Transcript Document

Evolution of Land Plants
Prior to the origin and diversitication of green plants in the mid-Silurian
(~450 mya), multicellular life was virtually entirely apapted to, and
confined to, aquatic lifestyles
Contintnenal Land Masses virtually unoccupied by multicellular organism
– multicellular-based ecosystems constituted tremendous potential for
adaptive radiation
Terrestrial life in a gaseous medium required evolutionary solutions to
structural, physiological and ecological challenges; Many of these
innovations can be regarded as exaptations of pre-existing traits of green
algae from which green plants diverged
Artist’s rendering of Carboniferous forest in a tropical river delta. Most of
the plants depicted here were nonseed tracheophytes 10 to 20 meters tall.
In the distance, earl seed plants up to 40 meters tall towered over the
forest.
Kingdom Plantae is monophyletic assemblage,
descended from Green algae
Chlorophyll a and b are homogous in Chlorophyta,
Charaphyta and Plantae
Currently includes over 250,000 described species
classified in 12 monophyletic phyla
Most are terrestrial, some are secondarily aquatic
Diversification in plants involved successive adaptive
radiations following evolution of key innovations that
increased efficiency in an gaseous (air) and solid
(Earth) environment
Major problems were posed by gravity and by
water loss/availability
-maintain body structure – resist gravity
-obtain, transport and retain water
-fertilize eggs and produce and protect
embryos
Major evolutionary innovations included
Green algae of phylum Chlorophyta, such as Chara sp.,
are most likely ancestors of plants. Copyright BPS.
-dimorphic body
-waxy cuticle and stomata
-vascular tissue;
-jacketed sex organs; antheridia and archegonia
-life history dominated by sporophyte
generation
-seeds embryo with nutritive tissue in
protective covering
-flowers; vehicles for pollination strategies
Dense matt of mosses colonizes old lava in
Iceland. Copyright BPS
Leafy liverwort (Lophocolea bidentata),
showing overlapping leaves
andcreeping growth form. Copyright
BPS.
Leafy liverwort (Lophocolea bidentata),
showing overlapping leaves and creeping
growth form. Copyright BPS.
Marchantia, a common liverwort. The
sporophytes are born within the tissues of
the umbrella shaped structures that arise
from the surface of the flat, green,
creeping gametophyte
Hornwort sporophytes. Unlike
other Bryophytes, hornwort
sporophytes are photosynthetic
Gametophytes of Sphagnum moss growing in a bog in central
Newfoundland. Copyright BPS.
Order Lycopodiales:
club moss
(Lycopodium
annotinum); Denali
National Park and
Preserve, AK.
Copyright BPS.
Fern (Blechnum magellanicum)
in rain forest of Chile's
Patagonian coast. Copyright
Alejandro Frid/BPS.
Tree ferns (Dicksonia
antarctica), in a forest of
Eucalyptus regnans;
Australia. Copyright
BPS.
Club Moss Big leaf
maples hung with
epiphytes, most of
which are club
mosses; Hoh Rain
Forest, WA. Copyright
BPS.
Simple determinate
inflorescence of shooting star
(Dodecatheon meadia).
Copyright J. Robert
Stottlemyer/BPS.
Family Arecaceae: desert
fan palm (Washingtonia
filifera); Colorado Desert,
CA. Copyright Jon Mark
Stewart/BPS.
Family Pinaceae: Colorado
blue spruce (Picea
pungens). Copyright
Pollock/BPS.
Family Pinaceae: Pinus
ponderosa, ponderosa pine,
is widespread in the
American West. Copyright
Sources: Freeman (2002), Purves et al (2001)
First extensive grassland
Overview of the evolutionary history of plants
Consider five intervals of evolutionary history, each defined
by at least one major evolutionary innovation
Archaefructus, an early flower
First Flowering Plant
Cones from Araucaria mirabilis, an early gymnsperm
First nectar-drinking insects
Carboniferous
(lycopods, seed ferns,
and horsetails
abundant)
First vessels
Seed fern leaves
1st seeds
1st vascular plant leaves
1st wood
1st roots
1st vascular tissue
1st stomata
1st megafossils
(small club
mosses and
other extinct
groups
1st lycopod
leave
Fragment of plant cuticle
Fossil frond of fern (Asterotheca
arborescens); late Carboniferous.
