title: Phosphorus uptake, partitioning and redistribution during grain filling in rice.
abstract: In cultivated rice, phosphorus (P) in grains originates from two possible sources, namely exogenous (post-flowering root P uptake from soil) or endogenous (P remobilization from vegetative parts) sources. This study investigates P partitioning and remobilization in rice plants throughout grain filling to resolve contributions of P sources to grain P levels in rice.
  
  
  
  Rice plants (Oryza sativa 'IR64') were grown under P-sufficient or P-deficient conditions in the field and in hydroponics. Post-flowering uptake, partitioning and re-partitioning of P was investigated by quantifying tissue P levels over the grain filling period in the field conditions, and by employing33P isotope as a tracer in the hydroponic study.
  
  
  
  Post-flowering P uptake represented 40-70 % of the aerial plant P accumulation at maturity. The panicle was the main P sink in all studies, and the amount of P potentially remobilized from vegetative tissues to the panicle during grain filling was around 20 % of the total aerial P measured at flowering. In hydroponics, less than 20 % of the P tracer taken up at 9 d after flowering (DAF) was found in the above-ground tissues at 14 DAF and half of it was partitioned to the panicle in both P treatments.
  
  
  
  The results demonstrate that P uptake from the soil during grain filling is a critical contributor to the P content in grains in irrigated rice. The P tracer study suggests that the mechanism of P loading into grains involves little direct transfer of post-flowering P uptake to the grain but rather substantial mobilization of P that was previously taken up and stored in vegetative tissues.
authors: Southern Cross Plant Science, Southern Cross University, PO Box 57, Lismore, NSW 2480, Australia Southern Cross GeoScience, Southern Cross University, PO Box 57, Lismore, NSW 2480, Australia cecile.julia@scu.edu.au terry.rose@scu.edu.au.
authors: Cécile
authors: C
authors: Julia
authors: Crop, Livestock and Environment Division, Japan International Research Center for Agricultural Sciences, 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan.
authors: Matthias
authors: M
authors: Wissuwa
authors: Genotyping Services Laboratory, International Rice Research Institute (IRRI), DAPO BOX 7777, Metro Manila, Philippines.
authors: Tobias
authors: T
authors: Kretzschmar
authors: Southern Cross Plant Science, Southern Cross University, PO Box 57, Lismore, NSW 2480, Australia Southern Cross GeoScience, Southern Cross University, PO Box 57, Lismore, NSW 2480, Australia.
authors: Kwanho
authors: K
authors: Jeong
authors: Southern Cross Plant Science, Southern Cross University, PO Box 57, Lismore, NSW 2480, Australia Southern Cross GeoScience, Southern Cross University, PO Box 57, Lismore, NSW 2480, Australia cecile.julia@scu.edu.au terry.rose@scu.edu.au.
authors: Terry
authors: T
authors: Rose
mesh_terms: D018527:Hydroponics; D012275:Oryza / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism; D010758:Phosphorus / Q000032:analysis / Q000378:metabolism*; D010761:Phosphorus Radioisotopes / Q000378:metabolism; D018515:Plant Leaves / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry; D012639:Seeds / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism
chemical_list: D010761:Phosphorus Radioisotopes; D010758:Phosphorus
keywords: 33P tracer; P fluxes; P loading into grains; P partitioning; P remobilization; post-flowering P uptake