Vegetative Parts of Plants
Spring
2014
Descriptive Terminology
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LEARN DESCRIPTIVE TERMINOLOGY =
PHYTOGRAPHY
- Vegetative
- Floral/inflorescence
- Fruit
ASSOCIATE STRUCTURES WITH TERMS
- Significant range of variation
- Learn to identify major structures and
modifications
R. W. Pohl Conservatory
5th floor – Bessey Hall
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AVAILABLE TO BIOLOGY 366 STUDENTS
- Free to look at plants to get a better idea of morphological
structures and taxonomic diversity.
OPEN HOURS ARE 9:00 a.m. to 5:00 p.m. Monday - Friday
- Some Friday afternoons conservatory is closed for
pesticide applications. Some research areas are not
available for general viewing.
- Access by the elevator. Pay attention to warning signs!
PLANTS AND PLANT PARTS ARE NOT TO BE REMOVED
- Pesticides have been applied to all plant material.
- Do not eat any plant products.
- Do not disturb any research areas.
Sequoia—tallest
Sequoiadendron—
most massive
Among the smallest plants in the world:
Duckweeds (Lemna, Araceae)
Root and 1-2 leaves; floating aquatic
Vegetative Parts of Plants
NON-REPRODUCTIVE ORGANS:
ROOTS - STEMS - LEAVES
Fig. 9.1 from Simpson
Roots
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FUNCTIONS
- Anchoring, support, storage
- Absorption of water and mineral nutrients;
mycorrhizae
STRUCTURE
- xylem and phloem usually in a central vascular
strand
- no cuticle (except on aerial roots), root hairs.
- branching pattern variable
- no nodes/internodes present in roots!
DESCRIPTIVE TERMS:
- Taproot (carrot) vs. fibrous roots (grass)
- Fibrous, adventitious, aerial, fleshy, prop
- Adventitious roots (from stems)
Fibrous roots
Tap root
Adventitious roots – roots
produced by structures other
than another root (e.g., stems)
Root modifications
storage
buttress
Fig. 9.2 from Simpson
pneumatophores
Root Modifications:
Ficus (Moraceae) “Strangler Fig”
Adaptation for anchoring
and nutrient gathering –
begins as an
epiphyte, and
sends down
adventitious
roots.
Prop roots (adventitious)
Pandanus (Pandanaceae)
Haustorial roots
Found in parasitic
plants.
Host stem
Dodder (Cuscuta,
Convolvulaceae)
Buttress roots
Modifications of Roots:
Mangroves – Anchoring, support, and
aeration (coastline habitats)
Mangrove:
Pre-dehiscence
germination
Root is already
emerged from
seed before it
is separated
from the tree.
Root Modifications: Aerenchyma in aquatics
Roots and other organisms
Mycorrhizal associations were critical
to the invasion of land by plants and
are nearly universal in plants.
endomycorrhizae
ectomycorrhizae
Some angiosperm families
(primarily the legumes,
Fabaceae) have root nodules
housing nitrogren-fixing
bacteria
Stems
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FUNCTIONS
- support and exposure of leaves to light, flowers to
pollination agents, fruits to dispersal agents
- vascular conduction of water/minerals and photosynthates
- sometimes the primary photosynthetic organ
STRUCTURE
- nodes and internodes; rearrangement of vascular tissues
- ring of bundles or scattered bundles in primary stems
- secondary growth produces secondary xylem (wood)
- epidermis in primary stems; bark in woody plants
- buds: terminal, axillary/lateral, bud scale scars
DESCRIPTIVE TERMS:
- Branching patterns; bulbs, herbaceous, woody
- Horizontal stems: above ground = stolons; below = rhizomes
- Vines, shrubs, trees, succulent, tendril, cladode, etc.
Fig. 9.1 from Simpson
Stems: Nodes and Internodes
Fig. 9.3 from Simpson
Herbaceous stems:
Stems: Some can be hollow;
loss of pith during maturation
Modifications in
the Petiolar Region
Swollen nodes:
Characteristic of the Pink
Family (Caryophyllaceae)
Vines and climbers:
Photosynthetic Stems
cladodes
succulent stems
Tussock:
In plants with a
graminoid (grasslike) habit, stems
may not be evident.
This example is a
‘tussock’ habit,
forming clumps.
Basal rosette:
No apparent stems!
Subterranean horizontal stems: Rhizomes
Rhizomes vs. roots
Tubers (underground storage stems):
wsu.edu
energyfarms.com
Bulbs: stems (internodes) are
shortened and leaves are fleshy
and protective.
Woody Stems – Arborescent or
shrubby habit
Stem Modifications:
Bark (phellem or cork +
2° phloem)
Most woody plants
produce bark, a growth of
the cork cambial layer, for
mechanical protection and
to reduce water loss.
Bark variation
lenticels
Leaves
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FUNCTIONS
- light capture, production of photosynthates, transpiration,
protection of growing point
STRUCTURE
- petiole, stipules, pulvinus, blade (lamina), veins (midrib)
- vestiture (minimally a cuticle), hairs, scales, etc.
- simple vs. compound (blade divided into discrete parts)
- many modifications, including extreme reduction
- virtually always with a bud or branch in the axil
DESCRIPTIVE TERMS:
- Many, based on leaf shape, size, color, venation, margin,
apex, base, arrangement, number, presentation
Basic leaf structure
Stipules
Modifications in
the Petiolar Region
Ocrea: stipular tube
(characteristic of most of the
Buckwheat Family,
Polygonaceae)
axillary bud
pulvinus
(lower)
Modifications in
the Petiolar Region
Sheathing leaf bases
Venation: Parallel vs. “Netted”
Unusual venation: Melastomataceae
Leaf blade:
Simple
Compound
Pinnate
Palmate
Compound
leaves
Fig. 9.9,
Simpson
Palmate Leaf – leaflets arise from one point
Once-pinnately compound
Twice-pinnately compound
Leaf Arrangement
Variation in leaf shape morphology:
Sassafras albidum (Lauraceae)
Leaf modifications: bracts
Leaf modifications
Leaf tendrils
Bud scales
Modifications for capturing insects
Droseraceae
Sarraceniaceae
Leaf Modifications:
Kalanchoe (Crassulaceae)
Adaptation for vegetative
propagation – sheds preformed plantlets from leaf
margins.
Bulbs: stems (internodes) are
shortened and leaves are fleshy
and protective.
Indument(um) (Vestiture): Surface Structures
Hairs, trichomes, scales
Hair types
Fig. 9.59 in Simpson
Armature: Thorns, spines, prickles
And the ultimate leaf modifications:
Summary
• Vegetative structures important in
describing plants.
• Variations on similar basic morphology can
be diagnostic for certain plant groups.
• An understanding of descriptive terms is
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essential for plant identification and to
understand morphological evolution.
Make lists of terms and their associated
structures; drawings or diagrams, however
crude, may also help, as will photos.
Be sure to observe, compare and contrast
related structures to avoid interpretation
errors.