Seed Formation in Gymnosperms & Angiosperms

Mosses and other nonvascular plants Fig. 30-2a Mosses and other nonvascular plants Gametophyte Dominant Reduced, dependent on gametophyte for nutrition Sporophyte Sporophyte (2n) Gametophyte (n) Example Figure 30.2 Gametophyte/sporophyte relationships in different plant groups

Ferns and other seedless vascular plants Fig. 30-2b Ferns and other seedless vascular plants Reduced, independent (photosynthetic and free-living) Gametophyte Sporophyte Dominant Sporophyte (2n) Example Figure 30.2 Gametophyte/sporophyte relationships in different plant groups Gametophyte (n)

Seed plants (gymnosperms and angiosperms) Fig. 30-2c Seed plants (gymnosperms and angiosperms) Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Gametophyte Sporophyte Dominant Gymnosperm Angiosperm Microscopic female gametophytes (n) inside ovulate cone Microscopic female gametophytes (n) inside these parts of flowers Microscopic male gametophytes (n) inside these parts of flowers Example Figure 30.2 Gametophyte/sporophyte relationships in different plant groups Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n) Sporophyte (2n)

Fig. 30-2 PLANT GROUP Mosses and other nonvascular plants Ferns and other seedless vascular plants Seed plants (gymnosperms and angiosperms) Reduced, independent (photosynthetic and free-living) Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Gametophyte Dominant Reduced, dependent on gametophyte for nutrition Sporophyte Dominant Dominant Gymnosperm Angiosperm Sporophyte (2n) Microscopic female gametophytes (n) inside ovulate cone Microscopic female gametophytes (n) inside these parts of flowers Sporophyte (2n) Gametophyte (n) Example Figure 30.2 Gametophyte/sporophyte relationships in different plant groups Microscopic male gametophytes (n) inside these parts of flowers Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n) Sporophyte (2n) Gametophyte (n)

Pollen and Production of Sperm Microspores develop into pollen grains, which contain the male gametophytes Pollination is the transfer of pollen to the part of a seed plant containing the ovules Pollen eliminates the need for a film of water and can be dispersed great distances by air or animals If a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule

The Evolutionary Advantage of Seeds A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat Seeds provide some evolutionary advantages over spores: They may remain dormant for days to years, until conditions are favorable for germination They may be transported long distances by wind or animals

Key Haploid (n) Diploid (2n) Pollen cone Mature sporophyte (2n) Fig. 30-6-1 Key Haploid (n) Diploid (2n) Pollen cone Microsporocytes (2n) Mature sporophyte (2n) Pollen grains (n) MEIOSIS Microsporangia Microsporangium (2n) Figure 30.6 The life cycle of a pine

Surviving megaspore (n) Fig. 30-6-2 Key Haploid (n) Ovule Diploid (2n) Ovulate cone Megasporocyte (2n) Integument Pollen cone Microsporocytes (2n) Mature sporophyte (2n) Megasporangium (2n) Pollen grain Pollen grains (n) MEIOSIS MEIOSIS Microsporangia Microsporangium (2n) Surviving megaspore (n) Figure 30.6 The life cycle of a pine

Key Haploid (n) Ovule Diploid (2n) Ovulate cone Megasporocyte (2n) Fig. 30-6-3 Key Haploid (n) Ovule Diploid (2n) Ovulate cone Megasporocyte (2n) Integument Pollen cone Microsporocytes (2n) Mature sporophyte (2n) Megasporangium (2n) Pollen grain Pollen grains (n) MEIOSIS MEIOSIS Microsporangia Microsporangium (2n) Archegonium Figure 30.6 The life cycle of a pine Female gametophyte Sperm nucleus (n) Pollen tube FERTILIZATION Egg nucleus (n)

Surviving megaspore (n) Seedling Fig. 30-6-4 Key Haploid (n) Ovule Diploid (2n) Ovulate cone Megasporocyte (2n) Integument Pollen cone Microsporocytes (2n) Mature sporophyte (2n) Megasporangium (2n) Pollen grain Pollen grains (n) MEIOSIS MEIOSIS Microsporangia Microsporangium (2n) Surviving megaspore (n) Seedling Archegonium Figure 30.6 The life cycle of a pine Seeds Female gametophyte Food reserves (n) Sperm nucleus (n) Seed coat (2n) Pollen tube Embryo (2n) FERTILIZATION Egg nucleus (n)

Seed coat (derived from integument) Fig. 30-3-3 Seed coat (derived from integument) Food supply (female gametophyte tissue) Figure 30.3c From ovule to seed in a gymnosperm Embryo (2n) (new sporophyte) (c) Gymnosperm seed

Angiosperms Angiosperms are seed plants with reproductive structures called flowers and fruits They are the most widespread and diverse of all plants

Flowers The flower is an angiosperm structure specialized for sexual reproduction Many species are pollinated by insects or animals, while some species are wind-pollinated

A flower is a specialized shoot with up to four types of modified leaves: Sepals, which enclose the flower Petals, which are brightly colored and attract pollinators Stamens, which produce pollen on their terminal anthers Carpels, which produce ovules

(Male) Stigma Carpel (or Pistil) Stamen Anther Style Filament Ovary Fig. 30-7 (Female) (Male) Stigma Carpel (or Pistil) Stamen Anther Style Filament Ovary Figure 30.7 The structure of an idealized flower Petal Sepal Ovule

