution at EC of 8.0 dS m−1 (salt treatment) for 40 days. Dry weight of shoots in maize was reduced by 58%, 65%, 62%, and 69% in CUBA1, B73, B5C2, and BR1, respectively, while that of sorghum was reduced by 51%, 56%, 56%, and 76% in SS304, NK7829, Sordan79, and KS585, respectively, in the salt treatment compared to their respective control. Salinity stress reduced all or some of the gas exchange parameters, leaf transpiration (E), stomatal conductance (gs), and net photosynthetic rate (Pn) in the late part of the experiment for both crops. Salinity treatment greatly increased Na

Impacts of copper oxide nanoparticles on bell pepper (Capsicum annum L.) plants: a full life cycle study

Several studies have explored the effects of copper nanoparticles (NPs) on different edible plants. However, no studies on bell pepper (Capsicum annum L.) plants have been reported. In this study, plants were grown for a full life-cycle assessment (90 days of exposure) in natural soil amended with nano CuO (nCuO), bulk CuO (bCuO), and ionic copper (CuCl2) at 0, 125, 250, and 500 mg kg−1. Based on our experimental findings, none of the treatments significantly affected stem elongation, plant dry biomass, foliar area, leaf chlorophyll content, and fruit productivity of bell pepper. However, ionic copper significantly decreased the gas exchange parameters, evapotranspiration, stomatal conductance, and photosynthesis by an average of 41%, 59%, and 38%, respectively, compared to the other treatments at select concentrations (p ≤ 0.05). The ICP-OES data showed that, except for bCuO at 500 mg kg−1, at 250 mg kg−1 and above, the three compounds significantly increased root Cu (196%, 184%, and 184%) with respect to the control. Only at 500 mg kg−1, ionic Cu gave significantly higher root Cu compared to the other Cu treatments. Additionally, at 125 mg kg−1, leaf P was 41% lower for nCuO, compared to the bCuO treatment. At 500 mg kg−1, nCuO reduced Zn by 55% in leaves and 47% in fruits, compared to the control (p ≤ 0.05); however, it is premature to assert that the reduction in fruit Zn compromises the nutritional quality of bell pepper. Overall, this investigation showed that, at the concentrations tested, nCuO presented low toxicity to bell pepper, with rare differences between nano and bulk treatment responses.

Propylene Glycol Vapor Contamination in Controlled Environment Growth Chambers: Toxicity to Corn and Soybean Plants

Abstract A major, often unrecognized variable regulating plant growth in semi-closed environment is air contaminant. The vapor of propylene glycol (PG), which was used as coolant in growth chambers, has been found to be toxic to corn (Zea mays L.) and soybean (Glycine maxL.) plants. PG solution leaked from a valve packing system and volatilized to vapor, which was trapped in a semi-closed growth chamber. Symptoms of leaf edge chlorosis, later developing into necrosis, were observed on the third day of emergence or on the third day after moving healthy plants into the chamber. For young soybean plants, symptoms were slightly different from those observed in corn plants; the chlorosis symptoms were not uniformly distributed on all leaves. Some soybean leaves curled up and others had white spots. This problem was identified by using a portable photoionization detector to obtain instantaneous readings of total volatile organic compound concentrations inside the chambers. The presence of PG in selected chambers was verified using sample collection with solid phase microextraction (SPME) followed by analysis with multi-dimensional gas chromatography mass spectrometry (MD-GC-MS). This information is pertinent to researchers who use controlled environment to grow plants.

Plant Factory as a Resource-Efficient Closed Plant Production System

Abstract To improve the resource use efficiency of a “plant factory with artificial lighting” (PFAL), it is important to understand the characteristics of the principal components of the PFAL. The primary input resources for the PFAL are light, water, CO2, and electricity and inorganic nutrients (fertilizer). This chapter describes and defines the resource use efficiency (RUE) for each component and explains the concept of a closed plant production system (CPPS) in order to improve RUE. The characteristics of the PFAL are compared with those of a greenhouse, mainly from the viewpoint of RUE. It is shown that the use efficiencies of water, CO2, and light energy are considerably higher in the PFAL than in a greenhouse. On the other hand, there is much room for improvement in the light and electric energy use efficiencies of the PFAL. Challenging issues for the PFAL and RUE are also discussed.

Challenges for the Next-Generation PFAL

Abstract Much of the technology used in plant factories with artificial lighting (PFAL) differs from that used in horticulture and agriculture, although the basic science and technology are the same. Thus, new ideas for PFAL technologies are needed. Examples include: upward lighting systems, use of green LEDs, breeding of vegetables and medicinal plants suited to PFAL, seed propagation, a hydroponic culture system with restricted root mass, year-round production of ever-flowering berries, and the use of natural energy in PFAL. This chapter discusses potential opportunities for the next-generation PFAL.