1. Plant Morphology (Root)
Weerachon Sawangproh, M.Sc. (Environmental Science)

2. Learning Objectives
Students are able to describe external structure of root
Students are able to describe several roots that are modified to perform unusual functions

3. Outline of Study
Kinds of root systems
Root functions
Modified roots

4. Root structure Taproot system or primary root system
2. Fibrous root system
3. Adventitious Roots

5. 1. Taproot system Emerge from the radicle (of seed)
In most dicots: the radicle enlarge to form a taproot that persists throughout the life of the plant with many smaller branch (lateral) roots

6. The type of root system consisting of a large taproot and smaller branch roots is called a taproot system

7. Shapes of taproots
Conical
Napiform/ Turbinate
Fusiform

8. Conical shape: broad at the base and tapering gradually towards the apex e.g. carrot and dandelion

9. Napiform/ Turbinate shape: very broad at the base and tapers suddenly like a tail at the apex e.g. turnip
turnip
radish
มันแกว

10. Fusiform shape: swollen in the middle and tapers towards the base and the apex e.g. radish

11. 2. Fibrous root system Most monocots:
a fibrous root system consisting of an extensive mass of similarly sized roots
the radicle is short-lived

12. Fibrous root system
Tuberous roots: look like tubers, but are swollen, nutrient-storing fibrous root
Fascicled root/ root tuber: swollen fibrous root that can have buds to produce new shoots, so this is a form of cloning

13. รากมันเทศ มันมือเสือ รากปทุมมา
Tuberous root
รากมันเทศ
มันมือเสือ
รากปทุมมา

14. Fascicled root
รากกระชาย
รากรักเร่
รากต้อยติ่ง

15. 3. Adventitious roots Roots that form on organs other than roots
Adventitious roots of most monocots begin growing soon after the seed germinates

16. Primary functions of root
Anchorage – locating water and minerals
Storage – storing large amounts of energy reserves e.g. carrot and sugar beet
Absorption – absorbing large amounts of water and dissolved minerals
Conduction – transporting water and dissolved nutrients to and from the shoot

17. Modified Roots Storage root Reproductive root Nodal roots
Aerial roots/ Pneumatophores
Prop or stilt roots
Buttress or tabular roots
Contractile roots
Haustorial/ parasitic root
Climbing roots
Photosynthetic root

18. Storage root
Storing starch e.g. beets, turnips, radish, dandelion, carrot, and cassava
Storing sugar e.g. sweet potato
Storing water e.g. dessert plants

19. Reproductive root produce adventitious buds called suckers for reproduction

20. Nodal roots (a type of mutualism in the roots of legumes) - cortical cells of the root infected with Rhizobium causing swellings called nodules

21. Aerial roots/ Aeration root - roots that are formed in and exposed to air e.g. by epiphytes and coastal swamp trees such as mangroves
Aerial roots have special air channels (lenticels) for gas exchange in the atmosphere

22. Aerial root of Banyan tree
Aerial root of bonsai

23. The root of mangrove trees called pneumatophores that import oxygen from the atmosphere
Pneumatophores contain as much as 80 % aerenchyma

24. Prop or stilt roots - adventitious roots that develop on a trunk that grow into a substrate to provide mechanical support

25. Buttress or tabular roots: vertically flattened roots that project out of the ground and lower trunk at the base of large trees to resist uprooting of large tropical trees

26. Contractile roots – root that pull a plant into the deeper soil, commonly found on corm and bulb-forming plants e.g. lily and Gladiolus, as well as on other plants e.g. ginseng and dandelion

27. Haustorial/ Parasitic root - roots that parasitize (intrude) other plants (the tissues of the host)

28. Mycorrhizal roots - the association between a root epidermis/ cortex and a fungus are called mycorrhizae (a type of mutualism) e.g. orchid and maple

29. Climbing root - roots that develop from the stems of certain climbing plants e.g. ivy to serve the attachment to its support

30. Velamen is a site of water storage
Photosynthetic root - roots that are flat and green serving as the photosynthetic site

31. Summary
Most roots have a variety of functions, including anchorage, absorption, and hormone production
Other roots may be specialized for other functions

32. References
Moore, R., Clark, W. D., Stern, K. R Botany. Wm. C. Brown Publishers, U.S.A. 824 pp.
Plant Structures: Stems (online document: PDF file). Colorado State University Extension. 6 pp. available at (online: 10 July 2010)