Two ways a seedling emerges

Seed germination occurs in two main ways. The difference is a single question: do the seed leaves come up out of the soil, or stay behind in it?

Hypogeal germination

The seed germinates and the plumule emerges above the soil, but the seed leaves remain within the soil.

The seed leaves and the endosperm supply the stored food needed for the growth of the seedling in its early stage, but the seed leaves do not produce food by photosynthesis.

The seeds of most monocotyledonous plants show hypogeal germination.

Examples — coconut, maize.

Figure to be added

Figure 14.19 a — hypogeal germination: a maize grain with its seed leaf staying below the soil while the shoot rises above it.

Epigeal germination

The seed germinates and, together with the plumule emerging above the soil, the seed leaves are raised above the soil as well.

Further, in addition to supplying the stored food needed for the growth of the seedling in its early stage, the seed leaves produce food by photosynthesis.

The seeds of most dicotyledonous plants show epigeal germination.

Examples — bean, tamarind.

Figure to be added

Figure 14.19 b — epigeal germination: a bean seed with its two seed leaves carried up above the soil and opening out.

Above ground, so they may as well work

The two differences are really one. Seed leaves that are lifted into the light can photosynthesise, so they do; seed leaves left in the dark cannot, so they only feed the seedling and then wither. The position decides the job.