Patterns of Structure and Function in Plants

Patterns of Structure and Function in Plants

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Vascular Plants

• Have transport system– Water – Nutrients

• Allows for larger size

Organization of Vascular Plant

• Below ground root system– Roots for absorption

• Above ground shoot system– Stems & leaves

• Both have growth zones

Tissue Types of Vascular Plants(Differentiated Tissue)

• Vascular tissue– Circulatory system

• Ground tissue– Embeds vascular tissue– Most of plant tissue– Stores carbohydrates

• Dermal tissue– Protective covering

Meristem Tissue(Undifferentiated Tissue)

• Area of cell division• Gives rise to other tissue types• Results in plant growth

Vascular Tissue

• Xylem– Transports

• Water• Nutrients

– Conducting cells• Tracheids • Vessel elements

– Cells die before becoming functional

Vascular Tissue

• Phloem– Conducts

• Carbohydrates • Minerals

– Cells • Sieve-tube members

– Living cells – Cytoplasm, no nuclei

• Companion cells– Nuclei – Secrete into & remove from sieve-tube

members

Ground Tissue

• Three cell types

– Parenchyma cells

– Collenchyma cells

– Sclerenchyma cells

Parenchyma • Photosynthesis and storage

• Thin walled

• Most common cell type

Collenchyma• Support tissue

• Unevenly thickened cells

• Bundles of supportive columns

Sclerenchyma• Help in support and strength

• Dead, hollow cells with thick walls

• Fibers and sclerids

• Covers plant

• Cells– Mostly epidermal (cuticle)– Guard cells

• Surround stomata

– Trichomes • Outgrowths of epidermis

• Bark replaces dermal tissue in woody plants

Dermal Tissue

Meristematic Tissue

• Meristems – Areas of undifferentiated cells– Undergoes mitosis

• Primary growth– At tips of roots & shoots

• Secondary growth– Cylinder of meristematic tissue– Found in woody plants

Organs of Vascular Plants

• Roots

• Stems

• Leaves

Roots• Absorb water & minerals• Anchor the plant• Storage (Some Roots)

Root Tissue Structure

Root Growth• Meristem tissue at tip of root

Root Hairs

• Increase surface area for absorption

Types of Roots

Taproot Prop Root Fibrous Root

Essential Nutrients Delivered by Roots

Need for Nutrients • Plants produce carbohydrates from nonmineral nutrients (photosysthesis)• Need nucleic acids, proteins, fats, & vitamins• These are produced from carbohydrates and mineral nutrients• Nutrient deficiency impairs growth

Stems• Support leaves• Transport fluids• Have many shapes• Storage

Stem Structures

• Nodes – Areas where leaves form on stem

• Internodes – Areas between nodes

• Lateral buds– Side shoots from stem

Stem Transport System

Vascular Cambium

• Growth tissue in woody stems

• New xylem & phloem is formed

Secondary Growth in Woody Stems

Wood of Trees

• Accumulated secondary xylem

• Hardwood – wood of dicot trees

• Softwood – wood of conifers

• Not accurate descriptions of wood density

Tissues in Tree Cross Section

Leaves

• Sites of photosynthesis

• Blade = flattened portion

• Petiole = stalk

Dicot vs. Monocot Leaves• Monocot – veins parallel

• Dicot – net-like

Internal Leaf Structure

Openings in Leaf Tissue• Used for respiration

• Stomata – openings

• Guard cells – regulate opening

Transpiration

• Water exiting leaf openings

• Fluids move by transpirational pull or (adhesion-cohesion-tension theory)– Water evaporates from airspaces within leaves– Water in mesophyle moves into empty spaces– Results in pull of water in xylem– Molecules pulled up (adhesion & cohesion)– Water (by osmosis) and minerals (by active transport)

enter through root

Bulk Flow or (pressure flow)

• Fluid (sap) is also transported by phloem

• Transports products of photosynthesis

• Bulk flow = pressure flow– Companion cells actively transport sucrose into sieve

tube member cells, water follows by osmosis– High pressure develops in phloem near the source– Low pressure in sink (where sucrose is used)– causing the rapid flow of sap

Nonvascular Plants

• No true roots, stems or leaves

• some have stems and leaf-like structures

• Outer layer of epidermis

• Parenchyma cells inside

• Some have central strand of water-conducting cells

• No other vascular tissues

Rhizoids• Anchor some nonvascular plants

• No role in absorption

End chapter 24