plants - lecture 2 Flashcards
What are the structure of parenchyma cell walls?
Have thin and flexible primary walls Lack secondary (lignified) walls
What are the functions of parenchyma cells?
- perform the most metabolic functions
- are least specialized
- retain the ability to divide and differentiate
What are the structural features of parenchyma cells?
- large central vacuole
- in leaves they contain chloroplasts
- in stems and roots they contain colourless plastids that store starch
What are the functions of collenchyma cells?
- grouped in strands and help support young parts of the plant shoot
- These cells provide flexible support without restraining growth
What are the cell walls of collenchyma cells like?
- they have thicker and uneven cells walls
- They lack secondary walls
What are sclerenchyma cells like?
rigid with thick secondary walls strengthened with lignin , they are dead at functional maturity
What are the two types of sclerenchyma cells?
- Sclereids
- fibers
What are sclereid cells like?
short and irregular in shape and have thick lignified secondary walls. Found in seed coats, nut shells, and the texture to pear fruits.
What are fiber cells like?
long and slender and arranged in threads
What are the two types of xylem cells?
- tracheids
- Vessel elements
What are tracheid cells?
- common to most plants
- Long, thin, tapered ends
Pitted walls:
for lateral movement of water
What are vessel elements in the xylem?
Higher plants’ (Angiosperms,
more robust (lignified) vascular tissue
Perforated end walls:
primarily for upward movement
How is there movement in plants for water?
Faciliated by transpiration in the day time. Creates a void, osmosis drawn due to this void. Capillary action creates the suction
What is apoplastic movement of water
Primary cells walls with no lignin in them at all. Water moves through the cell walls and the middle lamella.
What does casparian strip do?
prevents movement of water through the apopplatiwc pathway, via a Suberin coat
What is the symplastic movement of water?
through the cells and plasmodesmata
What are the cells making up the phloem?
Sieve tubes
What are meristems?
zones of stems cells which are essential for primary (elongation) and secondary (thickness)
What are the two types of meristem?
- apical
- axillary/lateral
What is the apical meristem for
: RAM (root) and SAM (stem)
What is the axillary meristem for?
SAM (stem)
What do apical meristems look like and where do leaves form from?
- A shoot apical meristem (SAM) is a dome-shaped mass of dividing cells at the shoot tip
- Leaves develop from leaf primordia along the sides of the apical meristem
Where do axillary buds develop from and what do they form?
Axillary buds develop from meristematic cells left at the bases of leaf primordia
Axillary buds give rise to lateral shoots
What are the two layers of mesophyll in eudicots?
- palisade mesophyll
- spongy mesophyll
What are the two phases of a plant life cycle?
- vegetative phase
- Reproductive phase
What is the vegetative phase of the plant life cycle?
indeterminate and determinate growth
What is the Reproductive phase of the Plant life cycle?
Generation of gametophytes
What are cambiums an e example of?
secondary growth
- woody
What is the shape of apical meristems and what type of growth is it?
- Tips of shoots or roots and is dome shaped
- vegetative growth;Mediate primary growth
Mitosis, elongation,
differentiation
What is a SAM
A shoot apical meristem
How is the reproductive phase triggered in a SAM?
Triggered by specific cues Multiple, contributory Redundant Some inhibitory Some activational Control floral patterning Sepals, petals, stamens, stigma
What phase are RAMS, axillary buds and root hairs in?
Always in a vegetative phase
Where does secondary growth occur?
In roots and stems and rare in leaves
In what plant types does secondary growth occur?
- Gymnosperms
- Many eudicots
What can thicken the stem?
Secondary xylem & phloem thicken the stem
What does the cork cambium develop from in secondary development?
from parenchyma cells
What are vascular rays?
radial files of parenchyma connecting secondary xylem & phloem for nutrient & water movement & repair
