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BOTANY The Study of Plants Where Do Plants Fit In • Domains: – Bacteria: most prokaryotes (no nucleus or intracellular organelle) – Archaea: have many biochemical differences from bacteria and often live in extreme environments – Eukaryotes (true nucleus): • Fungi • Plantae • Animalia Plant Classification • Non-vascular Plants - lack tissues to transport water and sap: • Green algae • liverworts • Mosses – Leaves are a single layer of cells Vascular Plants Tube like structures distribute water, nutrients and food throughout the plant. Ferns – Spores, (no seeds) Gymnosperms – “Naked” seeds (mostly conifers) Angiosperms – Flowers and seeds Gymnosperm - Pine Angiosperms Monocotyledons – One seed leaf grasses, lilies, palms, yuccas, agaves Reproductive parts in threes or multiple of three Three petals etc Dicotyledons –Two or more seed leaves Most deciduous trees & herbaceous plants Reproductive parts in fours or fives: four or five petals Monocots and Dicots A practical note: Some herbicides act differently on dicots vs monocots. Scientific names • Based on classification • In angiosperms based on flower structure • Uniformity among texts and discussions • Often tell us something about the plant PLANT CLASSIFICATION • Kingdom: Plantae • Division: Tracheophyta (vascular) • Class: Angiospermae (seeds in fruits) • Order: Campanulatae • Family: Asteraceae (Compositae) • Genus: Coreopsis • Species: lanceolata (lance-shaped) Vascular Plants-further classification Annuals: Complete a life cycle in one year. Most vegetables, grains, some ornamental plants. Plant may germinate in fall, live through the winter and die after making seeds the next year. Example: Poppies (An “annual” in our zone may be able to live more than one year if grown in tropics.) Biennials complete a life cycle in two years. Perennials live longer than one year. Herbaceous perennials die back to regrow the following growing season. Many ornamental garden plants. Asparagus. Woody perennials, either deciduous or evergreen, do not die back. Vascular Plants • Plants with: – Roots – Stems – Leaves – Vascular systems: extend from root tips up the stems and out into the leaves. ROOTS • • • • Have no nodes Never bear leaves or flowers directly Have a root cap Function: absorb water and nutrients – Anchor the plant – Furnish physical support for the stem – Serve a food storage Root Cap • Not present in “water roots” ROOTS Root growth in loose vs compact soil Specialized Roots • Tap root: large main root taps deep for water, develops from radicle and produces lateral roots • Fibrous root (a form of adventious root) common in monocots and seedless plants • Adventious root: not from radicle • Aerial root arises from stem (ivy, orchid) • Buttress root (Ficus) • Suckers • Pneumatophores provide oxygen in wet areas Mycorrhizae • From mykes or fungus and rhiza or root • Symbiotic relationships between fungi and plant roots: the fungi get sugars or food and the plants absorption of water and minerals is greatly enhanced • Occurs in >80% of vascular plants Mycorrhizae Specialized Roots • Tap root: large main root taps deep for water, develops from radicle and produces lateral roots • Fibrous root (a form of adventious root) common in monocots and seedless plants • Adventious root: not from radicle • Aerial root arises from stem (ivy, orchid) • Buttress root (Ficus) • Suckers • Pneumatophores provide oxygen in wet areas Plant Stems • Support the weight of leaves • Conduct water and minerals up to leaves and food down to roots in the vascular tissue • Complex growth: produces leaves and branches at nodes as well as lengthens Plant Stem Stem or Twig Vascular Cambium • Produces phloem peripherally which transports sap to the roots and back from the roots in early spring or late winter • Produces xylem internally which transports water • If completely interrupted, the plant will die Meristem or Cambium • Site of cell division and growth located between phloem and xylem. If this is destroyed the stem cannot form new cells for transport of water and sap. • At nodes and at the tip meristem tissue forms buds. – Flower parts are modified leaves Stem Cross Section Woody Stem Cross Section Apical Meristem Plant Stem Tip Specialized stems • Rhizome: horizontal underground stem with (nodes and buds); iris, bermudagrass • Bulbs: shortened, compressed stem surrounded by leaves (scales) that envelop a flower bud • Corm: similar to bulb with scales reduced to dry covering • Tuber: enlarged portion of underground stem; potato with nodes as “eyes” Rhizome • The iris has a large fleshy underground stem that runs parallel with the soil. Leaves • Site of photosynthesis. Plants are photoautotrophs: they use light to make their own organic compounds and oxygen. • Light is the energy source and CO2 is the carbon source. • Plants also respire but the net effect