The release of nanoparticles (NPs) to the environment poses an increasing potential threat to biological systems. This study investigated the phytotoxicity and accumulation of copper oxide (CuO) NPs to Elsholtzia splendens (a Cu-tolerant plant) under hydroponic conditions. The 50% effective concentration (EC50) of CuO NPs to E. splendens was about 480 mg/L, implying the tolerance of E. splendens to CuO NPs. The Cu content in the shoots treated with 1000 mg/L CuO NPs was much higher than those exposed to the comparable 0.5 mg/L soluble Cu and CuO bulk particles. CuO NPs-like deposits were found in the root cells and leaf cells. Cu K-edge X-ray absorption near-edge structure analysis further revealed that the accumulated Cu species existed predominantly as CuO NPs in the plant tissues. All these results suggested that CuO NPs can be absorbed by the roots and translocated to the shoots in E. splendens.

A chlorophyll meter can conveniently estimate foliar chlorophyll and nitrogen (N) contents in many species. The objective of this study was to evaluate the utility of a chlorophyll meter to inform nitrogen fertilization rates of tea (Camellia sinensis L.) at different places and times. Plot-scale (5 × 20 m) experiments with three replications were conducted in 2010. Each plot was treated with 248 kg pure N ha -1 per year as urea. At the same time, a field-scale (32 ha) experiment, with the same fertilization rate, was conducted at the same plantation. Tea leaves were sampled in August and November and analyzed with a chlorophyll meter in situ and in the lab. The chlorophyll and nitrogen contents and chlorophyll meter (SPAD) readings of tea leaves in August were greater than in November, and plot-scale values were greater than field-scale values. SPAD readings could estimate the chlorophyll content of tea leaves regardless of temporal and spatial considerations. However, space and time must be considered when using SPAD readings to estimate the nitrogen content of tea leaves.

Core Ideas This study aims to understand the relationships of Na, Nw, NNI, and SPAD values.We find it is more specific to analyze the effect of factors on SPAD values.Some efficient measures may enhance the accuracy of SPAD values.Relative personnel may use more efficiently and accurately the SPAD meter in rice. Determination of the nitrogen nutrition index (NNI) of a crop requires measurement of the amount and status of N in shoot biomass, which restricts its wide application in paddy fields under field conditions. Thus, a convenient and efficient method is required. We estimated the N concentration of leaves in the rice canopy on the basis of dry matter weight, Nw (%) and per unit area, Na (mg cm−2), and measured Soil–Plant Analysis Development (SPAD) values as a potential replacement for NNI. Two rice cultivars with six N fertilization rates (0, 75, 150, 225, 300, and 375 kg N ha−1) were used in a field study from 2010 to 2012 in Hangzhou, China. The SPAD values, Na, and Nw of the upper four leaves in the rice canopy were measured at three developmental stages (tillering, booting, and heading) alongside the NNI. The results showed that with increasing N rates the SPAD values, Na, Nw, and NNI increased in all developmental stages and leaf positions each year. The SPAD values, Na, and Nw showed linear regression with NNI, but the regression parameters varied between developmental stages. Once developmental stages were determined, the equation parameters did not differ among years, leaf positions, and cultivars. The relationships between Na and NNI, and SPAD values and NNI were closer than those between Nw and NNI, suggesting that SPAD values and Na may replace NNI for a quick and approximate prediction of rice plant N nutrition in the field.

It demonstrates a flexible optical network enabled “Network Restructuring as Traffic Changes” for 5G/B5G backhaul network, which realizes proactive cross-layer network generation and mitigation-based network recovery, powered by cognitive enhancement and decision deduction.

No abstract