Science fiction is a genre of fiction dealing with imaginative content such as futuristic settings, futuristic science and technology, space travel, parallel universes, extraterrestrial life, and paranormal abilities. Exploring the consequences of scientific innovations is one purpose of science fiction, making it a "literature of ideas". Science fiction has been used by authors as a device to discuss philosophical ideas such as identity, desire, morality, and social structure.
Thursday, September 26, 2013
Tropical roots
This article is about the part of a plant. For other uses.
Primary and secondary roots in a cotton plantIn vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. However, roots can also be aerial or aerating (growing up above the ground or especially above water). Furthermore, a stem normally occurring below ground is not exceptional either.Therefore, the root is best defined as the non-leaf, non-nodes bearing parts of the plant's body. However, important internal structural differences between stems and roots exist.
The first root that comes from a plant is called the radicle. The four major functions of roots are absorption of water and inorganic nutrients, anchoring of the plant body to the ground, and supporting it, storage of food and nutrients, vegetative reproduction. In response to the concentration of nutrients, roots also synthesise cytokinin, which acts as a signal as to how fast the shoots can grow. Roots often function in storage of food and nutrients. The roots of most vascular plant species enter into symbiosis with certain fungi to form mycorrhizas, and a large range of other organisms including bacteria also closely associate with roots.
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