f5 chap 6: sexual reproduction in flowers Flashcards
what are the flower’s structures?
peduncles, sepals, petals
whats stamen?
male reproductive organ
whats carpel?
female reproductive organ
what are the similarities of male & female flower parts
both produces gametes, both are located at flower’s organs
what are the differences between male & female flower parts
male flower part: consists of stamen, has filament and anther, produces pollen grains, projecting out from base of ovary
female flower part: consists of carpel, has stigma, style and ovary, produces embryo sac, located in the middle part of flower
what does stamen consist of?
anther, filament
what does carpel consist of?
stigma, style, ovary
explain formation of pollen grains in anther
- 4 pollen sacs is formed in each lobe during development of anther. each pollen sacs has 100s of microspore mother (diploid: 2n)
- microspore mother cell divides by meiosis to produce 4 haploid microspore cells (tetrad)
- each cell in tetrad develops into pollen grain
- nucleus in pollen grain divides by mitosis & produces 2 nuclei: generative & tube
- pollen grains are released when wall of pollen sacs break
explain formation of embryo sac in ovule
- megaspore mother cell divides by meiosis to produce 4 haploid megaspore cells
- 3 of megaspore cells degenerate & only 1 megaspore cell develops
- nucles of cell that has developed, divides mitotically 3 times to produce a cell with 8 nuclei
- 3 nuclei move to one end of embryo sac to form 3 antipodal cells, 3 nuclei move to opposite end of embryo to form 2 synergid cells & 1 egg cell
- 2 nuclei in centre of embryo sac form polar nuclei
pollinating agents that assist in pollination
insects, mammals, birds
formation of pollen tube & male gamete
- wall of anther from mature pollen will
dry, shrink dan split. Pollen grains in the
pollen sac are released. - released pollen grains are transferred
to the stigma of the same flower or different
flowers by pollinating agent. - pollen grains that have been transferred
to the stigma will germinate and form a pollen
tube. The pollen tube grows down towards the
ovule through the style. - generative nucleus will move along the
pollen tube towards the ovule. At the same
time, the generative nucleus will divide by
mitosis to form two male gametes (n). - The end of the pollen tube will secrete an
enzyme to digest the tissues of the style.
function of the 2 male gametes in double fertilisation?
first male gamete: fertilises the egg cell to form a diploid zygote
second male gamete: fuses with polar nuclei to form
triploid endosperm tissue.
what does double fertilisation involve?
2 male gametes
explain double fertilisation in the formation of diploid zygote and triploid nucleus
- When both the male gametes reaches the embryo
sac, the pollen tube will penetrate the ovule through the micropyle. The tube nucleus will degenerate and both male gametes enter the embryo sac. - One of the male gametes fertilises the egg cell and
produces a diploid zygote. The second male gamete fuses with the two polar nuclei to form a triploid endosperm nucleus.
importance of Double Fertilisation for the Survival of
Flowering Plants?
Genetic information is passed down from one generation to the next when fusion of one of the male gametes with the egg cell produces a zygote.
endosperm tissue function?
food storing tissue which surrounds and supplies nutrients to the embryo.
what happens after double fertilisation?
the triploid endosperm nucleus divides by mitosis and form the endosperm tissue.
what are the 2 cells zygote formed by dividing through mitosis
terminal cell, basal cell
zygote divides into larger cell & smaller cell through mitosis during embryo formation. the smaller cell will later become an embryo that consist of?
plumule, radicle and cotyledon
explain development of embryo (flower)
double fertilisation occurs, the triploid endosperm nucleus
divides by mitosis and form the endosperm tissue. zygote divides by mitosis to form two cells, a larger cell and a
smaller cell. The larger cell develops into a suspensor that anchors the embryo to the wall of the embryo sac. The smaller cell will become an embryo that consists of plumule, radicle and cotyledon
explain development of ovary into fruit after fertilisation
The ovule develops to become the seed in the fruit. The integument becomes two layers of seed coat that serves to protect the embryo. During the development of ovule and seed, the ovary develops into a fruit. Other flower parts such as the stigma and style degenerate and leave a scar on the ovary wall
The ovary wall becomes the pericarp of the fruit which consists of the exocarp, mesocarp and endocarp.
what does ovary wall consist of?
exocarp, mesocarp and endocarp.
state 3 importance of seeds for survival
- Seeds contain embryo that germinate to form seedlings.
- Seeds can form a dormant structure which enables the seeds to be stored for a long time.
- Seeds are enclosed by the testa which is strong and water
impermeable to prevent the seeds from spoiling.
what are the special features of seeds?
light, have spongy tissue, strong, doesnt spoil easily
