2.4 Cell Organisation In Plants

CELL ORGANISATION IN PLANTS

Cell organisation in plants Tissues - two main types: 1. Meristematic tissues 2. Permanent tissues PLANT TISSUES.doc

1. Meristematic tissues Consist of small cells – thin walls, large nuclei, dense cytoplasm and no vacuoles Comprise young & active dividing cells and not undergone differentiation Epical meristems – tip of root and buds of shoots which undergo miotic cell division (increase number of cell) Lateral meristems/cambia – peripheral areas of stems and root which responsible for secondary growth (add girth)

2. Permanent tissues consist of more mature cells which have undergoing differentiation or undergone differentiation 3 main types: a) Epidermal tissues b) Ground tissues c) Vascular tissues

a) Epidermal tissues Characteristics: - forms epidermis - parts that exposed to air are covered with cuticle - flat & have large vacuoles Functions: - the cuticle prevent the loss of excessive water, give protection & prevent invasion - root hair in roots increase the surface area for absorption of water & minerals - guard cells surround the stomata control the opening and closing the stomata

Root hair

Guard cells and stomata

b. Ground tissues Form the bulk of a plant Consist of iii) Parenchyma tissues - thin-walled cell, loosely arrange, have large vacuole - store starch & sugar - turgid and give support & shape to herbaceous plants

ii) Collenchyma tissues - unevenly thickened cell wall (thickened by cellulose & pectin), strong & flexible - support non-woody plants (herbaceous plant), young stems & petioles

iii) Sclerenchyma tissues - much more rigid, have uniformly thickened cell walls by lignin & may be dead - support & strengthens the plant body - provides protection

c. Vascular tissues Involve in the transport of substances between the root & the shoots 2 types:

i) Xylem - consist of xylem vessel extending from the roots to the leaves - cell wall thickened with lignin - transport water & minerals from the root to the leaves

ii) Phloem - consists mainly of sieve tubes which obtain nutrient from the adjacent companion cell - Transport organic nutrient from the leaves to all parts of the plants

Exercise  What are the main types of plant tissues?  Give the location of these tissues:

a) meristematic tissues b) epidermal tissues 7. Give the function of these tissues

a) parenchyma tissues b) xylem

Answers 1. Meristematic tissues 2. Permanent tissues a) Meristematic tissues – tips of the root/buds of shoot/peripheral area of stem b) Epidermal tissues – outermost layers that covers the leaves, stems & roots of young plant, the flowers, fruits & seed a) Parenchyma tissues - store starch & sugar/

give support to herbaceous plants b) Xylem -conducts water & minerals from the root to the leaves

ORGANS Examples: leaf, stem, root & flower Leaf – made up of ground tissues, epidermal tissues and vascular tissues.

SYSTEMS Not as specialised as in animal Have fewer organs 2 main systems:  Root system  Shoot system

Root system main organs are the roots absorptive system highly branched to absorb water & minerals from the soil & transport them to the main vascular system (xylem) – anchor the plant to the ground  – – –

2. Shoot system - main organs are the stems, leaves, buds, flowers & fruits - stems and branches act as support system, holding the leaves in a position that facilitate maximum absorption of sunlight & position flower for pollination - leaves are main photosynthesis system, the product transported via phloem to other parts of plants - flowers are the reproductive system of the plant which produce fruits and seeds

EXERCISE  Complete the table below: Organs a. Leaves

b. Stems and branches c. Flowers d. Roots

Function

Answers Organs a. Leaves

b. Stems and branches c. Flowers d. Roots

Function The site of photosynthesis act as support system • involved in pollination absorptive system anchor the plant to the ground

Things we have learn PLANT CELL ORGANISATION.doc