A vascular plant (a plant with a vascular cambium) is made up of many parts that perform different functions. This video will explore these different parts and their functions as well as some examples.    

• The root: is the fleshy or woody parts of a plant located underground. They secure a plant in the soil and absorb water and minerals from the soil. The are different types of roots: for example:
  • There are fibrous roots like those of imbabazane / umbabazane (Urtica dioica (Urticaceae), stinging nettle). 
  • There are solid roots like those of umlomo mnandi omncane (Glycyrrhiza glabra (Fabaceae), liquorice). 
  • There are fleshy roots like those of umsenge (Cussonia spicata (Araliaceae), cabbage tree). The fleshy roots are due to the stored moisture, hence these plants tend to be drought-resistant. 

• The rhizome: is a woody or fleshy elongated stem that usually grows horizontally below the ground. It is used to store food for the plant to survive unfavourable seasons. Examples of plants with rhizomes are: ikalamuzi (Acorus calamus (Acoraceae), sweet flag) and ibhuma (Typha capensis (Typhaceae), Cape bulrush). 

• The bulb: is the fleshy structure made up of numerous layers of bulb scales which are leaf based. It is an underground store (or storage structures) of nutrients to ensure a plant’s survival. Examples of popular bulbous plants are onion and garlic (Allium cepa & A. Sativum respectively (liliaceae)). Bulbous plants in traditional medicine are umaphipha (Albuca setosa (Hyacinthaceae)) and iguleni (Bowiea volubilis) Asparagaceae).

• The tuber: is a swollen, fleshy structure below the ground. It is an underground storage for nutrients. Examples include: izambane (Solanum tubersome (Solanaceae), potato) and ubhatata (Ipomoea batatas (Convolvulaceae), sweet potato). In traditional medicine, an example is: idangabane / idangabane elikhulu (Aneilema aequinoctiale (Commelinaceae), clinging aneilema).

• The corm: is a vertical fleshy underground stem (that is covered in scales) for storing nutrients to ensure the survival of the plant.. An example is amadumbe (Colocasia esculenta (Araceae), taro). In traditional medicine, examples include: ukhukazane / isidwa (Hesperantha baurii (Iridaceae), kaffr lily), ilabatheka / inkomfe (Hypoxis hemerocallidea (hypoxidaceae), the African potato) and undwendweni (Gladiolus dalenii (Iridaceae), dragon’s head sword lily).

So, what exactly is the difference between the root, rhizome, bulb, tuber, and corm.

The root absorbs water and minerals from the soil and if the root is a fleshy root it also stores the water and minerals to use during the drought season. The rhizome, bulb, tuber, and corm do the same thing but they look different. Some are woody, some are fleshy, some are fleshy with scales, some are fleshy and vertical, and some fleshy and horizontal.

That is why, most people just refer to the root, rhizome, bulb, tuber, and corm as simply the root because it can be difficult to distinguish which is which.      

• The bark: the bark is the outermost protective layer of a tree trunk and is formed by layers of dead phloem. Phloem transports the nutrients (which are the carbohydrates made in the leaves during photosynthesis) from the plant to the rest of the plant. There are usually high concentrations of the active ingredients in the bark, hence its popular use in traditional medicine. An examples of a plant with a bark that is used for medicine is: uwatela (Acacia mearnsii (Fabaceae), black wattle).

• The stem / wood: is the wood or the thick stem that provides support for the plant enabling it to stand upright. The stem also transports water, minerals, and nutrients up and down the plant. Only woody plants, such as shrubs and trees have a woody stem. Herbaceous plants have a non-woody stem. Examples of plants where the wood is used to make medicine include: umvuthwamini / udakane (Canthium inerme (Rubiaceae), Turkey berry) and umvumvu (Celtis africana (Cannabaceae), white stinkwood).

• The leaf: is the part of the plant where photosynthesis occurs.  The leaves are the food factories of plants and they are adapted to fit the plant’s environment. Plant’s can have broad leaves, narrow leaves, strap-like long leaves, reduce or needle-like leaves. Leaves are very similar to roots in that they tell you the kind of environment that the plant is created for. For example, plants with reduced or needle-like leaves do well in environments with little water while plants with broad leaves thrive in environments with a lot of water. [Of Course there are some caveats with this]. An example of a plant whose leaves are used in traditional medicine is: inhlungunyembe (Acokanthera oppositifolia (Apocynaceae), poison bush).

• Aerial parts: are all the parts of the plant found above the ground or soil. This includes the stems, leaves, petioles, flowers, fruit and seeds. Very often the plants, which have useful aerial parts, are harvested when flowering. Examples of plants where the aerial part is used in traditional medicine are: insangu (Cannabis sativa (Cannabaceae), dagga) and ushisizwe (Crassula obovata (Crassulaceae), jade plant) 

• The flower: is the reproductive part of the plant. The flower is usually striking and attractive in order to attract pollen from pollinators (such as birds, bees, and insects) and they produce a distinct smell to prevent from being eaten. After the pollen gets into the stigma of the plant, fertilisation begins. After fertilisation, the flower develops into a fruit containing seeds. An example of a plant whose flowers are used in traditional medicine is uqadolo (Bidens pilosa (Asteraceae), black jack) 

• The fruit: is the fleshy or woody ripened ovary of the flower. The fruit is a container for seed(s) and edible fruit help spread the seed(s). A plant whose fruit is used in traditional medicine is: isinama / inamathela (Desmodium incanum (Fabaceae), creeping beggarweed).

• The seed(s): are contained in the fruit and they house the embryo that will grow into a new plant.  Examples of plants whose seeds are used in traditional medicine are: uhlakuva (Ricinus communis (Euphorbiaceae), castor oil) and imbozisa (Foeniculum vulgare (Apiaceae), fennel).

• The gum: is a sap consisting of mixtures of polysaccharides. They are water soluble and are partially digested by humans. Gum sometimes flow from a damaged stem as a defense mechanism or sometimes as a protective system against the invasion of bacterial and fungal rots. A plant with gum that is used in traditional medicine is umkhayikhayi / umkhaya omhloshana (Acacia senegal (Fabaceae), bushy three-horn thorn). The gum of this plant is used to make a natural product called Gum Arabic, an important ingredient in making chocolates, marshmallows, gummy bears, and chewing gums.     

• The resin: is a sap that is excreted from specialised cells or ducts when the plant is cut or injured. The resin consists of a mixture of essential oils and polymerized terpenes, usually insoluble in water. A plant exuding resin that is used in traditional medicine is: isifice / isifico (Ozoroa paniculosa (Anarcadiaceae), common resin tree).

• The fatty oils: are the non-volatile, insoluble oils pressed either from the seeds or from the fruits of plants. Oils are often referred to as glycerides because they are derived from glycerol molecules. Umhlwathi (Olea europaea (Oleaceae), African olive) is used to make oil for therapeutic purposes and the oil is also used in carriers as liquid formulations and ointments.

References and further reading: 

• Prashant, T., Dheeraj, A. and Shubhangi, D., 2014. Impact of plants having potential action on CNS: An overview. Asian Journal of Pharmacy and Technology, 4(2), pp.100-105.