Konvensyen Myprospec tumpu revolusi industri 4.0

Rising atmospheric concentrations of CO 2 (C a) can reduce stomatal conductance and transpiration rate in trees, but the magnitude of this effect varies considerably among experiments. The theory of optimal stomatal behaviour predicts that the ratio of photosynthesis to transpiration (instantaneous transpiration efficiency, ITE) should increase in proportion to C a. We hypothesized that plants regulate stomatal conductance optimally in response to rising C a. We tested this hypothesis with data from young Eucalyptus saligna Sm. trees grown in 12 climate-controlled whole-tree chambers for 2 years at ambient and elevated C a. Elevated C a was ambient + 240 ppm, 60% higher than ambient C a. Leaf-scale gas exchange was measured throughout the second year of the study and leaf-scale ITE increased by 60% under elevated C a, as predicted. Values of leaf-scale ITE depended strongly on vapour pressure deficit (D) in both CO 2 treatments. Whole-canopy CO 2 and H 2O fluxes were also monitored continuously for each chamber throughout the second year. There were small differences in D between C a treatments, which had important effects on values of canopy-scale ITE. However, when C a treatments were compared at the same D, canopy-scale ITE was consistently increased by 60%, again as predicted. Importantly, leaf and canopy-scale ITE were not significantly different, indicating that ITE was not scale-dependent. Observed changes in transpiration rate could be explained on the basis that ITE increased in proportion to C a. The effect of elevated C a on photosynthesis increased with rising D. At high D, C a had a large effect on photosynthesis and a small effect on transpiration rate. At low D, in contrast, there was a small effect of C a on photosynthesis, but a much larger effect on transpiration rate. If shown to be a general response, the proportionality of ITE with C a will allow us to predict the effects of C a on transpiration rate

Reactions to cadmium stress in a cadmium-tolerant variety of cabbage (Brassica oleracea L.) : is cadmium tolerance necessarily desirable in food crops?

Cadmium is a cumulative, chronic toxicant in humans for which the main exposure pathway is via plant foods. Cadmium-tolerant plants may be used to create healthier food products, provided that the tolerance is associated with the exclusion of Cd from the edible portion of the plant. An earlier study identified the cabbage (Brassica oleracea L.) variety, Pluto, as relatively Cd tolerant. We exposed the roots of intact, 4-week-old seedlings of Pluto to Cd (control ∼1 mg L−1 treatment 500 μg L−1) for 4 weeks in flowing nutrient solutions and observed plant responses. Exposure began when leaf 3 started to emerge, plants were harvested after 4 weeks of Cd exposure and the high Cd treatment affected all measured parameters. The elongation rate of leaves 4–8, but not the duration of elongation was reduced; consequently, individual leaf area was also reduced (P0.1). Phytochelatins (PCs) and glutathione (GSH) were present in the roots even at the lowest Cd concentration in the nutrient medium, i.e. ∼1 μg Cd L−1, which would not be considered contaminated if it were a soil solution. The Cd concentration in these roots was unexpectedly high (5 mg kg−1 DW) and the molar ratio of –SH (in PCs plus GSH) to Cd was large (>100:1). In these control plants, the Cd concentration in the leaves was 1.1 mg kg−1 DW, and PCs were undetectable. For the high Cd treatment, the concentration of Cd in roots exceeded 680 mg kg−1 DWand the molar –SH to Cd ratio fell to ∼1.5:1. For these plants, Cd flooded into the leaves (107 mg kg−1 DW) where it probably induced synthesis of PCs, and the molar –SH to Cd ratio was ∼3:1. Nonetheless, this was insufficient to sequester all the Cd, as evidenced by the toxic effects on photosynthesis and growth noted above. Lastly, Cd accumulation in the leaves was associated with lowered concentrations of some trace elements, such as Zn, a combination of traits that is highly undesirable in food plants

Evaluation of a combined soil EC and moisture sensor and its use to co-manage soil moisture and vine nitrogen in grapevines (cv. shiraz) under deficit irrigation

It is possible the commonly used practice of deficit irrigation could affect the movement of nitrate to the root surface, and subsequent uptake of nitrate in grapevines. A sensor which measures both soil moisture and EC concurrently, the TriSCAN sensor (Sentek Sensor Technologies) was evaluated in a drying soil system. Data from the TriSCAN sensors and leaf nitrate levels were then used to study the relationship between deficit irrigation and nitrate dynamics in the rootzone of grapevines. The TriSCAN sensors were arranged in arrays of 12 sensors per dripper and the data used to generate figures which clearly show changes in the distribution of EC in the soil root zone associated with fertigation, leaching and uptake of nutrients by the vines

Transpiration influences cadmium uptake by baby leaf spinach (Spinacia oleracea L.)

Cadmium (Cd) is a toxic heavy metal whose concentration in soils is rising. This study investigated the effect of transpiration on Cd uptake by plants using soil conditions akin to those experienced by field crops. Two experiments were performed using baby leaf spinach (Spinacia oleracea L.) grown in soil containing Chloride (Cl) at a typical concentration of 70 mg kg−1. Experiment 1 explored plant response to Cd over the range ~0.04 to 10 mg kg−1 so that a non-toxic concentration could be selected for Experiment 2. Experiment 2 tested the hypothesis that transpiration and Cd uptake were related using soil amended to 70 mg Cl kg−1 and 0.24 mg Cd kg. Differences in transpiration were achieved by manipulating atmospheric CO2 (~400 and~640 µL CO2 L−1 ) and air temperature (22/14, 26/18 and 30/22°C day/night). In Experiment 1, Cd in the foliage variedfrom ~2 to ~100 mg kg−1 DW, yet there was no evidence of Cd toxicity. In Experiment 2, temperature and [CO2] caused large differences in plant growth. [Cd] was lower in chambers with increased temperature and higher in those with elevated CO2. Despite differences in growth, transpiration and foliar Cd uptake were positively and strongly correlated, even when both parameters were expressed on a DW basis. The data are consistent with Cd transport by mass flow towards the roots being a substantial contributor to Cd uptake. Higher [Cd] at elevated CO2 raises concerns about future chronic dietary exposure to Cd. The findings challenge the interpretation of earlier studies on the effects of CO2 and temperature on Cd uptake and may partly explain the inter-seasonal variation in Cd uptake by field crops

