Growth

We often ask pupils to investigate the conditions necessary for the growth of seeds, but we need to distinguish between germination and growth. Most pupils would agree that water and warmth are required. Many would suggest that light is also necessary. But this is not so for germination (although, in some cases, for example poppies, it acts as a regulator, like frost, in triggering germination). Seedlings require light to photosynthesise once the seed has produced its first leaves. Until this stage, light is of little use because there is no chlorophyll available for photosynthesis. The seed needs oxygen to respire its food reserves in order to germinate and then to grow. When pupils set up conditions for plant growth investigations, we need to be clear whether they are investigating the growth of seedlings (light needed) or germination of seeds (light not needed).

Teaching point. Seeds can be collected from trees in the autumn. Some can be put in the freezer for a week, and others left in the classroom. All seeds are then planted in warm, moist conditions, and pupils can see which germinate most successfully. They can also consider the advantage of germinating only after a big freeze.

TABLE 14.1 Fruit, vegetable or seed?

SCIENTIFIC

KITCHEN

CLASSIFICATION

CLASSIFICATION

FOOD

PART OF PLANT

Vegetable

Fruit

Seed

Vegetable

Fruit

Nut

Tomato

Ovary (fleshy)

Rhubarb

Stem

Cucumber

Ovary (fleshy)

Potato

Stem

Onion

Leaf - bulb

Plum

Ovary (fleshy)

Beetroot

Root

Apple

Receptacle (fleshy)

Carrot

Root

Melon

Ovary (fleshy)

Coconut

Seed

Hazelnut

Seed

Runner bean

Ovary (fleshy)

Sweetcorn

Seed

Cauliflower

Flower

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