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My name is Poon Cheng Moh. I have been teaching biology in SMK(P) Raja Zarina, Port Klang for 26 years. I sincerely hope that this blog on SPM Biology will be useful to both teachers and students.

Saturday, August 11, 2012

Answers to Hands-on Pg 50-53


Aim : To study the growth pattern of maize plant (Zea mays)

Variables : Manipulated variable : Time of growth
                   Responding variable : Mass of seedlings
                   Fixed variable : Amount of water, fertilizer

Time (weeks)
Mass of 3 seedlings (g)
Mean mass of 1 seedling (g)
Fresh
Dry
Fresh
Dry
0
0.90
0.60
0.30
0.20
1
0.60
0.45
0.20
0.15
2
0.90
0.60
0.30
0.20
3
1.20
0.90
0.40
0.30
4
2.40
1.80
0.80
0.60
5
4.20
3.15
1.40
1.05
6
6.00
5.25
2.00
1.75
7
8.85
7.50
2.95
2.50
8
11.40
10.20
3.80
3.40
9
14.10
13.20
4.70
4.40
10
15.30
14.70
5.10
4.90
11
15.90
15.00
5.30
5.00
12
16.20
15.30
5.40
5.10

Draw a graph based on the above table

Discussion :
  1. Sigmoid growth curve
  2. Week 5 to week 8
  3. Growth rate is negative from the beginning of the activity ti week 1.  This is because the germinating seeds use food stored in the endosperm.  Week 1 to wek 4 shows slow growth rate because young leaves are starting to grow and photosynthesis has just begun.  Week 5 – 8 shows highest growth rate.  The growth rate slows down from week 8 onwards because the plant has reached maturity.
Conclusion :
The growth pattern of the maize seedling represented by a graph of the mass of maize seedlings against time is a sigmoid curve. The hypothesis is accepted.

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