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Plant Structure and Growth Overview Lifecycles – Annual, biennial, perennial Basic Plant parts Plant cell walls, simple tissue types Plant growth: – – – – – Meristems Primary Tissues Primary growth – apical meristems Secondary growth – lateral meristem Secondary tissues Flowering Plant Lifecycles • Annual – germinates, flowers set seeds and dies in one growing season • Biennial- germinates grows first season, storing up energy underground. Second spring plant use energy to quickly bloom (bolting) set seed and die. • Perennial grows for several seasons until mature, Blooms and sets seed for years. bolting Basic Plant Parts • Shoot system: photosynthesis, reproduction – Stems with nodes – Leaves - axilliary bud at base of each – Flowers and fruits (cones in gymnosperms) • Root system ; Anchors plant; Storage organs; absorption of water and nutrients. – Roots, root hairs – Mycorrhizae – Nitrogen fixing bacteria Angiosperm Diversity BASAL ANGIOSPERMS Amborella trichopoda Star anise (Illicium floridanum) Water lily (Nymphaea “Rene Gerard”) MAGNOLIIDS Southern magnolia (Magnolia grandiflora) Eudicots Monocots Magnoliids Star anise and relatives Water lilies Amborella HYPOTHETICAL TREE OF FLOWERING PLANTS MONOCOTS EUDICOTS Monocot Characteristics Orchid (Lemboglossum rossii) Eudicot Characteristics California poppy (Eschscholzia californica) Embryos One cotyledon Two cotyledons Leaf venation Veins usually parallel Pygmy date palm (Phoenix roebelenii) Pyrenean oak (Quercus pyrenaica) Veins usually netlike Stems Lily (Lilium “Enchantment”) Vascular tissue usually arranged in ring Vascular tissue scattered Root Barley (Hordeum vulgare), a grass Root system Usually fibrous (no main root) Dog rose (Rosa canina), a wild rose Taproot (main root) usually present Pollen Pollen grain with one opening Pea (Lathyrus nervosus, Lord Anson’s blue pea), a legume Pollen grain with three openings Flowers Anther Stigma Filament Ovary Floral organs usually in multiples of three Floral organs usually in multiples of four or five Zucchini (Cucurbita Pepo), female (left) and male flowers Fig. 35.2 Simple Plant Tissue Types • Tissues- cells with a common structure and function and specialized connections. • Parenchyma- Soft, rounded cells with thin primary cell walls, air spaces between cells – Many are Totipotent Cells- undifferentiated that can still divide – Some are specialized: chlorenchyma, phloem • Collenchyma- irregularly thicken primary cell wall, no air spaces. Elastic support. • Sclerenchyma – rigid secondary cell wall. May have no cytoplasm left: Wood, Xylem, vessels, fibers, tracheids. Also seed coat. Fig 35.11 Xylem • • • • • • • • Sclerenchyma Dead at maturity Hollow Grows to size first then makes secondary cell wall Tracheids Vessel elements Secondary xylem is true wood. Conducts water from roots to leaf Young Xylem • We’ll go over different types in lab Phloem • Transports sugar solution from source to sink. • Parenchyma-Living tissue, uses active transport. • Sieve tube members and companions cells Plant Tissues comprise Organs • Dermal tissues cover the plant – Epidermis, stomata, trichomes, bark • Vascular Tissues transport materials – Xylem carries water – Phloem carries sugar solution • Ground Tissues – metabolic functions, growth – Meristems, photosynthesis, storage • Organs-groups of tissues forming a larger structure, with a common structure and function. Fig 35.7 Plant cell wall structure • Adjoining cells held together by middle lamella (polysaccharides of pectin) • Cells first make thin, flexible primary cell walls. • Plant cells can still enlarge / divide with primary cell wall. • Some cells lay down three rigid secondary cell wall layers with ligin inside primary cell wall. • Plasmodesmata connect cytoplasm between neighboring cells through cell walls. Fig 6.28 Cell Elongation • How cellulose microfibrils are laid down determine the direct of elongation. • Elongation takes place when a cell only has primary cell wall. • Once proper size and shape is attained, secondary cell wall material is added inside the primary cell wall. Plane of Cell division • Determines the cell shape Plane of symmetry Plant Growth • Indeterminate growth • Primary growth: cells derived from the apical meristems (both root and shoot). – Makes the plant grow taller and roots deeper. – Makes leaves, flowers fruits • Secondary Growth: cells derived from the lateral meristems. – Adds girth to plant – Vascular cambium makes secondary xylem (wood) and secondary phloem. – Cork cambium adds to bark • Meristems- localized areas of cell divisions – Plants grow in zones, not all over whole organism Fig. 35.12 Fig. 35.17 Apical Meristem • Divides cells that form primary meristem tissues – Protoderm – further divides to make dermal layers – Procambium – divides to form xylem and phloem, residual layer becomes vascular cambium – Ground Meristem – forms pith and cortex • Plants grow like building a brick wall- add bricks at top (primary growth), then add girth to sides (secondary growth). Primary growth • Herbaceous – no true wood • May have tough parts – Collenchyma or Sclerenchyma. • All cells derived from apical meristem • Forms separate vascular bundles in stem. • You fall madly in love with you’re a lab mate in 131 – and hand in hand you both carve you initials 4 feet off the ground on the Bishop Pine (Pinus muricata) in the turn-around by the LS building. • The Bishop Pine grows 3 feet a year. • Two years later you return to DVC after finishing up at UC Santa Cruz in Organismal Biology to visit you old favorite Biology instructor. • How far off the ground are your initials then? Secondary Growth • In Ferns, Gymnosperms and Eudicots, not in monocots • Vascular cambium layer begins to form. – Divides off more cells. – Cells to the inside become secondary xylem (wood) Cells to outside become secondary phloem. • Adds girth, pushing outer layer farther out. • Parenchyma in phloem rays fill-in space until cork cambium starts making bark. Fig. 35.20 Annular growth rings • In temperate or wet /dry seasonal zones • In spring new growth use a lot of water, xylem cells grow very large (early wood). • Under water stress late in the season xylem cells very narrow (late wood). • Evidence of past climates, period of drought. Monocot and Eu-dicot • Monocots do not have secondary growth. – Palm trees, bamboo - not true wood!! • We’ll compare anatomical variation between these groups in lab – Learn differences between monocot , dicot anatomy of leaves, stems, roots.