Chapter 7 Flashcards
(31 cards)
What are the three organs in plants
- roots
- stem
- leaf
What are the types of plant tissue
- dermal tissue (epidermal and endodermal tissue)
- vascular tissue (xylem and phloem)
- ground tissue
What is ground tissue and what are its types
Ground tissue includes all tissues except vascular bundle and epidermis
- parenchyma
- collenchyma
- sclerenchyma
What are the features of parenchyma, collenchyma, sclerenchyma cells
Parenchyma:
- thin cell wall
- functions: photosynthesis, storage of nutrients, cell division
- examples: some cortical cells, pith cells, mesophyll cells
Collenchyma:
- thicker cell wall
- functions: structural support
- examples: outer cortical cells
Sclerenchyma:
- thickest cell wall (has lignin)
- functions: non-living, only for support
- examples: cortical cells of harder stems / tree branches
What are tissues made of
Tissues are made of many cells
What does vascular tissue include
Xylem and phloem tissue
What are the different types of cells in xylem tissue
- Vessel elements / xylem vessels
- Tracheids
- Fibres
- Parenchyma cells
What are the different types of cells in phloem tissue
- Sieve tube elements (joined end to end to form sieve tubes)
- companion cells
What are the functions of xylem
1.structural support
2. Transport of water from root to leaves to atmosphere
What does the appearance of xylem under the microscope look like
- cell wall have lignin bands, in addition to cellulose
- lignin = strong, hard, waterproof substance
- bands can have different patterns (e.g. rings, spiral, reticulated)
- thicker cell wall observed
- safranine dye stains xylem in red
What are xylem vessels
- also known as vessel elements
- made of elongated cells joined end to end
What are the structural features of xylem vessels
- They are non-living
- They have thick cell walls made of cellulose
- Their cell walls contain lignin
- They have no end walls
- They have a large lumen
- They have pits
Why are xylem vessels non-living
- xylem vessels are non living
- they have no cytoplasm, no organelles and a hollow lumen
- so more space for greater volume of water to flow
- and less resistance to flow of water
Why do xylem vessels have thick cell walls made of cellulose
- thick cell walls made of cellulose
- for structural support
- allows adhesion of water
Why do xylem vessels have cell walls containing lignin
- cell walls contain lignin
- prevents inward collapse as xylem vessel is under tension
- also waterproof to prevent loss of water
Why do xylem vessels have no end walls
- no end walls
- less resistance to flow of water
- forms a continuous tube joined end to end
Why do xylem vessels have a large limes
- large lumen
- large volume of water can be transported
Why do xylem vessels have pits
- pits
- formed from plasmodesmata
- no lignin
- allow lateral (sideways) movement of water
- to connect all parts of plant
- if there’s an air bubble blocking vessel, pits allow water to move out into another xylem vessel and bypass airlock
What is the function of the phloem
- transport of assimilates (substance produced by photosynthesis) (e.g. sucrose, amino acids)
- form source = site of synthesis of photosynthetic products
- to sink = site where assimilates are stores/used
- via translocation
What are sieve tube elements
- elongated sieve elements are joined end to end to form a continuous column = sieve tube
- sieve elements are living cells
What are the structural features of sieve tube elements
- Have many plasmodesmata
- Have strong cellulose walls
- Have few organelles
- Have a peripheral cytoplasm that lines cell walls
- Have sieve plate
- Have many sieve pores
- Cytoplasm of cells are connected
Why do sieve tube elements have many plasmodesmata
- have many plasmodesmata
- allow loading of sucrose from companion cells
- for rapid entry of water near source
Why do sieve tube elements have strong cellulose cell walls
- strong cellulose cell walls
- prevent excessive cell bulging under pressure
Why do sieve tube elements have a few organelles
- has few organelles
- has cellulose cell wall, plasma membrane, few mitochondria and ER only
- has no nucleus, ribosomes, vacuoles
