I placed leek stems of equal thickness and length (3.0cm) into 1%, 2%, 4%, 7% and 10% salt solution. After 25 minutes, I recorded the length of the inner surface (cortex), as shown below.
Pictures:
Results:
Precautions I took:
- I ensured that the leek stems were all fully submerged in the salt solutions.
- I used the same volume (40cm3) of salt solutions for all set-ups.
- I placed the leek stems into the petri-dishes with salt solution at the same time.
Question to think about:
- When we cut the leek stem, why does it curve?
The inner cortex of the leek stem is thin, therefore allowing water to enter and escape easily. However, the outer epidermis of the leek strip is thick and rigid. The inner cortex is also more flexible and can expand or contract easily white the outer epidermis is rigid, waxy and more waterproof. Hence, due to the difference in flexibility of the cortex and the epidermis, the leek stem will bend outwards.
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