Video: Flower Blooming (time lapse) A carpel (or pistil) consists of an ovary at the base and a style leading up to a stigma, where pollen is received Video: Flower Blooming (time lapse)

Animation: Fruit Development Fruits A fruit typically consists of a mature ovary but can also include other flower parts Fruits protect seeds and aid in their dispersal Mature fruits can be either fleshy or dry Animation: Fruit Development

Tomato Ruby grapefruit Nectarine Hazelnut Milkweed Fig. 30-8 Tomato Ruby grapefruit Nectarine Figure 30.8 Some variations in fruit structure Hazelnut Milkweed

Various fruit adaptations help disperse seeds Seeds can be carried by wind, water, or animals to new locations

Wings Seeds within berries Barbs Fig. 30-9 Wings Seeds within berries Figure 30.9 Fruit adaptations that enhance seed dispersal Barbs

The Angiosperm Life Cycle The flower of the sporophyte is composed of both male and female structures Male gametophytes are contained within pollen grains produced by the microsporangia of anthers The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma Most flowers have mechanisms to ensure cross-pollination between flowers from different plants of the same species

The Angiosperm Life Cycle (cont) A pollen grain that has landed on a stigma germinates and the pollen tube of the male gametophyte grows down to the ovary The ovule is entered by a pore called the micropyle Double fertilization occurs when the pollen tube discharges two sperm into the female gametophyte within an ovule

The Angiosperm Life Cycle (cont) One sperm fertilizes the egg (now a zygote (2n)), while the other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm (3n) The endosperm nourishes the developing embryo Within a seed, the embryo consists of a root and two seed leaves called cotyledons

Mature flower on sporophyte plant (2n) Microsporocytes (2n) Fig. 30-10-1 Key Haploid (n) Diploid (2n) Microsporangium Anther Mature flower on sporophyte plant (2n) Microsporocytes (2n) MEIOSIS Generative cell Microspore (n) Tube cell Male gametophyte (in pollen grain) (n) Pollen grains Figure 30.10 The life cycle of an angiosperm

http://bio.rutgers.edu/~gb101/lab8_angio_repro/8a3m-microgpyt.html Each microspore divides by mitosis to form two haploid nuclei (the tube nucleus and the generative nucleus); A diploid microsporocyte, or microspore mother cell, divides to give rise to four haploid microspores. After landing on the stigma, the pollen germinates forming a pollen tube; the generative nucleus then divides by mitosis to form two haploid sperm nuclei.

Mature flower on sporophyte plant (2n) Microsporocytes (2n) Fig. 30-10-2 Key Haploid (n) Diploid (2n) Microsporangium Anther Mature flower on sporophyte plant (2n) Microsporocytes (2n) MEIOSIS Generative cell Microspore (n) Ovule (2n) Tube cell Male gametophyte (in pollen grain) (n) Ovary Pollen grains MEIOSIS Megasporangium (2n) Megaspore (n) Antipodal cells Central cell (or polar bodies that form endosperm) Synergids Egg (n) Figure 30.10 The life cycle of an angiosperm Female gametophyte (embryo sac)

http://bio.rutgers.edu/~gb101/lab8_angio_repro/8a3m-microgpyt.html The remaining megaspore nucleus undergoes three mitotic divisions to form eight haploid nuclei. A diploid megasporocyte (megaspore mother cell) undergoes meiosis, giving rise to four haploid megaspore nuclei (3 of which disintegrate). Nuclear migration and cytokinesis occur to form the mature megagametophyte

Mature flower on sporophyte plant (2n) Microsporocytes (2n) Fig. 30-10-3 Key Haploid (n) Diploid (2n) Microsporangium Anther Mature flower on sporophyte plant (2n) Microsporocytes (2n) MEIOSIS Generative cell Microspore (n) Ovule (2n) Tube cell Male gametophyte (in pollen grain) (n) Ovary Pollen grains MEIOSIS Stigma Megasporangium (2n) Pollen tube Sperm Megaspore (n) Style Antipodal cells Central cell Synergids Egg (n) Figure 30.10 The life cycle of an angiosperm Female gametophyte (embryo sac) Pollen tube Sperm (n) FERTILIZATION Egg nucleus (n) Discharged sperm nuclei (n)

Mature flower on sporophyte plant (2n) Microsporocytes (2n) Fig. 30-10-4 Key Haploid (n) Diploid (2n) Microsporangium Anther Mature flower on sporophyte plant (2n) Microsporocytes (2n) MEIOSIS Generative cell Microspore (n) Ovule (2n) Tube cell Male gametophyte (in pollen grain) (n) Ovary Pollen grains MEIOSIS Germinating seed Stigma Megasporangium (2n) Pollen tube Embryo (2n) Endosperm (3n) Seed coat (2n) Sperm Seed Megaspore (n) Style Antipodal cells Central cell Synergids Egg (n) Figure 30.10 The life cycle of an angiosperm Female gametophyte (embryo sac) Pollen tube Sperm (n) Nucleus of developing endosperm (3n) FERTILIZATION Zygote (2n) Egg nucleus (n) Discharged sperm nuclei (n)

Practice!!! http://bio.rutgers.edu/~gb101/lab8_angio_repro/index.html