Copyright Barbara J. Miller/BPS.
Fossil stem of oldest known
lycopod genus (Bothrodendron
minutifolium); late Devonian. LM.
Copyright Phil Gates/BPS.
Cells in fossil stem of Rhynia
major (extinct Phylum
Rhyniophyta); late Silurian and
Devonian. LM. Copyright Phil
Gates/BPS.
Spores in fossil Rhynia major; late
Silurian and Devonian. LM.
Copyright Phil Gates/BPS
Our current understanding of Plant
phylogenetic relationships is based on
analysis of both morphological and
molecular characters
•SSU rRNA and Rubisco
•presence/absence of vascular tissue,
leaves, seeds…
•The broad picture of plant evolutionary
relationships includes…
•Divergenge of entire clade from green algae
•indicates a single transition to land
•indicates freshwater to land
transition (because almost all modern
Charopytans are freswater
inhabitants)
•All Plantae lineages; cellulose-based cell
walls, chlorophyll a and b, starch as storage
molecule in chloroplasts
•Two of the three earliest lineages (nontracheophytes) lack water transport cells;
mosses have have limited numbers of them
Rubisco catalyzes a reaction in the CalvinBenson cycle of photosynthesis in which
carbon from CO2 is added to a five-carbon
chain.
Our current understanding of Plant
phylogenetic relationships is based on
analysis of both morphological and
molecular characters
•SSU rRNA and Rubisco
•presence/absence of vascular tissue,
leaves, seeds…
The broad picture of plant evolutionary
relationships includes…
•Divergenge of entire clade from green algae
•All Plantae lineages; cellulose-based cell
walls, chlorophyll a and b, starch as storage
molecule in chloroplasts
•Two of the three earliest lineages (nontracheophytes) lack water transport cells;
mosses have have limited numbers of them
•Seedless vascular plants (nonseed
tracheophytes) have vascular tissue and
leaves, but reproduce by making spores; no
seeds
Gymnosperms and Angiosperms have
vascular tissue, they have complex leaves,
and they produce seeds.
Early lineages dependent on wet habitats
and more recent ones not – adaptive
radiations into mesic and xeric conditions
Key Evolutionary Innovations and Trends in the
Transition of Plants to Land
-reducing water loss; cuticle and stomata
-transporting water; vascular tissue and wood
-transporting gametes and prtoecting embryos;
pollination mechanisms and nutrititive, protective
seeds
Key evolutionary innovations and trends for
capturing energy from sunlight
-Photosynthetic Pathways C3 and C4
-Crassulacean acid metabolism
-growth habits and life forms
Nature 389, 33 - 39 (1997) © Macmillan Publishers Ltd.
The origin and early evolution of plants on land
PAUL KENRICK AND PETER R. CRANE
the Swedish Museum of Natural History, Box 50007, S-10405, Stockholm, SwedenThe Field Museum,
Roosevelt Road at Lake Shore Drive,
Chicago, Illinois60605, Department of the Geophysical Sciences, University of Chicago, USA.
The origin and early evolution of land plants in the mid-Palaeozoic era, between about 480 and 360
million years ago, was an important event in the history of life, with far-reaching consequences for
the evolution of terrestrial organisms and global environments. A recent surge of interest, catalysed
by palaeobotanical discoveries and advances in the systematics of living plants, provides a revised
perspective on the evolution of early land plants and suggests new directions for future research.
Figure 1 Morphological diversity among basal living land plants and potential land-plant sister groups.
a,Coleochaete orbicularis (Charophyceae) gametophyte; magnification × 75 (photograph courtesy of L.
