Plant Structure Willow shoot

Plant Parts

Monocot vs Dicot

1.Dermal tissue 2.Vascular tissue 3.Ground tissue Plant organs are composed of three tissue systems:

Plant Cell Structure cell wall chloroplastchloroplast nucleusnucleus central vacuole

Cell Wall Structure middle lamella primary cell wall secondary cell wall

Cell Wall Structure plasmodesmataplasmodesmata

Plant Cell Types XylemXylem –Tracheids –Vessel elements PhloemPhloem –Sieve-tube members –Companion cell XylemXylem –Tracheids –Vessel elements PhloemPhloem –Sieve-tube members –Companion cell

Vascular tissue: runs continuous throughout the plant transports materials between roots and shoots. –Xylem transports water and dissolved minerals upward from roots into the shoots. (water the xylem) –Phloem transports food from the leaves to the roots and to non-photosynthetic parts of the shoot system. (feed the phloem) Vascular Tissue

The water conducting elements of xylem are the tracheids and vessel elements. Xylem

XylemXylem TracheidsTracheids –Characteristics tapered elongated cellstapered elongated cells connect to each other through pitsconnect to each other through pits secondary cell walls strengthened with ligninsecondary cell walls strengthened with lignin dead at functional maturitydead at functional maturity –Functions transport of water plus dissolved mineralstransport of water plus dissolved minerals supportsupport TracheidsTracheids –Characteristics tapered elongated cellstapered elongated cells connect to each other through pitsconnect to each other through pits secondary cell walls strengthened with ligninsecondary cell walls strengthened with lignin dead at functional maturitydead at functional maturity –Functions transport of water plus dissolved mineralstransport of water plus dissolved minerals supportsupport

Xylem Vessel ElementsVessel Elements –Characteristics shorter and wider than tracheidsshorter and wider than tracheids possess thinner cell walls than tracheidspossess thinner cell walls than tracheids Aligned end-to-end to form long micropipesAligned end-to-end to form long micropipes dead at functional maturitydead at functional maturity –Functions transport of water plus dissolved mineralstransport of water plus dissolved minerals supportsupport Vessel ElementsVessel Elements –Characteristics shorter and wider than tracheidsshorter and wider than tracheids possess thinner cell walls than tracheidspossess thinner cell walls than tracheids Aligned end-to-end to form long micropipesAligned end-to-end to form long micropipes dead at functional maturitydead at functional maturity –Functions transport of water plus dissolved mineralstransport of water plus dissolved minerals supportsupport

Water conducting cells of the xylem

Food and minerals move through tubes formed by chains of cells, sieve-tube members. –sieve plates –companion cell Phloem

PhloemPhloem Sieve-tube MembersSieve-tube Members –Characteristics living cells arranged end-to-end to form food- conducting cells of the phloemliving cells arranged end-to-end to form food- conducting cells of the phloem lack lignin in their cell wallslack lignin in their cell walls mature cells lack nuclei and other cellular organellesmature cells lack nuclei and other cellular organelles alive at functional maturityalive at functional maturity –Functions transport products of photosynthesistransport products of photosynthesis Sieve-tube MembersSieve-tube Members –Characteristics living cells arranged end-to-end to form food- conducting cells of the phloemliving cells arranged end-to-end to form food- conducting cells of the phloem lack lignin in their cell wallslack lignin in their cell walls mature cells lack nuclei and other cellular organellesmature cells lack nuclei and other cellular organelles alive at functional maturityalive at functional maturity –Functions transport products of photosynthesistransport products of photosynthesis

PhloemPhloem Companion CellsCompanion Cells –Characteristics living cells adjacent to sieve-tube membersliving cells adjacent to sieve-tube members connected to sieve-tube members via plasmodesmataconnected to sieve-tube members via plasmodesmata –Functions support sieve-tube memberssupport sieve-tube members may assist in sugar loading into sieve-tube membersmay assist in sugar loading into sieve-tube members Companion CellsCompanion Cells –Characteristics living cells adjacent to sieve-tube membersliving cells adjacent to sieve-tube members connected to sieve-tube members via plasmodesmataconnected to sieve-tube members via plasmodesmata –Functions support sieve-tube memberssupport sieve-tube members may assist in sugar loading into sieve-tube membersmay assist in sugar loading into sieve-tube members

Food conducting cells of the phloem

Ground tissue fills the interior of the plant. It contains three basic cell types: –Parenchyma cells –Collenchyma cells –Sclerenchyma cells Ground Tissue Dermal tissue Vascular tissue Ground tissue

