Responses of a Semi-dwarf Wheat to Temperatures Representing a Tropical Dry Season. II. Extreme Temperatures

Abstract

SUMMARYUnder controlled environment conditions a semi-dwarf wheat, Mexico 120, was subjected to temperature regimes representative of the extremes that occur during the dry (winter) season of the Ord River valley in northern Australia. High temperatures (35°C by day: 18°C by night) such as occur at the beginning and end of the dry season were compared with low temperatures (30°C by day: 13°C by night) such as occur in mid-season. Day length was constant at 12 hours. High temperatures from floral initiation onwards adversely affected floret development, and after ear emergence reduced grain filling to nil. Net assimilation rates were reduced by high temperatures. Major effects on yields were caused by high temperatures well before anthesis. The critical temperature after anthesis is apparently between 32° and 35°C.