Angiosperm Seed Structure

_____________________________ – a mature ovule containing an embryo, and bound by a protective seed coat.

Embryonic plant – A young sporophyte consisting of epicotyl, hypocotyl,

radicle, and one or more cotyledons.

Seeds contain embryonic plants in a dormant state. Seeds have the following structures…

_____________________________ – the outer, protective boundary layer of a seed; developed from the integument(s) of the ovule.

_____________________________ – a pore or opening in the integuments of an ovule (that will develop into a seed) through which a pollen tube gains access to an embryo sac or archegonium of a seed plant.

a. Later, when the seed matures and starts to germinate, the

micropyle serves as a minute pore through which water enters.

_____________________________ – a small scar that marks the point at which the ovule was attached to the ovary wall (In seeds, the funiculus serves as the “umbilical cord” between the parent plant & the developing seed. The hilum is the scar from the funiculus, equivalent to our bellybutton).

_____________________________ – food-storage organ for the embryonic plant that also function as the first “seed leaves” of the seedling plant. (Remember that monocots have only one cotyledon, dicots have two.)

a. Remember that the baby plant can’t photosynthesize & make its own

food until it emerges from the soil. Therefore, the seed must store some

food for the baby plant until it can fend for itself.

b. _____________________________ – Storage tissue surrounding the

embryo in flowering plants; provides nourishment to the developing

embryo. (In some plants, like corn, the cotyledon(s) don’t supply a

significant amount of food to the embryonic plant. The endosperm serves

as the bulk of the food-storage tissue.)

_____________________________ – the terminal bud of the embryo of a seed plant (located at the upper end of by embryo axis, it has undeveloped leaves and a meristem).

_____________________________ – the very short part of the stem of the embryonic plant above the cotyledon(s).

_____________________________ – the portion of the embryonic stem located under the cotyledons & above the radicle.

_____________________________ – the embryonic root in a developing plant embryo.

______________________________ is the absorption of water by a seed that results in the seed swelling and the seed coat splitting.

Below are diagrams of a bean seed. In the image on the left, the bean has the seed coat still on, and is viewed from the top. In the image on the right, the bean is viewed in a cross section. Please label the indicated structures using terms from the previous page.

Below is a diagram showing the germination of three seed types. We are especially interested in the following…

a) The garden bean is a dicot. Notice that the cotyledons (the bulk of the seed) emerge from the soil during germination and become “seed leaves.” The embryonic plumule provides the first true leaves.

b) A garden pea germinating – not of particular interest to us at this time.

c) The corn seed is a monocot. Kindly notice that the cotyledons have been used during production of the embryonic plant. The endosperm stores food for germination. Also notice the coleorhizae and coleoptiles, structures which are note present in dicots. Further, notice that when the monocot germinates, the bulk of the seed remains in the soil.