| Abstract: | This study provides an assessment of the suitability of solution culture for screening plants for phosphorus (P) efficiency. Two varieties of wheat (Triticum aestivum L.), Brookton and Krichauff, were compared. In a low-phosphorus soil Brookton was found to be more P-efficient than Krichauff, accumulating 32% more P with a similar dry weight. However, when the two cultivars were grown in solution culture this difference was no longer evident and in some cases was reversed. High-affinity phosphate transport characteristics of the roots were also similar for Brookton and Krichauff and there were no differences between the two cultivars in P deficiency-induced root exudates (acid phosphatase or organic acids). The only notable difference between the two varieties when grown in solution culture related to morphological features of the root system. Although similar root weights and root surface areas were observed for both cultivars, Brookton had a 37–39% higher maximum root length. In other words, Brookton grew fewer but longer roots, with fewer laterals than Krichauff. This morphology may be advantageous in soil environments where there is nutrient heterogeneity since it would permit a large volume of soil to be explored with minimal expense of energy, preceding a localised proliferation of lateral roots and root hairs in patches of nutrient-rich soil. Overall, it was found that the growth characteristics of wheat plants in solution culture were not reliable indicators of P efficiency, and that important traits for P efficiency are likely to be linked to efficient exploration of nutritionally heterogeneous soil. |
