Corm (cocoyam), Carrots (Daucus carota), and potato (Solanum tuberosum).

A corm is a short, vertical underground stem which grows vertically and is swollen with food.

It has terminal buds that give rise to new aerial shoots, and axillary (lateral) buds give rise to a new corm

Corms have nodes, and internodes and scale leaves arise from the nodes

Adventitious roots develop from the base of the sides of the stem and contractile roots to push the corm into the soil.

Observable Features of Biological Significance in Corms

• Short vertical underground stem
• Swollen with food
• Buds for vegetative propagation
• Perennating organ
• Scale leaves for protection
• Adventitious roots for absorption and anchorage
• Nodes and internodes

Examples of corms:

• Cocoyam,
• Gladiolus,
• Colocasia

The Corm as a Vegetative Propagative Organ

• At the beginning of the favourable season,
• The terminal bud and some lateral buds develop into aerial shoots using stored food from the corm.
• The aerial shoot then manufactures food in the leaves, which the plant uses.
• Excess manufactured food is sent to the superficial areas of the corn
• These areas become swollen with food and develop into new corms (daughter corms)
• The old corm, which gives up its food to the aerial shoot, slowly shrivels up
• At the end of the favourable season, the aerial shoot dies off and the old leaf base remains as sheathing scale leaves on the surface of the stem.
• The corms remain dormant during the unfavourable season, using stored food to sustain their tissues.

Similarities between a corm and a rhizome

• Presence of scale leaves
• Possess leaf scars
• Presence of nodes
• Presence of internodes
• Terminal buds
• Axillary buds
• Adventitious roots
• Swollen with stored foods
• Underground stems

CARROT

Carrot is a Root tuber and a Vegetable crop

Observable features or characteristics.

• Lateral roots develop from the taproot
• Taproot swollen
• The terminal bud develops into a new plant
• Short stem supports leaves
• Leaves (if seen) for photosynthesis
• Pith
• Cortex stores food

Adaptive features in the carrot plant to its habitat

• The leaf base protects the bud
• Bud develops into a plant
• Green leaves for photosynthesis
• Root tuber stores food for the developing bud
• Lateral roots provide anchorage and absorption of water and mineral salts

Biological significance of the carrot tuber

• Stores food
• Vegetative propagation
• Root tuber/ swollen tap root
• Perennating organ

Economic importance of the carrot

• Source of food and nutrients
• Source of income
• Source of employment

Nutrients found in carrots

• Vitamin A
• Mineral salts
• Water
• Glucose/Carbohydrates

Importance of Vitamin A

• Night vision (Synthesis of rhodopsin)
• Healthy throat
• Healthy eyes
• Healthy skin
• Normal growth
• It controls normal epithelial structure and growth

Similarities between a carrot and any underground stem

• Food storage and Perennating organs
• Vegetative propagation
• Both are tubers if the underground stem is an Irish potato
• Both have terminal buds.

Differences between the Irish potato tuber and the carrot tuber

SWEET POTATO

Sweet potato is a root tuber and a runner.

It is a food storage, vegetative propagation, and perennating organs

The class of food found in sweet potatoes is carbohydrate, and the tissue that stores food is the cortex

Observable Features of Biological Interest in Sweet Potato Tuber

• Food storage organ
• Root tuber
• Vegetative propagation
• Swollen ends of roots form tubers
• Detached tubers from the parent plant produce adventitious buds, which produce new shoots for vegetative propagation
• Numerous small roots absorb water and mineral salts
• Thick roots provide anchorage.
• Stem above the ground for the colonisation of a wide area

Reproduction

• Vegetative by stem, which has axillary and terminal buds and nodes
• Vegetative by root tubers, which can produce adventitious buds in the soil

Advantages of runners

• Can colonise a wide area
• Damage to plant parts does not affect the entire plant
• Equal exposure of leaves to sunlight

Disadvantages of runners

• Easily attacked by herbivorous animals
• It may be covered from sunlight by other standing plants.
• Provide habitats for pests

Economic Importance:

• Source of food
• Cover crop reduces soil erosion
• Increases the moisture content of soil /cover crop

Differences between cassava tuber and Irish potato

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