Responses of wheat photosynthesis and yield to elevated CO2 under heat and water stress

Climate change involves rising CO2 and temperature, varying rainfall patterns as well as increased frequency and duration of heat stress (HS) and water stress (WS). It is important to assess the impact of climate change, including extreme events on crop productivity to manage future food security challenges. Elevated CO2 (eCO2) boosts leaf photosynthesis and plant productivity, however plant responses to eCO2 depend on environmental conditions. The response of wheat to eCO2 has been investigated in enclosures and in field studies; however, studies accounting for eCO2 interactions with HS or WS are limited. My PhD project addresses this knowledge gap. The broad aim of this thesis was to investigate the response of two commercial wheat cultivars with contrasting agronomical traits to future climate with eCO2 and more extreme events, in order to develop a mechanistic approach that can potentially be incorporated in current crop models, which, so far, fail to predict accurate yields under stressful conditions. Consequently, I investigated the interactive effects of eCO2 with either heat HS or WS on photosynthesis, crop growth and grain yield of the two wheat cultivars Scout and Yitpi grown either in the glasshouse or in a dryland field. In the first glasshouse experiment, the two cultivars were grown at current ambient (450 ppm) and future elevated (650 ppm) CO2 concentrations, 22/14oC day/night temperature, supplied with non-limiting water and nutrients and exposed to 3-day moderate HS cycles at the vegetative (38/14oC) and flowering stage (33/14oC). At aCO2, both wheat lines showed similar photosynthetic temperature responses; while larger and greater-tillering Yitpi produced slightly more grain yield than early-maturing Scout. Elevated CO2 stimulated wheat photosynthesis and reduced stomatal conductance despite causing mild photosynthetic acclimation, while moderate HS did not inhibit photosynthesis at 25oC but slightly reduced photosynthesis at 35oC in aCO2-grown plants. Elevated CO2 similarly stimulated final biomass and grain yield of the two wheat cultivars not exposed to moderate HS by variably affecting grain size and number. The main distinct outcomes of this chapter were the insignificant effect of moderate HS on wheat yield and the reduced grain nutrient quality of high tillering Yitpi at eCO2. In the second glasshouse experiment, a single cultivar Scout was grown at current ambient (419 ppm) and future elevated (654 ppm) CO2 concentrations, 22/14oC day/night temperature, supplied with non-limiting water and nutrients and exposed to 5-day severe HS cycle at the flowering stage (39/23oC). Growth at eCO2 led to downregulation of photosynthetic capacity in Scout measured at common CO2 and leaf temperature in control plants not exposed to severe HS. Severe HS reduced light saturated CO2 assimilation rates (Asat) in aCO2 but not in eCO2 grown plants. Growth stimulation by eCO2 protected plants by increasing electron transport capacity under severe HS, ultimately avoiding the damage to maximum efficiency of photosystem II. Elevated CO2 stimulated biomass and grain yield, while severe HS equally reduced grain yield at both aCO2 and eCO2 but had no effect on biomass at final harvest due to stimulated tillering. In conclusion, eCO2 protected wheat photosynthesis and biomass against severe HS damage at the flowering stage via increased maximal rate of RuBP regeneration (Jmax), indicating an important interaction between the two components of climate change, however grain yield was reduced by severe HS in both CO2 treatments due to grain abortion. The field experiment investigated the interactive effects of eCO2 and WS on two wheat cultivars Scout and Yitpi grown under dryland field conditions using free air CO2 enrichment (FACE). Plants were grown at two CO2 concentrations (400 and 550 ppm) under rainfed or irrigated conditions over two growing seasons during 2014 and 2015. Irrigation in dryland field conditions created contrasting soil water conditions under aCO2 and eCO2. Elevated CO2 and WS responses of biomass and grain yield differed in the two growing seasons. Elevated CO2 stimulated photosynthesis, biomass and grain yield, but reduced photosynthetic capacity evident from lower maximal rate of RuBP carboxylation (Vcmax) and flag leaf N only in 2015. Water stress reduced above-ground biomass and grain yield in both cultivars and CO2 treatment more strongly in 2014 relative to 2015. However, marginal growth stimulation by eCO2 did not protect plants from WS. Biomass, grain yield and grain quality were antagonistically affected by eCO2 and WS. When all data were considered together, I observed that Scout and Yitpi responded differently to growth conditions in the glasshouse and responded similarly in the field. Under well-watered conditions, Scout and Yitpi slightly benefited from moderate HS but were adversely impacted by severe HS. At the flowering stage, severe HS caused grain abortion decreasing grain yield in both CO2 treatments. Elevated CO2 alleviated photosynthetic inhibition but did not stop grain yield damage caused by severe HS. Water stress reduced net photosynthesis, biomass and grain yield in both CO2 treatments and no interaction between eCO2 and WS was observed for any of the measured parameters. Grain yield was stimulated by eCO2 more in the glasshouse than in the field. Grain nutrient quality was reduced by eCO2 and unaffected by either HS or WS (in both season average)

