Waterlogging Tolerance Among a Diverse Range of Trifolium Accessions is Related to Root Porosity, Lateral Root Formation and 'Aerotropic Rooting' |
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| Authors: | Gibberd Mark R; Gray John D; Cocks Phillip S; Colmer Timothy D |
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| Institution: | CSIRO Plant Industry, P.M.B., Merbein, 3505, Victoria, Australia Plant Sciences, Faculty of Agriculture, The University of Western Australia, Nedlands, 6907, Western Australia Centre for Legumes in Mediterranean Agriculture, 35 Stirling Highway, Crawley, 6009, Western Australia |
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| Abstract: | Waterlogging tolerance, root porosity and root anatomy wereevaluated for 20 Trifolium accessions (species and sub-species,all annuals) selected from the eight Sections of the genus.Nine accessions were sensitive relative growth rate (RGR) reducedby up to 80%] to waterlogging, nine accessions were tolerant(RGR not reduced), and in two accessions RGR increased (up to1.9-fold), when compared to drained controls. Growth of themain (i.e. tap) root axis was severely reduced in all accessionswhen waterlogged. Lateral roots formed the bulk of the rootsystem of tolerant accessions when grown in waterlogged soil.Lengths of the longest lateral roots were up to three-timeslonger than the main root axis. Root porosity varied from 0.7–12%among accessions when grown in aerated solution and from 1.1–15.5%in plants grown in hypoxic (0.031–0.045 mol O2m-3) solution.In some accessions aerenchyma formed by cell lysigeny; in othersit formed by schizogenous cell separation, or a combinationof both processes. O2consumption rates of expanded lateral roottissues varied by up to 1.7-fold (on a mass basis) among thesix accessions tested and was reduced by an average of 24% forroots of plants grown in hypoxic solution prior to measurements.Accessions with the highest root porosity tended to have longerroots when grown in waterlogged soil. Three accessions formed‘aerotropic roots’ and the lateral root lengthsof these plants exceeded those of all other accessions, suggestingenhanced O2movement to the submerged lateral root axis via theaerotropic roots. Waterlogging-tolerant accessions were identifiedin seven of the eight Sections in Trifolium, and the tolerantaccessions tended to be those with extensive lateral root systemsof relatively high porosity. Copyright 2001 Annals of BotanyCompany Waterlogging, Trifolium, aerenchyma, hypoxia, flooding, root respiration, clover, root anatomy, root porosity, pasture, aerotropic roots |
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