Osmotic Adjustment in Lolium perenne; Its Heritability and the Nature of Solute Accumulation |
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Authors: | THOMAS HENRY |
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Institution: | AFRC Institute for Grassland and Environmental Research Welsh Plant Breeding Station, Plas Gogerddan, Aberystwyth, Dyfed SY23 3EB, UK |
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Abstract: | Plants derived from Lolium perenne L. cv. Mellewere selected on the basis of extreme high or low lamina solutepotential ( s) and pair-crossed to produce divergent G2 lines.The high and low lines had mean lamina s values significantlydifferent from each other and from Melle, andshowed an enhanced range of phenotypic expression of s duringdrought. Both mature lamina s and meristem s values of droughtedplants were highly heritable. Extreme G2 genotypes were selectedand clonally replicated for further study. During drought mean 2 values fell from 1·21 to1·80 MPa. Fructans of large molecular weight,and total free amino acids, especially proline, all accumulatedwhen estimated on a dry-matter (DM) or plant-water (PW) basis.Oligosaccharide content was largely unchanged. Minerals declinedwhen estimated on a DM basis but accumulated on a PW basis becausehydration (g water in turgid tissue per g DM) declined morerapidly. In comparison with genotypes having high constitutive s, low- sgenotypes (a) were larger, had faster leaf extension rate, hadfewer tillers, and were proportionally more affected by drought,(b) showed greater osmotic adjustment, (c) contained and accumulatedmuch more fructan (but not oligosaccharides), and amino acids,especially proline, and (d) accumulated more mineral ions ona PW basis, but less on a DM basis. The relatively high repeatabilitiesfor organic solutes in particular show that further divergentselection for individual solutes would not be difficult. Solutes accumulated, probably because they were not consumedin growth. There was no evidence of competitionbetween growth and osmotic adjustment for metabolites, or thatplants which accumulated more solutes were better able to recoverwhen water deficits were relieved. Perennial ryegrass, drought, genetic variation, carbohydrate, amino acids, proline, mineral uptake, Lolium perenne L. cv. Melle |
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