Post on 29-Dec-2015
Plant tissue types:
• Dermal: – epidermis (outer skin) with
waxy cuticle lining made of cutin
• Vascular: – xylem and phloem cells for
transport
• Ground: – tissues between the dermal
and vascular
• Meristem: – growth cells
dermalvascularground
Ground tissues
• Parenchyma: – primary wall (soft)
• Collenchyma:– unevenly thickened primary wall
(flexible)
• Sclerenchyma: – primary wall + thick secondary wall
(rigid)
Vascular tissue: xylem cells
• Conducts (transports) water and minerals from roots to leaves
• Tracheids: – long and thin
(mostly in gymnosperms)
• Vessel elements: – short and wide
(mostly in angiosperms)– Dead when mature!
Vascular tissue: phloem cells
• Sieve tube elements:– anucleated (no nucleus)
when mature, “empty” cell to conduct sugars
• Companion cell:– nucleated, controls the
activities of the sieve tube cell
• Sieve plate: – separates sieve tube
elements in the sieve tubes
Types of Root Systems (p.584)
• Fibrous =– many, spreading,
branching roots– good for binding
soil to prevent erosion
Types of Root systems
• Taproot =– one long, main
root from which all others branch
– good for growing toward water source
Types of Root systems
• Adventitious =– specialized roots
that grow above ground
– Ex: aerial rootsor prop roots
Regions of the Root Tip
• Root Cap = – covers and protects the
delicate cells in the meristematic region
• Meristem Region (region of cell division) – area where new cells are
created by mitosis
Regions of the Root Tip
• Region of Elongation – area where cells grow in length
• Region of Differentiation (maturation) – area where cells become specialized for different jobs,
I.e. storage, protection, transport, etc.
Inner Layers of Roots• Epidermis = outer
layer of cells, for protection and absorption
• Cortex = inside epidermis, main storage area of roots
• Endodermis = single layer of cells that controls flow of water into the vascular cylinder
Vascular Cylinder
• Xylem = innermost star-shaped cells for transporting water upward
• Phloem = small bundles between rays of star, for transporting food down to cortex for storage
• Pericycle = cells between others that give rise to secondary (lateral) roots
Types of Stems (p.590)
Herbacious = soft, green & short-lived Ex: tomato plants
Woody = hard, brown & long-lived Ex: trees & shrubs
Parts of a twig
• Node = point of growth along a twig
• Internode = spaces between nodes
• Lateral buds = buds along the side of the twig; may be for new leaves, flowers or branches
• Terminal buds = buds at the end of the twig; only for extending length of stem
• Bud-scale scar (determines age of twig)
Herbacious Stems• Epidermis = outer layer, for
protection• Cortex = below epidermis, for
storage• vascular bundles =
contain phloem (outside) & xylem
(inside) • Arrangement: radially around
cambium in dicots & randomly scattered in monocots
• Pith = innermost; for storage
Woody Stems
• BARK consists of four layers:
• 1) CORK = rough, outermost; for insulation
• 2) CORTEX = below cork; for storage
• 3) PHLOEM= “arching” through cortex; for carrying food downward
• 4) CAMBIUM = inner layer; gives rise to secondary growth (outward)
Woody Stems
• WOOD consists of only XYLEM = transports water upward
• 1) Sapwood = outer, lighter, still active(the “sap” is still flowing)
• 2) Heartwood = inner, darker, inactive(this area is “dead” & may only provide support)
• PITH (young stems) for storage
External features of leaf
• Blade =– flat green portion
• Petiole =– supporting stalk
(dicots)
• Veins = – vascular tissue
(parallel in monocots & branching in dicots)
Internal features of leaf (p. 596)• Cuticle =
– waxy covering to prevent water loss (not a cell layer)• Epidermis =
– single protective layer without chloroplasts for sun to shine through
• Mesophyll = – central layers where photosynthesis occurs
Mesophyll layers
• Palisade = – elongated tightly
packed cells near top of dicot leaf where most of photosynthesis occurs
• Spongy = – irregularly packed cells
with air spaces for gas exchange to occur
Vascular tissue within veins
• Xylem = – transports water & minerals upward from the
roots to the leaves (to be used during photosynthesis)
• Phloem =– transports food downward from the leaves to
the roots (for storage)
• Guard cells = – kidney-shaped cells in lower epidermis that
regulate the opening and closing of the stomata (only epidermal cells with chloroplasts)
(p. 596)
• Stomata = – openings for the exit of water & oxygen and the
entrance of carbon dioxide
Transpiration (p.600)
• Water absorbed by roots by osmosis
• Water sticks to other molecules by cohesion & adhesion
• Water moves up xylem by capillary action
• Water is pulled out of leaf by evaporation process called transpiration