Subphylum spermosida THE SEED BEARING PLANTS LIFE CYCLE

Subphylum spermosida THE SEED BEARING PLANTS

LIFE CYCLE: GYMNOSPERM

THE ANGIOSPERMS

THE ANGIOSPERMS In angiosperms the flowers are the structures that are specialized for sexual reproduction. Flowers in mature sporophytes produce male and female gametophytes.

THE ANGIOSPERMS Some plants produce male and female gametophytes on separate plants (willow). Some plants produce male and female gametophytes on different parts of the same plant, some even in the same flower.

THE ANGIOSPERMS Structure of a typical flower

THE ANGIOSPERMS Part Location, Structure & Function 1. Sepal -Outermost circle of flower parts -Green and resemble leaves. -Enclose the flower bud before it opens and protects the flower while developing. 2. Petals -Make up the second circle of flower parts -Usually brightly coloured, produce no gametophytes, called sterile leaves. -Act as an advertisement to attract insects or other pollinators. 3. Stamen -First circle of fertile leaves. -The male part of the flower, consists of the anther and the anther filament.

THE ANGIOSPERMS Part Location, Structure & Function 4. Anther -Produce the male gametophytes : pollen. -Little bags or sacs where pollen is made. 5. Filament -The stalk that supports the anther. 6. Carpels -The centermost circle of the flower. -Produced from rolled up fertile leaves. -These rolled up leaves put the female gametophyte on the inside rather than the outside like gymnosperms. 7. Pistil -One or more carpels form the pistil. -Pistil made up of base (ovary), stalk (style) and stigma at the top of the style.

THE ANGIOSPERMS Part Location, Structure & Function 8. Ovary -Female part of the plant. -At the base of the pistil. -When the eggs are located inside ovules, later it will swell to become fruit. 9. Style -Stalk that supports the stigma. 10. Stigma -Top of the style. -Place where pollen lands during pollination. -Secretes sticky substance to hold pollen.

THE ANGIOSPERMS Angraecum sesquipedale - - This orchid has a nectar tube that is 2530 cm in length. How does it get pollinated?

By this moth! Xanthopan morgani praedicta

Life Cycle Step 1 : The flower is the sporophyte. (Diploid generation -2 N)

Life Cycle Step 2: Within the ovary, ovules (2 N) are produced. The ovules mature to produce a structure (embryo sac) with several nuclei (meiosis occurs). -This is the female gametophyte. -There are 8 nuclei (N). -2 polar nuclei. -The egg will later be fertilized.

Life Cycle Step 3: Within the anther, meiosis occurs to produce pollen grains consisting of 2 nuclei. When mature, the pollen grains are released. - Tube nucleus – will later degenerate. - Generative nucleus – will later divide into 2 sperm nuclei.

Life Cycle Step 4: Pollination occurs – the transfer of pollen from anther to stigma. Types of pollination: A) self-pollination: pollen falls from the anther to the stigma of the same plant. B) cross-pollination: pollen is transferred from the anthers of one plant to the stigma of another plant. A sticky substance on the stigma stimulates the growth of a pollen tube.

Life Cycle Step 5: A pollen tube grows down to the stigma, style, ovary into the ovule. The generative nucleus has divided into 2 sperm nuclei. Now there are 3 nuclei: 2 sperm nuclei and 1 tube nucleus.

Life Cycle Step 6: Sperm are released into the ovule. 1 sperm fertilizes the egg to produce a zygote which later grows into a multicellular embryo. The other sperm fertilizes the 2 polar nuclei which then becomes triploid (3 N). This triploid cell later becomes the endosperm that will be the embryo’s food supply while developing. This is called double fertilization. http: //www. youtube. com/watch? v=X 7 u. H 46 X 0 G 5 Y

Life Cycle Step 7: After fertilization, sepals, petals, and stamens wither. The ovary swells, and the ovule grows. The ovary ripens into the fruit. The ovules mature into seeds which are found within the ovules. Seeds are dispersed by insects, animals, wind and rain.