lecture 17

Question 1

explain the process of double fertilization

Answer 1

1. the pollen grain adheres to the stigma, which contains two cells: a generative cell and a tube cell
2. the pollen tube cell grows into the style. the generative cell travels inside the pollen tube. it divides to form two sperm
3. the pollen tube penetrates an opening in the ovule called a micropyle
4. one of the sperm fertilizes the egg to form the diploid zygote. the other sperm fertilizes two polar nuclei to form the triploid endosperm, which will become a food source for the growing embryo

Question 2

what is embryonic development controlled by?

Answer 2

precise cell division, cell elongation and differentiation

Question 3

endosperm abundance in dicots

Answer 3

endosperm is consumed/used up during embryo development. nutrients is instead stored in large cotyledons

Question 4

what is the seed coat?

Answer 4

the outer layer of a seed; develops from the maternal integuments of the ovule

Question 5

what is the embryo?

Answer 5

a young, diploid sporophyte plant, produced by mitotic divisions of the zygote within the ovule

Question 6

what is the endosperm?

Answer 6

a triploid tissue, containing stored food that is absorbed by the embryo before or after seed maturation; unique to angiosperms

Question 7

what is the purpose of seed dormancy?

Answer 7

provides a mechanism for plants to delay germination until conditions are optimal for survival of the next generation

Question 8

endosperm abundance in monocots

Answer 8

endosperm persists, forming an abundant supply of food that surrounds the embryo in mature seeds