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Interactions among cluster‐root investment, leaf phosphorus concentration, and relative growth rate in two Lupinus species
Author(s) -
Wang Xing,
Veneklaas Erik J.,
Pearse Stuart J.,
Lambers Hans
Publication year - 2015
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.1500268
Subject(s) - relative growth rate , lupinus , biology , phosphorus , nutrient , specific leaf area , botany , horticulture , growth rate , zoology , ecology , photosynthesis , chemistry , geometry , mathematics , organic chemistry
PREMISE OF THE STUDY: Cluster‐root (CR) formation is a desirable trait to improve phosphorus (P) acquisition as global P resources are dwindling. CRs in some lupine species are suppressed at higher P status. Whether increased growth rate enhances CR formation due to a “dilution” of leaf P concentration is unknown. We investigated interactive effects of leaf P status and relative growth rate (RGR) on CR formation in two Lupinus species, which differ in their CR biomass investment. Variation in RGR was imposed by varying day length. METHODS: Lupinus albus and L. pilosus were grown hydroponically with KH 2 PO 4 at a day length of 6, 10, or 14 h. We used a slightly higher P supply at longer day lengths to avoid a decline in leaf P concentration, which would induce CRs. Cluster‐root percentage, leaf P concentrations, and RGR were determined at 22, 38, and 52 d after sowing. KEY RESULTS: Lupinus species grown at similar root P availability, but with a faster growth rate, as dependent on day length, showed a greater CR percentage. Because our aim to achieve exactly the same leaf P concentrations at different day lengths was only partially achieved, we carried out a multiple regression analysis. This analysis showed the CR percentage was strongly and negatively correlated with plant P status and only marginally and positively correlated with RGR. CONCLUSIONS: The two Lupinus species invariably formed fewer cluster roots at higher leaf P status, irrespective of RGR. Differences in RGR or leaf P concentration cannot explain the species‐specific variation in cluster‐root investment.