Translocation of phosphorus from nodal roots in two contrasting genotypes of white clover (Trifolium repens)

Abstract

1993. Translocation of phosphorus from nodal roots in two contrastinsj genotypes of white clover {TrifoUum repens). -Pbysiol. Plant. 89: 323-330.Patterns of translocation of recently-assimilated phosphorus (P) exported from "young" source roots (located 3-4 nodes from the stolon apex) and 'old" source roots (located near the ba.se of the stolon) on the primary stolon of clonal plants of the forage legume white clover {TrifoUum repens L.) were determined using '-P Plants of a small-leaved genotype and of a large-leaved genotype were grown in sand culture at two notionally Umiting or near-limiting rates of P supply and one non-limiting rate of supply. The small-leaved genotype showed little response in growtb rate to the full range of P treatments whereas growtb of the large-leaved genotype at tbe non-limiting rate of P supply was 2.4 times greater than at the two low rates of P supply. Source roots of both genotypes exported only 26-309f of the P they acquired to the shoot within 24 h when P supply was limited whereas at the bigh-P rate 54% of recently-assimilated P was exported. Patterns of translocation of exported P to specific sinks differed little between tbe genotypes and the P treatments: brancbes were the main sink, accounting for nearly 80% of the estimated amounts of P (|xg day') exported from young and old roots combined. Translocation patterns from individual roots were detennined largely by tbe modular structure of plants and by the location of the root relative to the major sinks, and were therefore consistent with the same source-sink principles which govern carbohydrate translocation in clonally-growing species. There were strong suggestions that storage of P in stolons and roots played a mucb greater role in the growth of the small-leaved plants tban of the large-leaved plants.

Influence of xylem vascular architecture on the translocation of phosphorus from nodal roots in a genotype of Trifolium repens during undisturbed growth

“…Measurement of the ^^P activity of all dissection categories, including fed roots, follow-ed methodology of Chapman & Hay (1993). Where dry weight…”

“…One nodal root within each plant was selected for ^'P feeding so that uptake and translocation of '"P could be measured using the methodology of Chapman & Hay (1993). These nodal roots originated at one of three positions (Eig.l); (1) on the parent axis at a node with a developed branch, or on a branch at either (2) the second adaxial node, or (3) the second abaxial node (respectively the third or fourth node along the branch from its junction with the parent stolon).…”

“…However in many Although utilization of P by T. repens for shoot regions inadequate phosphorus (P) supply severely growth involves translocation and partitioning prolimits the productivity of pastures based on T. cesses of botb recently-assimilated and re-mobilized repens. As T. repens competes poorly with associated P at the organ, cell and sub-cellular levels, as yet the principles governing the distribution of recentlyassimilated P even at tbe organ level still merit attention (Chapman & Hay, 1993;Kemball & Marsball, 1994). Studies of translocation of ^^P from a single nodal root have all found movement to be predominantly acropetal when plants are making stoloniferous growth (Ueno & Williams, 1967;Hosbino, 1974;Cbapman & Hay, 1993;Kemhall & Marshall, 1994).…”

Distribution of phosphorus and calcium from nodal roots of Trifolium repens: the relative importance of transport via xylem or phloem

“…Branches distal to but not at the node with the source root were allowed to de^'elop. Branch de\'elopment was restricted in order to increase the transport of radioisotopes into the parent axis and distal branches because the branch at the node with the source root is a strong sink for resources exported from the root (Chapman & Hay, 1993;Kemball & Marshall, 1994;Hay & Sackville Hamilton, 1996). When the fifth leaf distal to the source root reached leaf stage 0-5 (morphological development scale for unfolding leaves; Carlson, 1966) plants were labelled with radioisotopes.…”

Responses to Low P-Supply in Breeding Lines of White Clover (Trifolium Repens L.) Reveals Two Tiers of Responses

“…The mechanisms of uptake and partitioning of phosphate have been characterized (Chapman and Hay, 1993;Dunlop and Gardiner 1993;Lötscher and Hay 1996) and some characterisation of the root acid phosphatases has also been undertaken (Hunter and McManus, 1999;Zhang and McManus, 2000). More recently, root morphology and root growth in response to P supply has been assessed Jahufer et al, 2008) with examination of genotypic variation underpinning such studies.…”