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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