Variation of dry matter accumulation at definite positions within wheat ears and levels of indole-3yl acetic acid (IAA)

By sterilization-treatments grain weights in defined positions within the wheat (Triticum aestivum L. cvs. Oskar, Kolibri, Norin 10) ear were varied. Main shoot ears were partitioned into basal, central and apical regions and further into proximal and distal grains. The central region was used for treatments and investigations. Proximal grains were sterilized in order to vary the dry weights of distal grains. Dry matter ac= cumulation and IAA levels were investigated during the grainfilling period. Results from two seasons are presented. In both seasons sterilization treatments accelerated the dry matter accumulation of distal grains in all cultivars, but treatment effects on IAA concentration depended upon interactions between years and cultivars. A parallel variation in grain weights and IAA concentrations occurred only in 1981 in the cultivar Oskar. In 1982, however, IAA concentrations were reduced in all cultivars. The results contradict an assumed causal correlation between dry matter storage and IAA concentration, but they do not exclude a possible role of IAA in regulating grain growth.