The Angiosperm Body Two Classes based on Embryo s: 1. Monocots: single Cotyledon (seed leaf) 2. Dicots: two cotyledons • Three Basic Organs • Roots • Stems/Shoots • Leaves
Root System Dicots have main Taproot: one large vertical root, small lateral roots, firm anchor. Energy storage Root crops harvested before flowering Monocots: fibrous roots, thread like, short, Root Hairs: tiny fibers increase surface area, have Mycorrhizae. Adventitious roots: roots that rise up above ground, or other unusual area
Modified Shoots Shoot System • Vegetative shoots with leaves, floral shoots • May be • Vegetative (leaf bearing) • Reproductive (flower) • Stems • Nodes: point where leaves are attached • Internode: b/w nodes • Auxillary Bud • Terminal Bud • Apical Dominance • Apical Meristem
Modified Leaves • Blade: leaf structure, photosynthesis • Petiole: stalk that joins leaf w/ node of stem Grasses lack petiole; Monocots have parallel veins in leaves, Dicots have multi-branched network. Pattern can be used to ID plant. Specialized for photosynthesis or other functions
Three Systems of Tissues • Dermal Tissue System: epidermis, covers and protects. Root hairs, cuticle of leaves secrete waxes. • Vascular Tissues Systems: Xylem, Phloem • Ground Tissue Systems: b/w dermal and vascular tissues. Mostly parenchyma. • Xylem moves water/minerals upwards from root • Phloem moves food from leaves to roots
Water/Food Conducting Cells • Xylems: elongated cells to conduct water. Two types: • 1. Tracheids: long thin, tapered • 2. Vessel elements: wider, shorter, end to end • Both dead at maturity, Various sections: • Pits: thin regions of primary walls, found in tracheids • Xylem vessels: end walls perforated, water flows freely Phloem: food conducting; sieve tube members, no nucleus Chains of Sieve-tube members: alive at maturity, Angiosperms have sieve plates b/w cells w/ pores. Each sieve tube member has companion cells,connected to sieve tube by plasmodesmata, helps ST and loads sugar into phloem.
Basic Structure of Plant Cell • General Structure of cell with modifications. • Cell Wall (Primary, Secondary (3), Lamella) • Chloroplast • Vacuole • Tonoplast • Plasmodesmata
Growth Annuals/Perennials: Meristems Apical Meristems • Primary Growth: elongation of AM in tips of roots/buds. • Secondary Growth: thickening of roots/shoots (lateral meristems) • Quiescent Center: cells divide slowly in AM. function as reserves • Primary Meristems:protoderm, procambium, ground meristem (produce 3 tissues of root dermal, vascular, and ground)
Root Tissues • Protoderm: • gives rise to outermost meristem, epidermis, single layer of cells covering roots • Procambrium • Stele :develop from procambrium, xylem/phloem vascular bundle development. Single central cylinder, xylem radiates out, phloem forms around.(Pith in monocots). • Ground: • Cortex: b/w stele and epidermis, ground tissue development. • Endodermis: innermost layer of cortex, one cell thick • Pericycle: layer of cells that may become meristmatic, produces lateral roots.
Primary Growth of Shoots • Apical Meristem: dome shape, terminal end of bud. Gives rise to protoderm, procamrium, and ground meristem • Axillary Buds: meristem islands that will form branches later on. • Lateral roots develop from w/i main root, Lateral branches develop from axillary buds. • Vascular tissue located near surface.
Primary Tissue of Stems • Vascular Tissues/Vascular Bundles: lengthwise in stem, grouped in bundles in center and spread outwards, (roots found in center). Surrounded by ground tissue. • Dicots: arranged in rings w/ piths and cortex external to ring. Xylem face towards pith. Phloem face cortex. • Monocots: VB scattered in ground tissue. Ground tissue mostly parenchymal cells. • Sclerenchyma Cells form fibers for support
Tissue Organization of Leaves • Epidermis: • covered by dermal cells, interlocking cells. • Has stomata’s tiny pores flanked by guard cells (epithelial cells). • Transpiration= loss of water by evaporation. • Upper and Lower regions • Mesophyll: paranchymal cells b/w upper and lower epidermal layers • Chloroplasts • Distinct regions in Dicots • Palisade cells: • Spongy Parenchyma: spongy, air space, CO2 and O2 circulates, gas exchange • Vascular Bundle: Xylem, Phloem and Fibers for support
Secondary Growth • Secondary plant body: tissue produced during secondary growth in diameter. Two Lateral Meristem Functions • Vascular Cambium: produces secondary vascular bundle • Xylem produced towards interior • Phloem produced towards exterior • Forms from paranchymal cells, b/come meristemic • Cork Cambium: produces tough thick covering for stems and roots. Replaces epidermis. • Cork: waxy substance, suberin. Die early, barrier • Periderm: cork and cork cambium • Bark: secodary phloem, cork cambium, cork • (phloem and periderm)
Cork Cambium Production of Periderm • Cork Cambium produces cork cells (waxy).Fixed size. Cork acts as barrier. • Periderm: cork + cork cambrium. • Bark: all tissue external to vascular cambrium • Lenticels: areas of bark which is spongy, gas exchange for cellular respiration.
Growth Plane: directional growth Asymmetrical Growth:one daughter cell receives more of cytoplasm Guard Cells need both asym., and plane division Preprophase Band: microtubules in cortex set plane of division