Chapter 23
angiosperms contain the greatest number living species 257,000
called magnolilphyta
Monocots
Changing concepts about early angiosperms
The point is that we must not think about evolution as a linear progression forward and upward with each new group leaving the previous ones behind
in most angiosperm carpels, the edges of sporophyll primordia crowd against each other and grow shuts sometimes leaving a visible suture, sometimes closing so completely that no sign of a seam remains
called a closed carpel
double fertilization is universal in flowering plants
primitively vesselless
basal angiosperms
Primitively vesselless
having wood without vessels
about 100 years ago C.E. Bessy developed the hypothesis of the ranalean flower
a magnolia flower was thought to be relictual
this flower is known to be generalized that is it has all parts and is arranged spirally
many paleobotanist and taxonomists believe that the transition from gymnosperm to angiosperm occurred during the jurassic and lower cretaceous periods of the mesozoic era
the earliest leaf fossils definitely considered to be those of angiosperms are from the lower cretaceous period approx. 130 million years ago
the oldest wood that seems to be from an angiosperm comes from the Aptian Epoch 125 million years ago from japan
much attention is now being given to gymnosperms of the jurassic and Triassic period and the focus is centering on cycadophytes and glossopterids
Classification of Flowering plants
magoliophyta is a large group with many families, genera, and species that it is rare fro an individual taxonomist to attempt to study and classify the entire group
soon after their origin flowering plants began to follow two distinct lines of evolution and currently almost angiosperms are classified as monocots or eudicots
no single character always distinguishes a monocot from a eudicot
their leaves have parallel veins because the leaves are elongate and strap shaped
flowers of monocots have their parts arranged in groups of threes
three sepals
three petals
three stamens
three carpels
Eudicots have two cotyledons and reticulate venation in the leaves vascular bundles occur in only one ring in the stem
the monocot/eudicot divergence did not occur right away
early angiosperms diverged into several clades now called basal angiosperms
Basal angiosperms
living descendants of several groups that originated while angiosperms were still a young clade
nymphaceaceae are water lilies
they are small soft-bodied herbs with vascular bundles scattered like those in monocots and they completely lack any wood
stems must be kept underwater
magnolia flowers have numerous stamens and carpels are not fused together into a pistil as occurs in almost all monocots and eudicots
being on land would kill them
flowers are pollinated by animals
eudicots have three germination pores
other magnoliids are laurels and avocado and pepperomias
widely believed to have arisen from early angiosperms approximately 80 to 100 million
because all monocots lack ordinary secondary growth and wood their ancestors were probably herbs with either no vascular cambium or little cambial activity
the perianth members are called tepals
in the evolutionally lines of broadleaf monocots such as palms, philodendrons and dieffenbachias
Hydrocharis, Najas, and Hydrilla are found in swamps and marshes
most often these plants are found submerged
although many species retain a large number pf [;isomorphic features others have become highly modified in response to the unusual selection pressures associated with an aquatic habitat
sea grasses grow completely underwater in the ocean
they have no transportation and thus mutations that result in the loss of stomata are not selectively disadvantageous
do not waster carbon and energy by producing fibers that are not needed for support
In most alismatales flowers are large and showy
Liliales
defined broadly as a large group with many highly derived families
it was defined as the petaloid monocots those with large colorful flowers
DNA evidence indicates this is a smaller clade with 11 families and 1300 species
Asparagales
large clade
many families
many species
and many types of biology
most form nectaries in an unusual way
carpels fuse side by side starting at their bases the fused sides being called septa
they do not fuse all the way up to the style however and the open areas secrete nectar these are septal nectaries
extremely diverse in morphology
the orchidaceae is the largest and most divers family of asparagales
commelinoid monocots
four orders of monocots are known as the commelinoid monocots
epiticilar wax
Arecales
contains familiar plants
palms
has solitary trunk
leaves of palms always occur only near the shoot apex never distributed along the length of the stem
all species have simple leaves
leaves are torn by the wind into a pinnate pattern or palmate pattern
Poals
grass family
cattails and bromeliads
8000 species
include most foods that we eat
all grasses are wind pollinated
sepals and petals are of little importance
Eudicots
sedges and rushes
bromeliaceae contains tropical epiphytes
Zingiberales
house plants
maranta, calathea, canna, and gingers
banana is also a species
showy flowers
need to be pollinated by insects
larger group than monocots
more diverse than monocots
Basal Eudicots
Ranuculaceae with flowers that have little fusion
poppy family, Papaveraceae is well known for their ornamental species
hamamelids
once thought to be basal angiosperms
contains many staminate flowers
Caryophyllales
anthocyanin pigments
has water soluble pigments called betalains
nucleus cells proliferate and from a nutrient tissue called perisperm which surrounds the developing embryo
postulated to have arisen from ancestors similar to ranuculacea
Santales
small order
highly modified
parasitic plants
appears to be an ordinary tree but roots attach to other roots and parasitizes them
Rosid Clade
named after the order rosales
very diverse in every way
consists of several small orders and two big groups
two large clades of rosins are the abides
then there is the malvids
the two clade contain 100 families
none of them has ant highly relictual features found in many basal angiosperms
pinnately compound leaves
this is an ancestral condition
roses are not considered typical they are a large group of many
rose family is not also an evolutionary sense but also economically
Fabaceae are the lentils and peanuts aka its the legume family
many species have nodules
Astrid Clade
clade of the eudicots
large clade
contains plants like the sunflower, periwinkle and petunia and moving glory
they have sympetalous flowers their flowers are fused together into a tube
they always have a few stamens
stamens alternate with petals
astrids exploit very specialized pollinators that recognize complex floral patterns and such plants could not evolve before derived
they have iridoid compounds which are rarely outside this group
two orders are lamiids and campanulids
many are importantly medically
apocynaceae the oleander family,
extracted vinblastine and vincristine
two important anticancer drugs