Evolutionary adaptation of plants to phosphorus deficiency: the multifaceted role of cluster roots

A. Silber, J. Ben-Jaacov
Phosphorus (P), a non-renewable natural resource, is essential for plant development, and is the least accessible macronutrient in many ecosystems. It is produced from mineral deposits and continuously depleted over years of use; as a result, even an underestimate of the global annual growth of P consumption indicates that within some decades, about half of the world’s P resources will be depleted. Adsorption on the soil solid phases and precipitation of insoluble compounds governs the solubility of orthophosphate (Pi), the main P form taken up by plants. Consequently, low Pi availability is often the limiting factor for yield production, even in fertilized soils. During evolution, plants have developed several physiological mechanisms for improving P uptake. The two common responses of plants to P-deficient soils are: i) modification of the root system to improve the efficiency of nutrient acquisition; and ii) modification of the root environment to improve nutrient availability. The Proteaceae originated in Australia and South Africa, where most species grow on leached soils, which are poor in available minerals. In the past, the presence of proteoid roots in Proteaceae plants were ascribed to vigorous development. Numerous studies indicated that the primary role of proteoid roots is associated with modification of the root environment, i.e., by exudation of organic acids (mainly citric) that enhance P mobilization toward the plant root. Today, it is well accepted that under deficient conditions, the proteoid roots play a key role in nutrient uptake whereas under satisfactory conditions, their role is limited.
Silber, A. and Ben-Jaacov, J. (2022). Evolutionary adaptation of plants to phosphorus deficiency: the multifaceted role of cluster roots. Acta Hortic. 1347, 51-62
DOI: 10.17660/ActaHortic.2022.1347.9
citrate, cytokinin, IAA, P crisis, Proteaceae, proteoid root

Acta Horticulturae