Chapter 44 Plant Reproduction and Development Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc Chapter 44 At a Glance 44 1 How Do Plants Reproduce 44 2 What Is the Function and Structure of the 44 3 How Do Fruits and Seeds Develop 44 5 How Do Plants and Their Pollinators Flower Interact Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 1 How Do Plants Reproduce Many plants can reproduce either sexually or asexually During asexual reproduction part of an existing plant uses mitotic cell division to produce a new plant Asexually produced offspring therefore are genetically identical to the parent Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 1 How Do Plants Reproduce The plant sexual life cycle alternates between diploid and haploid stages The sexual life cycles of organisms vary in the timing of when mitotic and meiotic cell division occur and whether the adult body forms are haploid or diploid The plant sexual life cycle is called alternation of generations because it alternates between two distinct multicellular reproductive stages one diploid and one haploid that give rise to each other Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 1 How Do Plants Reproduce Alternation of generations In angiosperms flowering plants the multicellular diploid form is called the sporophyte In angiosperms sporophytes are the plants of gardens orchards forests and fields that produce flowers The diploid body form is called a sporophyte or spore bearing plant because it produces specialized reproductive cells often called mother cells that undergo meiotic cell division to form haploid cells called spores In angiosperms spores are formed in the male and female reproductive structures of the flower Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 1 How Do Plants Reproduce Why are these cells spores and not gametes Gametes do not divide rather they fuse to form a diploid cell the zygote Spores do not fuse to form a diploid cell instead spores undergo mitotic cell division to produce a multicellular haploid body form called the gametophyte the gamete bearing plant Angiosperms and gymnosperms conifers and their relatives produce separate male and female gametophyte stages Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 1 How Do Plants Reproduce Alternation of generations continued In some other types of plants a single gametophyte may produce both sperm and eggs although in separate reproductive structures In either case some of the cells of the gametophyte differentiate into sperm or eggs because they are already haploid the cells of the gametophyte can produce gametes without going through meiotic cell division Eggs are retained within the female reproductive structures so sperm must travel to the egg usually either by swimming through a film of water mosses and ferns or carried within a pollen grain gymnosperms and angiosperms Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 1 How Do Plants Reproduce Alternation of generations continued A sperm fertilizes an egg producing a diploid zygote The zygote undergoes repeated mitotic cell divisions followed by differentiation of the resulting daughter cells to form an embryo and eventually a new adult sporophyte plant Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 1 How Do Plants Reproduce Alternation of generations continued Although alternation of generations is the sexual life cycle of all plants the relative size complexity and life span of the sporophyte and gametophyte stages vary considerably among different types of plants In mosses and liverworts the gametophyte stage is an independent plant that dominates the life cycle Sperm fertilize eggs that are retained in the gametophyte Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 1 How Do Plants Reproduce Alternation of generations continued The resulting zygote develops into a sporophyte that grows directly on the gametophyte and relies on the gametophyte for nourishment The sporophyte is never an independent plant In ferns as in mosses and liverworts sperm fertilize eggs retained in an independent gametophyte and the zygote begins growing on the gametophyte However eventually the sporophyte develops its own roots and leaves and becomes the dominant stage of the life cycle the fern commonly seen in moist shady woods Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 2 What Is the Function and Structure of the Flower Flowers are the reproductive structures of angiosperms Flowers are the sexual reproductive structures of angiosperms produced by the diploid sporophyte A complete flower such as that of a petunia rose or lily consists of four sets of modified leaves the sepals petals stamens and carpels Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 2 What Is the Function and Structure of the Flower Flowers are the reproductive structures of angiosperms continued There are two groups of flowering plants the dicots and monocots The sepals are located at the base of the flower In dicots sepals are usually green and leaflike In monocots sepals typically resemble the petals In either case sepals surround and protect the flower bud as the remaining three structures develop Just above the sepals are the petals which are often brightly colored and fragrant advertising the location of the flower to potential pollinators Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 2 What Is the Function and Structure of the Flower Flowers are the reproductive structures of angiosperms continued The male reproductive structures the stamens are attached just above the petals Each stamen usually consists of a slender filament bearing an anther that produces pollen In the center of the flower are one or more female reproductive structures called carpels A typical carpel is somewhat vase shaped with a sticky stigma mounted atop an elongated style Pollination occurs when pollen from an anther of a stamen lands on the stigma of a carpel Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 44 2 What Is the Function and Structure of the Flower Flowers are the reproductive structures of angiosperms continued The style connects the stigma with the bulbous ovary at the base of the carpel Inside the ovary are one or more ovules a female gametophyte develops inside each ovule After fertilization each
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