Effects of Short Periods of Drought and High Temperature on Grain Growth and Starch Accumulation of Two Malting Barley Cultivars

Abstract

Short periods (3-5 days) of high maximum temperature (>35�C), often accompanied by drought, commonly occur during grain filling of cereals. Short periods of high temperature have been shown to reduce grain weight and baking quality in wheat, but little is known about their effects on barley. Consequently, we examined the effects of high temperature and drought, alone or combined, on grain growth for two barley cultivars, Schooner and Franklin. Treatments started 15 days after anthesis and consisted of the factorial combination of three temperatures and three water regimes. The high temperature (maximum 40�C for 6 h day-1) and drought treatments were maintained for 5 or 10 days. Drought reduced individual grain weight much more (ca 20%) than high temperature (ca 5%) for both cultivars. Franklin appeared to be more sensitive to heat stress than Schooner. The reduction in individual grain weight was greatest when both stresses were combimed (ca 30%). The reduction in mature grain weight under high temperature was due to a reduction in duration of grain growth for Schooner and to a reduction in both rate and duration of grain growth for Franklin (8-12%). The reduction in duration of grain growth was the most important cause of reduced grain weight at maturity under drought alone (12-25%) or combined with high temperature (25-33%). Nitrogen content per grain was quite high and similar for all treatments, and nitrogen percentage increased when stress was severe enough to reduce starch accumulation, confirming that starch accumulation is more sensitive to post- anthesis stress than nitrogen accumulation. We conclude that drought, particularly when combined with high temperature, is more likely than heat stress to cause large reductions in grain weight of barley under field conditions.

Impacts of Heat Stress on Wheat: A Critical Review

“…The studies suggested that the combined effects of drought and heat stress had significantly detrimental effects on growth and productivity of crops than separate application of each stress [51]. Moreover, it also alters the physiological processes such as photosynthesis, accumulation of lipids and transcript expression [52,53].…”

Molecular basis of barley quality

“…While it can be demonstrated that total starch content and composition can be significantly affected by environmental conditions, it appears that protein percentage is less sensitive to high temperatures (Bhullar and Jenner 1996;Savin and Nicolas 1996). On a macro scale, environmental conditions can have a significant effect on protein percentage (Eagles et al 1995;Zhang et al 2001), often determining whether a barley cultivar will meet the grain receival standards.…”

Combine Effects of Drought and High Temperature on Water Relation Traits in Wheat Genotypes under Late and Very Late Sown Condition

“…of crops compared with each stress applied individually (Savin and Nicolas, 1996;Shah and Paulsen, 2003).…”