2.Plant Growth and development B.Requirements for seed germination The germination of seeds is dependent on both internal and external conditions. The most important external factors include: temperature-affects cellular metabolic and growth rates. water-is required before cellular metabolism and growth can resume. oxygen-is required by the germinating seed for metabolism. light or darkness(sometimes)-can be a type of environmental trigger for germination in seeds. ■▣RA opyright reseved by Long M College of animal science,Northwest Agriculture&Forestry University 西北农林科技大学动物科技学院草业科学系__________________________________________________________________ College of animal science, Northwest Agriculture & Forestry University  西北农林科技大学动物科技学院草业科学系 Copyright reseved by Long Mingxiu B.Requirements for seed germination • The germination of seeds is dependent on both internal  and external conditions. • The most important external factors include: temperature­ affects cellular metabolic and growth rates.  water­is required before cellular metabolism and growth can  resume. oxygen ­ is required by the germinating seed for metabolism .  light or darkness (sometimes) ­can be a type of environmental trigger for germination in seeds .  2.Plant Growth and development