Fibrous root system
From Wikipedia, the free encyclopediahttp://en.wikipedia.org/wiki/Fibrous_root_system
A fibrous root system (sometimes also called adventitious root system) is the opposite of a taproot system. It is usually formed by thin, moderately branching roots growing from the stem. A fibrous root system is universal in monocotyledonous plants and ferns.
Most trees begin life with a taproot, but after one to a few years change to a wide-spreading fibrous root system with mainly horizontal surface roots and only a few vertical, deep anchoring roots. A typical mature tree 30-50 m tall has a root system that extends horizontally in all directions as far as the tree is tall or more, but well over 95% of the roots are in the top 50 cm depth of soil.
A few plants with fibrous root systems:
* Coconut palm 
* White clover (Trifolium repens)
From Wikipedia, the free encyclopediahttp://en.wikipedia.org/wiki/Taproot
A taproot is an enlarged, somewhat straight to tapering plant root that grows vertically downward. It forms a center from which other roots sprout laterally.
The taproot of Carrots.
Plants with taproots are difficult to transplant. The presence of a taproot is why dandelions are hard to uproot—the top is pulled, but the long taproot stays in the ground, and resprouts.
The taproot system contrasts with the fibrous root system with many branched roots.
Most plants start with a taproot, which is one main root forming from the enlarging radical of the seed. The tap root can be persistent throughout the life of the plant but is most often replaced later in the plant's development by a fibrous root system. A persistent taproot system forms when the radical keeps growing and smaller lateral roots form along the taproot. The shape of taproots can vary but the typical shapes include:
* Conical root: this type of root tuber is conical in shape, i.e. widest at the top and tapering steadily towards the bottom: e.g. carrot.
* Fusiform root: this root is widest in the middle and tapers towards the top and the bottom: e.g. radish.
* Napiform root: the root has a top-like appearance. It is very broad at the top and tapers suddenly like a tail at the bottom: e.g. turnip.
Many taproots are modified into storage organs.
Some plants with taproots:
* Poppy mallow
Taproots develop from the radicle of a seed, forming the primary root. It branches off to secondary roots, which in turn branch to form tertiary roots. These may further branch to form rootlets. For most plants species the radical dies some after seed germination, causing the development of a fibrous root system, which lacks a main downward-growing root. Most trees begin life with a taproot, but after one to a few years the main root system changes to a wide-spreading fibrous root system with mainly horizontal-growing surface roots and only a few vertical, deep-anchoring roots. A typical mature tree 30–50 m tall has a root system that extends horizontally in all directions as far as the tree is tall or more, but well over 95% of the roots are in the top 50 cm of soil.
Soil characteristics strongly influence the architecture of taproots; for example, deep rich soils favor the development of vertical taproots in many oak species such as Quercus kelloggii, while clayey soils promote the growth of multiple taproots.