Shoot And Leaf systems Flashcards
Describe buds. What kind of tissue is found in buds?
Mass of meristematic tissue.
-Cells divide and mature resulting in elongation, enlargement and maturation into stem/flowers/leaves
What is the function of the stem?
Support of the crown
Conduct water and nutrients
What is the terminal bud? What is its role?
Terminal bud is at the end of a shoot and is responsible for elongation.
What is the lateral bud? what does it do?
Forms branches (external origin) forming outside stem.
what is the difference between lateral stems and lateral roots?
Lateral stems arise from buds (outside) the stem.
lateral roots arise from periderm (inside root) internal origin
What are lenticels?
Raised pores on bark that carry out radial gas exchange by connecting to ray cells
What are leaf scars?
Places on the twig where leaves have senesced and the vascular tissue has been severed. The hole is filled by cork to prevent entry of pathogens.
What are bud scars?
Rings of seasonal growth on a twig where bud scales fell away. Can be counted to gauge the age of the twig.
How is bark formed?
Epidermis splits due to secondary growth. New cork cambium arises from cortex to fill the gap and produce new cork cells. The successive layers of cork along with the cork cambium and phelloderm compose the periderm. (Outer bark)
What is cambium?
Continual cylinder of meristematic tissue that gives rise to secondary xylem and phloem.
What is an annual ring?
layer of xylem formed by one years growth. Circumference of cambium increases as more xylem is pushed to the inside each year.
What is cork cambium? What is its function?
Continual cylinder that develops from parenchyma in outer cortex
- produces suberized cork cells that are compacted between the phelloderm and the epidermis.
- Protects inner cells vs. evaporation and injury
What are the differences between woody tissue in gymno/angiosperms?
In xylem angiosperms have Vessel elements and tracheary elements wheras gymnosperms only have tracheary elements.
In phloem angiosperms have seive tube elements with companion cells wheras gymnosperms have sieve cells with albuminous cells
p.s.-albuminous cells can be called companion cells
What is heartwood?
Xylem that has become plugged with protrusions of cells .
Increase in tanins /resins/gums/pigments.
Protects against pathogens
Provides rigid structural support
What is sapwood?
Exterior xylem that still conducts. Living cells.
What are springwood and summerwood?
also referred as early and late wood.
Spring wood
- Inner band of annual xylem ring, lighter in color
- large thin walled cells
Summerwood
- smaller, thick walled cells
- Darker in color
Outline conduction by xylem
- Upward transport of water and dissolved salts from roots to crown
- in early spring xylem will sometimes conduct stored food up from roots to leaves but this is an exception.
Outline conduction by phloem
Downward conduction from leaves to roots
Outline conduction by vascular rays
- extend radially through xylem and into phloem
- function in transverse conduction of water/gas by linking with lenticels
Where Does food storage occur in plants?
Parenchyma of cortex, rays, pith, xylem and phloem. Roots store allot of food but generally food is stored throughout the plant in non green parenchyma.
What are some methods of stems reproducing?
Runners
Rhizome branching - (Bracken fern!)
Formation of new bulbs from old ones
Where do leaves arise and what is their function?
Arise at nodes on a twig and possess a bud at their axil. (lateral meristem)
Mainly function in photosynthesis. (manufacture of food)
What are the two types of epidermal cells and their function?
Epidermis
- Ordinary epidermal cells
- -Protect from dessecration/evap./injury/pathogens
- -secrete cutin
- Guard cells (stomata)
- -occur in pairs and regulate gas exchange. Open in presence of light.
What are the layers of a leaf?
Epidermis
Pallisade mesophyll
Vascular bundles
Spongy mesophyll
What are the two types of mesophyll? how do they differ?
Pallisade mesophyll
- Vertically elongated
- High in chlorophyll
- Parenchyma
Spongy mesophyll
Irregularly spaced, loosely packed cells
also high in chlorophyll
What are veins? What are their function?
Branched continuations of vascular bundles from petiole into mesophyll of leaf.
- Xylem above/Phloem below
- Transport water to leaf and products of photosynthesis down to roots
- Large veins are surrounded by thick walled strengthening cells.
What is the layer that forms over leaf scars when they senesce
Abscission layer
-corky and waterproof (suberized)
What triggers leaves to fall?
Senescence is a process by which a tree goes into dormancy to conserve energy. Triggered by seasonal changes and exposure to red and far red light. Photochrome is the pigment that keeps track of the light and triggers the dormancy response. Before dropping their leaves, trees suck out the remaining nutrients.
