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Botany for Master Gardeners Dr. Anne Alerding, Associate Professor of Biology Director, VMI Herbarium Virginia Military Institute [email protected] Botanical Life forms Fungi Lichen (symbiosis: fungus + algae/ cyanobacterium) Moss (nonvascular plant) Fern (seedless vascular plant) Algae (photosynthetic protist) Flowering plants (seeds in fruits) Conifers (naked seeds) Gymnosperms produce “naked” seeds Scale (modified leaf) Seed not covered by a fruit Ovule (future seed) Longitudinal section through a female pine cone, showing the ovules (which develop into seeds) borne on scales. Angiosperms produce seeds enclosed in a “vessel” or fruit Fruit (swollen ovary wall) seed Angiosperms are also called the “flowering plants” • Phylum: Anthophyta “anthus” = flower “phyta” = plant As a Master Gardener, you will learn to identify MANY plants! Every plant has a name…. but learning names can be confusing since there are “common names” and “Latin” names All living organisms are classified using the binomial (2-name) system Have membrane-bound organelles Domain Kingdom Phylum Class Order Family Genus Species Eukarya Multicullular, photosynthetic autotrophs Plantae Flowering plant Anthophyta One cotyledon (seed leaf) Monocotyledonae Small flower parts; dry, oneCommelinales seed fruits; elongated leaves Poaeceae Grasses (hollow stems, achene fruits) Zea Tall, annual grass; male and female flowers mays corn Species are sometimes further subdivided Variety Cultivar Metha piperata var. variegata Glycine max “Hutcheson” Scientific names often have relevant meanings… • Pinus virginiana – Virginia pine • Quercus rubra – red oak (rubra = red in Latin) • Trifolium repens (white clover) – Trifolium = three leaflets – repens = creeping stems (stolons) • Poa pratensis (kentucky bluegrass) – pratensis = grows in meadows Parts of a “typical” flowering plant Developing fruit Nodes (areas of leaf and axillary bud attachment) Flower Shoot system Axillary bud Internode (area between adjacent nodes) Petiole Blade Stem Leaf Rosette of basal leaves Root system Taproot Branch roots Vegetative “vegetables” Reproductive “seeds or fruits” Vegetable (vegetative) vs. Fruit (reproductive) Vegetable any non-reproductive part of a plant i.e. the “vegetative” non-flowering portion Fruit – the swollen ovary or accessory tissue (from a flower) Seed – develops after egg in ovule is fertilized, embryo Plants can be classified (broadly) in different ways • Stem structures – Herbaceous versus woody • Life cycle – Annual, biennial, perennial Herbaceous versus Woody Tomato is an annual (1 year for its life cycle to complete) Carrot is a Biennial (2 years to complete its life cycle) Year 1 Growth: taproot and shoot Year 2 Growth: reproduction (flowers and seeds), which drain reserves from taproot Perennials (multiple years, generally do not reproduce until reach a certain size, then every year or so after) Parts of a Plant: Cells, tissues, and Organs • Cells, Tissues • Organs – Stems – Roots – Leaves – Reproductive (flowers, fruits) Parts of a Plant Cell, highlighting parts that are unique and important to plants Cell wall Vacuole (stores water; pushes water against the cell wall to keep plants upright) Vacuole Mitochondrion (respiration) O2 Chloroplast (photosynthesis) CO2 O2 CO2 Fig. 3-3, p. 49 Cells are distributed into 3 tissue systems Leaf Dermal (enclosing) Vascular (conducting) Ground (filler; multifunctional) Dermal Vascular Ground Stem Dermal Vascular Ground Root What are the functions of roots, stems, and leaves? Dermal (enclosing) Vascular (conducting) Ground (filler; many functions) Leaves: Leaf produce sugars, cool the plant, can be animal attractants Dermal Vascular Ground Stems: support leaves and fruits, conduct Stem sugars, water and nutrients (translocate), storage Dermal Vascular Roots: Ground anchor, absorb water and nutrients, Root conduct water Stems STEMS can be herbaceous or woody Herbaceous Woody growth growth growth Internal tissue structures of herbaceous vs. woody stems pith no pith In young woody stems, you can still see the internal pith cells, which are diagnostic features used to Identify Species All growth is initiated at meristems (zones of cell division) contained in “buds” leaf leaves Apical meristem of an active bud Coleus Dormant bud Area of cell maturation Root hairs Area of cell elongation Area of cell division Root Apical meristem Root cap Fig. 5-11, p. 105 Bud scale Terminal bud One year’s growth Terminal bud scale scar Axillary bud Leaf scar Bundle scars Lenticels Node Internode Node In winter, woody stem bark and bud structures are also diagnostic features Black ash Black oak Virginia Tech online tree identification keys http://dendro.cnre.vt.ed u/dendrology/idit.htm “other” stems… Rhizome (underground stem) potato with swollen rhizome extensions called tubers Iris also has rhizomes (e.g. Iris, ginger) Leaf scars Corm – underground swollen stem covered with modified papery leaves called scales (gladiolus) Bulb –underground modified bud (e.g. onion, lilies, tulips) Wild onion bulbs… Bulb Fleshy leaves Stem Adventitious roots Fig. 7-14c, p. 147 Stolons/runners – aboveground horizontal stems e.g. strawberry “runners” Roots Root Systems Taproot (deep) Fibrous roots (shallow) Like stems, roots can be woody or herbaceous new root growth = herbaceous; can absorb water and nutrients http://www.agry.purdue.edu/turf/weeds/violet/violet%20root.htm Woody roots cannot uptake (cells coated with a wax) http://www.tlcfortrees.info/root_system.htm Most absorption occurs in ROOT HAIRS, which extend from epidermal cells of fine roots Root hair Soil air Soil water Soil particles radish seedling Epidermis Fig. 6-3b, p. 114 Movement upward Water and mineral nutrient absorption Epidermis Water and dissolved nutrient minerals Root hair Fig. 6-6, p. 119 Lateral root roots emerge from the internal tissues of older roots Ruptured epidermis Lateral root Prop Roots – aboveground support Corn (Zea mays) Young mangrove tree (Rhizophora mangle) Pneumatophores – obtaining oxygen! Young mangrove tree (Rhizophora mangle) Two most important root crops globally are fibrous, tuberous roots (Sweet Potato and Cassava) Sweet Potato (Ipomoea batatas) 20% starch Cassava (Manihot esculenta) 5% protein 30% starch Vitamins A&D, iron, calcium 1.5% protein Vitamin C, Manganese Leaves Broad Leaf Blade (Lamina) Veins Narrow Leaf Petiole Axillary bud Stipules Stem Fig. 8-1, p. 152 Broad Leaf Blade Shapes Mid-rib Leaf tip (apex) and base shapes Narrow Leaf Blade Shapes Blade Sheath Leaf arrangement on the stem Alternate Opposite Whorled Fig. 8-2, p. 154 Leaf forms – simple vs. compound with leaflets Simple Pinnately compound Palmately compound Leaf venation patterns Parallel Pinnately netted netted = reticulate Palmately netted Leaf margins Toothed/ serrated smooth, no bumps deep sinuses Some leaves have “leaf hairs/trichomes” to reflect light (Lamb's Ear Stachys byzantina) Soybean trichomes Internal leaf structures Cuticle (waxy cutin); secreted by epidermis Upper Epidermis Lower epidermis Stoma Stoma (air pore) Guard cells Fig. 8-3, p. 155 Close up view of a STOMA (air pore) which is open because the two guard cells are swollen, full of water Guard cells Stoma Epidermal cells Open and Closed stomata open closed Scanning Electron Micrograph X800. partially open Reproductive: flowers and fruits Female floral parts Male floral parts Male floral parts Female floral parts Pollen grain (each will produce two sperm cells) Stigma Style Carpel(s) Gynoecium (or pistil) = all carpels Anther Ovary Filament Ovules (each makes one egg cell) Petal Receptacle Sepal Peduncle Calyx = all sepals Corolla = all petals Perianth = calyx + corolla Stamen Androecium = all stamens Sometimes sepals look like petals! 3 Sepals in outer whorl 3 petals in next whorl Flowers are classified based on which of the four “parts” they possess Complete flower – has all four parts Incomplete flower – missing 1 or more parts Perfect flower – has at least the male and female parts Imperfect flower – has only one functional set of sexual parts (male or female) -male “staminate” flower (stamens, no pistils/carpels) -female “pistillate” flower (pistils, no stamens) Plants with Imperfect Flowers • Are classified as… – Monoecious (produces pistillate and staminate flowers on the SAME plant) OR – Dioecious (produces pistillate and staminate flowers on DIFFERENT plants) Corn is MONOECIOUS: Males Females MALE flowers and FEMALE flowers on the SAME plant MONOECIOUS “One House” Staminate and Pistillate Corn flowers (usually mature at different times so one plant’s stigma is pollinated with another plant’s pollen) Staminate flower w/ 3 stamens Female silks are styles Male Tassel Each “kernel” you eat is a fertilized and ripened ovary http://www.backyardnature.net/fl_corn.htm Squash is also monoecious Ovary becomes the “squash” http://blogs.icta.net/plover/files/2009/08/zucchini-blossom-male-femalecsu-23jul04-lah033s.jpg Maples are DIOECIOUS (they produce female flowers and male flowers on separate plants) Acer rubrum (red maple) flowers Gynoecium of female “pistillate” flowers Androecium of male “staminate” flowers Reproduction in Flowering Plants involves… • 1. POLLINATION – In seed plants, the transfer of pollen grains from the anther to the stigma • 2. After pollination, FERTILIZATION, or fusion of gametes (egg/sperm), occurs – forming the zygote which develops into an embryo (baby plant) Anther Pollen grains Pollen tube Stigma 1Pollination Ovary Ovule Pollen grain Two