Roots undergo various modifications for performing various physiological (storage and respiratory) and mechanical (plant support/anchoring) functions which are essential for plant survival. Storage roots are also the modified forms of roots, necessary for the storage of water and food materials. These modified roots are usually swollen and can modify into different forms such as spindle-shaped, top-shaped, cone-like, indefinite shape, etc. These swollen or thickened roots serve as organs for the storage of food. In various plants, the food is stored in either cortex or xylem or in both regions. These types of roots are usually found underground to avoid being eaten by herbivores. The type of root modifications that occur in tap roots and adventitious roots for food storage are shown in the following diagram.
Examples of plants undergoing root modifications for food storage are-
1. Daucus carota
Daucus carota (Umbelliferae-dicot) is the scientific name for carrot, a root vegetable. Carrots possess tap roots and these roots undergo several modifications for performing various functions like food storage. Carrot roots undergo modifications and form cone-like structures; therefore, are categorized under conical root modifications. These types of roots are thickest towards the base and gradually tapering towards the apex. The hypocotyl and the base of the stem after sloughing off the cortex become fleshy through the development of parenchyma in the phloem. Parenchyma is a simple permanent tissue that makes the storage tissue. The storage roots of this plant are usually swollen for the storage of various food materials.
Radish, also known as Raphanus sativus, is a Cruciferae- dicot and an edible root vegetable belonging to the Brassicaceae family. Radish has a spindle-shaped structure, thickest from the middle and narrow from the ends, and is an example of fusiform tap root modification. The tapering/narrow ends include the base of the stem and the apex of the root. Xylem is the chief region for food storage but the storage also takes place outside the xylem region. Fleshy roots of radishes show a proliferation of parenchyma in the pith and the secondary xylem, accompanied by differentiation of concentric vascular bundles within this parenchyma. Radish is a rich source of antioxidants (calcium and potassium) and helps to lower high blood pressure levels and reduce the risk of heart diseases.
|Sub-species||R. raphanistrum sativus|
Its fusiform roots consist of swollen hypocotyl near the base and swollen taproot in the rest of the region. It is usually long and white color in appearance.
In European Radish, the taproot only forms the terminal tapering fleshy part of the root while the hypocotyl forms the middle fleshy parts. It is usually a short, red-colored taproot.
Brassica rapa, the scientific name of turnip, is a cruciferous vegetable that belongs to the Brassicaceae family. Turnips are also called top-shaped roots because of their structure and are categorized under napiform tap root modifications for food storage. The phloem and the cortex of turnip roots are narrow; therefore, food storage largely takes place in the xylem region. The massive swollen part of the turnip is the hypocotyl, while the taproots are present at the tapered/narrow end of the turnip. Various health benefits of turnip include-
- Help in lowering blood pressure
- Reduce the risk of cancer
- Help in weight loss
- Improves digestion
- Lowers the risk of intestinal problems
Beta Vulgaris or beetroot is a Chenopodiaceae-dicot that belongs to the Amaranthaceae family. In beetroots, the alternate layers of the xylem and phloem leads to the formation of successive cambia. The secondary tissues of these roots accumulate starch in various parenchymatous and sclerenchymatous cells of the xylem and the phloem. Both the hypocotyl and roots of beet form swollen structure which helps to store food, starch, and water. Beetroot has a top-shaped structure and is an example of napiform taproot modification. Beetroots are rich in folate (vitamin B-9) which helps in cell growth and functioning. Folate helps to control the damage of blood vessels, thus reducing the risk of heart attack and stroke. Beetroot is also a rich source of diverse minerals such as potassium, sodium, phosphorous, calcium, magnesium, copper, iron, zinc, and manganese.
5. Mirabilis jalapa (Four O’ Clock plant)
Mirabilis Jalapa is commonly known as a four O’ clock plant because the flowers of this plant open up in the late afternoon to produce a strong, sweet-smelling fragrance throughout the night and gets closed again in the morning. It is a perennial, herbaceous, bushy plant which belongs to the Nyctaginaceae family and is mainly found in temperate zones. Tap roots undergo modifications to form tuberous roots for storage purposes. Tuberous roots are the modified lateral roots for nourishment storage to store food and minerals. Tuberous roots produced in mirabilis jalapa are swollen, which stores nourishment and helps them to perennate through dry and cold periods.
6. Trichosanthes (Vern. Parwal)
Trichosanthes dioca, also known as pointed gourd, is a tropical perennial cucurbit plant which belongs to the Cucurbitaceae family. In regions of India and Bangladesh, it is also known as parwal or palwal. Trichosanthes plant has tuberous roots which are the modifications of tap roots for storage purposes. This plant is cultivated mainly as a vegetable, and also the leaves of this plant are used for its antipyretic, diuretic, cardiotonic, laxative, and antiulcer effects.
