1.

D

2.

D

The one megaspore cell divides once to give two daughter cells, these then divide (division two) to give four and these divide (division three) to give eight cells. [What are the names of those cells (or nuclei)?]

3.

B

The pollen tube delivers a tube nucleus and two cells, the sperm cells. One sperm cell fuses with the egg to give the embryo, which is diploid. The other sperm cell fuses with the two polar nuclei to give the endosperm, which is triploid. What does the endosperm do? A: the tube nucleus disintegrates after the pollen tube has reached its distinction. C: the synergids are present in the embryo sac with the egg and polar nuclei; their function is unclear but they could place a role as nurse cells for the egg or take its place if it is damaged.

4.

B

The ovule becomes the seed; the ovary part of the carpel becomes the fruit. It is the egg, along with one sperm cell, that forms the embryo (A). The stima and style (B) are part of the carpel along with the ovary--what roles do they perform? Zygote and endosperm (D) are the products of double fertilization, see 8.

5.

C

Fly pollinated flowers often smell of rotting meat and have no distinctive color; their dish shape allows the flies to roam around collecting and depositing pollen. Red colored flowers are often bird pollinated (A) and yellow petals, nectar guides and a sweet odor often mean bee pollination. No petals, hairy stigmas and much pollen is wind pollination (D). Refer to the handouts for this material.

6.

C

Unripe or immature fruits has as its mission the protection of the young seed. A specialized feature of the papaya immature fruit is the production of papain in laticifers. When the fruit ripens, the latex and enzyme break down. (How and why does this occur?) The other features given, pretty colors (A), sweet taste due to glucose (B) and cellulase and pectinase production to soften the fruit (D) are all characteristic of fruit after ripening when they want to attrack animals to disperse the seeds.

7.

B

The hypocotyl is the region connecting the shoot of the embryo (with its cotyledons and young shoot apex) and the radicle (with its young root apex). This connecting region must persist throughout the entire life of the plant--although it changes greatly due to secondary growth. (Be sure to know what secondary growth is.) The cotyledon (A) and the suspensor (C) are embryonic organs that function for only a short period and then die. The seed coat (D) is strictly speaking, not an embryonic organ--it is formed from the integuments that surround the ovule and are part of the ovary--that is, they come from maternal tissue.

8.

C

Grasses and cereals are monocots and have one cotyledon. In cereals and grasses, it is modified: the cotyledon is rolled so that it grows out like a tube which pushes up from the seed deep in the soil. The young and tender shoot can then grow through the tube during germination and not be torn by soil particles. The bending of the coleoptile towards light, as in other phototropic bending, is caused by auxin (indoleacetic acid) moving more to the dark side than to the light and causing more cell elongation on the dark side.

9.

B

Gibberellic acids causes cell elongation and stem elongation in genetically drawf plants. Auxins (A) like indolecacetic acid will not cause cell elongation when sprayed on intact plants. Neither abscisins (C) or zeatin (D), a cytokinin, causes much plant elongation.