Ali soaks a bean seed and a grain of maize overnight…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Ali soaks a bean seed and a grain of maize overnight. He peels the bean and splits it, and he cuts the maize grain along its length. (a) How many cotyledons does each have? (b) Which of the two keeps a bulky endosperm? (c) Which part of the maize embryo is the cotyledon? (d) Name the sheath over the young root of the maize embryo. (e) Name the scar on the bean seed coat.
Need a reminder? The key ideaShow
A fruit is a mature ovary; a parthenocarpic fruit forms without fertilisation, as in banana. The pericarp has epicarp, mesocarp and endocarp. Mango and coconut are drupes from a monocarpellary superior ovary, with one seed. A seed has a seed coat (testa and tegmen), hilum, micropyle and an embryo. Dicot seeds such as gram and pea have two cotyledons and no endosperm; castor keeps endosperm. Maize has a membranous coat fused with the fruit wall, a bulky endosperm, an aleurone layer, one cotyledon called the scutellum, the coleoptile and the coleorhiza.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The cotyledons. The bean, a dicot, has two. The maize, a monocot, has one.
Step 2. The endosperm. The maize grain keeps a bulky endosperm. The bean seed has none, so it is non-albuminous.
Step 3. The maize cotyledon. It is the shield-shaped scutellum.
Step 4. The sheath. The young root is covered by the coleorhiza.
Step 5. The scar. The scar on the seed coat of the bean is the hilum.
Answer: (a) bean two, maize one; (b) maize; (c) the scutellum; (d) the coleorhiza; (e) the hilum.
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