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Life 103 Notes *adapted from the lecture notes of Dr. Dale Lockwood* Plant Structure ctn. (see week 5 notes) • Plant Tissues (see textbook figure 35.8)-Three types of tissues ~Dermal ~Ground ~Vascular • Dermal Tissue System -Epidermis ~In non-woody plants -Cuticle ~Waxy coating ~Helps prevent water loss from the epidermis -Pericardium ~In woody plants ~Protective tissues ~Replaces the epidermis in older regions of stems and roots -Trichomes are outgrowths of the shoot epidermis and can help with insect defense • Vascular Tissue System-Carries out long-distance transport of materials between roots and shoots -Two vascular tissues -Xylem conveys water and dissolved minerals upward from roots into the shoots -Phloem transports organic nutrients from where they are made to where they are needed • Vascular Tissue-The vascular tissue of a stem or root is collectively called the stele -In angiosperms, the stele of the rot is a solid central vascular cylinder -The stele of stems and leaves is divided into vascular bundles, strands of xylem and phloem• Ground Tissue System-Tissues that are neither dermal nor vascular -Pith ~Ground tissue internal to the vascular tissue -Cortex ~Ground tissue external to the vascular tissue -Ground tissue includes cells specialized for storage, photosynthesis, and support Cellular Structure in Plants• Cells (see textbook figure 35.10)-Plants have a diversity of cells that perform a variety of functions ~Consider 5 general types -Parenchyma
-Collenchyma -Sclerenchyma -Water conducting cells of the xylem -Sugar-conducting cells of the phloem • Ground Tissue -Composed of ~Parenchyma ~Collenchyma ~Sclerenchyma • Ground Tissue Cells-Mature parenchyma cells ~Have thin and flexible primary walls ~Large central vacuole ~Lack secondary walls ~Are the least specialized ~Perform the most metabolic functions -Store nutrients -Photosynthesize ~Retain the ability to divide and differentiate -Key for cloning -Collenchyma cells ~Grouped in strands and help support young parts of the plant shoot ~They have thicker and uneven cell walls ~They lack secondary walls ~These cells provide flexible support without restraining growth ~Example: strings in a celery stalk are bundles of collenchyma cells -Sclerenchyma cells ~Rigid because of thick secondary walls strengthened with lignin ~Dead at functional maturity ~Have very thick cell walls relative to the cell inside the walls ~Example: pears are grainy when bitten into due to bundles of sclerenchyma cells ~There are two types -Sclereids are short and irregular in shape and have thick lignified secondary walls ~Source of hardness in nutshells and seed coats -Fibers are long and slender and arranged in threads ~Source of linen (flax fibers) and rope (hemp fibers) -Linen is made from extracting fiber cells from the plant • Vascular Tissue Cells -Xylem cells ~Cells are dead at functionality because it’s not easy to move water through living cells because of the thick cytoplasm, while it’s easy to move water through dead, hollow cells
~Each cell has to be connected to allow water to move all the way through the plant ~Tracheids-Found in all vascular plants -Tubular, elongated and dead -Water transfers via pits in the tracheids ~Vessel Elements-Larger diameter and shorter -Aligned end-to-end to form vessels -End walls have perforation plates -Phloem Cells ~Sieve-tube elements-Alive at functional maturity ~Active transport is always required for sugar to get into a cell, which can only be performed by a living cell -They lack organelles, including nucleus -Allows sugars to flow more easily ~Sieve plates-The porous end walls that allow fluid to flow between cells along the sieve tube ~Companion cell-One for each sieve-tube element -Nucleus and ribosomes serve both cells ~Sends proteins etc. to sieve-tube elements to keep it alive and able to perform active transport while not having any organelles itself Cell growth • Growth -Indeterminate growth- growing throughout an organism’s life ~Example: roots and shoots -Determinate growth- some plant organs cease to grow at a certain size ~Example: leaves -Annuals complete their life cycle in a year or less -Biennials require two growing seasons and only bloom the second year -Perennials live for many years • Where growth occurs-Meristems ~Perpetually embryonic tissue ~Maintains indeterminate growth ~Functionally similar to animal stem cells -Apical Meristems ~Located at the tips of roots and shoots and at the axillary buds of shoots
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School: Colorado State University
Course: Biology of Organisms-Animals and Plants
Professor: Jennifer Dewey
Term: Fall 2016
Name: Life 103-Week 6 Notes
Description: These notes cover part of Plant Structure, Cellular Structure in Plants, Cell growth, Plant Anatomy, and part of Water and Sugar.