Development of Winter Wheat under Increased Atmospheric CO² and Water Limitation at Tillering

Abstract

Atmospheric CO 2 concentrations are increasing world‐wide and are expected to double within the next century. This study was conducted to determine the combined effects of CO 2 enrichment and dehydration stress on development of ‘TAM W‐101’ winter wheat ( Triticum aestivum L.) at the tillering stage. Seedlings (one per pot) were grown in growth chambers maintained at 350 (ambient) or 700 (enriched) fiL L ‐1 CO 2 , and subjected to three levels of soil moisture (well watered, medium stress, and severe stress). Plastochron (the developmental time for one leaf) decreased 2 to 3% at all water levels under CO 2 enrichment. Averaged over CO 2 treatments, water limitation increased plastochron from 90 thermal units under well‐watered conditions to 126 under medium stress and 141 under severe stress. Similarly, water limitation reduced tiller number from 26 to 14 and 12 under medium and severe stress, respectively. The ratio of leaf dry wt. to leaf area (specific leaf wt.) and water use efficiency were significantly higher in plants grown under CO 2 enrichment. Although CO 2 enrichment had positive effects on growth and development of winter wheat at tillering, these were insufficient to counterbalance the debilitating effects of water limitation.