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Root nodules apparently have evolved three times within the Fabaceae but are rare outside that family. The propensity of these plants to develop root nodules seems to relate to their root structure. In particular, a tendency to develop lateral roots in response to abscisic acid may enable the later evolution of root nodules. [21]
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 [1] Grass; Rosemary; Fibrous roots grow fairly close to the surface of the ground.
The most distinctive characteristics that allow rhizobia to be distinguished apart are the rapidity of their growth and the type of root nodule that they form with their host. [60] Root nodules can be classified as being either indeterminate, cylindrical and often branched, and determinate, spherical with prominent lenticels.
Growth from any such meristem at the tip of a root or shoot is termed primary growth and results in the lengthening of that root or shoot. Secondary growth results in widening of a root or shoot from divisions of cells in a cambium. [8] In addition to growth by cell division, a plant may grow through cell elongation. This occurs when individual ...
The fibrous-root system (A) is characterized by many roots with similar sizes. In contrast, plants that use the taproot system (B) grow a main root, with smaller roots branching off. The letters indicate where the root systems begin. A taproot is a large, central, and dominant root from which other roots sprout
Adventitious roots arise out-of-sequence from the more usual root formation of branches of a primary root, and instead originate from the stem, branches, leaves, or old woody roots. They commonly occur in monocots and pteridophytes, but also in many dicots , such as clover ( Trifolium ), ivy ( Hedera ), strawberry ( Fragaria ) and willow ( Salix ).
A fine root is most commonly defined as a plant root that is two millimeters or less in diameter. [1] Fine roots may function in acquisition of soil resources (eg. nutrients, water) and/or resource transport, making them functionally most analogous to the leaves and twigs in a plant's shoot system. [1]
In botany and dendrology, a rhizome (/ ˈ r aɪ z oʊ m / RY-zohm) [note 1] is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. [3] Rhizomes develop from axillary buds and grow horizontally. The rhizome also retains the ability to allow new shoots ...