organisation of plant tissues and growth Flashcards
chapter 1 in biology form 5 syllabus
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
how to know age of plants living in temperate cilmate?
- based on annual growth rings in stem
- 2nd growth happens at diff, rates according to seasons
- spring, enough water supply, & sunlight, 2nd xylem is bigger and thinner wall, the colour is brighter
- summer, smaller and thicker walls and darker in colour
Example of monocots?
draceana sp.
aloe sp.
agava sp.
What are the importance of primary growth?
- allows max elongation of plants to absorb sunlight
- transport products of photosynthesis
- transport water & mineral salts
- provide support
What are the importance of secondary growth to plants?
- provide stability by increase stem & root diameter to suit plants height
- provide mechanical support
- replace old and damaged vascular tissue
- able to live longer by increasing chances of seed production
What are the similarities between primary growth?
- increase plant size permanently
- occur in woody plants
- involve cell division (mitosis)
differences between 1st and 2nd growth?
direction of growth
1st; longtidunally
2nd; radially
presence of woody tissue
1st; doesn’t have
2nd; have
presence of annual ring
1st; absence
2nd; present
what is the economic importance of secondary growth plants?
- have strong & hard woods as structures for houseboats, etc
- presence of annual rings makes furniture look attractive & decorative items
- commercialised fruits (mangoes, mangosteen) generate income & boost economic growth
what are the types of life cycles?
annual, biennial and perennial
what is annual plants?
plants that have only one life cycle for a season or a year. die after completing biological cycle
example of annual plants
paddy plant, pumpkin & watermelon
what is biennial plants?
plants which take 2 years with 2 seasons of growth to complete their life cycle
how do biennial plants grow?
- First growth season is vegetative growth (roots,stems & leaves growth) while the second is reproduction. They briefly stop growth process during winter.
- During spring & summer, growth continues as preparation of reproduction by flowering. They produce fruits & seeds and die
example of biennial plants?
grow in temperate regions like cabbage, carrot
what is perennial plants?
plants which live more than two years & can be classified to two types; woody and herbaceous. They are able to flower & bear fruits many times & have structures that are adaptable to surroundings & temp. changes
example of perennial plants
grass, hibiscus, mango
why dry mass decrease in stage A at annual plant growth curve?
food stored in cotyledon is used for germination before the leaves emerge to carry out photosynthesis
why constant dry mass in growth curve?
- the rate of growth is zero
- plant is matured at this stage
Growth curve of biennial plants is consist of?
two sigmoid curves.
explain the two seasons of biennial plants growth curve.
first growth season
- plants produce leaves, photo.
- food is stored in tubers
second growth season
- the food stored is used to produce flowers and seeds.
the growth curve of perennial plants consist of?
a series of small sigmoid curves.
How is rate of growth in spring and summer?
- rate of growth is high
- high light intensity increase rate of photosynthesis.
how is rate of growth in winter?
rate of growth decrease in winter.
