Uptake and utilization of applied phosphorus in oilseed rape (Brassica napus L. cv. Hayola) plants at vegetative and reproductive stages: Comparison of root with foliar phosphorus application

Abstract

<p>In order to compare plants’ response to phosphorus (P) application through roots and leaves, oilseed rape (<i>Brassica</i> <i>napus</i> L. cv. Hayola) plants were cultivated until vegetative or reproductive stages and were pretreated with an adequate (+P) or low (−P) supply of P. Thereafter, these plants were treated with 0.3 mM P as sodium dihydrogen phosphate (NaH₂PO₄) either through roots (root application, RA) or leaves (leaf application, LA). Shoot biomass was observed to be suppressed under −P conditions at both stages, whereas root growth was comparatively improved in −P plants at the vegetative stage but not at the reproductive stage. Both RA and LA were able to compensate for the growth of vegetative shoot and roots at both stages; however, LA reduced P and dry matter partitioning into the fruits. At the vegetative stage, recovery of applied P was similar between RA and LA treatments, and was extensive in −P plants compared with the +P ones. At the reproductive stage, in contrast, significantly lower recovery of P was observed likely due to the lower capacity of leaves for P absorption and/or their lower re-translocation ability through the phloem. Data of P utilization efficiency showed that −P plants, at both vegetative and reproductive stages, efficiently use leaf-applied P for biomass production when compared with the +P plants. Activity of acid phosphatase was sharply inhibited by RA in −P plants, whereas it was preferably increased by LA in both +P and −P plants. Results indicated that under P-deficiency conditions, plants had higher ability to utilize foliar-applied P, and in contrast to RA, LA may enable plants for a continuous higher capacity of P uptake from P-deficient <i>soil</i>; however, RA was superior to LA in terms of fruit growth.</p