Effects of pH and bicarbonate on the nutrient status and growth of three Lupinus species
High pH, and high bicarbonate (HCO3−) and calcium (Ca) availability characterise calcareous soils. High [Ca] only partially explains why some Lupinus species are calcifuge, so we explored high [HCO3−] and high pH.
We grew six Lupinus genotypes in hydroponics with pH 5, 6.5 and 8a (adjusted by KOH), and 8b (adjusted by KHCO3). Leaf symptoms and areas, root appearance and biomass were recorded; whole leaf and root nutrient concentrations, and leaf cellular phosphorus (P), Ca and potassium (K) concentrations were determined using elemental X-ray microanalysis.
Chlorosis was observed in young leaves at high pH for L. angustifolius and L. cosentinii, and P deficiency at high pH for all genotypes. High pH decreased iron (Fe) and zinc (Zn) uptake in all genotypes. It also decreased lateral root growth, the uptake of P, K, Ca, and manganese (Mn) by all sensitive species; and translocation of P, Fe, Zn, Mn, and Ca to leaves in most sensitive species. However, leaf [Ca], leaf [K], [K] within each measured cell type, and translocation of K and Ca to leaves of L. pilosus and L. cosentinii at pH 8 were greater than at pH 5 and 6.5. Compared with pH 8a, all L. angustifolius genotypes translocated more P, Fe, Zn, Mn and K from roots to leaves at pH 8b. High pH did not affect the leaf cell types that accumulated P and Ca, but decreased the leaf cellular [P].
Lupinus angustifolius and L. cosentinii were sensitive to high [HCO3−] and/or high pH; L. pilosus was relatively tolerant. High pH decreased lateral root growth and nutrient uptake, inhibiting growth of sensitive species. High [HCO3−] diminished the negative effect of pH 8 on nutrient translocation to leaves in most L. angustifolius genotypes. This knowledge provides critical insights into the habits of Lupinus species to guide breeding of calcicole plants.
KeywordsHigh pH High bicarbonate Lateral root growth Leaf chlorosis Phosphorus deficiency X-ray microanalysis
Wenli Ding was supported by a Scholarship for International Research Fees (SIRF) and a University International Stipend (UIS) and UIS Top-Up scholarship. This research project was supported by an Australian Research Council (ARC)-funded Discovery Project grant (DP130100005) awarded to H.L. and P.L.C, and by the UWA Institute of Agriculture. We acknowledge the scientific and technical assistance of the Australian Microscopy & Microanalysis Research Facility at the Centre for Microscopy, Characterisation & Analysis (CMCA), the University of Western Australia, a facility funded by the University, State and Commonwealth Governments. Thanks to Lyn Kirilak for her technical support in CMCA. Thanks to Xinhou Zhang for assisting with this experiment, Jon Clements for providing seeds, Patrick E. Hayes for internal review, and Jon E. Shaff for helping with the use of GeoChem-EZ.
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