Osmotic Relations during Elongation Growth in Coleoptiles of Five Cereal Species

Abstract

Summary The relationship between growth, change in cell osmotic pressure and accumulation of osmotic solutes was investigated in coleoptiles of seedlings of maize (Zea mays L.), oats (Avena sativa L.), wheat (Triticum aestivum L.), rye (Secale cereale L.) and barley (Hordeum vulgare L.). In dark-grown maize coleoptiles, cell osmotic pressure decreased by 25 % between days 3 and 8 after sowing. In etiolated seedlings of oats, wheat, rye and barley, coleoptile growth in darkness was accompanied by a 40–50% decrease in cell osmotic pressure, depending on species. One day after transfer to white light coleoptile growth ceased due to the emergence of the primary leaves. In irradiated coleoptiles of maize and oats a substantial decrease in cell osmotic pressure occurred, but in wheat, rye and barley only minor changes were detectable. In all five species investigated coleoptile growth in darkness was accompanied by a corresponding increase in the amount of osmotic solutes. After irradiation with white light a loss of osmotic solutes occurred, possibly as a consequence of an enhanced membrane permeability during coleoptile senescence.