RELATIONSHIP OF MIXED-LINK BETA-GLUCAN ACCUMULATION TO ACCUMULATION OF FREE SUGARS AND OTHER GLUCANS IN THE DEVELOPING BARLEY ENDOSPERM

Accumulation of free sugar, starch, mixed-link beta-glucan and hemicellulose in developing barley endosperms was investigated using a sequential enzymatic procedure. Bomi grown in a growth cabinet, the three cultivars Minerva, Lami and Triumph, grown in the field, and Minerva and Triumph growh under a range of water supply regimes in the phytotron were studied. The first experiments showed that initiation of synthesis occurred in the order hemicellulose, starch, mixed-link beta-glucan 10 days, 11 days, and 17 days after fertilization, respectively. The second experiment indicated two separage accumulation patterns for mixed-link beta-glucan, one shared by Lami and Triumph, the other followed by Minerva. When moisture content declined to 40-50%, the accumulation rate increased sharply in Lami and Triumph, but not in Minerva. A similar sharp increase in the rate of accumulation of hemicellulose was observed in Minerva and Triumph. The moisture stress experiment showed that water supply and humidity are the major factors mediating the response of beta-glucan content to environment, but that Triumph, a low-content genotype, was always lower in beta-glucan content than Minerva. Some implications of the results for elucidation of the control of endosperm development are discussed. © 1979 Carlsberg Laboratory.