Transcript SHOW-6-2005
Cell Walls Cell walls are: – Structural – Provide defense against invading pathogens – Provide signaling pathways for cells Cell Wall Chemistry • Cell walls contain cellulose, pectin and lignin • Cellulose is the major component – Most abundant polymer in the world ~40-60% of dry weight of plants – Form strong strands of parallel chains called Cellulose Microfibrils – Cellulose strands are cemented together by pectins TEM photograph Pectin and Lignin • Pectins are polymers of a-galacturonic acid – Flexible, long molecules that link Microfibrils together…like ‘glue’ • Lignin is very hard, tough, rigid – Chemistry is not fully elucidated – Polymer of complex, amino-acid derived monomers – Creates strong cell walls And don’t forget the 5 colors ! Plant Tissues • Tissues are groups of cells that form a structural and functional unit • Vascular plants have three tissue systems: – Dermal tissue Outer covering for the plant body – Ground tissue Photosynthesis, storage and support – Vascular tissue Water and nutrient conduction system Functions for Plant Epidermis 1) Prevent water loss in shoot (waxy surface and bark) 2) Controlling exchange of gases in shoot (stomates) 3) Absorption by roots (root hairs) 4) Produce hairs, called trichomes, that shade the leaf or protect from herbivores (physically or chemically) A Gymnosperm B Dicot C Monocot Yam D Monocot E Monocot Do Animals have epidermis? What is animal epidermis called? What does this have to do with Safe Sex? Cheek cells Jicama -- Pachyrhizus erosus (L.) Jicama -- Pachyrhizus erosus (L.) Eaten in celebration of Day of the Dead November 1st Mexico Plant Tissues • Tissues are groups of cells that form a structural and functional unit • Vascular plants have three tissue systems: – Dermal tissue Outer covering for the plant body – Ground tissue Photosynthesis, storage and support – Vascular tissue Water and nutrient conduction system Vascular Tissues - Xylem • Xylem conducts water and nutrients from roots to the rest of the plant • Two types – Tracheids • Dead at maturity • Main water-conducting cells of fern and gymnosperms • Relatively few plasmodesmata in end of cell in pit fields, thin areas w/only primary cell wall – Vessel elements • Dead at maturity – stacked on top of each other • Broader than tracheids, large holes in ends of cell • Much more efficient at water transport End wall with perforations Xylem carries water & soil nutrients Pits Cell wall Lumen Tracheids Vessels (a) (b) Xylem Vessel Xylem Tracheid Vascular Tissues - Phloem • Transports food materials • Provides structural support • Two types: - Sieve tube cells • Alive at maturity • Extensive holes via sieve plate at cell ends, with shared cytoplasm between cells • Reduced cellular organelle volume – some lose nucleus – Companion cells • Nucleated, support cells for sieve tubes • Connected by many plasmodesmata to sieve tube cell • Involved in sugar transport to sieve tube cell Sieve plate Sieve tube member Phloem parenchyma cells Lateral sieve area Plasmodesma Companion cell (c) (d) Fig. 31.05cd Companion Cell Sieve Tube Cell Xylem and Phloem Cells Fiber Cells Xylem & Phloem: (in Squash) Fibers Phloem Xylem Xylem Vascular Cambium Epidermis Phloem Vascular Cambium Xylem Notice that the vascular cambium circles all the way around Fibers Dicot stem Hemp Jute for burlap Examples of plant fibers from stem vascular bundles Sisal = fiber from monocot stem Epidermis Vascular Bundles (scattered) Monocot Stem Monocot Stem Air Space Xylem (big cells & smaller ones in circle Phloem (all cells within box Secondary Growth Secondary Growth……Why? * Plant is getting bigger so needs more materials * Old vascular tissue gets “clogged up” 1, 2, 3 years Of age Pith Rays in wood Tree Borer For assessing tree rings Bristlecone Pine How old are these trees? Oldest one is 4,800 years old The oldest living trees on earth. The Curly Redwood Lodge is one of northern California’s most unique lodges. It was built from one curly