Vegetative Parts of Plants

Spring 2014

Descriptive Terminology• 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 Conservatory5th floor – Bessey Hall

• 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• 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 otherthan another root (e.g., stems)

storage buttress pneumatophores

Fig. 9.2 from Simpson

Root modifications

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 parasiticplants.

Host stem

Dodder (Cuscuta,Convolvulaceae)

Buttress roots

Modifications of Roots: Mangroves – Anchoring, support, and aeration (coastline habitats)

Mangrove:

Pre-dehiscence germination

Root is alreadyemerged fromseed before itis separatedfrom the tree.

Root Modifications: Aerenchyma in aquatics

Mycorrhizal associations were criticalto the invasion of land by plants andare nearly universal in plants.

endomycorrhizae ectomycorrhizae

Roots and other organisms

Some angiosperm families(primarily the legumes, Fabaceae) have root nodules housing nitrogren-fixing bacteria

Stems• 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 PinkFamily (Caryophyllaceae)

Vines and climbers:

Photosynthetic Stems

cladodes

succulent stems

Tussock:

In plants with agraminoid (grass-like) 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):

energyfarms.com

wsu.edu

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.

lenticels

Bark variation

Leaves• 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)

pulvinus(lower)axillary bud

Modifications in the Petiolar Region

Sheathing leaf bases

Venation: Parallel vs. “Netted”

Unusual venation: Melastomataceae

Leaf blade:

Pinnate

Simple Compound

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

Sarraceniaceae

Droseraceae

Leaf Modifications:

Kalanchoe (Crassulaceae)

Adaptation for vegetativepropagation – sheds pre-formed plantlets from leaf margins.

Bulbs: stems (internodes) are shortened and leaves are fleshy and protective.

Indument(um) (Vestiture): Surface Structures Hairs, trichomes, scales

Hair typesFig. 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

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.