Poster: Mineral nutrition

Abs # 191: Taxonomic variation in shoot potassium concentrations

Presenter:	Craighead, Anthea N, anc34@cam.ac.uk
Authors	Craighead, Anthea N (A)   Leigh, Roger A (A)
Affiliations:	(A): Department of Plant Sciences, University of Cambridge

Potassium is an essential plant nutrient that is important in functions as diverse as enzyme activation, cell expansion and phloem transport. Potassium is not metabolized and is present as its ion in both the cytosol and vacuole, dominating the cation content of both compartments under K-sufficient conditions. Although there is good evidence that maximum K concentration in tissue water is regulated to particular species- and tissue-specific values (Leigh, 2001, J. Plant Nutr. Soil Sci. 164: 193-198), there has been no systematic study of the variation of K across a wide taxonomic range of species. This study investigated shoot K concentrations of 250 taxonomically diverse species (from 41 orders and 97 families) obtained from the collections growing at the University of Cambridge Botanic Gardens. Across all species, measured K concentrations showed a large variation range, between 5 mM and 515 mM. Variation was similar within families, but smaller within genera. This variation was not attributable to differences in either soil readily-exchangeable K concentrations nor water content of the shoots. All data were reproducible when selected plants across the range were resampled later. More detailed investigations of selected Poaceae, Solanaceae, Brassicaceae, and Rosaceae grown under controlled nutrient conditions in a glasshouse confirmed (1) that the values measured in the sampled species were the maximum K concentrations in tissue water achievable by each species, and (2) that the variation was large between species and small within genera. These results show that there is a surprisingly large range of maximum K concentrations in shoots and that there has been no convergence to particular values during evolution.