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Pea (pisum in Latin) is a pulse, vegetable or fodder crop, but the word often refers to the seed or sometimes the pod of this flowering plant species. Carl Linnaeus gave the species the scientific name Pisum sativum in 1753 (meaning cultivated pea).
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]
The function of all root hairs is to collect water and mineral nutrients in the soil to be sent throughout the plant. In roots, most water absorption happens through the root hairs. The length of root hairs allows them to penetrate between soil particles and prevents harmful bacterial organisms from entering the plant through the xylem vessels. [1]
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.
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 ).
The loosely packed cells of root cortex allow movement of water and oxygen in the intercellular spaces. [4] One of the main functions of the root cortex is to serve as a storage area for reserve foods. [4] The innermost layer of the cortex in the roots of vascular plants is the endodermis. The endodermis is responsible for storing starch as ...
Most trees begin life with a taproot, [3] 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 ...
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 ...