A soil-plant-atmosphere approach to evaluate the effect of irrigation/fertigation strategy on grapevine water and nutrient uptake, grape quality and yield

Water is a scarce resource worldwide and a particular problem for producers of wine grapes in Australia, where drought occurrences are frequent, determining severe limitations to vine growth and productivity. Consequently, most vineyards are irrigated and the development of efficient water and nutrient management and monitoring practices are required. This research presents preliminary results of the application of a soil-plant-atmosphere approach to accurately assess vine water and nutrient uptake on grapevines (Vitis vinifera L. var. Shiraz) located in Richmond New South Wales (NSW) (season 2004-05). Soil water and nutrient monitoring (measured as volumetric soil moisture and soil electric conductivity changes, respectively) was carried out by using the newly developed TriSCAN® probes (Sentek Pty. Ltd., Australia). The TriSCAN®probes were distributed in a 3D array close to the root-zone to create 3D animations of soil wetting patterns and nutrient patterns of fully irrigated (FI) and regulated deficit irrigation (RDI) treatments. Soil water and nutrient dynamics were studied in post-harvest for this paper in a period of 17 days. Animations of soil moisture and nutrient patterns were obtained using the WPA copyright software. Through animation analysis, it was found that the zones of maximum root water and nutrient uptake occurred initially near the vine trunk and then progressed to deeper layers of the active root-zone. Whole vine transpiration rates were measured using sap flow probes (compensated heat-pulse) and plant water status was measured as midday stem water potential (ψs) for irrigation scheduling purposes. Weather data were collected from a meteorological station close to the trial site. For the studied season, only mild vine water stress was achieved in RDI treatments (ψs values between -0.8 to -1.1 MPa), therefore, no significant differences were found in grape quality and yield between fully irrigated and RDI vines. However, significant reduction in water application was achieved in RDI compared with fully irrigated vines (36% less). A soil-plant-atmosphere assessment throughout the whole season allows accurate irrigation/fertigation practices minimising fertiliser leaching losses, therefore reducing the negative environmental impacts of irrigation

Equilibrating stable Cd isotopes with acidic soils

Cadmium (Cd) in the soil solution is in dynamic equilibrium with the reservoir of bioavailable Cd attached to the solid phase, i.e. the labile pool (CdE). Traditionally, CdE is estimated using the radioisotope 109Cd, which has severely restricted access to estimates of CdE. Using stable isotope dilution and isotope ratio measurement by inductive coupled plasma-quadrupole mass spectroscopy (ICP-QMS) would increase access to estimates of CdE; however, detail remains scant about the optimal conditions for equilibration and measurement. We report optimal conditions for spiking with 110Cd, batch equilibration and ICP-QMS measurement of the ratio of 110Cd to 111Cd using results for six acidic soils with total Cd concentrations of 0.19–6.4 mg Cd kg−1, suspended in three background electrolytes (10 mM CaCl2, 1 M NH4NO3, and 1 M NH4Cl). Our optimised procedure produces robust estimates of CdE. Application of this approach will greatly increase access to estimates of CdE and to the investigation of its role in Cd uptake by plants

Whole-tree chambers for elevated atmospheric CO2 experimentation and tree scale flux measurements in south-eastern Australia : the Hawkesbury Forest Experiment

Resolving ecophysiological processes in elevated atmospheric CO 2 (C a) at scales larger than single leaves poses significant challenges. Here, we describe a field-based experimental system designed to grow trees up to 9m tall in elevated C a with the capacity to control air temperature and simultaneously measure whole-tree gas exchange. In western Sydney, Australia, we established the Hawkesbury Forest Experiment (HFE) where we built whole-tree chambers (WTC) to measure whole-tree CO 2 and water fluxes of an evergreen broadleaf tree, Eucalyptus saligna. A single E. saligna tree was grown from seedling to small tree within each of 12 WTCs; six WTCs were maintained at ambient C a and six WTCs were maintained at elevated C a, targeted at ambient C a +240μmolmol -1. All 12 WTCs were controlled to track ambient outside air temperature (T air) and air water vapour deficit (D air). During the experimental period, T air, D air and C a in the WTCs were within 0.5°C, 0.3kPa, and 15μmolmol -1 of the set-points for 90% of the time, respectively. Diurnal responses of whole-tree CO 2 and water vapour fluxes are analysed, demonstrating the ability of the tree chamber system to measure rapid environmental responses of these fluxes of entire trees. The light response of CO 2 uptake for entire trees showed a clear diurnal hysteresis, attributed to stomatal closure at high D air. Tree scale CO 2 fluxes confirm the hypothesised deleterious effect of chilling night-time temperatures on whole-tree carbon gain in this subtropical Eucalyptus. The whole-tree chamber flux data add an invaluable scale to measurements in both ambient and elevated C a and allow us to elucidate the mechanisms driving tree productivity responses to elevated C a in interaction with water availability and temperature