7. Echinocystis lobata
Wild cucumber is the common name for Echinocystis lobata which belongs to the Cucurbitaceae family. This plant also contains tuberous roots and is categorized under tap root modifications for storage purposes. The tuberous roots in echinocystis lobata are lobed and weigh as much as 22 kg. Wild cucumber has decorative and novelty uses in gardening and dried arrangements. In addition to this, it also holds some medicinal and herbal values. Indigenous peoples used teas made from the roots of this plant for curing various kidney or stomach ailments. The roots of this plant are also used to manufacture poultices (a pharmaceutical drug) for headaches.
Cassava, scientifically known as Manihot esculenta, belongs to the Euphorbiaceae family. It possesses tuberous roots which are modified forms of tap roots used for the storage of food and minerals. Cassava storage roots are vegetative storage organs with an indeterminate growth system that has a central cylinder (edible part) developed by the swelling of the primary root and crown roots. Cassava is mainly a root vegetable but is also used for various medicinal purposes which are not scientifically proven. The assumed therapeutic effects of cassava are health rejuvenation, helping with dehydration in people suffering from diarrhea, sepsis, and help to induce labor. Cassava root and leaves are edible and are eaten as food. Cassava plants are a good source of resistant starch, which supports gut health and blood sugar management. It is also rich in dietary fiber as well as vitamin C, thiamin, folic acid, manganese, and potassium.
9. Ruellia tuberosa
Ruellia tuberosa, commonly known as cracker plant/minnieroot, is a small biennial plant from the Acanthaceae family containing thick fusiform tuberous roots (storage roots). Fusiform tuberous roots are modified forms of tap roots developed for storage purposes. The storage roots of this plant get swollen and fleshy to store food and minerals and the fruits of this plant are 2-3 cm long spindle-shaped capsules. Ruellia tuberosa is traditionally used as a diuretic, antipyretic, analgesic, anti-hypertensive, anthelmintic, abortifacient, and as an emetic in various disorders like bladder disease, kidney disorder, bronchitis, gonorrhea, and syphilis.
10. Sweet Potato
Ipomoea Batatas (sweet potato) is a ConvoIvulaceae-dicot that belongs to the morning glory family, Convolvulaceae. They are an example of simple tuberous adventitious root modifications and do not possess any particular/definite shape. In this type of plant, food is stored in the xylem region to a large extent, but food in these species can also be stored outside the xylem area. A complicated type of anomalous secondary thickening is present in sweet potatoes and the root is either a pentarch or a hexarch in its primary state. The cortex is delimited/separated from the stelar region by a single-layered distinct endodermis. Normally developed but highly parenchymatous primary and secondary xylem develops anomalous cambia around individual vessels or vessel groups and produces phloem, rich in the parenchyma, with laticifers away from vessels and with tracheary elements towards them. Large amounts of storage parenchyma cells are developed forming modified tuberous adventitious roots; thus helping in the storage of water and food materials.
Turmeric (Curcuma longa) is a rhizomatous herbaceous perennial plant of the ginger family, Zingiberaceae which is native to tropical South Asia. It is a flowering plant and rhizomes of this species are used in cooking. Storage roots of turmeric are the modified adventitious roots commonly called nodulose roots, which are mainly found swollen at the apex or tips. These nodulose roots help turmeric to store food, water, and minerals which are necessary for the physiological functioning of the plant. Favorable conditions for their survival involve, temperatures between 20 and 30 °C (68 and 86 °F) and a considerable amount of annual rainfall. Benefits of turmeric include-
- Help in controlling diabetes
- Might prevent cancer
- It helps in lowering cholesterol levels
- Treat various skin conditions
- Beneficial for people suffering from depression
- Helps in controlling weight
- It may help to cure gastrointestinal conditions
12. Curcuma amada
Mango ginger is the common name for Curcuma amada which belongs to the Zingiberaceae family. Curcuma amada has nodulose roots storage roots which are modified adventitious roots for storing minerals, food, and water. These storage roots of Curcuma amada are generally found swollen from the tips due to the accumulation of food. Both turmeric and mango ginger belong to the same genus but the difference between them is that turmeric has rich yellow tissue, whereas mango ginger has a pale yellow core. Mango ginger is also known for its large-extent medicinal effects like antioxidant, antibacterial, antifungal, anti-inflammatory, platelet aggregation inhibitory effects, cytotoxicity, antiallergic, hypotriglyceridemic, brine-shrimp lethal effects, enterokinase inhibitory effects, CNS depressant, and analgesic activity.
