Plant Structure and Function Plant Cells and Tissues

Plant Cells Three basic types Parenchyma Collenchyma Sclerenchyma

Parenchyma Loosely packed w/large central vacuole Cubed – shaped or elongated Involved in Photosynthesis Water storage Nutrition or healing Bulk of nonwoody plants Fleshy parts of fruit

Collenchyma Thicker cell walls Irregular shape Support for plant

Sclerenchyma Thick, even, rigid cell walls Support and strengthen plant Dead at maturity Hardness of shells around nuts

Plant Tissue Systems Dermal Ground Vascular

Dermal Tissue Forms outside covering Cuticle Epidermis Parenchyma cells Cuticle Roots develop hair – like extensions Stomata Woody stems/roots replaced by dead cork cells (parenchyma)

Ground Tissue Surrounded by dermal tissue All three types of plant cells Make up majority of nonwoody plants Main function Storage Metabolism Support

Vascular Tissue Surrounded by ground tissue Made up of Xylem Conducts water, mineral nutrients from roots upward Provides structural support Phloem Conducts organic compounds, some mineral nutrients Alive a maturity Adapted to different environmental conditions Xylem support and strength May be absent in aquatic species

Plant Growth Flowering plants (Angiosperms) Gymnosperms Dicotyledons Monocotyledons Number of cotyledons or seed leaves in a plant embryo Gymnosperms Have two or more cotyledons

Monocot and Dicots Plant type Embryo Leaves Stems Flower Parts Examples Monocots One cotyledon Parallel Venation Scattered vascular bundles Usually occur in threes Lilies, irises, onions, grasses Dicots Two cotyledons Net venation Radially arranged vascular bundles Usually occur in fours or fives Beans, oaks, lettuces, maple, roses, cactuses, carnations

Plant Growth Originates in meristems Continuous cell division Apical meristem (primary growth, length) Lateral meristem (secondary growth, diameter) Some monocots grow in length Intercalary meristems Located above the base of the leaves or stems (grasses) Allows plants to regrow quickly after being grazed on

Lateral Meristems Gymnosperms and most dicots Allow stems and roots to increase in diameter Located outside of stem

Lateral Meristem Two types Vascular cambium Cork cambium Located b/w xylem and phloem Cork cambium Located outside phloem Produces cork Replaces epidermis Provides protection and prevents water loss

Plants have three kinds of organs Roots Stems Leaves

Roots Anchor the plant in the soil Absorb and transport water and mineral nutrients Storage for water and organic compounds

Types of Roots Taproot Fibrous root system Adventitious roots Primary root Rarely more than one – two meters Fibrous root system Numerous small roots Adventitious roots Specialized roots grow from other places Leaves and stems corn and epiphytic orchid (aerial roots)

Root Structures Root cap Root hairs Covers apical meristem Produces oil Root hairs Extensions of epidermal cells Increase surface area Dependent on stems and leaves for energy Store starch

Primary Growth in Roots Increase length through cell division of the apical meristem Dermal tissue matures for form the epidermis Ground tissue matures into Cortex Endodermis Large portion of the root is made up of parenchyma cells

Endodermis Inner most boundary of cortex Semipermeable membrane (waxy layer) Controls the flow of dissolved substances

Vascular tissue Makes up innermost core of root Dicots and gymnosperms Xylem makes up central core Usually forming an X Pockets of phloem b/w lobes Monocots Xylem occurs in patches that circle the pith (parenchyma) Phloem occurs b/w the xylem patches

Outermost layer of vascular tissues Pericycle Form lateral roots