Plant morphology
Transcript of Plant morphology
Plants have three basic organs: roots, stems, and leaves
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
ROOT
• Root is a non-green, underground, descending portion of the plant axis
• Develops from radicle
Characteristics of root
i. Descending part
ii. Negatively phototrophic
iii.Non-green
iv.Root cap /root pockets
v. Unicellular root hair
vi.No nodes
vii.Lateral roots Endogenously
Regions of typical roota) Root cap – mucigel to
lubricate
b) Zone of cell division
c) Zone of elongation
d) Zone of root hair or
absorption
e) Zone of maturation or
differentiation
Functions of root
a) Anchorage
b)Absorption
c) Conduction of water
& minerals
d)Transport of nutrients
Types of root system1. 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 SystemThe 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
Modifications of root for mechanical support
1. Epiphytic rootsclinging roots
Hanging roots -
velamen tissue
Absorbing roots
eg. Orchids
Modifications of root for Physiological functions
1. Pneumatophores
or
Breathing roots
eg. Avicennia,
Rhizophora,
Sonneratia
Modifications of root for Physiological functions
1. Parasitic roots /
Haustoria / Sucking
roots
eg. Total parasite – Cuscuta
Partial - Loranthus
StemStem is the
ascending axis
of a plant and
develops from
the plumule and
epicotyle of the
embryo
Node
InternodeShoot
system
Characteristics of stem
Terminal bud for growthAscending axisDeveloping from plumule &
epicotylePhototrophicNodes & internodesBranches & leaves
exogenousMulticellular hairBears flowers & fruits
BUDS
Young underdeveloped shoot consisting of a shoot apex, compressed axis and a number of tender leaves arching over the growing apex
BUDS
Mixed Buds
Produce both vegetative &
floral branches
Apical bud
Borne at the apex of main
branch
Axillary Bud
Occur in theaxis of
leaf
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
1. Underground stem Modifications
Herbaceous plants to overcome
unfavorable season
Examples
RhizomePerennial stem of the plant grows below soil
surface.Fleshy due to storage of foodNodes, internodes, scaly leaves, axillary buds,
& adventitious roots
Straggling rhizome
Root stock
Bulb Stem underground,
disc like, small & modified and reduced
Convex / conical , compressed internodes
Nodes bear fleshy scales
Leaves in concentric Axillary buds Adventitious roots
Bulb
Tunicated bulb
(scaly leaves covering fleshy leaves in
concentric)
Scaly or naked bulb
No covering / overlap one another
Tulip
3. Aerial modificationA. Tendril
weak stem Requires support Axillary buds
spring like tendrils
Sensitive to touch Coil around Support to climb
up Expose leaves to
sunlightPassiflora
GrapesApical bud tendrilCucumberExtra axillary bud
3. Aerial modificationB. Thorn
Xerophytic plants Vascular
connections with stem
Axillary branches hard sharp pointed thorns
Protects from animals
Reduces transpiration & desiccation
Citrus DurantaBougainvillea
3. Aerial modificationC. Phylloclade
Xerophytic plants Leaves stem flat green
phylloclade Check the rate of
transpiration
Opuntia
3. Aerial modificationD. 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
3. Aerial modificationE. Bulbil Axillary Bud / vegetative bud large & fleshy due to
storage of food
Helps in vegetative ReproductionDioscorea
AgaveAllium
Functions
Primary
Bears & Holds
Conduction
Lateral growth
Flowers
Fruits & seeds
Secondary
Perennation
Vegetative propagation
Helps in photosynthesis
Check transpiration
Climbing
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
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.
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.
BUDS o A bud is an undeveloped shoot
from which embryonic leaves or flower parts arise
o A leaf bud is composed of a short stem with embryonic leaves
o A flower bud is composed of a short stem with embryonic flower parts.
o Buds are named for the location they inhabit on the stem surface.
o Enlarged buds or parts of buds form the edible portion of some horticultural crops