Arrowroot, scientifically known as Maranta arundinacea, is a large perennial herb found mostly in rainforest habitats and belongs to the Marantaceae family. Arrorroots exhibit storage roots which are modified forms of adventitious roots, commonly known as nodulose roots. When the cluster of long cylindrical roots becomes swelled and enlarged from the tips forming nodules are called nodulose roots. These roots store food and water which are essential for the proper functioning of plant. Arrowroot is a root vegetable and an edible rhizome native to countries such as America and the West Indies. It is usually processed in powder form, commonly known as arrowroot flour. Arrowroot is popularly known for its culinary and medicinal uses, but a unique application of arrowroot is that it also holds great significance in the cosmetic industry.
Dahlia is the genus of bushy, herbaceous perennial plants native to Mexico and Central America. It contains fasciculated tuberous roots (modified form of adventitious roots) for food storage and for vegetative propagation. These fasciculated roots develop in clusters at the stem base and become thick and fleshy for food storage. Both the roots and flowers of dahlia are edible, but roots can be eaten either raw or cooked only after removing the peel/outer skin. Dahlia is used in various fields for distinct purposes such as in landscaping, in floristry as a cut flower, in the pharmaceutical industry, in the cosmetic industry, in the food industry, and as raw material for the extraction of dyes.
15. Rose moss
Portulaca grandiflora, the scientific name of rose moss, is a fast-growing annual plant reaching a height of up to 30 meters. It belongs to the Portulacaceae family and is commonly known for its moniliform storage roots. Moniliform roots, also known as beaded roots, are modified forms of adventitious roots which are swollen at frequent intervals like beads of a necklace. Rose moss usually prefers hot and dry environment conditions for suitable growth; therefore, they have very fleshy succulent leaves and stems. Rose moss has various medicinal uses which include-
- Helps in the treatment of hepatitis
- Used in the treatment of cirrhosis of liver with ascites
- Helps in relieving swelling and pain in the pharynx
Cephaelis ipecacuanha, the scientific name for ipecac, is a species of flowering plant which belongs to the Rubiaceae family. Ipecac contains annulated roots which are the modified form of adventitious roots. Roots modification takes place for various physiological and mechanical purposes. Annulated roots are formed in the ipecac plant as storage roots for reserving food and minerals. The roots of this plant are also used in the manufacturing of various therapeutic syrups and medicaments. The therapeutic effects of the ipecac plant are used to treat numerous disorders like bronchitis, diarrhea, and cancer. Ipecac can also be used as an expectorant to thin mucous and make coughing easier.
Grasses come under the Poaceae family which includes a large species of grasses like cereal grasses, bamboo, and the grasses of natural grassland. They have annulated storage roots for the storage of food and minerals. Annulated roots in grasses are modified fibrous adventitious roots which do not penetrate deep into the soil and; therefore, are surface feeders. These roots consist of clusters of thin roots which arises from the base of the stem.
18. Bitter gourds
Bitter gourd, scientifically known as Momordica charantia, is a tropical and sub-tropical vine belonging to the Cucurbitaceae family. It possesses annulated storage roots which are the modified form of adventitious roots. Annulated roots of bitter gourds give an appearance as if they are formed of numerous discs placed one above the other. Bitter gourd is a rich source of beta-carotene, vitamin A, and vitamin C. Vitamin A and beta-carotene are beneficial for our eyes’ health and help improve vision, whereas vitamin C helps to fight numerous diseases and helps in wound healing. Bitter gourd is packed with polyphenols which are known for their ability to lower inflammation in the body. Other health benefits of bitter gourd include-
- It supports healthy gut bacteria favoring digestion and nutrient absorption
- It is low in calories, fat, and carbohydrates
- Helps in weight management
- Helps in lowering blood sugar levels in diabetic patients
Asparagus, a monocot, is a genus of flowering plants which belong to the family Asparagaceae. Asparagus roots are an example of fasciculated adventitious roots because it has multiple roots and the starch is stored in these roots in form of multiple fasciculated bundles. Asparagus arises from the underground root system of fleshy storage roots attached to the rhizome, an underground stem. Consumption of asparagus has a number of potential health benefits including weight loss, improved digestion, healthy pregnancy outcomes, and lower blood pressure. Asparagus is also a rich source of various nutrients, including fiber, folate(vitamin B-9), and vitamins A, C, and K.