Phosphorus (P) recycling or reuse by pyrolyzing crop residue has recently elicited increased research interest. However, the effects of feedstock and pyrolysis conditions on P species have not been fully understood. Such knowledge is important in identifying the agronomic and environmental uses of biochar. Residues of three main Chinese agricultural crops and the biochars (produced at 300°C-600°C) derived from these crops were used to determine P transformations during pyrolysis. Hedley sequential fractionation and 31 P NMR analyses were used in the investigation. Our results showed that P transformation in biochar was significantly affected by pyrolysis temperature regardless of feedstock (Wheat straw, maize straw and peanut husk). Pyrolysis treatment transformed water soluble P into a labile (NaHCO 3 -P i ) or semi-labile pool (NaOH-P i ) and into a stable pool (Dil. HCl P and residual-P). At the same time, organic P was transformed into inorganic P fractions which was identified by the rapid decomposition of organic P detected with solution 31 P NMR. The P transformation during pyrolysis process suggested more stable P was formed at a higher pyrolysis temperature. This result was also evidenced by the presence of less soluble or stable P species, such as such as poly-P, crandallite (CaAl 3 Contents lists available at ScienceDirectScience of the Total Environment j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n v P forms at higher pyrolysis temperature although their solubility or stability requires further investigation. Results suggested that a relatively lower pyrolysis temperature retains P availability regardless of feedstock during pyrolysis process.

BackgroundMitochondrial respiration in the dark (R dark) is a critical plant physiological process, and hence a reliable, efficient and high-throughput method of measuring variation in rates of R dark is essential for agronomic and ecological studies. However, currently methods used to measure R dark in plant tissues are typically low throughput. We assessed a high-throughput automated fluorophore system of detecting multiple O2 consumption rates. The fluorophore technique was compared with O2-electrodes, infrared gas analysers (IRGA), and membrane inlet mass spectrometry, to determine accuracy and speed of detecting respiratory fluxes.ResultsThe high-throughput fluorophore system provided stable measurements of R dark in detached leaf and root tissues over many hours. High-throughput potential was evident in that the fluorophore system was 10 to 26-fold faster per sample measurement than other conventional methods. The versatility of the technique was evident in its enabling: (1) rapid screening of R dark in 138 genotypes of wheat; and, (2) quantification of rarely-assessed whole-plant R dark through dissection and simultaneous measurements of above- and below-ground organs.DiscussionVariation in absolute R dark was observed between techniques, likely due to variation in sample conditions (i.e. liquid vs. gas-phase, open vs. closed systems), indicating that comparisons between studies using different measuring apparatus may not be feasible. However, the high-throughput protocol we present provided similar values of R dark to the most commonly used IRGA instrument currently employed by plant scientists. Together with the greater than tenfold increase in sample processing speed, we conclude that the high-throughput protocol enables reliable, stable and reproducible measurements of R dark on multiple samples simultaneously, irrespective of plant or tissue type.Electronic supplementary materialThe online version of this article (doi:10.1186/s13007-017-0169-3) contains supplementary material, which is available to authorized users.

To further our understanding of how sustained changes in temperature affect the carbon economy of rice (Oryza sativa), hydroponically grown plants of the IR64 cultivar were developed at 30°C/25°C (day/night) before being shifted to 25/20°C or 40/35°C. Leaf messenger RNA and protein abundance, sugar and starch concentrations, and gas‐exchange and elongation rates were measured on preexisting leaves (PE) already developed at 30/25°C or leaves newly developed (ND) subsequent to temperature transfer. Following a shift in growth temperature, there was a transient adjustment in metabolic gene transcript abundance of PE leaves before homoeostasis was reached within 24 hr, aligning with Rdark (leaf dark respiratory CO2 release) and An (net CO2 assimilation) changes. With longer exposure, the central respiratory protein cytochrome c oxidase (COX) declined in abundance at 40/35°C. In contrast to Rdark, An was maintained across the three growth temperatures in ND leaves. Soluble sugars did not differ significantly with growth temperature, and growth was fastest with extended exposure at 40/35°C. The results highlight that acclimation of photosynthesis and respiration is asynchronous in rice, with heat‐acclimated plants exhibiting a striking ability to maintain net carbon gain and growth when exposed to heat‐wave temperatures, even while reducing investment in energy‐conserving respiratory pathways.

