Chapter 6 - Stems Flashcards
Anatomy of a woody twig
- Nodes
- Internodes
- Leaves
- Axiallary bud
- Terminal bud
Leaves
- Petiole (Sessile)
- Blade
- Stipules ( estipulate)
- Axil - the angle between leave and stem. Inside is the axillary bud
- Leaf scar - when leaf brakes off.
Terminal bud
- bigger than the axillary bud
- Apical meristem
- Bud scales - grow to protect buds. has antifreeze. there are bud scale scars that distinguish from last years growth to this year
Shoot apical meristem at growing tip:
- Protoderm - formed from posteior part
- Ground meristem -
- Procambium - forms vascular bundles. (Stele)
Stele Patterns
- Protostele - xylem in center and phloem around it
- Siphonostele - pith is in the center and vascular tissues are around it
- Eustele - common in flowering plants
Procambium
- stele patterns
- leaf and bud gaps
Origin of secondary growth
Vascular cambium
Cork cambium
Vascular Cabimum
- in Dicots
- Between primary xylem and phloem
- Divide horizontally
- Form secondary xylem (inside) & phloem (outside), between is the vascular cambium
Bulb vs. Corm
In a Corm the food is stored in the stem itself, not the leaves.
Cladophyll
Photosynthetic stem/Branch, usually flat
examples; prickly pear cactus, broccoli, asparagus
Thorns, Spines and prickles
Thorns are modified stems.
Spines are modified leaves.
Prickles are an outgrowth of the epidermis
Tendril
a specialized stem that wraps around objects. It can be a modified stem.
Tissue Patterns in Stems
- Herbaceous Dicots
- Woody Dicots & Conifers
- Monocots
Herbaceous Dicots
- Almost all growth is primary
- Vascular bundles in cylinder
- Have rays of parenchyma
Woody Dicots & Conifers
EFFECT OF CELL DIVISION IN VASCULAR CAMBIUM
- Cambium cells divide laterally
- Ring of vascular tissue forms, gaps for rays
- Xylem
- Phloem
—Crushed or to cork cambium
— Lactifers - secrete latex, milky white substance example: rubber and gum
- Vascular rays - living parenchyma cells, rays cells extend multiple year. Conducts water and dissolves nutrience.
- Resin Canals
Vascular Rays
XYLEM rays
- Conducts Water & nutrience from xylem
- Food Storage
- Transport waste to old xylem
— Tyloses
— Heartwood
— Sapwood
PHLOEM rays
Resin Canals
Resin poses out of the tree for protective purposes
Example: Frankensence and myrrh
Effect of cell division in Cork Cambium
Forms somewhat unevenly and forms islands of cork cambium
The cork cambium has to be renewed from within.
Components of Bark
- Inner bark: Phloem + cambium
- Outer bark: Cork cambium + cork
Monocots - Vascular bundles scattered throughout stem:
- Surrounded by parenchyma
- Xylem toward center of stem
- Only sieve tube elements and companion cells
- No vascular cambium
- Surrounded by bundle sheath
- Some have extra sclerenchyma tissue
- Some have intercalary meristems
Specialized Stems
- Rhizomes
- Stolons
- Tubers
- Bulbs
- Corms
- Cladophylls
- Thorns
