Nutrients in the rhizosphere: A meta-analysis of content, availability, and influencing factors.

Nutrient deficiency in most terrestrial ecosystems constrains global primary productivity. Rhizosphere nutrient availability directly regulates plant growth and is influenced by many factors, including soil properties, plant characteristics and climate. A quantitatively comprehensive understanding of the role of these factors in modulating rhizosphere nutrient availability remains largely unknown. We reviewed 123 studies to assess nutrient availability in the rhizosphere compared to bulk soil depending on various factors. The increase in microbial nitrogen (N) content and N-cycling related enzyme activities in the rhizosphere led to a 10% increase in available N relative to bulk soil. The available phosphorus (P) in the rhizosphere decreased by 12% with a corresponding increase in phosphatase activities, indicating extreme demand and competition between plants and microorganisms for P. Greater organic carbon (C) content around taproots (+17%) confirmed their stronger ability to store more organic compounds than the fibrous roots. This corresponds to higher bacterial and fungal contents and slightly higher available nutrients in the rhizosphere of taproots. The maximal rhizosphere nutrient accumulation was common for low-fertile soils, which is confirmed by the negative correlation between most soil chemical properties and the effect sizes of available nutrients. Increases in rhizosphere bacterial and fungal population densities (205-254%) were much higher than microbial biomass increases (indicated as microbial C: +19%). Consequently, despite the higher microbial population densities in the rhizosphere, the biomass of individual microbial cells decreased, pointing on their younger age and faster turnover. This meta-analysis shows that, contrary to the common view, most nutrients are more available in the rhizosphere than in bulk soil because of higher microbial activities around roots.

Standardising the cataract referral process for public hospitals: perspectives of optometrists in New South Wales, Australia.

BACKGROUND: Previous research has shown that cataract surgery referral letters to major metropolitan public hospitals in New South Wales have insufficient detail to inform patient triage or apply prioritisation tools. This study aimed to canvass the views of optometrists working in New South Wales and the Australian Capital Territory (NSW/ACT) on standardising the referral process for public hospital cataract surgery. METHODS: An online survey was sent to all NSW/ACT members of Optometry Australia in October 2017. Respondents were asked to select clinical and personal information to be included on a referral template using a list of 25 items. Data were also gathered on preferences for the cataract referral process and sources of cataract referral guidelines. RESULTS: Two hundred and thirteen (response rate 13 per cent) optometrists completed the survey. There was close to universal support for inclusion of items like visual acuity (99 per cent), whereas other items had low support, including the date and details of previous refraction (26 per cent), history of falls (29 per cent) and health insurance status (29 per cent). Three-quarters of optometrists stated they would be willing to administer and report data from a patient survey about the functional impact of their cataract and level of visual disability. The preferred format of a standardised cataract referral template varied, although time efficiency and ease of completion were commonly cited reasons for preferences. Confirmation of receipt of referral from the public hospital, and a copy of the referral letter for the optometrist's records were also desirable. For the 61 per cent of respondents who reported accessing guidelines for cataract referral, 69 per cent stated the main source was Optometry NSW/ACT with fewer accessing guidelines directly from a public hospital or the NSW Health website. CONCLUSION: Optometrists' preferences will be useful to inform the design and implementation of a standardised cataract referral template.

Visualization of Enzyme Activities in Earthworm Biopores by In Situ Soil Zymography.

Earthworms produce biopores with strongly increased microbial and enzyme activities and consequently they form microbial hotspots in soil. In extremely dynamic microhabitats and hotspots such as earthworm biopores, the in situ enzyme activities are a footprint of process rates and complex biotic interactions. The effect of earthworms on enzyme activities inside biopores, relative to earthworm-free soil, can be visualized by in situ soil zymography. Here, we describe the details of the approach and discuss its advantages and limitations. Direct zymography provides high spatial resolution for quantitative images of enzyme activities in biopores.