Given the importance of plants it is no surprise that there is endless research into their biology. One aspect that seemed relevant to our project was studies into the factors that affect root architecture. Phosphorus (P) and iron (Fe) deficient soils have been shown to increase root growth in certain botanical families. These are essential elements for plant survival and so if they are not readily available the plant produces more roots to locate them.
Furthermore, certain families produce proteoid roots. These are dense, tight clusters of roots that form under certain conditions. While they increase the surface area for nutrient uptake they appear to be more than passive. Often in poor soils there are still mineral P that has bound to metal cations. Proteoid roots actively mobilize P, Fe and other elements that are bound in soils. This is facilitated by secretion of organic anions, especially citrate. In one study when a lupin species was grown in calcareous soil the proteoid root developed clusters of white calcium citrate. This raises the possibility of intimately controlling the growth and composition of a root system, while still maintaining a healthy plant body.
References
Shane, MW & H Lambers. 2005. Cluster Roots: A curiosity in context. Plant and Soil 274: 1001-125
Watt, M & Evans, JR. 1999. Proteoid Roots. Physiology and Development. Plant Physiology 121: 317-323
Zhou J, et al 2008. OsPHR2 Is Involved in Phosphate-Starvation Signalling and Excessive Phosphate Accumulation in Shoots of Plants1[C][W][OA] Plant Physiology, Vol. 146:1673–1686,
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