Vegetative Parts of Plants Spring 2013 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 5th 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 - 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 • • • 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 • • • 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) 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 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): 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 • • 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.