is the production of oxygen in excess of carbon dioxide. Leaf Structure • 1. Cutin, 4. Spongy parenchyma • 2. Epidermis 5. Air space • 3. Palisade layer 6. Stoma • Leaf Arrangement • Simple. Opposite, alternate, whorled • Compound: Leaflets Palmate, Pinnate or Double Pinnate • **Leaves attach to stems at nodes and buds occur only at nodes. • (a common error is to mistake a leaflet for a leaf) Simple leaves Leaf arrangement Compound Leaves Sexual Reproduction Occurs in all plants. Involves meiosis or halving the number of chromosomes so that sperm and ova are produced. These then unite to produce a new combination of chromosomes and genes. Gymnosperm Flower Structure Gymno vs Angiosperm Pollination and Fertilization Pollination: Pollen is carried by wind, insect, bird, water….from the anther to a stigma. Fertilization: The sperm cell unites with the egg cell in the ovule. SEEDS • Develop from ovule • Cotyledon--seed leaf • Radicle--first root Seed Germination • Period of dormancy • Factors: scarification, stored food – Temperature: some require a period of cold – Moisture – Light – Oxygen (water logged soil may prevent germination) Seed Dispersal • • • • • Plumes: butterfly weed, dandilions, maples Fruit: acorns, hollies, apples Water: coconuts Spines and barbs: beggar’s tick Explosive fruits: jewel weed Hybrid • Hybrid: a plant or animal which is the offspring of parents differing in one or more characteristics. The parents may be of the same or different species. • Species:a group of individuals if nearly identical structure and behavior which can ordinarily interbreed and maintain their characteristic in nature. Red crossed with white produces pink (hybrid) flowers Genetic variability • In a given species or variety a gene may have quite a variable expression. • Example: apple trees have so much variability that to propagate a standard one must use grafted stock. If one uses seeds the two parent trees contribute such different characteristics that one usually gets something very different from either parent. Gene Dominance • If S is dominant over s when SS is mated to ss all of the offspring will appear S. The offspring will be Ss. (The Ss is the hybrid.) If Ss is mated to Ss, the offspring will be SS, Ss or ss and the ss will appear different. If there are multiple genes acting in such a way the offspring of the hybrids may have many differences from the hybrids. Genetic variability • In a given species or variety a gene may have quite a variable expression. • Example: apple trees have so much variability that to propagate a standard one must use grafted stock. If one uses seeds the two parent trees contribute such different characteristics that one usually gets something very different from either parent. Gene Dominance • If S is dominant over s when SS is mated to ss all of the offspring will appear S. The offspring will be Ss. (The Ss is the hybrid.) If Ss is mated to Ss, the offspring will be SS, Ss or ss and the ss will appear different. If there are multiple genes acting in such a way the offspring of the hybrids may have many differences from the hybrids. Propagation from Seeds • The offspring may vary from the parents because of genetic variability or if the parent was a hybrid. • This may be desired in some cases, but in apples usually the offspring are not tasty. PLANTS: Bryophytes • Bryophytes (moss-plants) non-vascular, seedless: Mosses: sphagnum, rock mosses, “true mosses, Liverworts, Hornworts Cell walls of cellulose Do not produce flowers MOSS • MOSS Moss Cultivation • Mosses need moisture to complete their life cycle. Many can survive dry periods but the spores need water. • Generally does well in shade, often grows on rocks. • Grows in wide range of pH. • Plant other garden plants first then add the moss LIVERWORT • Seedless Vascular Plants • Lycophyta: club mosses, selaginellas, quillworts • Sphenophyta: horsetails • Pterophyta: ferns Clubmoss • Lycopodium Selaginella Selaginella Equisetum (Horsetail) Equisetum Ferns • Need moisture to complete the life cycle but often grow in a variety of conditions Life Cycle of Fern Ferns • Maidenhair Non-flowering Plants • Can be interesting as well as beautiful additions to outdoor and indoor gardens. • They often need high humidity and some shade – The north side of the house is often a good habitat for selaginellas and ferns Adaptations of Plants • Drought tolerance – Succulents have large vacuoles to store water – Waxy coats to avoid water loss – Small leaves or needles to decrease surface area (less effect from wind) – Stomata close during the day (cacti) – Hairs on leaves to collect moisture Seed Dispersal • Plumes: butterfly weed, dandilions, maples • Fruit: acorns, hollies, apples • Water: coconuts • Spines and barbs: beggar’s tick • Explosive fruits: jewel weed Galls Oak Leaf Gall Urchin Gall Monarch on Milkweed • Monarchs prefer more than one species of milkweed