LEAF EXTENSION IN THE SLENDER BARLEY MUTANT - DELINEATION OF THE TONEOF CELL EXPANSION AND CHANGES IN TRANSLATABLE MESSENGER-RNA DURING LEAF DEVELOPMENT

The slender mutant of barley (Hordeum vulgare L.) results from an alte ration to a single nuclear gene. Plants homozygous for the mutant alle le have long, attenuated leaves as a result of a greatly increased ext ension rate, Although the growth rate at any one position in the exten sion zone appears not to differ between slender and normal (wildtype) barley, in slender the length of the zone over which cells extend is a pproximately 50% greater than that in normal barley, Epidermal cells a re both longer and narrower in slender, so the whole-plant phenotype i s mirrored at the cell level, Translation in vitro of RNA extracted fr om successive sections of the young primary leaf, followed by one-dime nsional SDS-PAGE separation, facilitated the alignment of equivalent d evelopmental stages in the two genotypes, but failed to demonstrate ma jor differences between the two genotypes, Two-dimensional separation of translation products from total leaf tissue revealed a few small di fferences between normal and slender, Growth of plants at 8 degrees C compared with 20 degrees C caused changes in some translation products , with one (unknown) product decreasing in abundance in cold-treated n ormal tissue but not in slender tissue.