Effect of High Temperature During Grain-filling on the Structure of Developing and Malted Barley Grains

High temperatures (up to 35 °C) were applied to plants ofmalting barley,Hordeum vulgareL. (‘Schooner’) fora period of 5 d during grain-filling. Heat treatment had a profoundeffect on the structure of the mature barley grain. There wasevidence of degradation of endosperm storage products in heat-treatedgrain. Starch granule development was reduced in sub-aleuronecells following heat treatment and alterations to starch granuledistribution and growth were observed in the endosperms of thesegrains. Endosperm cell wall and crushed cell layer (CCL) developmentwere sensitive to high temperatures, with the reduced thicknessof the CCL and generally patchy Calcofluor fluorescence of endospermcell walls indicative of partial hydrolysis of ß-glucans.Increased growth of the embryo took place in heat-treated grainscompared with control grains. Endosperm texture was generallymore friable in heat-treated grains than in control grains,and these grains overmodified during malting, with considerabledegradation of starch in the form of extensive pitting of A-typestarch granules. Evidence is presented for developmental andgermination events occurring simultaneously within the developinggrain.Copyright 1998 Annals of Botany Company Barley,Hordeum vulgareL., starch granules, crushed cell layer, scutellum, embryo, fluorescence microscopy, scanning electron microscopy, confocal microscopy, malting quality.