AbstractTwelve fertile alloplasmic wheat lines, produced by substituting four nuclear genomes ofTriticum aestivuminto the cytoplasms ofT. timococcumKostoff,T. timopheeviZhuk., andAegilops ventricosaTausch, were examined for cytoplasmic effects on falling number and α‐amylase activity during grain development in different environments. Nuclear genome, cytoplasm and environment were important sources of variation for falling number. In one environment, where the plants were exposed to very hot, dry conditions, the levels and patterns of change in α‐amylase activity were also significantly affected by the cytoplasm. The data indicated that alien wheat cytoplasms might result in useful additional variation in specific environments where sprouting is a pr