Vegetative Parts of Plants Spring 2012

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 Conservatory 5 th 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 and support - 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; adventitious roots - no nodes/internodes present in roots! DESCRIPTIVE TERMS: - Taproot (carrot) vs. fibrous roots (grass) - Fibrous, adventitious, aerial, fleshy, prop

fibrous storagebuttresspneumatophores Fig. 9.2 from Simpson

Fibrous roots Tap root

Adventitious roots – roots produced by structures other than another root (e.g., stems)

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

Mycorrhizal associations were critical to the invasion of land by plants and are nearly universal in plants. endomycorrhizaeectomycorrhizae

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 Pink Family (Caryophyllaceae)

Vines and climbers:

Photosynthetic Stems cladodes succulent stems

Tussock: In plants with a graminoid (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) Most woody plants produce bark, a growth of the cork cambial layer, for mechanical protection and to reduce water loss.

Leaves FUNCTIONS - light capture, production of photosynthates, transpiration STRUCTURE - petiole, stipules, pulvinus, blade (lamina), veins - 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)

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

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 vegetative propagation – sheds pre- formed plantlets from leaf margins.

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

Indumentum: Surface Structures Hairs, trichomes, scales

Hair types Fig in Simpson

Armature: Thorns, spines, prickles

And the ultimate leaf modifications:

Summary Vegetative structures important in describing plants. Vegetative structures important in describing plants. Variations on similar basic morphology can be diagnostic for certain plant groups. 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. 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. 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. Be sure to observe, compare and contrast related structures to avoid interpretation errors.