Extraction, purification and characterization of hyaluronic acid from Rooster comb

Hyaluronic acid, is extract by different procedures from various sources like pig, rabbit, oxes and human are available, but these processes have certain imitations like low yield, and also it requires the killing of these animals which is against the experimental ethics. In the present study, we have carried out the extraction of hyaluronic acid from cock’s comb which was further analyzed with qualitative test, viscosity, UV absorption, endotoxin detection assay. Also, the protein contamination of extracted hyaluronic acid was determined by using SDS-PAGE of hyaluronic acid was studied for checking the protein contaminants and it was noted that there were no bands observed in the well loaded with extracted hyaluronic acid sample indicating that the final extract of hyaluronic acid is not contaminated with the protein. The extraction and purification of hyaluronic acid by using the method reported here give pure hyaluronic acid. The viscosity of extracted hyaluronic acid was found to be 2.55 poise which is economical and can be used for industrial production of hyaluronic acid having clinical application

Enhanced field emission properties of Au/SnSe nano-heterostructure: a combined experimental and theoretical investigation

We report the field emission properties of two-dimensional SnSe nanosheets (NSs) and Au/SnSe nano-heterostructure (NHS) prepared by a simple and economical route of one-pot colloidal and sputtering technique. Field Emission Scanning Electron Microscope (FESEM) analysis reveal surface protrusions and morphology modification of the SnSe NSs by Au deposition. By decorating the SnSe NSs with Au nanoparticles, significant improvement in field emission characteristics were observed. A significant reduction in the turn-on field from 2.25 V/µm for the SnSe NSs to 1.25 V/µm for the Au/SnSe NHS was observed. Emission current density of 300 µA/cm2 has been achieved at an applied field of 4.00 and 1.91 V/µm for SnSe NSs and Au/SnSe NHS, respectively. Analysis of the emission current as a function of time also demonstrated the robustness of the present Au/SnSe NHS. Consistent with the experimental data, our complementary first-principles DFT calculations predict lower work function for the Au/SnSe NHS compared to the SnSe NSs as the primary origin for improved field emission. The present study has evidently provided a rational heterostructure strategy for improving various field emission related applications via surface and electronic modifications of the nanostructures

Current technologies and target crops : a review on Australian protected cropping

Protected cropping offers a way to bolster food production in the face of climate change and deliver healthy food sustainably with fewer resources. However, to make this way of farming economically viable, we need to consider the status of protected cropping in the context of available technologies and corresponding target horticultural crops. This review outlines existing opportunities and challenges that must be addressed by ongoing research and innovation in this exciting but complex field in Australia. Indoor farm facilities are broadly categorised into the following three levels of technological advancement: low-, medium- and high-tech with corresponding challenges that require innovative solutions. Furthermore, limitations on indoor plant growth and protected cropping systems (e.g., high energy costs) have restricted the use of indoor agriculture to relatively few, high value crops. Hence, we need to develop new crop cultivars suitable for indoor agriculture that may differ from those required for open field production. In addition, protected cropping requires high start-up costs, expensive skilled labour, high energy consumption, and significant pest and disease management and quality control. Overall, protected cropping offers promising solutions for food security, while reducing the carbon footprint of food production. However, for indoor cropping production to have a substantial positive impact on global food security and nutritional security, the economical production of diverse crops will be essential

