organisation of plant tissues and growth Flashcards
chapter 1 in biology form 5 syllabus (46 cards)
where are apical meristem located?
at tips of plant shoots & roots
what are lateral meristems?
the consist of vascular cambium & cork cambium
What are the zones of cell growth?
zone of
- cell differentiation
- cell elongation
- cell differentiation
Explain the zone of cell differentiation.
- takes place at apical meristems which actively divide meristem cells through mitosis
- increase no. of cells increases elongation of plant stem
- former cells are pushed to cell elongation zone
give an explanation about zone of cell elongation.
- increase in size through osmosis & nutrients absorption
- vacoulation happens (small vacs form big vac.)
- diffused water exerts pressure against cell wall which pushes, elongates & widens cell
- organelle vac. prominent
What are permanent tissue?
matured tissue which have experienced or are experiencing differentiation.
Types of permanent tissue?
epidermal, ground and vascular
structure epidermal tissue
- layers outermost surface
- cell wall have a waxy waterproof layer (cuticle)
- cuticle reduces loss of water through evaporation
- protects leaves from mechanical injuries & pathogen
Give modified epidermal calls & function.
- GUARD CELL- control opening of stoma
- ROOT HAIR CELL- increase SA of root for water & mineral salts absorption
Structure & function of Parenchyma Tissue?
- thinnest cell walls & don’t differentiate
- in turgid state providing support and maintain shape of herbaceous plants
- helps photo, gas exchange, storage of starch
- repair & regeneration of plant tissue
explain collenchyma tissue structure.
- flexible mature cells
- cell walls made of pectin & hemicellulose
- provide mechanical support & elasticity
what is the structure and function of sclerenchyma? q
- dead matured cells & thickest cell walls
- provide mechanical support & tranpsort of water & nutreints
what is xylem tissue structure and function?
- made of dead cells w/o cytoplasm
- cell wall contain lignin
- vessels elongated, hollow & connected to each other from roots to leaves
transport water & mineral salts
what is phloem tissue structure and function?
- made of companion cells & sieve tubes (w cytoplasm)
- don’t have organelles as they decompose at maturity stage
- transport sugars from photo. to leaves & storage organs
explain cell differentiation
- cells differentiate when reached max. size
- form permanent tissue & change shape and structures
- epidermal cell in leaves diff to guard cells
what is primary growth?
growth that occurs after germination & it take place in all plants to elongate their stems & roots
when does primary growth start?
when meristem cells actively dividing
how does primary growth happens at shoot tips?
leaf primordia & shoot primordia grow to form new leaves and shoots and increase height
how primary growth at root tips?
root cap become exhausted when penetrating soil so root cap cells are replaced by meristem cells
what is secondary growth?
occurs mainly in eudicots & small no. of monocots to increase circumference/diameter of plant stem/root
can eudicots go through secondary growth?
for non-woody plants, 2nd growth doesn’t happen
what does lateral meristem consist of?
vascular cambium & cork cambium
How secondary growth happens in stem?
- Vascular cambium divides actively (mitosis)
- cambium ring cells divide inwards (new xylem) & outwards (new phloem, becomes secondary xylem and phloem
- 1st xylem pushed towards pith & 1st phloem towards epidermis. 1st xylem are compressed to form stronger wood layer because xylem walls are thickened with lignin.
- when 2nd xylem is compressed, circumference is added which cause epidermis of stem to stretch & crack. C.C form crok cells on outes & cortex on inner side. Cork layer protects from insect & pathogen attack when epidermis cracked
how does secondary growth in roots?
- V.C divide inwards to form 2nd xylem & outwards to form 2nd phloem
- V.C divide inwards to form 2nd xylem & outwards to form 2nd phloem
