* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Traits shared by charophyceans and land plants The first land plants
Photosynthesis wikipedia , lookup
Gartons Agricultural Plant Breeders wikipedia , lookup
Plant stress measurement wikipedia , lookup
Plant tolerance to herbivory wikipedia , lookup
Plant secondary metabolism wikipedia , lookup
Plant nutrition wikipedia , lookup
Plant use of endophytic fungi in defense wikipedia , lookup
Plant defense against herbivory wikipedia , lookup
History of herbalism wikipedia , lookup
Venus flytrap wikipedia , lookup
History of botany wikipedia , lookup
Plant breeding wikipedia , lookup
Plant physiology wikipedia , lookup
Historia Plantarum (Theophrastus) wikipedia , lookup
Ornamental bulbous plant wikipedia , lookup
Plant ecology wikipedia , lookup
Plant morphology wikipedia , lookup
Perovskia atriplicifolia wikipedia , lookup
Plant evolutionary developmental biology wikipedia , lookup
Flowering plant wikipedia , lookup
Sustainable landscaping wikipedia , lookup
Evolutionary history of plants wikipedia , lookup
Figure 29.1 Some highlights of plant evolution Traits shared by charophyceans and land plants • Very similar plastids (structurally similar, but especially similar chloroplast DNA) • Very similar cellulose cell walls (cellulose is even produced by a similar rose-shaped structures) • Anti-photorespiration enzymes packaged in peroxisomes • Similar structure of flagellated sperm • Similar structures during cell division (phragmoplasts) Figure 29.7 Land plant evolution. Figure 29.2x Chara The first land plants: bryophytes (“non-vascular” plants) 1. Traits shared by land plants, and lacking in the charophyceans 2. The earliest land plants: bryophytes (mosses, liverworts, hornworts) Figure 29.5 Land plant trait #1: Apical meristems, which are localized regions of cell division at the tips of shoots (left) and roots (right) 1 Figure 29.4 Land plant trait #2: Multicellular, dependent embryos, which develop from zygotes contained within tissues of the female parent. Parental tissues provide nutrients for the embryo. Land plants are also known as the embryophytes. Figure 29.6 Land plant trait #3: Alternation of generations life cycle, with two very different generations (one usually much larger & more prominent). Some algae also have alternation of generations, but not the charophyceans. Embryo Maternal tissue Figure 29.6 Land plant trait #4: Walled spores produced by a multicellular sporangium. A polymer called sporopollenin, the most durable organic material known, makes up the walls. Figure 29.5 Sporangium of a moss (a bryophyte) sporophyte Figure 29.5 Land plant trait #5: Gametangia, multicellular organs that produce gametes. Note: the most modern land plants, the flowering plants, do not have gametangia. Figure 29.9 Land plant trait #5: Gametangia, multicellular organs that produce gametes. Shown below are the Archegonium (egg-producing organ) of Marchantia (left), and the Antheridium (sperm-producing organ) of a hornwort (right). Note: the most modern land plants, the flowering plants, do not have gametangia. 2 Land plant trait #6: Specialized epidermis for water conservation, including a cuticle and stomata. Cuticle of a stem from Psilotum (a pteridophyte) is shown below. Figure 36.14 Guard Cells regulate water loss through opening and closing of stomata. guard cell stomate Land plant trait #7: Adaptations for water transport, especially vascular tissue. Found in all land plants except for most bryophytes. The stem of Polypodium, a fern (a pteridophyte), is shown below. Note: true leaves, stems, and roots are defined by the presence of vascular tissues. Land plant trait #7: Adaptations for water transport, especially vascular tissue. Found in all land plants except for most bryophytes. The stem of Polypodium, a fern (a pteridophyte), is shown below. Note: true leaves, stems, and roots are defined by the presence of vascular tissues. true vascular tissues contain lignin Land plant trait #8: Secondary compounds: a diversity of chemicals with many functions related to living on land, including protection from UV radiation, signaling with symbiotic bacteria, deterring attack by pathogens or herbivores, and providing structural support. Quinine, a secondary compound produced by plants, is used by humans to help prevent malaria. Derived traits of land plants • Apical meristems – Plants “move” by growing • Multicellular, dependent embryos – thus “Embryophytes” • Alternation of generations – Heteromorphic 3 Derived traits of land plants • Walled spores produced by multicellular sporangia • Multicellular gametangia producing gametes – Except in flowering plants (still have gametes) • Spore vs. Gamete – Spores grow directly into multicellular bodies – Gametes need to undergo fertilization first The first land plants: bryophytes (“non-vascular” plants) Derived traits of land plants • Epidermis for water conservation – Cuticle, stomata • Vascular tissues (except bryophytes) – True vascular tissues have lignin – True roots, stems, and leaves have vascular tissue • Secondary compounds – Protection, signaling, defense, support Figure 29.1 Adaptation to living on land catalyzed a great deal of evolutionary diversification. Why? 1. Traits shared by land plants, and lacking in the charophyceans 2. The earliest land plants: bryophytes (mosses, liverworts, hornworts) Figure 29.8 The life cycle of Polytrichum, a moss (Layer 3) Traits of bryophytes • Most lack true vascular tissue, which places limits on their thickness and height. • In their alternation of generations life cycle, the gametophyte is the larger, conspicuous stage. The sporophyte is smaller, and when it grows, it is dependent on the gametophyte for nutrients. Liverworts have especially small sporophytes. • Many mosses can live in extremely dry or cold habitats, because they can almost completely dry out without dying. 4 Figure 29.16x Stages of the moss life cycle. Key features of bryophyte life cycle • Gametophyte is dominant generation • Sporophyte is smaller, dependent on gametophyte (but still multicellular) • Fertilization is dependent on free water carrying sperm from antheridia to archegonia Life Cycle of a bryophyte Life Cycle of a bryophyte Marchantia Polymorpha Marchantia Polymorpha Note the Male and female gametophytes Note the Male and female gametophytes Note the reduced sporophyte Note the reduced sporophyte Note antheridia and archegonia Note antheridia and archegonia Ecology of bryophytes Figure 29.19 Sphagnum, or peat moss: Peat bog in Oneida County, Wisconsin (top), closeup of Sphagnum (bottom left), Sphagnum "leaf" (bottom right) • All are photoautotrophs, primary producers • Mostly live in moist habitats, although some mosses live in very cold and/or dry environments • All need free water for fertilization, and this ultimately restricts their distribution 5 Figure 29.19x A peat moss bog in Norway. This landscape is probably similar to much of earth during the first 100 million years after land plants evolved: the only plants were short bryophytes. Why are bryophytes short? Peat (Sphagnum) bogs… • Cover nearly 1% of the Earth’s land surface • Dead peat resists decompostion, thus peat bogs store tremendous amounts of carbon (400 billion tons worldwide) • Structure of peat moss is highly absorbent, making it useful to people • Fuel • Soil Conditioner Figure 29.10 Sphagnum, or peat moss: Harvesting for human use Seedless Vascular Plants 1. Traits and adaptations of the first vascular plants: Pteridophytes 2. Two phyla of seedless vascular plants: Lycophyta (lycophytes) and Pterophyta (ferns & their relatives) 3. Overview of evolutionary transition to seed plants Figure 29.7 Land plant evolution. Figure 29.21x1 Lycophyte (club mosses) 6 Figure 29.21x2 Horsetail (Equisetum): Pterophyta Traits and adaptations of the first vascular plants 1. 2. 3. 4. 5. Figure 29.23x1 A fern Figure 29.20 Cooksonia, a vascular plant of the Silurian period. Note tall stature and large branched sporophyte with numerous sporangia. True lignified vascular tissue system (xylem and phloem), and thus true leaves, stems, and roots in most taxa Dominant sporophyte generation that is branched and becomes independent of the parental gametophyte No seeds Traits 1 & 2 are shared by the other two groups of vascular plants: gymnosperms and angiosperms Many adaptations to land inherited from bryophytelike ancestor (meristems, embryos, alt. of gen. life cycle, walled resistant spores, gametangia, specialized epidermis, secondary compounds)—see previous lecture Figure 29.13 Hypotheses for the evolution of leaves Microphylls, small (usually) leaves which have only a single strand of vascular tissue, are thought to have evolved from a small stem outgrowth or flap, into which a strand of vascular tissue grew. Megaphylls, large (usually) leaves with a branched vascular system, support more photosynthetic capacity than microphylls. They are thought to have evolved through the flattening and joining (via tissue webbing) of multiple branches. Rhizome (underground horizontal stem) Figure 29.22 Hypotheses for the evolution of leaves Microphylls, small (usually) leaves which have only a single strand of vascular tissue, are thought to have evolved from a small stem outgrowth or flap, into which a strand of vascular tissue grew. Megaphylls, large (usually) leaves with a branched vascular system, support more photosynthetic capacity than microphylls. They are thought to have evolved through the flattening and joining (via tissue webbing) of multiple branches. 