ZnO/CuSCN nano-heterostructure as a highly efficient field emitter: a combined experimental and theoretical investigation

We report the synthesis of two-dimensional porous ZnO nanosheets, CuSCN nanocoins, and ZnO/CuSCN nano-heterostructure thin films grown on fluorine-doped tin oxide substrates via two simple and low-cost solution chemical routes, i.e., chemical bath deposition and successive ionic layer adsorption and reaction methods. Detail characterizations regarding the structural, optoelectronic, and morphological properties have been carried out, which reveal high-quality and crystalline synthesized materials. Field emission (FE) investigations performed at room temperature with a base pressure of 1 × 10–8 mbar demonstrate superior FE performance of the ZnO/CuSCN nano-heterostructure compared to the isolated porous ZnO nanosheets and CuSCN nanocoins. For instance, the turn-on field required to draw a current density of 10 μA/cm2 is found to be 2.2, 1.1, and 0.7 V/μm for the ZnO, CuSCN, and ZnO/CuSCN nano-heterostructure, respectively. The observed significant improvement in the FE characteristics (ultralow turn-on field of 0.7 V/μm for an emission current density of 10 μA/cm2 and the achieved high current density of 2.2 mA/cm2 at a relatively low applied electric field of 1.8 V/μm) for the ZnO/CuSCN nano-heterostructure is superior to the isolated porous ZnO nanosheets, CuSCN nanocoins, and other reported semiconducting nano-heterostructures. Complementary first-principles density functional theory calculations predict a lower work function for the ZnO/CuSCN nano-heterostructure (4.58 eV), compared to the isolated ZnO (5.24 eV) and CuSCN (4.91 eV), validating the superior FE characteristics of the ZnO/CuSCN nano-heterostructure. The ZnO/CuSCN nanocomposite could provide a promising class of FE cathodes, flat panel displays, microwave tubes, and electron sources

Energy minimisation in a protected cropping facility using multi-temperature acquisition points and control of ventilation settings

Energy management in protected cropping is critical due to the high cost of energy use in high-tech greenhouse facilities. The main purpose of this research was to investigate the optimal strategy to reduce cooling energy consumption, by regulating the settings (opening/closing) of either vents or curtains during the day, at the protected cropping facility at Western Sydney University. We measured daily changes in air temperature and energy consumption under four treatments (open/closed combinations of vents and shade screens) and developed an optimal cooling strategy for energy management using multi-temperature acquisition points at different heights within a greenhouse compartment. The optimal treatment (vents open/curtains closed) reduced energy load at the rooftop, thereby maintaining a desirable plant canopy temperature profile, and reducing cooling energy. Daily energy consumption was lowest for vents open/curtains closed (70.5 kWh) and highest for vents closed/curtains open (121 kWh). It was also found that delaying the operation of opening and closing of vents and curtains until the plant canopy temperature reached 25 ◦C reduced cooling energy consumption and decreased heating energy consumption in the morning (e.g., 08:00 to 10:00). The estimated savings of 1.83 kWh per 1 ◦C cooling between the optimal (vents open/curtains closed) and least optimal (vents closed/curtains open) conditions had the potential for significant energy savings at 494 kWh per ◦C over a crop cycle of nine months in warm weather conditions. However, selection of the optimal cooling strategy utilising control of vents and curtains must also account for the impact from other greenhouse environmental factors, including light, humidity, and CO2 concentration, which may be crop specific

