Download Plant Structure - Biology for Science - Lecture Notes and more Study notes Biology in PDF only on Docsity! Chapt. 35 – Plant Structure, Growth & Development Flowering plants: 2 main groups: Monocots and Eudicots [See Fig. 30.12] Monocot (e.g., corn) seedlings each have 1 cotyledon (seed leaf); in monocots the cotyledon often remains within the confines of the seed Eudicot (e.g., bean & peanut) seedlings each have 2 cotyledons (seed leaves) ORGAN SYSTEMS OF FLOWERING PLANTS [See Fig. 35.2] Root System Primary root – first to appear Eudicot – Taproot system Monocot – Fibrous root system Root hairs are extensions of epidermal cells Root hairs dramatically increase a root’s surface area for absorbing water and nutrients Food storage is a function of all roots, but some (e.g., carrot taproots) are highly modified for storage Aboveground (aerial or prop) roots give extra support “Breathing” roots conduct oxygen to waterlogged roots The roots of many orchids are photosynthetic Shoot System Some plants (e.g., baobab tree, saguaro cactus) have specialized water-storage stems Stolons (“runners”) are horizontal, wandering, aboveground stems (e.g., strawberries) Rhizomes (e.g., edible base of a ginger plant) are horizontal, belowground stems Tubers (e.g., potatoes, yams) are the swollen ends of rhizomes, specialized for food storage Bulbs (e.g., onions) are vertical, underground stems consisting mostly of the swollen bases of leaves specialized to store food Thorns are rigid, sharp branches that deter potential herbivores (especially mammalian browsers) Terminal buds generally exercise apical dominance over axillary buds Simple vs. compound leaves [See Fig. 35.6] Some arid-adapted plants have succulent leaves Leaves specialized into spines help defend against herbivores Docsity.com Tendrils are specialized leaves or stems that twist around structures to lend support Leaves specialized to trap animals occur in carnivorous plants Leaf hairs (trichomes) help reduce water loss and provide some protection against herbivores Undifferentiated meristematic cells occur in buds Whole plant growth is indeterminate, but growth of some organs is determinate When a cell divides, the daughter cells grow… and they may differentiate (specialize), depending especially on where they are located during development Differentiated cells contribute to 3 tissue systems [See Fig. 35.8] Dermal tissue (epidermis) Generally a single cell layer that covers the plant Absorption in root system Water retention in shoot system, aided by waxy cuticle Vascular tissue [See Fig. 35.9] Xylem – transports water and dissolved minerals Cells are dead at functional maturity Phloem – transports sugars dissolved in water Cells are alive at functional maturity Ground tissue All non-epidermal, non-vascular tissue Three principal cell types: Parenchyma Thin-walled, live cells Perform most metabolic functions of plant photosynthesis, food storage, synthesis and secretion Collenchyma Cells with unevenly thickened walls that lack lignin Alive at maturity Grouped into strands or cylinders to aid support without constricting growth Sclerenchyma Very thick walls, hardened with lignin Dead at maturity Give strength and support to fully grown parts of the plant Docsity.com