7 Sporphylls - modified leaves that bear sporangia Note: some plants are homosporous and some are heterosporous. Homosporous Sporophyte Single type of spore Heterosporous Bisexual gametophyte (with both kinds of gametangia) Strobili Eggs & sperm Microspore Male gametophyte Sperm Megaspore Female gametophyte Eggs Sporophyte Sori (inside the spore) Clusters of sporangia, usually on the underside of sporophylls The heterosporous life cycle was important in the evolution of the seed, which we’ll discuss next week. “Cones”, usually on the tips of shoots/branches Figure 29.7 Land plant evolution. Seedless Vascular Plants 1. Traits and adaptations of the first vascular plants: Pteridophytes 2. Two phyla of seedless vascular plants: Lycophyta (lycophytes) and Pterophyta (ferns & their relatives) 3. Overview of evolutionary transition to seed plants Figure 29.21 Pteridophytes (seedless vascular plants): Lycopodium (a club "moss“, top left), Psilotum (a whisk fern, top right), Equisetum (a horsetail, bottom left), fern (bottom right). The latter three represent phylum Pterophyta, and Lycopodium represents phylum Lycophyta. Another genus in Lycophyta, which we will see in lab, is Selaginella. Figure 29.14 Lycopodium (a club "moss”) in the phylum Lycophyta. Many grow on tropical trees as epiphytes Others grow on temperate forest floors Tiny gametophytes, sometimes underground Upright stems with many small leaves (microphylls) 8 Figure 29.14 Selaginella (a spike "moss”) in the phylum Lycophyta. Figure 29.14 Isoetes (a quillwort) in the phylum Lycophyta. Small, low to the ground Grow horizontally Represented today by a single genus Live in marshy areas Figure 29.7 Land plant evolution. Figure 29.14 Equisetum (horsetail) in the phylum Pterophyta. Often have separate vegetative and fertile stems “Jointed plants” with rings of small leaves or branches at each joint Bulk of photosynthesis in stem Air canals carry oxygen to roots, which are often in waterlogged Soil Homosporous Modern Equisetum essentially identical to Equisetites from 300 mya. Equisetum may be the oldest surviving genus of plants on Earth. calamites were horsetails that grew into trees up to 18m tall and 45 cm thick during the Devonian (~300 mya) Figure 29.14 Psilotum (whisk fern) in the phylum Pterophyta. Dichtomously branching stems, no roots (like first vascular plants) Stems have small scale-like outgrowths without vascular tissue - unclear if they predate leaves or are reduced leaves 9 Figure 29.14 Polypodium (a fern) in the phylum Pterophyta. Figure 29.12 The life cycle of a fern: note the dominant diploid (sporophyte) generation, and the reduced gametophyte FERNS ~12,000 species Most are in tropics •Note megaphylls - fronds •Most are homosporous •Gametophytes shrivel and die •Can produce LOTS of airborne spores Figure 29.23x2 Life cycle of a fern: sorus, a cluster of sporangia (~1 mm diam.) Figure 29.24c Closeup of a fern sorus. Note the sporangia. Figure 29.24b Underside of fern sporophyll, a leaf specialized for spore production. Note the numerous sori (clusters of sporangia) Figure 29.7 Land plant evolution. 10 Among the seedless plants: Figure 29.25 Artist’s conception of a Carboniferous forest, ~300 mya. Dead plants did not completely decompose, were later covered by seas and marine sediments, and then were transformed by heat and pressure into vast beds of coal. • Mostly homosporous • Spike mosses and quillworts (both Lycophytes) are heterosporous • But, heterospory appears to have evolved independently in first seed plants (i.e., analogous), since seed plants appear more related to Pterophytes than Lycophytes Seedless Vascular Plants Figure 30.1 Three variations on gametophyte/sporophyte relationships. Note the progression in evolutionary time from left to right. 1. Traits and adaptations of the first vascular plants: Pteridophytes 2. Two phyla of seedless vascular plants: Lycophyta (lycophytes) and Pterophyta (ferns & their relatives) 3. Overview of evolutionary transition to seed plants Figure 30.3 From ovule to seed Advantages of the Seed • Multicellular embryo gets a “head start” at the germination stage • Stored food for embryo also allows a head start, and allows for extended dormancy • Multicellular, larger and more complex than a spore = more resistant to harsh conditions • Larger and more complex = increased capacity to develop dispersal adaptations 11 Figure 30.2 From ovule to seed Disadvantage of the Seed • More energetically costly to produce • To some extent, trade off quantity for quality Figure 30.3 Winged seed of a White Pine (Pinus strobus), a gymnosperm. Remember: Alternation of generations is thought to have evolved via delayed meiosis. What might be the advantage of this more complex life cycle, for living on land? Multicellular sporophyte = more than 4 spores produced by meiosis. Remember, algal sperm are flagellated, swim to eggs. This requires water. Harder to do on land. 12