Heterosis or hybrid vigor has been used widely for more than a decade in Canola (Brassica napus) production. Canola hybrids show heterosis in a variety of traits compared to parents, including increased biomass at the early stages of seedling establishment, which is a critical developmental step that impacts future plant growth and seed yield. In this study, we examined transcriptomes of two parental lines, Garnet (Gar) and NX0052 (0052), and their reciprocal hybrids, Gar/0052, at 4 and 8 days after sowing (DAS). In hybrids, early seedling biomass heterosis is correlated with earlier expression of genes in photosynthesis pathways relative to parents. The hybrids also showed early expression of genes in the auxin biosynthesis pathway, consistent with the higher auxin concentrations detected in hybrid seedlings at 4 DAS. Auxin is a key phytohormone that regulates plant development promoting cell expansion and cell proliferation. Consistent with the increased levels of auxin, hybrids have larger and more palisade cells than the parents at the same time point. We propose a possible mechanism of early biomass heterosis through the early establishment of photosynthesis and auxin biosynthesis, providing insights into how transcriptional changes in hybrids are translated into phenotypical heterosis. This finding could be utilized in future Canola breeding to identify hybrid combinations with the superior early seedling establishment and strong levels of hybrid vigor in later plant development.

No abstract

Soil moisture is a key element in hydrological processes, and the accessibility of the moisture in the soil controls the mechanisms thereof amid land surface and atmospheric progressions. Many studies have examined the role of the land surface temperature (LST) and normalised difference vegetation index (NDVI) in changes in soil moisture. Nevertheless, an understanding of the influence of the temperature vegetation dryness index (TVDI), which combines the LST and the NDVI, on soil moisture remains elusive, including in the transition zone area from the Chengdu Plain region to the Longmen Mountains (TZ). In this study, the TVDI was calculated based on the NDVI and LST, using LANDSAT 8 operational land imager/thermal infrared sensor (OLI/TIRS) images. From the TVDI, regression models were trained by using 96 observation points of in situ soil moisture measurements to calculate the soil moisture in the transition zone. The results revealed that there is a strong and significant negative correlation between the TVDI and the in situ measured soil moisture (P < 0.05, r = 0.710, R 2 = 0.504). This indicates that the TVDI can reflect the soil moisture status in the TZ. The overall spatial patterns of soil moisture content were relatively high in the northwestern and central mountainous areas but were relatively low in the southeastern plains. Our study uniquely illustrates the spatial patterns of the relationship between TVDI variability and soil moisture variability in the TZ, western China and provides an approach for using remotely sensed soil moisture to optimise the parameterisation of soils in agricultural water management.

The NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner.

In crop improvement programs, hybrid vigour (heterosis) is an important breeding strategy but the molecular mechanisms of hybrid vigour are still unclear. Grain yield declines after F1 generation due to phenotypic segregation. We found that, at the early seedling stage in hybrids derived from the temperate japonica rice varieties ‘Doongara’ and ‘Reiziq’, hybrid vigour was approximately 40% greater than in the better parents. Inbred high-yielding lines (Hybrid Mimics) were developed from the ‘Doongara’ × ‘Reiziq’ F1 by selfing and recurrent selection for F1-like plants in the F2 through to the F5 generation. Grain yields are stable over subsequent generations in the Hybrid Mimic lines. The importance of photosynthesis in early seedling development was demonstrated. Photosynthesis-related genes were expressed in the hybrid earlier than in the parents; physiological evidence using gas exchange indicated the early commencement of photosynthesis. Dark germination experiments supported the requirement for photosynthesis for early vigour in hybrids.