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Vascular Plant Organization

• Comprises two main systems:

  • Root System: Absorbs water and nutrients from the soil.

  • Stem System: Supports the plant and facilitates nutrient transportation.

Vascular Tissue

• Conducts fluids such as water and dissolved minerals throughout the plant.

• Consists of multiple cell types.

  • Meristem:

    • Located at tips of stems and roots.

    • Composed of small cells with large nuclei; referred to as stem cells in plant biology.

    • Capable of self-renewal and differentiation into specialized cells.

  • Important for growth and development of primary tissues.

Cell Differentiation and Gene Expression

• Meristem cells undergo changes in gene expression to differentiate into various cell types.

• They maintain the potential to become specialized cells while also producing more meristem cells.

Root Structure

• Longitudinal section shows growth patterns from root to stem.

• Roots are delicate structures, needing protection.

• Visuals from lab observations demonstrate root hairs increasing surface area for absorption.

Dermal Tissue

Function is to provide protection and facilitate absorption.

• Guard Cells:

  • Found in leaves and help regulate gas exchange through stomata.

  • Important for photosynthesis and respiration.

• Trichomes:

  • Hairs found on leaves and roots for protection and sometimes aid in absorption.

• Root Hairs:

Ground Tissue Types

• Parenchyma:

  • Living cells involved in storage and photosynthesis.

• Collenchyma:

  • Provides support while allowing flexibility; living cells.

• Sclerenchyma:

  • Provides rigidity; has thick, dead cell walls at maturity for structural support.

Vascular Tissue Function

• Xylem:

  • Responsible for transporting water and dissolved minerals from roots to other parts of the plant.

  • vessels → continuous tubes of dead cylindrical cells

  • Tracheids → dead cells, tape, and overlap one another

• Phloem:

  • Transports sugars and nutrients produced during photosynthesis.

  • sieve cell

  • Companion cells

• Both xylem and phloem play crucial roles in plant physiology and nutrient transfer.

Root Anatomy

• Cortex: Exterior layer, involved in storage and transport.

• Endodermis: Contains the Casparian strip, controlling the flow of water and nutrients into the vascular system.

• Pericycle: Layer just inside the endodermis, allows for the growth of lateral roots.

• Zone of cell division: derived from rapid divisions of the root apical Maristem

  • Contains mostly cuboidal cells with small vacuoles and large nuclei

  • Protoderm, procambium, and ground meristem

• Zone of elongation: roots, lengthen, because cells becomes several times longer, no further elongation above this zone

• Zone of maturation: elongated cells become differentiated in specific cell types

  • Root surface cells become epidermal cells (thin cuticle, root hair, and non-root hair cells)

  • Cells produced by cortex (ground meristem)

    • Inter boundary becomes endodermis (Casparian strips)

    • Stele → tissues, interior to endodermis (pericycle)

Stems

• Contains the three plant tissues (dermal, ground, vascular)

• Undergo growth from cell division and apical + lateral stems

• Shoot apical meristem initiates stem tissue + intermittently produces primordia

External stem structure

• Node → point point of attachment of leaf to stem

• Internode → area of stem between two nodes

• Blade → flattened part of leaf

• Petiole → stalk that attaches the leaf blade to the stem

• Axil → the upper angle between the leaf stalk and the stem, often where buds or branches may develop.

• Axilary bud → develops into branches with leaves, or may form flowers

• Terminal bud → extends the shoot system during growing season

Monocot vs. Dicot Stems

• monocot → vascular bundles are usually scattered throughout ground tissue system

• dicot stems → vascular tissue is arranged in a ring with internal ground tissue (pith) and external ground tissue (cortex)

Vascular Tissue Arrangement

directly related to stems ability for secondary growth

• Dicots → a vascular cambium develops between the primary xylem and phloem

  • Connects the ring of primary vascular bundles

• Monocot → no vascular cambium – no secondary growth

Growth Rings and Aging

• Growth rings in trees represent annual growth and can be counted for aging.

• Terminal Bud Scale Scars: Indicate past longitudinal growth patterns.

Lenticiles

Cork cambium produces unsuberized cells that permit gas exchange to continue

Leaves

• Initiated as primordia by the apical meristems

• Principal site of photosynthesis

• Expand by cell enlargement and cell division

• Determinate in structure – growth stops at maturity

• Different patterns adaptive in different environments

Leaf Morphology

• Microphyll → Leaf with one vein branching from the vascular cylinder of the stem and not extending the full length of the leaf

• Megaphylls → several to many plant, most plants

Eudicot Leaves

• flattened petiole (slender stalk)

• leaf flattening increases photosynthesis

Leaf Epidermis

• surface covered by transparent epidermal cells (most w/ no chloroplasts)

• waxy cuticle

  

Mesophyll in Eudicots and Monocots

Dicot

• Palisade mesophyll → usually two rows of tightly packed chlorenchyma cells

• Spongy mesophyll → loosely arranged cells with many air spaces in between

  • Function in gas exchange and water vapor exit

    

Monocot

• not differentiated into palisade/spongy layers

3 tissues table

Dermal Ground Vascular

epidermal (everywhere) parenchymal xylem

guard cells (leaves) sclerenchyma (dead at maturity) - vessels: small

trichomes (leaves) collenchymal - traicheds: big

root hairs phloem

- sieve cells

- companion cells