Exam 2 Flashcards
(122 cards)
Sources and Sinks
Sources - Areas where certain molecules are FORCED INTO phloem by pumps
Sinks- areas where pumps of phloem EXTRACT molecules
Sieve Elements/members
Describes both types of conducting cells in phloem.
The two sieve elements are sieve cells and sieve tube members.
Sieve Cell
The conducting cells of the phloem of nonangiosperms.
Don’t have sieve plates like sieve tubes do, and all sieve areas are small and uniformly spread on all walls.
Sieve Pores
The actual small hole in the primary wall of a sieve area, through which hte cytoplasm of one sieve element is in contact with the cytoplasm of the next.
Sieve Areas
Modified primary pit fields in the wals of sieve elements.
Mediate transfer of nutrients from one sieve element to the next.
the plasmodesmata have been modified into sieve pores.
Sieve Plates
The end wall of a sieve tube member.
Simple Sieve Plates
sieve plate that has only a single sieve area
Compound Sieve Plate
A sieve plate that has more than one sieve area
Sieve Tube
A long, multicellular structure composed of many sieve tube members interconnected by their sieve plates.
Companion Cells
A cytoplasmic cell in the phloem of angiosperms. The have extensive cytoplasmic connections to the enucleate sieve tube members and are thought both to control their metabolism and to participate in the loading and unloading of nutrients.
Albuminous Cells
Same as companion cells, but these are found in nonangiosperms
Intermediary Cells
A type of parenchyma cell in the phloem of many angiosperms. Intermediary cells are responsible for the loading and unloading of nutrients into the adjacent sieve elements.
Refractive Spherules
A small round body that occurs in the sieve elements of many cryptogams
Nacreous Layer
A layer of opalescent wall material in sieve elements
Callose
A polymer of glucose with Beta (1-3) glycosidic bonds that is present in sieve elements; when the element is damaged, the callose precipitates and contributes to sealing the wound.
Connecting Strand
The strand of cytoplasm that runs through a sieve pore, connecting the protoplasm of one sieve elements with that of the adjacent sieve element
Mictoplasm
Watery cytoplasm that results when the vacuolar membrane breaks down during sieve element development and the cytoplasm mixes with the contents of the vacuole.
P-Type Plastids
A special type of plastid that occurs in sieve tube members; these plastids contain protein.
S-Type Plastids
A special type of plastid that occurs in sieve tube members; these plastids contain starch.
P-Protein
The protein filaments that occur in sieve elements, formerly called slime.
P-Protein Plug or slime plug
When the element is damaged and surging occurs, the P-protein forms a plug over the sieve area formerly called a sieve plug
Wound Callose
Sieve elements contain large amounts of callose which is pressure sensitive; When the element is damaged and surging begins, the callose precipitates and contributes to the plugging action
Def: Callose penetrates many areas and actually fills the sieve pores in response to injury.
Definitive Callose
When a sieve elements has completed its functioning, the cell collapses and the callose precipitates naturally and seals the sieve area completely
Nectary
A gland or trichome that secretes nectar (sugar water)
