Life 103 1st Edition Exam 2 Study Guide Lectures 11 20 Lecture 11 February 16 Roots Anchor Absorb nutrients Storage Taproot main vertical root deeply penetrates Lateral roots branch off taproot Root hairs finer roots that have very high surface area access nutrients and water grow off lateral roots Stem Stalk upon which leaves grow Shoot system stem leaves Node point on stem where leaves are attached Internodes stem segments between nodes Axillary bud structure that can form a lateral shoot growth inhibited by proximity to apical bud Apical terminal bud elongation point of a growing shoot leaves nodes and internodes Leaf Blade petiole Anatomy terms Prop roots support tall top heavy plants ex maize Storage roots tore food and water in their roots ex beets Rhizomes horizontal shoot that grows just below the surface Bulbs stem with fleshy or leaf bases acts as storage Stolons horizontal shoots that grow along the surface can reproduce asexually Tubers enlarged ends of rhizomes or stolons specialized for storing food ex potato Simple single undivided blade Compound multiple leaflets Doubly compound multiple leaflets on one petiole Tendrils coils seen with peas attachment when climbing Spines cacti Bracts modified leaf with cluster of flowers at axel poinsettia Tissues Dermal outer protective layer epidermis cuticle waxy Vascular long distance transport between roots and shoots xylem phloem these two make up the stele eudicots only Ground dermal nor vascular pith internal to vascular tissue cortex Plant Development Differentiated Plant Cells Alive parenchyma collenchyma sieve tube elements Dead sclerenchyma vessel elements Photosynthetic tissue is found in ground tissue of parenchyma Differentiation developmental changes in a cell s cytoplasm organelles and or cell wall during development Parenchyma alive metabolic functions such as photosynthesis and nutrient storage Collenchyma celery structure flexible support Sclerenchyma dead strengthened by lignin Types sclerids short irregular source of hardness fibers long slender source of linen and rope Water conducting cells of xylem tracheids long and thin and vessel elements wider shorter Sugar conducting cells of the phloem sieve tube elements long and narrow lack organelles sieve plates porous allow movement between site and companion cells have ribosomes and a nucleus used by sieve tube elements and sieve plates alive Meristems Apical Vascular Cork cambium Divided tissue that is perpetually embryonic Apical meristem located at apical bud of shoots and roots primary growth xylem in middle and phloem on outside Lateral meristem secondary growth stem thickening in woody plants vascular meristem adds layers of secondary xylem and phloem cork cambium replaces epidermis with tough periderm Primary growth Length Secondary growth Girth Root Growth Root cap cluster of protective cells that protect the apical meristem 3 zones Zone of division meristem area where mitosis and cytokinesis produce new cells Zone of elongation cells lengthen Zone of differentiation cells become a distinct cell type Lecture 12 February 18 Pericycle vascular bundle surrounded by a ring of endodermis cells Lateral roots come from endodermis Shoot Growth Leaf primordia embryonic leaf tissues that develop into leaves Shoot elongation for most plants lengthens at cells beneath the shoot tip but for grasses the intercalary meristem at the leaf base pushes new tissue up that helps grasses endure grazing Secondary Growth Lateral meristems add thickness to woody plant Vascular cambium between xylem and phloem produces them Cork cambium produces cork cells that replace the epidermis outside the secondary phloem Bark periderm cork cambium cork secondary phloem Tree Rings Wood lots of layers of secondary xylem Early wood produced in spring thinner Late wood produced in summer or fall thicker Lecture 13 February 20 Production of the Plant Body Plane of cell division determines direction of growth depends on how microtubules are connected use molecular signals to determine polarity To differentiate into the correct cell type cells must get information about where they are Control by expression of GLABRA 2 genes Homeotic Genes Master regulatory genes that determine the differentiation fate of groups of cells code for proteins that bind to DNA and affect which genes are transcribed ABC Model of Flower Development 2 gene products A B C and each gene product can act on two organs A and C gene products are mutually exclusive Homeotic genes Mutant lacking A gene would not have petals or sepals Mutant lacking B gene would not have petals or stamens Mutant lacking C gene would not have stamens or carpels Active Transport Proteins Proton pumps use ATP to pump H out of cell to create a gradient that has potential energy Lecture 14 February 23 Water Potential Sum of the factors that determine the direction of osmosis psi value of pure water 0 Addition of solutes lowers more negative Water moves towards regions of lower water potential Units are megapascals MPa pressure Plant water tidbits Turgor loss of pressure causes wilting Aquaporins membrane proteins that help with water transport Major pathways of transport Apoplast continuous space joining everything outside the cell membrane Symplast continuous cytosol joined between cells by plasmodesmata transport across cell wall and membrane once Transmembrane repeated crossing of apoplast cell membrane and symplast Xylem tubes have no cell membrane example of apoplastic transport Transport proteins have an effect on Transmembrane route Soil to xylem transport of water and minerals into roots Endodermis inner most root cortex cells last gate for selective permeability waxy Casparian strip stops apoplastic route Tension cohesion theory Water loss out of stomata dries the cell wall surface of internal leaf cells Water is attracted out of the xylem to re wet these cell walls this pulls water up xylem because water molecules are strongly cohesive Transpiration Where is the force generated that draws the water up the plant Through evaporation that pulls up the water water film advances and draws water out of the cell away from the xylem tubes to the wetting surfaces water tension and cohesion Lecture 15 February 25 Leaf Guard cell used to open and close the vacuole CO2 goes down when the stoma closes Stomata water loss open when guard cells are turgid that is set by active pumping K across membranes Cues to open guard cells light internal CO2