What is Growth ? a permanent increase in size, weight & complexity of an organism involves Cell Division (Mitosis) & Cell Enlargement.

What is Growth ?What is Growth ?• a permanent increase in size, weight &

complexity of an organism• involves Cell Division (Mitosis) & Cell

Enlargement

What is Mitosis ?What is Mitosis ?• Mitosis occurs when…

– cell divides during growth– an organism reproduces asexually– repairing a damage part of body

• 2 daughter cells have exactly the same number & kinds of chromosomes as the parent cell

• significance: keep the number of chromosomes constant after cell division

Chromosomes appear as chromatins at resting stage

Stage of MitosisStage of Mitosis

Chromatin threads condense to form distinct chromosomes. The chromosomes become shorter & thicker - each seems to consist of two identical chromati

ds

Stage of MitosisStage of Mitosis

Chromosomes line up in the middle part (equatorial region) of the cell

Stage of MitosisStage of Mitosis

Two chromatids of each chromosome separate & move to oppos

ite poles of the cell

Stage of MitosisStage of Mitosis

The chromatids become chromosomes of the two daughter cells

Stage of MitosisStage of Mitosis

Growth in PlantsGrowth in Plants

• Primary growth– grow in length

• by apical meristem (the plant tissue that retain the ability for cell division)

meristem

Growth in PlantsGrowth in Plants• Secondary growth

– grow in diameter (only in dicotyledonous plants)

– by cambium to produce secondary xylem and secondary phloem which forms annual ring

– cork cambium : to form cork layer to replace the broken epidermis

(6-yrs)

Root Tip (L.S.)

• root cap – to protect the growing point

• region of cell division (growing point)– to increase the number of cells for growth

• region of cell elongation – actual cell elongation region (growth)– about 2 to 4 mm from the tip

Root TipRoot Tip

Root Tip (L.S.)

• region of differentiation– similar cells differentiate to

different tissues• region of root hair (maturation)

– various tissues fully developed– main water absorption area

Root TipRoot Tip

Measurement of Growth in length of

the Main Root using marking ink

Do all parts of the radicle grow during the experiment ?Ans: No. Growth occurs only in the region beh

ind the tip.

pin cork

cotton wool

cork

beaker

strip of filter paperwater

radicle marked at 1mm intervals

Where is the region of maximum growth in the root ?Ans: The region of elongation which is locate

d immediately behind the tip.

pin cork

cotton wool

cork

beaker

strip of filter paperwater

radicle marked at 1mm intervals

Growth Patterns in PlantsGrowth Patterns in Plants

drymass

time

annual plant

biennial plant

Growth Patterns in PlantsGrowth Patterns in Plants

time

drymass

unlimited growth

perennial plant

drymass

time

Growth Patterns in PlantsGrowth Patterns in Plants

Animal GrowthAnimal Growth

• different parts have different growth rate

• eg. the brain grows first in baby• eg. the reproductive system grow

s only at puberty

age

relativegrowth

head & brain

general body

reproductive system

limited growth

Animal GrowthAnimal Growth

How to Measure Growth ?How to Measure Growth ?• by height / length

– defect : do not take into account the growth in other dimensions

• by fresh weight– defect : the amount of water always varies

• by dry weight– defect : too destructive (the organisms die)– defect : too time consuming

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