Phosphorus starvation induced root-mediated pH changes in solublization and acquisition of sparingly soluble P sources and organic acids exudation by Brassica cultivars

Akhtar M. Shahbaz, Yoko Oki, Tadashi Adachi, Yoshiyuki Murata, Md Harunar Rashid Khan

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Plant species and cultivars elicit a diverse array of sophisticated metabolic and developmental strategies to enhance phosphorus (P) solublization and acquisition from P-deficient rooting media. Scavenging of phosphate (Pi) from extracellular sparingly soluble P sources may be aided by organic acids (OAs) exudation and root-mediated pH changes under a P-stress environment. Root exudates were collected to quantify short-term (4 h, 8 h) carboxylate exudation using hydroponically grown Brassica cultivars. Malic and citric acids were the dominant OAs and efficient cultivars exuded 2-3-fold more OAs than inefficient cultivars under P-deficient conditions. However, the exudation rate of both resistant and sensitive cultivars decreased with time. Experiments in nutrient solution were conducted to evaluate growth responses and the P solublization and acquisition ability of six genetically diverse Brassica cultivars. Pre-germinated seedlings were grown in nutrient solution containing ammonium di-hydrogen phosphate (AP), tri-calcium phosphate (TCP) and rock phosphate (RP) (TCP at 0.2 g L -1 and RP at 2 g L -1, in a bid to maintain deficiently buffered solution-P concentration) as different P sources. The cultivars exhibited substantial growth differences (P <0.001) in terms of biomass accumulation, P acquisition and P utilization efficiency (PUE). Biomass production correlated significantly (P <0.01) with their shoot P uptake and PUE at both P sources, indicating that cultivars efficient in P solublization accumulated more biomass. Higher P uptake by all cultivars was significantly related to the drop in root medium pH, which was presumably owing to H + efflux from the roots supplied with TCP and RP. Higher shoot dry matter of the cultivars at TCP was related to better P acquisition ability, which in turn was related to higher Ca uptake. Thus, cultivars with efficient Ca accumulation ability can acquire higher amounts of P from P-deficient soils and can adapt well to such low-P soil conditions.

Original languageEnglish
Pages (from-to)623-633
Number of pages11
JournalSoil Science and Plant Nutrition
Volume52
Issue number5
DOIs
Publication statusPublished - Oct 2006

Fingerprint

exudation
Brassica
starvation
organic acid
organic acids and salts
cultivar
phosphorus
cultivars
tricalcium phosphate
phosphate
phosphate rock
rock phosphate
calcium
uptake mechanisms
nutrient solutions
biomass production
biomass
shoot
phosphates
shoots

Keywords

  • Brassica cultivars
  • Citrate
  • Malate
  • P solublization
  • P uptake
  • PUE
  • RP
  • TCP

ASJC Scopus subject areas

  • Soil Science
  • Agronomy and Crop Science

Cite this

Phosphorus starvation induced root-mediated pH changes in solublization and acquisition of sparingly soluble P sources and organic acids exudation by Brassica cultivars. / Shahbaz, Akhtar M.; Oki, Yoko; Adachi, Tadashi; Murata, Yoshiyuki; Khan, Md Harunar Rashid.

In: Soil Science and Plant Nutrition, Vol. 52, No. 5, 10.2006, p. 623-633.

Research output: Contribution to journalArticle

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AU - Murata, Yoshiyuki

AU - Khan, Md Harunar Rashid

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AB - Plant species and cultivars elicit a diverse array of sophisticated metabolic and developmental strategies to enhance phosphorus (P) solublization and acquisition from P-deficient rooting media. Scavenging of phosphate (Pi) from extracellular sparingly soluble P sources may be aided by organic acids (OAs) exudation and root-mediated pH changes under a P-stress environment. Root exudates were collected to quantify short-term (4 h, 8 h) carboxylate exudation using hydroponically grown Brassica cultivars. Malic and citric acids were the dominant OAs and efficient cultivars exuded 2-3-fold more OAs than inefficient cultivars under P-deficient conditions. However, the exudation rate of both resistant and sensitive cultivars decreased with time. Experiments in nutrient solution were conducted to evaluate growth responses and the P solublization and acquisition ability of six genetically diverse Brassica cultivars. Pre-germinated seedlings were grown in nutrient solution containing ammonium di-hydrogen phosphate (AP), tri-calcium phosphate (TCP) and rock phosphate (RP) (TCP at 0.2 g L -1 and RP at 2 g L -1, in a bid to maintain deficiently buffered solution-P concentration) as different P sources. The cultivars exhibited substantial growth differences (P <0.001) in terms of biomass accumulation, P acquisition and P utilization efficiency (PUE). Biomass production correlated significantly (P <0.01) with their shoot P uptake and PUE at both P sources, indicating that cultivars efficient in P solublization accumulated more biomass. Higher P uptake by all cultivars was significantly related to the drop in root medium pH, which was presumably owing to H + efflux from the roots supplied with TCP and RP. Higher shoot dry matter of the cultivars at TCP was related to better P acquisition ability, which in turn was related to higher Ca uptake. Thus, cultivars with efficient Ca accumulation ability can acquire higher amounts of P from P-deficient soils and can adapt well to such low-P soil conditions.

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