Parenchyma CharacteristicsCharacteristics –least specialized cell type –only thin primary cell wall is present –possess large central vacuole –generally alive at functional maturity FunctionsFunctions –make up most of the ground tissues of the plant –storage –photosynthesis –can help repair and replace damaged organs by proliferation and specialization into other cells CharacteristicsCharacteristics –least specialized cell type –only thin primary cell wall is present –possess large central vacuole –generally alive at functional maturity FunctionsFunctions –make up most of the ground tissues of the plant –storage –photosynthesis –can help repair and replace damaged organs by proliferation and specialization into other cells

Parenchyma

CollenchymaCollenchyma CharacteristicsCharacteristics –possess thicker primary cell walls the that of parenchyma –no secondary cell wall present –generally alive at functional maturity FunctionsFunctions –provide support without restraining growth CharacteristicsCharacteristics –possess thicker primary cell walls the that of parenchyma –no secondary cell wall present –generally alive at functional maturity FunctionsFunctions –provide support without restraining growth

Collenchyma

SclerenchymaSclerenchyma CharacteristicsCharacteristics –have secondary cell walls strengthened by lignin –often are dead at functional maturity –two forms: fibers and sclereids FunctionsFunctions –rigid cells providing support and strength to tissues CharacteristicsCharacteristics –have secondary cell walls strengthened by lignin –often are dead at functional maturity –two forms: fibers and sclereids FunctionsFunctions –rigid cells providing support and strength to tissues

Two other sclerenchyma cells, fibers and sclereids, are specialized entirely in support. –Fibers are long, slender and tapered, and usually occur in groups. Those from hemp fibers are used for making rope and those from flax for weaving into linen. –Sclereids, shorter than fibers and irregular in shape, impart the hardness to nutshells and seed coats and the gritty texture to pear fruits.

Fiber Cells

Sclereids

Meristems – embryonic tissue. –These cells divide to generate additional cells. –Initials- generative cells that remain in the meristem. –Derivatives- Those that are displaced from the meristem,and continue to divide for some time until the cells they produce begin to specialize within developing tissues. Plant Growth & Development

Apical meristems: located at the tips of roots and in the buds of shoots, supply cells for the plant to grow in length. –Primary growth initial root and shoot growth produced by apical meristem elongation occurs restricted to youngest parts of the plant, i.e, tips of roots & shoots Locations of Meristematic Tissues

–Secondary growth: thickening of roots and shoots. Produced by lateral meristems Develop in slightly older regions of roots and shoots Examples: vascular and cork cambium. Lateral meristems: allow the plant to increase in girth Locations of Meristematic Tissues

Meristems

Types of Primary Meristems Protoderm: forms dermal tissue systemProtoderm: forms dermal tissue system Procambium: forms vascular tissue systemProcambium: forms vascular tissue system Ground Meristem: forms ground tissue systemGround Meristem: forms ground tissue system Protoderm: forms dermal tissue systemProtoderm: forms dermal tissue system Procambium: forms vascular tissue systemProcambium: forms vascular tissue system Ground Meristem: forms ground tissue systemGround Meristem: forms ground tissue system

Root Cap: covers root tip & protects the meristem as the root pushes through the abrasive soil during primary growth. –The cap also secretes a lubricating slime. Growth in length is concentrated near the root ’ s tip, where three zones of cells at successive stages of primary growth are located. –zone of cell division –zone of elongation –zone of maturation Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Primary Growth in Roots

The procambium gives rise to the stele, which in roots is a central cylinder of vascular tissue where both xylem and phloem develop. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Stele

Dicot RootMonocot Root

Monocot Root Anatomy cortex epidermis endodermis pith phloem xylem pericycle cortex pith stele

Dicot Root Anatomy cortex epidermis endodermis phloem xylem pericycle cortex stele

Plant Shoot

Primary Growth of the Shoot

Stem Anatomy

Monocot StemDicot Stem

Monocot Stem Anatomy epidermis vascular bundles ground tissue xylem phloem parenchyma sclerenchyma

Dicot Stem Anatomy vascular cambium vascular cambium xylem pith cortex epidermis vascular bundle phloem

Anatomy of a Tree Trunk After several years of secondary growth, several zones are visible in a stem.

Leaf Anatomy

Typical Dicot Leaf X-Section Palisade Parenchyma Spongy Parenchyma Vascular bundles Epidermis Cuticle Stoma Guard Cells

Typical Monocot Leaf X-Section Xylem Phloem Bulliform Cells Stoma Epidermis Midvein Vein Bundle sheath cell

Leaf Stomata: Allow Gas Exchange Guard cells Stoma