Weeds are plants existing at places and/or times at which they are considered undesirable by man. Thys, man‘s primary interest in weeds is in dinging methods for eliminating their presences. Understanding the physiology of weeds and how it differs from that of crop plants is becoming increasingly important in discovering new chemical, genetic, and cultural methods of controlling weeds. The two volumes of this book will aim to discuss the following; the physiology of weed production the ecophysiology of weeds, the mechanisms of herbicide action, and the mechanisms of herbicide resistance and tolerance.