Plant morphology

1. Plant Morphology By Jacob Thomas

2. Plants have three basic organs: roots, stems, and leaves Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3. ROOT Root is a non-green, underground, descending portion of the plant axis Develops from radicle

4. Characteristics of root Descending part Negatively phototrophic Non-green Root cap /root pockets Unicellular root hair No nodes Lateral roots Endogenously

5. Regions of typical root Root cap – mucigel to lubricate Zone of cell division Zone of elongation Zone of root hair or absorption Zone of maturation or differentiation

6. Functions of root Anchorage Absorption Conduction of water & minerals Transport of nutrients

7. Types of root system Tap root system Roots develops, usually from the radicle of an embryo of seed is called tap root & the system is called tap root system. 2. Fibrous Root System The roots which develop from any other part of the plant except the radicle is called adventitious root and this system is called adventitious or fibrous root system. eg . Monocot plants

8. Tap root system Fibrous root System

9. Modifications of root for storage Conical roots eg . Carrot ( Daucus carota )

10. Modifications of root for storage b) Fusiform roots eg . Radish ( Raphanus sativus )

11. Modifications of root for storage c) Napiform roots eg . Beet ( Beta vulgaris )

12. Modifications of root for mechanical support Epiphytic roots clinging roots Hanging roots - velamen tissue Absorbing roots eg . Orchids

13. Modifications of root for mechanical support Stilt roots eg . Maize, Jowar , Sugarcane

14. Modifications of root for Physiological functions Pneumatophores or Breathing roots eg . Avicennia , Rhizophora , Sonneratia

15. Modifications of root for Physiological functions Parasitic roots / Haustoria / Sucking roots eg . Total parasite – C uscuta Partial - Loranthus

16. Stem Stem is the ascending axis of a plant and develops from the plumule and epicotyle of the embryo Node Internode Shoot system

17. Characteristics of stem Terminal bud for growth Ascending axis Developing from plumule & epicotyle Phototrophic Nodes & internodes Branches & leaves exogenous Multicellular hair Bears flowers & fruits

18. BUDS Young underdeveloped shoot consisting of a shoot apex, compressed axis and a number of tender leaves arching over the growing apex

19. BUDS Vegetative buds Grow to only leafy shoot

20. BUDS Mixed Buds Produce both vegetative & floral branches Apical bud Borne at the apex of main branch Axillary Bud Occur in theaxis of leaf

21. Modifications of stem The structural and functional change in the normal form and structure of the stem due to change in normal function of the stem is called modification of the stem

22. 1. Underground stem Modifications Herbaceous plants to overcome unfavorable season Examples Rhizome Perennial stem of the plant grows below soil surface. Fleshy due to storage of food Nodes, internodes, scaly leaves, axillary buds, & adventitious roots Straggling rhizome Root stock

23. Bulb Stem underground, disc like, small & modified and reduced Convex / conical , compressed internodes Nodes bear fleshy scales Leaves in concentric Axillary buds Adventitious roots

24. Bulb Tunicated bulb (scaly leaves covering fleshy leaves in concentric) Scaly or naked bulb No covering / overlap one another Tulip

25. Tuber The tuber stores starch as reserve food material

26. Corm Fleshy underground round stem Buds at nodes Adventitious roots Food storage

27. 2. Sub-aerial modifications Delicate stem unable to stand erect A. Runner Oxalis Oxalis Doob grass

28. 2. Sub-aerial modifications B. Stolon Fern Nepenthes

29. 3. Aerial modification A. Tendril weak stem Requires support Axillary buds  spring like tendrils Sensitive to touch Coil around Support to climb up Expose leaves to sunlight Passiflora Grapes Apical bud  tendril Cucumber Extra axillary bud

30. 3. Aerial modification B. Thorn Xerophytic plants Vascular connections with stem Axillary branches  hard sharp pointed thorns Protects from animals Reduces transpiration & desiccation Citrus Duranta Bougainvillea

31. 3. Aerial modification C . Phylloclade Xerophytic plants Leaves stem  flat green phylloclade Check the rate of transpiration Opuntia

32. 3. Aerial modification D. Cladode Xerophytic plants Modification of stem & branches of limited growth Phylloclade with one or two internodes  Cladode Asparagus Asparagus  needle like, slightly flattened, green, appear in clusters in the axil of a scaly leaf Ruscus  looks like leaf. Develops from axil of a scaly leaf. Bearing floral bud

33. 3. Aerial modification E . Bulbil Axillary Bud / vegetative bud  large & fleshy due to storage of food Helps in vegetative Reproduction Dioscorea Agave Allium

34. Functions Primary Bears & Holds Conduction Lateral growth Flowers Fruits & seeds Secondary Perennation Vegetative propagation Helps in photosynthesis Check transpiration Climbing

35. Leaf Structure A leaf is held away from its stem by a stem-like appendage called a petiole. The base of the petiole is attached to the stem at a node. The blade is the expanded thin structure on either side of the midrib and is usually the largest, most conspicuous part of a leaf

36. Leaf Parts The cuticle is part of the epidermis It produces a waxy layer called cutin , which protects the leaf from dehydration and disease. On the top and bottom is a layer of thick, tough cells called the epidermis . Its primary function is to protect the other layers of leaf tissue.

37. Leaf Parts Continued Special epidermal cells called guard cells open and close in response to environmental stimuli, such as changes in weather and light. They regulate the passage of water, oxygen, and carbon dioxide into and out of the leaf through tiny openings called stomata . Located between the upper and lower epidermis is the mesophyll . Located within the mesophyll cells are chloroplasts , where photosynthesis takes place.

38. BUDS A bud is an undeveloped shoot from which embryonic leaves or flower parts arise A leaf bud is composed of a short stem with embryonic leaves A flower bud is composed of a short stem with embryonic flower parts. Buds are named for the location they inhabit on the stem surface. Enlarged buds or parts of buds form the edible portion of some horticultural crops