polar nuclei Meiosis and mitosis Fertilization Zygote Egg 3 Sperm cells Fig. 9-10, p. 184 FRUITS and SEEDS develop after fertilization… In flowering plants, FRUIT is a mature, ripened ovary that often provides protection and dispersal for enclosed SEEDS Embryo Food supply (endosperm) Seed coat Germination and growth True leaves 2 Cotyledons (embryonic seed leaves) Hook Shriveled cotyledon Fig. 9-22, p. 194 Fruits evolved to assist in dispersing the baby plant (seed) away from the parent Wind Dispersal Self Dispersal Animal Dispersal Water Dispersal Acorn Milkweed Squirting cucumber Cocklebur Coconut Let’s look an example Fruit and Seed Development in Lily…. A lily ovary is 3 fused carpels, each containing ovules Ovary wall Ovule Lily Ovary cross section FRUITS/SEEDS develop after fertilization… FRUIT – develops from OVARY SEED - develops from OVULE and contains an egg. Lily Ovary cross section Lily fruit develops from a lily ovary Lily Fruit Lily fruit dries at maturity and opens along 3 sutures/seams to expose the seeds inside Immature Fruit (fleshy) Mature Fruit (dry) Physiology CO2 Leaves are the “alveoli” of plants O2 OVERVIEW OF PHOTOSYNTHESIS, which occurs inside chloroplasts Light (energy that drives photosynthesis) 6CO2+12 H2O → C6H12O6 +6O2 +6H2O Substrates Sugar = goal product The substrates for photosynthesis diffuse into leaf cells: 1. CO2 diffuses through stomata Palisade mesophyll Vein Air space Spongy mesophyll 2. H2O diffuses from xylem in vein Energy (light photons) penetrates through epidermis into mesophyll cells Stoma Fig. 4-4a, p. 70 Once inside the cells, CO2 and H2O diffuse into chloroplasts, where photosynthesis occurs Mesophyll cells Outer membrane Thylakoid membrane Inner membrane Stroma Thylakoid lumen Granum (stack of thylakoids) Fig. 4-4bc, p. 70 Light-Dependent Reactions and Calvin Cycle Reactions occur in DIFFERENT locations in the chloroplast STROMA THYLAKOIDS HOW is water moved through a plant? Is it PUSHED up from the bottom or is it PULLED from the top? BOTH OCCUR • Pulling from leaf surfaces= “Tension Cohesion Model” – Most water moves this way! • Pushing from soil into roots = “Root Pressure” – Not as common - mostly short plants that are not actively moving water; spring-time Water vapor evaorates 1 (transpiration) from the surfaces of leaf mesophyll cells to the drier atmosphere through Water stomata. This produces a molecules tension that pulls water out of leaf xylem toward mesophyll cells. 2 Cohesion of water molecules, caused by hydrogen bonding, allows unbroken columns of water to be pulled up narrow vessels and tracheids/vessels of stem xylem. Stoma Tension Cohesion Model 3 This, in turn, pulls water up root Root hair xylem, forming a continuous column of water from root xylem to stem xylem to leaf xylem. Movement of water upward in root produces a pull that causes soil water to diffuse into the root. Fig. 10-13, p. 214 Root Pressure Causes Guttation (water droplets are expelled via hydathode openings along margins of leaves) Fig. 8-13, p. 166 Plants release 99% of the water they take in through evaporation (transpiration) via stomata in leaves and stems. Only 1% is lost through the epidermis because epidermal cells secrete a cuticle made of a waxy (waterproof) substance called cutin. Palisade mesophyll Cuticle Vein (vascular bundle) Spongy mesophyll Upper epidermis Bundle sheath Xylem Phloem Stoma (plural = stomata) Fig. 8-3, p. 155 Air space in spongy mesophyll Stoma Guard cells Lower epidermis Downside of transpiration? • Too much water loss results in plant cells losing turgor and WILTING. • If enough water in soil, plants can recover by taking in water at night Fig. 8-12, p. 166 My research on invasive plants: Garlic Mustard (Alliaria petiolata) Year 1: Juvenile (vegetative rosette) http://www.oardc.ohio-state.edu/weedguide/singlerecord.asp?id=330# Year 2: Adult (reproductive) Mid 1800s Long Island http://plants.usda.gov Northeastern forest invasion by garlic mustard decreases plant diversity Plant Diversit y # of Garlic mustard per 16m2 plot Stinson et al., 2007 Northeastern Naturalist 14:73–88. Garlic mustard harms mutualistic fungi of native plants ectomycorrhizae http://www.ctacf.org/index.cfm/2007/3/1/Mycorrhizae-and-the-American-Chestnut-An-Underground-Tale-of-Mystery endomycorrhizae Research Question: Do detritivores respond to Garlic Mustard invasion? Litter detritivores: Microarthropods Soil Mites: Order Oribatida Springtails: Order Collembola http://www.fcps.edu/islandcreekes/ecology/soil_mite.ht m http://en.wikipedia.org/wiki/File:Orchesella_cincta.jpg Total Springtails are more abundant in invaded sites Springtail Density (#.m-2) 1400 P = 0.003 (invasion) P = 0.174 (date) 1200 1000 800 Invaded 600 Uninvaded 400 200 0 28-Jun 5-Jul Sampling Date 13-Jul