Effects of timing of heat stress and drought on growth and quality of barley grains

In order to determine the importance of timing of short periods of high temperature and drought on grain weight and grain quality, a glasshouse experiment was carried out in which Schooner barley was exposed to short periods of heat stress (40°C for 6 h/day for 5 consecutive days) or drought at early grain filling (10–15 days after anthesis, DAA), mid grain filling (20–25 DAA), or late grain filling (30–35 DAA). Individual grain weight was most sensitive to heat stress and drought treatments imposed early in grain filling and was less sensitive to later treatments. The reduction in grain weight was greater under heat stress (average 13%) than under drought in this study (average 6%). Starch was reduced in amount and quality, especially with early stresses during grain filling, but grain nitrogen percentage was similar between treatments.