lecture 9 part 1 Flashcards
sporophyte
A sporophyte is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores from which the gametophyte arises
dominant phase in vascular plants
allows for success of complexity of plants
What is the formal, scientific name for the vascular plants?
tracheophytes
Name the major apomorphies of the vascular plants.
roots
sporophytic leaves in a shoot sysytem
independent, long-lived sporophyte
endodermis
sieve elements (of phloem)
tracheary elements (of xylem)
sclerenchyma
lignin in lignified secondary cell walls
How was the evolution of lignin a major adaptive feature of the vascular plants?
Gave structural support to cells, enabling plants to grow taller, bigger, outcompete others.
What is the difference between a primary and secondary cell wall in terms of time of deposition and
chemistry?
Primary: form during primary growth, as cells are elongating, composed of a primary cell wall of cellulose and pectin.
Secondary: form after cell elongation has ceased, composed of primary and secondary cell walls, the latter containing lignin.
Is the secondary cell wall formed inside or outside the plasma membrane? inside or outside the
primary cell wall?
secondary wall is btwn plasma membrane and primary wall
What are the general characteristics of sclerenchyma cells?
Nonconductive cells that have a thick, lignified secondary cell wall, typically with pits, and that are dead at maturity.
What is the function of tracheary elements?
Tracheary elements:
specialized cells
* Conduction of water and
dissolved mineral nutrients,
generally from the roots to
other parts of the plant
- generally elongated cells, are dead at maturity, and have lignified secondary cell walls.
What is xylem?
the vascular tissue in plants that conducts water and dissolved nutrients upward from the root and also helps to form the woody element in the stem
Name the two types of tracheary elements and cite how they differ structurally
Two types of tracheary
elements – according to the
junction between adjacent
cells
* Tracheids: imperforate,
water and minerals flow
through the primary cell
walls at pits
* Ancestral condition
* Vessels: perforate,
continuous perforations
with no cell wall
interruptions
* Perforation plates
* Evolved independently in
several groups
What is a perforation plate?
large openings in end walls of xylem tissue
The pores help the passage of water through them. Without any pores, there is no possibility of passage of water.
(can be simple/single or compound)
In what taxa are vessels found?
angiosperms and some gymnosperms
What is the function of sieve elements?
Conduction of sugars
* From sugar-rich sources to
sugar-poor sinks (e.g., leaves
or mature storage organs, to
dividing cells, reproductive
organs, or developing
storage organs
What is the phloem comprised of?
sieve elements and parenchyma
What is a sieve area and what compound is associated with them?
Sieve elements: elongated
cells without secondary wall
* Specialized pores aggregated
into “sieve areas”
* Continuous holes in the
primary cell wall
* Tube-like continuum
