Exploring Plants Plant Structure & Function

Tissues  Vascular tissue form strands that conduct water, minerals, & nutrients through a plant  Dermal tissue  forms protective outer layer of plant  Ground tissue  consists of roots, stems, & leaves

Dermal Tissue  Dermal tissue forms a “skin”  epidermis  Waxy cuticle that prevents water loss  Dermal tissue on woody stems & roots is made up of dead cells  cork  Dermal tissue also functions in gas exchange

Ground Tissue  Makes up inside of most plants  Ground tissue in leaves, is made up of chloroplasts (used for photosynthesis)  Ground tissue in stems & roots functions in storage of water, sugar, & starch  It also surrounds & supports vascular tissue

Vascular Tissue - 2 types  xylem & phloem - Both act as plumbing system, carrying fluids & dissolved substances through a plant

Xylem  Thick-walled cells that conduct water & mineral nutrients from a plant’s roots, through stems to its leaves  Xylem is made up of vessels  allow water to flow more quickly

Phloem  Cells that conduct sugars & nutrients throughout plant’s body  Conducting strands in phloem are called sieve tubes

Plant Transport

Roots  Plants are anchored down by roots - which absorb water and nutrients  Roots can function in storage of nutrients  Taproot system  large caproot (carrot)  Fibrous system  many roots

Roots  Cortex  ground tissue surrounding vascular tissue  Root Hairs  epidermal cells just behind root tip - increase surface area to absorb water and minerals  Root Cap  mass of cells that covers & protects actively growing root tip

Stems  Shoots of most plants consist of stems & leaves  Stems supports the leaves and house the vascular tissue  Leaves are attached to stems at points called nodes  Space between 2 nodes  internodes

Parts of Plant

Nonwoody Stems  Herbaceous plant  plant with stems that are flexible & usually green  Stems of herbaceous plants contain bundles of xylem & phloem  vascular bundles  Vascular bundles arranged in ring  Ground tissue outside ring  cortex  Ground tissue inside ring  pith

Woody Stems  Trees, shrubs (pines, oaks, roses, & hollies) have woody stems  Woody stems are stiff & non-green  Buds, which form new growth, are found at the tips and at the nodes of woody stems  Heartwood  wood in the center of a mature stem or tree trunk Xylem that can no longer conduct water, provides support Xylem that can no longer conduct water, provides support

Woody Stems  Sapwood  outside heartwood, conducts water with vessel cells

Leaves  Primary photosynthetic organ in plants  Most leaves have flattened portion  blade  Blade attaches to stem by a stalk  petiole  Leaf blade may be divided into 2 or more sections  leaflets  Stomata- tiny holes that allow gas exchange to occur in plants

Movement of Water  Transpiration  loss of water vapor from a plant  More than 90% of water, taken in by roots, is lost by transpiration

Guard Cells & Transpiration  Stoma is surrounded by 2 guard cells  Changes of water pressure in guard cells cause the stoma to open or close  Loss of water from guard cells causes stomata to close, prevents further water loss  Transpiration: loss of water vapor in plants