redwood tree that produced 57,000 board feet of lumber. The tree (cut down in 1952) was 18 feet wide at the trunk. Curly redwood is unique because of the curly grain of the wood, unlike typical straight grained redwood. http://www.curlyredwoodlodge.com/rooms.htm 1952 Jewelry meant for Queen Nerfititi (Egypt) was found on a sunken wooden ship that was built in 1316 B.C. King Midas (Turkey) was buried in a funeral mound built with logs that were cut in 718 B.C. Lost Colony of Roanoke, Virginia Can also study when major forest fires occurred in the past. A researcher in Tennessee noticed that hurricanes cause heavy-oxygen to accumulate in “late wood” (because hurricanes usually occur in late fall). She has been accurate back to 100 years ago….wants to go back 500 years. • Two small, old-mining towns that are currently military posts (Arizona and Nevada) • Unusually high levels of childhood leukemia cases • High levels of tungsten in the urine of townspeople • Is there a cause:effect relationship between tungsten (a heavy metal, like lead or mercury) exposure and leukemia? …still being investigated • But tree-ring specialists have discovered that the levels of tungsten in the environment have increased dramatically in the last 20 years….each annual ring captured whatever chemicals that might have occurred in the environment that year!!! September, 2002 Sapwood Heartwood Sycamores Cork Fibers Phloem Xylem Girdling can kill plants Carpenters talk about two kinds of wood: Softwood and Hardwood Softwood = light, easy to put nails/screws into…so are best for construction. Gymnosperms generally make softwoods. Since Pines grow so fast they are the most popular. Paper is made from pine mostly. Hardwood = from Dicot trees mostly; more of a mixture of xylem cells (including fibers); that makes them more dense. Used for furniture and art/crafts. Gymnosperms like pines, junipers, spruce, fir, and redwood. Most of the xylem cells are one kind...called Tracheids. Also, little or no Fibers. Dicots like oak, maple, ash, hickory, walnut. Contain both tracheids and vessels and fibers. The fibers make the wood harder to cut and nail into, But will also be sturdier for Making furniture, flooring, art, etc. Not all Hardwoods are actually “harder” than Softwoods, and not all Softwoods have wood that is “softer” than Hardwoods. Hickory (Hardwood) •Wright Brothers plane •Pioneer wagon wheels •Baseball bats • Skis •Axes, hammer handles, etc. • Golf clubs • wooden floors Mostly tracheids & fibers with A very large vessels interspersed. Very slow growing. Some nonvascular cells are gelatinous of Wheat Starchy food supply (Endosperm) Dietary Fiber Scutellum = Cotyledon Embryo It is believed that the early hominids were eventually forced to live in a biome that was different than the Tropical Rainforest. This might have been due to: 1) globalclimate change, or 2) rising competition for resources due to population pressures, or 3) a combination of these two factors. Which biome do you think they would have ended up in (according to this scenario)? Primates typically live in Tropical Rainforests (using hands & feet to climb trees)…. …they eat leaves, fruits, seeds & insects. < Living in the Savanna?? Primates typically live in Tropical Rainforests (used hands & feet to climb trees)…. …eats leaves, fruits, seeds & insects. Chimpanzee (5 million years ago) …eats leaves, fruit, seeds, resin, bugs Australopithecus (3 million years ago) ...eating more roots, grains & meat Roots, tubers, bulbs, rhizomes Savanna Tropical Rainforest More difficult life…more challenges: • Bipedalism (to move further & to see predators & prey better & get less sun & use hands to carry things • Develop use of tools • More social organization (language?) • Larger brains • Larger teeth to eat roots & grains & meat < Climate-change…more Savanna-like Primates typically live in Tropical Rainforests (used hands & feet to climb trees); eat leaves, fruits, and insects. Taro root Carrots Cassava Parsnips