Chapter 38 textbook notes

Chapter 38 textbook notes - Chapter 38 I Flowers Double...

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Chapter 38 I. Flowers, Double Fertilization, and fruits are unique features of the Angiosperm Sporophyte (diploid) produces haploid spores by MEIOSIS These spores then divide by MITOSIS, giving rise to multicellular gametophytes which are the male and female haploid plants that produce gametes (egg and sperm) Fertilization- fusion of gametes; results in DIPLOID zygotes, which then divide by MITOSIS to form new sporophytes In angiosperms, the sporophyte us the dominant generation Angiosperm life cycle: o Flowers o Double Fertilization o Fruits A. Flower Structure and Function Flowers- reproductive shoots of angiosperm sporophyte o Composed of the floral organs o Have determinate shoots stops growing Floral organs: all attached to the receptacle o Sepals- sterile o Petals-sterile o Stamen- reproductive organ o Carpel- reproductive organ Sepals- enclose and protect the floral bud; usually more green than petals Stamen- consists of the filament and anther (within the anther are microsporangia that produce pollen) Carpel- has an ovary at the base and a long slender neck called the style o At the top of the style is a stick structure called the stigma that’s serves as landing platform for pollen
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o Pistil us a term used to refer to a single carpel or group of carpels Complete flowers- have all 4 floral organs Incomplete Flowers- lack one or more of the floral organs (grass does not contain petals) 1. Development of Male Gametophytes in pollen grains Each anther contains 4 microsporangia (pollen sacs) Within the microsporangia, there are many diploid cells call microsporocytes (microspore mother cells) Each microsporocyte undergoes MITOSIS, producing a male gametophyte consisting of only 2 cells: generative cell and tube cell Generative cell, tube cell, and spore wall constitute a pollen grain During Maturation, the generative cell passes into the tube cell and the spore wall is complete After microsporangium breaks open and releases pollen, a pollen grain may be transferred to a receptive surface of a stigma There, the tube cell produces the pollen tube -long cellular protuberance that delivers sperm to the female gametophyte As pollen tube elongates through the style, the generative cell usually divides and
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