Last Updated on August 26, 2018 by Naeem Javid Muhammad Hassani
- Root may be defined as, “Cylindrical plant organ which is devoid of chlorophyll, bearing no buds or leaves, and tending to grow downloads away from light.” _ (LoF)
- Roots are positively Geotropic and Negatively Phototropic ie they grow downward into the soil and away from light.
- Roots are Positively Thermotropic and exhibit Positive Hydrotropism ie they bend in the direction of temperature and have a tendency to grow in the direction of moisture.
- Roots having several functions, including the absorption and conduction of water and dissolved minerals, food storage, and anchorage of the plant in the soil.
- The root is distinguished from the stem by its structure, by the manner in which it is formed, and by the lack of such appendages as buds and leaves.
- When a seed germinates, radical gradually elongates and form primary roots. The primary root may give off branches, the secondary roots which in turn branch off to produce tertiary and quaternary roots.
- In dicotyledonous plants, the primary root becomes the main root and is termed as a taproot. Monocotyledonous plants, generally, lack taproot. In turn, these produce roots from the base of the stem which is strong and vigorous. These roots are known as adventitious roots.
- The root is composed of three types of tissue: the epidermis, or surface layer; the ground tissue, or cortex; and the vascular core, situated at the center of the root. (Fig)
- Certain cells of the epidermis are modified for an absorptive function. Long, tube-like projections, called root hairs, grow from these cells into the absorptive surface of the root and anchor the root to soil particles.
- Water absorbed by root hairs is transferred across the cortex, the region of water and food storage, and into the vascular core, which carries it up into the stem.
- Organization of the vascular core in a root is markedly different from that in a stem.
- In the stem, the vascular tissues xylem and phloem are grouped together in vascular bundles. In the root, a central core of xylem has radial bands that extend outward toward the cortex, and between these bands are strands of phloem. (See figure)
- Other parts of the root are shown in the figure.
The parts include:
- Meristematic zone: it is the zone of elongation of root ie for growth
- Meristematic tissue: these are the tissues which divide and help in growth ie
- Apical Meristem
- Root cap
- Under normal conditions, the growth of roots is influenced chiefly by gravity and by the presence of water. Roots tend to grow downward into the soil unless water is more readily available at the surface.
- In addition to the primary growth in length occurring at the apex of the root, a secondary growth occurs that adds xylem, or wood, to the inside of the root and phloem toward the outside. Phloem produced in this manner becomes involved in the formation of bark, which covers old roots as well as old stems. Old roots often are virtually identical therefore with old stems.
- Because in many plants roots can be formed from a cut end of a stem, cuttings may be used for plant propagation.
- Some plants, such as the willow or geranium, root quite easily, whereas others, such as the conifer, rarely root without special treatment.
- Root formation can be stimulated on cuttings of many plants by the application of the so-called root hormones, substances found naturally in the plant when new roots are formed.
- Most commercial preparations of root hormones contain indoleacetic acid, one of the most common root-stimulating substances.
- Occasionally roots may be formed from leaves, which may be propagated by rooting the cut end of a leaf base in water.
- Roots of many plants are edible and contain considerable quantities of food materials, particularly starch.
- Root crops important in agriculture include the sweet potato, beet, turnip, carrot, parsnip, and cassava.
- Other functions of root include:
- Absorption of food from the soil
- Store food
- Absorb moisture
- Provide shelter to Nitrogen Fixing bacteria.
- Provide extra support to plant
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NJMH is working as Deputy Conservator of Forests in Balochistan Forest & Wildlife Department (BFWD). He is the CEO of Tech Urdu (techurdu.net) Forestrypedia (forestrypedia.com), Majestic Pakistan (majesticpakistan.pk), All Pak Notifications (allpaknotifications.com), Essayspedia, etc & their YouTube Channels). He is an Environmentalist, Blogger, YouTuber, Developer & Vlogger.