Upon germination, the embryo grows into a seedling. Seed germination is a process by which a seed embryo develops into a seedling. The presence of tocochromanols extends seed longevity, and promotes successful germination and seedling growth. Germination is a process by which the seed develops into a seedling. The numerous hybrids are propagated mainly by grafting on to seedling rootstock. Damping off may occur on seedling grown plants. Their activities harvesting and hoarding tree seeds play a crucial role in seedling establishment. Trampling grazers kill seedling trees but not grasses. The female cone then opens, releasing the seeds which grow to a young seedling. It is named after Maria Ann Smith, who propagated the cultivar from a chance seedling. For a tree seedling to grow into an adult tree it needs light. The existence of nurse plants is critical to seedling establishment. The fruit contains large cotyledons that surround the new stem of a seedling. Their consumption of seedling trees has led some to consider them as pests. There are high variations in kernel qualities and production between seedling trees.