Plant-Phosphate Interactions

The acquisition of phosphate by plants is a complex process, aggregating soil, microbial and plant interactions. These interactions take place primarily at the interface between the soil and the plant root, within the rhizosphere, where the plant plays a central role in the development and regulation of these processes. Since the availability of phosphate is often limiting in natural ecosystems, plants have evolved numerous adaptations to enhance the availability and acquisition of phosphate from the soil. These adaptations include interactions and associations with soil micro-organisms, including bacteria and mycorrhizal fungi, to manipulate the availability of phosphate and its acquisition from the rhizosphere and beyond, the development of the root system to exploit greater volumes of the soil for available phosphate and target regions with higher phosphate contents, the release of carboxylates to aid the release of phosphate bound to soil particles, and the release of enzymes to release phosphate from organic sources in the soil. Internally, plants have also evolved adaptations to conserve the use of phosphate when the availability of phosphate is low. These include the recycling of phosphate from old to new tissues and the use of alternative non-phosphate containing compounds in structural and metabolic processes.

Signalling low phosphate availability and the regulation of these adaptations by plants is gradually being resolved at the molecular genetic level in model systems. This includes the identification of several key transcription factors and miRNA species that are essential for co-ordinating plant adaptations to low phosphate availability.

Whilst the availability of phosphate in natural ecosystems is often low, to maintain crop yields and quality, plant production systems require additional phosphate, mainly in the form of inorganic fertilisers. Since over 85% of mined phosphate is used in food production and consumption of this non-renewable resource at current rates could lead to a “peak phosphorus” scenario, it is likely that, there will be increasing pressures on phosphate fertiliser availability and cost in the future. These pressures will be exacerbated by increasing demands on food production systems as the human population increases and by increasing oil prices. Inappropriate use of inorganic phosphate fertilisers can also perturb the nutrient balance of natural ecosystems and reduce biodiversity.

Therefore, breeding crops that acquire phosphate and/or use it more efficiently is one strategy to reduce the use of phosphate fertilisers and contribute to long-term sustainable plant production systems. Alternative agronomic solutions, which conserve phosphate in the agro-ecosystem or optimise applications and/or recovery of phosphate fertilisers by the crop, also play an important role in integrated solutions to improving phosphate use in plant production systems.

The scope of this research topic is to collate a range of articles, from original research articles, methods articles, reviews, mini-reviews to perspective articles that contribute to our knowledge of the physiology and genetic regulation of plant adaptations to low soil phosphate availability, plant interactions with soil micro-organisms that increase the availability and plant uptake of phosphate within and beyond the rhizosphere, identification of breeding targets for improved phosphate-use efficiency in crop plants, agronomic solutions to optimising phosphate fertiliser use in the field, and future prospects for global phosphate resources and the implications for plant production systems.