Root strategies for phosphorus acquisition


Lynch, J.P.; Brown, K.M.


The ecophysiology of plant-phosphorus interactions, Springer. In press. (2008)
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Low soil phosphorus bioavailability is a primary constraint to plant growth on earth. Phosphorus is highly immobile in soil, and its distribution in the soil is non-uniform. Root growth and architecture are critically important for phosphorus acquisition by permitting exploration of a heterogeneous substrate and its exploitation at fine spatial scale. Biomass allocation to roots must be carefully balanced with the metabolic costs of root development, including carbon and phosphorus consumption. Traits that enhance soil exploration at minimal or reduced metabolic cost, such as root hair development, root etiolation, aerenchyma formation, and adventitious root development are therefore valuable for developing phosphorus efficient crops. Root architecture determines the soil domains explored and permits efficient deployment of strategies like rhizosphere modification and upregulation of transporters. Since phosphorus bioavailability is typically greatest in the topsoil, root architectural traits that enhance topsoil foraging, including basal root gravitropism, adventitious rooting, and lateral root branching, are associated with enhanced phosphorus acquisition. Reproductive delay increases root foraging duration, allowing more time for phosphorus acquisition and utilization. Ecological and physiological tradeoffs and interactions among these traits are poorly understood but are likely to be important in determining the functional utility of these traits, especially in competitive environments. A better understanding of these traits is needed to guide the development of more P efficient crops for developing nations, and to understand how ecosystems will respond to global climate change.