Phosphorus acquisition and allocation patterns in species of Hakea follow phylogenetic relationships under high phosphorus supply, but not low phosphorus supply

Phosphorus (P) is essential for plant growth and development. The sources of P in the environment are finite and disappearing due to continued human dependence. Thus, the price of P fertilisers is likely to increase in future and may result in increases in food prices; therefore, it is important to find ways to reduce the P usage by crop plants to decrease their reliance on P fertiliser. Understanding the mechanisms that P-efficient plants use to acquire and remobilise P within their tissues may assist us in the long-term production of P-efficient crops, helping us to produce enough food when facing P limitation in the environment. The main form of plant available P is phosphate (Pi). The genus Hakea (Proteaceae) contains species that are able to live and survive on some of the most P-impoverished soils in the world , such as those in Western Australia. It has been reported that Hakea prostrata was highly efficient in P acquisition and utilisation and showed P toxicity symptoms at lower P supplies than other plants. However, there is not much information available on the variability of these traits within the Hakea genus. In this study, seven phylogenetically closely-related species of Hakea were compared with respect to Pi acquisition and P allocation within the tissues under low Pi supply. H. pritzelii was found to be somewhat more efficient than H. prostrata in Pi accumulation and allocation, and in the conversion of Pi to organic P. In addition, four of these Hakea spp. were tested for Pi allocation and remobilisation within their tissues, and P sensitivity under low and high Pi supplies. Results of this experiment illustrated that although some other species of Hakea were more sensitive to Pi, H. prostrata was the most efficient species in Pi accumulation and allocation to its leaves under high Pi supplies. In addition, while all the examined species were able to regulate Pi accumulation and allocation to the leaves to some extent, H. drupacea was the most efficient species in regulating Pi accumulation under high Pi supply. In conclusion, this study shed light on the mechanisms used by Hakea spp. for Pi acquisition and P allocation within the tissues. This information, in the long term, may assist in the production of crop species that are capable of surviving with less P fertilisation.