تغيير ساختار كانوپي در برخي ارقام گندم اصلاح شده ايراني

Changes in Canopy Structure of Some Iranian Wheat Cultivars

Canopy structure of some Iranian wheat cultivars, developed for cold and temperate-cold climates within the last 50 years, were studied in two separate trials during 1998 and 1999 in the Research Station of College of Agriculture, Ferdowsi University of Mashhad. In both trials 6 wheat cultivars were investigated in a randomized complete block design with 3 replicates. In the first experiment all cultivars were sown at the same date and with the equal planting density and N fertilization. However, in the second experiment cultivars were sown under the recommended sowing date, plant density and N rate for maximum yield. Other management practices were identical in both years. New wheat cultivars had a greater light extinction coefficient (K) and positioned a higher proportion of their leaf area at the top canopy layers. Such a canopy structure led to better absorption of radiation at top canopy layer in new cultivars. A decreasing profile of specific leaf nitrogen (SLN), specific leaf area (SLA) and leaf nitrogen content (LNC) were observed from top to bottom of the canopy with a negative correlation between SLW and LNC.