Life 103 1st EditionExam # 2 Study Guide Lectures: 11 - 20Lecture 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 DevelopmentDifferentiated 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), aliveMeristems-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 ofsecondary xylem and phloem) + cork cambium (replaces epidermis with tough periderm)) Primary growth-LengthSecondary growth-GirthRoot 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 genesHomeotic 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 carpelsActive Transport Proteins-Proton pumps- use ATP to pump H+ out of cell to create a gradient that has potential energyLecture 14 (February 23)Water Potential -Sum of the factors that determine the direction of osmosis -Ψ: “psi” value of pure water = 0. Addition of solutes lowers Ψ (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