Smart glass film reduced ascorbic acid in red and orange capsicum fruit cultivars without impacting shelf life

Smart Glass Film (SGF) is a glasshouse covering material designed to permit 80% trans-mission of photosynthetically active light and block heat-generating solar energy. SGF can reduce crop water and nutrient consumption and improve glasshouse energy use efficiency yet can reduce crop yield. The effect of SGF on the postharvest shelf life of fruits remains unknown. Two capsicum varieties, Red (Gina) and Orange (O06614), were cultivated within a glasshouse covered in SGF to assess fruit quality and shelf life during the winter season. SGF reduced cuticle thickness in the Red cultivar (5%) and decreased ascorbic acid in both cultivars (9–14%) without altering the overall morphology of the mature fruits. The ratio of total soluble solids (TSSs) to titratable acidity (TA) was significantly higher in Red (29%) and Orange (89%) cultivars grown under SGF. The Red fruits had a thicker cuticle that reduced water loss and extended shelf life when compared to the Orange fruits, yet neither water loss nor firmness were impacted by SGF. Reducing the storage temperature to 2◦C and increasing relative humidity to 90% extended the shelf life in both cultivars without evidence of chilling injury. In summary, SGF had minimal impact on fruit development and postharvest traits and did not compromise the shelf life of mature fruits. SGF provides a promising technology to block heat-generating solar radiation energy without affecting fruit ripening and marketable quality of capsicum fruits grown during the winter season

Light-limited photosynthesis under energy-saving film decreases eggplant yield

Glasshouse films with adjustable light transmittance and energy-efficient designs have the potential to reduce (up to 80%) the high energy cost for greenhouse horticulture operations. Whether these films compromise the quantity and quality of light transmission for photosynthesis and crop yield remains unclear. A “Smart Glass” film ULR-80 (SG) was applied to a high-tech greenhouse horticulture facility, and two experimental trials were conducted by growing eggplant (Solanum melongena) using commercial vertical cultivation and management practices. SG blocked 85% of ultraviolet (UV), 58% of far-red, and 26% of red light, leading to an overall reduction of 19% in photosynthetically active radiation (PAR, 380–699 nm) and a 25% reduction in total season fruit yield. There was a 53% (season mean) reduction in net short-wave radiation (radiometer range, 385–2,105 nm upward; 295–2,685 nm downward) that generated a net reduction of 8% in heat load and reduced water and nutrient consumption by 18%, leading to improved energy and resource use efficiency. Eggplant adjusted to the altered SG light environment via decreased maximum light-saturated photosynthetic rates (Amax) and lower xanthophyll de-epoxidation state. The shift in light characteristics under SG led to reduced photosynthesis, which may have reduced source (leaf) to sink (fruit) carbon distribution, increased fruit abortion and decreased fruit yield, but did not affect nutritional quality. We conclude that SG increases energy and resource use efficiency, without affecting fruit quality, but the reduction in photosynthesis and eggplant yield is high. The solution is to re-engineer the SG to increase penetration of UV and PAR, while maintaining blockage of glasshouse heat gain

Highly efficient field emission properties of vertically aligned 2D CuSe nanosheets: an experimental and theoretical investigation

We report the synthesis of klockmannite (CuSe) via a three-probe electrochemical set-up (chronoampereometry). The structural properties are examined by X-ray diffraction and Raman spectroscopy. Field emission scanning electron microscopy (FESEM) analysis revealed the formation of vertically aligned CuSe nanosheets with an average thickness of 34 nm and an average lateral size of 700 nm. The CuSe nanosheets exhibit impressive field electron emission characteristics with a turn-on field of 1.4 V/µm for 10 µA/cm2 emission current density. Also, a high current density of 5.8 mA/cm2 is observed at a relatively low applied field of 3.1 V/µm. Complementary first-principles DFT calculations show that CuSe displays metallic conductivity, and the (001) surface has a low work function of 5.12 eV, which is believed to be responsible for the impressive field emission characteristics