E.Graham). b, Chara (Charophyoceae) gametophyte; magnification × 1.5 (photograph courtesy of M.Feist).
c, Riccia (liverwort) gametophyte showing sporangia (black) embedded in the thallus; magnification× 5
(photograph courtesy of A. N. Drinnan). d, Anthoceros (hornwort) gametophyte showing
nbranchedsporophytes; magnification × 2.5 (photograph courtesy of A. N. Drinnan). e, Mnium (moss)
gametophyteshowing unbranched sporophytes with terminal sporangia (capsule); magnification × 4.5
(photographcourtesy of W. Burger). f, Huperzia (clubmoss) sporophyte with leaves showing sessile yellow
sporangia;magnification × 0.8. g, Dicranopteris (fern) sporophyte showing leaves with circinate
vernation;magnification × 0.08. h, Psilotum (whisk fern) sporophyte with reduced leaves and spherical
synangia(three fused sporangia); magnification × 0.4. i, Equisetum (horsetail) sporophyte with whorled
branches,reduced leaves, and a terminal cone; magnification × 0.4. j, Cycas (seed plant) sporophyte
showing leavesand terminal cone with seeds; magnification × 0.05 (photograph courtesy of W. Burger).
Figure 2 a, Longitudinal section of part of a silicified early fossil gametophyte (Kidstonophyton discoides
from the Rhynie Chert). Antheridia (male sexual organs) are located on the upper surface of the branch;
magnification × 3.4. b, Longitudinal section of antheridium of Lyonophyton rhyniensis from the Rhynie
Chert; magnification × 40. c, Longitudinal section of archegonium (female sexual organ) of Langiophyton
mackiei from the Rhynie Chert; magnification × 80. a–c are from the Remy Collection (slides 200, 90 and
330), Abteilung Paläobotanik, Westfälische Wilhelms-Universität, Münster, Germany (photographs
courtesy of H. Hass and H. Kerp). d, Scanning electron micrograph of Tetrahedraletes medinensis
showing a spore tetrad of possible liverwort affinity from the Late Ordovician (photograph courtesy of W.
A. Taylor); magnification × 670.
Figure 3 Sporophyte diversity in Early Devonian rhyniophyte fossils. a, Cooksonia pertoniiapiculispora:
sporophyte (incomplete proximally) with terminal sporangium15; magnification × 15. b,Tortilicaulis offaeus:
sporophyte (incomplete proximally) with terminal sporangium81; magnification × 40.c. Tortilicaulis offaeus:
sporophyte (incomplete proximally) with terminal bifurcating sporangium81;magnification × 30. d, Transverse
section of sporangium showing thick wall and central spore mass;magnification × 70. e, Details of epidermis at
rim of sporangium; magnification × 45. f, Stomate with tworeniform guard cells (stippled); magnification × 120.
Figure 5 Diversity of water-conducting cells (tracheids) in early land plants (median
longitudinal sectionthrough cells, basal and proximal end wa. lls not shown; cells are 20–40
m diameter). a, Top,bryophyte hydroid; bottom, details of hydroid wall showing distribution of
plasmodesmata-derivedmicropores (10–50 nm diameter; stipple)84. b, Top, S-type tracheid
(fossil) of Rhyniopsida; bottom,details of S-type cell wall showing distribution of
plasmodesmata-derived micropores (stipple) and'spongy' interior to thickenings19. c, Top,
G-type tracheid (fossil) of basal extinct eutracheophytes, whichclosely resemble the
tracheids of some living vascular plants; bottom, details of G-type cell wall showingpores
distributed between thickenings19. d, Top, scalariform pitted P-type tracheid (fossil) typical
oftrimerophyte grade plants (euphyllophytes); bottom, details of P-type cell wall showing pit
chambers andsheet with pores that extends over pit apertures26.