 Plants reproduce sexually, often relying on pollinators to bring sperm and egg together.  The sporophyte (diploid) develops from the zygote by mitosis; it consists of roots, stems, leaves, and flowers  Meiosis of cells within flowers produces the small haploid gametophytes, which in turn produce either sperm or eggs.

 The specialized parts of the flower grow from the modified end of the floral shoot – the receptacle.  Sepals: (collectively called the calyx) are the outermost green, leaflike parts.  Petals (collectively called the corolla) are the colored parts of located between the reproductive structures and the sepals.

 Flowers differ from the other tissues of the plant in their fragrance and colors (Carotenoids and anthocyanins), which are attractive to pollinators.

 Male parts – called stamens are located inside the corolla  Stamen consist of a slender stalk (filament) capped with an anther  Inside the anthers are pollen sacs in which pollen grains develop  Look at the previous picture to see the male parts in a diagram

 Female parts are located in the central part of the flower  Carpel is the vessel-shaped structure with an expanded lower chamber (ovary), slender column (style) and upper surface (stigma) for pollen landing.  In ovary eggs develop, fertilization occurs and seeds mature.  Refer to diagram

 Perfect flowers have both male and female parts (may or may not be on the same plant)  Imperfect flowers is missing one of the sex

 In anthers, each diploid “mother” cell divides by meiosis to form four haploid microspores.  Each microspores will divide to form pollen grains  One cell in each pollen grain will produce the sperm; the other will form the pollen tube

 In carpel, a mass of tissue forms an ovule (potential seed) enclosed by integuments.  A diploid “mother” cells divides by meiosis to produce haploid megaspores, one of which will undergo mitosis three times to produce a cell with eight nuclei  The nuclei migrate resulting in an embryo sac (female gametophyte) with seven cells; one cell has two nuclei and will become the endoperm (nutrition for embryo); another cell will be the egg

 Pollination is the transfer of pollen to the surface of the stigma by the actions of insects, birds, or other agents.  In germination, a pollen tube forms producing a path that the two sperm will follow to the ovule.

 When the pollen tube reaches an ovule, it penetrates the embryo sac, and the two sperm are released.  One sperm fuses with the egg nucleus to form a diploid zygote  The other sperm nucleus fuses with the two endoperm nuclei to yield a triploid “Primary endosperm cell” that will nourish the young sporophyte seedling.

 The zygote undergoes repeated divisions to form an embryo sporophyte as a part of an ovule and is accompanied by formation of fruit.  Cotyledons (seed leaves) develop for the purpose of utilizing the endosperms during germination  Cotyledons (seed leaves) develop for the purpose of utilizing the endosperms during germination.

 From zygote to embyro, the plant supplies nutrition until the time when the connection between the ovule and ovary wall is broken  The mature ovule integuments thicken inot seed coats around the seed (a mature ovule containing embryo and food reserve)

 Embryo is inactive  Seed dehydrates (5 -15% water)  Embryo surrounded by endosperm, enlarged cotyledons or both

 A fruit mature ovary with seeds (ovules) inside; they may be classified as simple aggregate, multiple or accessory.  The pericarp of a fruit consists collectively of endocarp (around the seed), mesocarp (fleshy portion), and exocarp (the skin)

 Immature fruit protects the seed (green, bitter, sour, etc.)  Mature fruit aids in dispersal (colorful and tasty)  Forms from ovary  Does not provide nutrient for seeds

 Seeds have coevolved with particular dispersing agents – currents of air or water, or animals passing by  Example: Pericarp of maple seeds extends out like wings to catch the wing and be transported  Some fruits are dispersed by sticking on animal bodies or by passing through the digestive tract to be deposited in the feces  Humans are perhaps the grand dispersing agents by virtue of the long distances to which they carry seeds

 Seed frequently undergo a period of dormancy. WHY???  Requires water, oxygen, and warm temperatures  Root emerges first. WHY AGAIN?

 Vegetative growth modes includes: runners, rhizomes, corms, tubers, and bulbs.  Parthenogenesis, embryo development from an unfertilized egg, can produce new orange plants.

 Vegetative propagation (“Cuttings”) can result in new plants produced from leaves that form roots.  Tissue Culture propagation can result in whole plants produced from a group of cells.

 THE END!!