Seed Plants II: Angiosperms
Changing concepts about early angiosperms
C.E. Bessey develops hypothesis of ranalean flower
Magnolia type flower was thought to relictual
such a flower was generalized
contained all parts (sepals, petals, stamens, and carpels) and arranged spirally
all existing flower types come from this generalized ancestor
angiosperms= monophyletic
double fertilization and developmental plasticity did not evolve more then once
transition from gymnosperms to angiosperms occurred during the Jurassic and Lower Cretaceous Periods
represent monocot and dicot leaves
Classification of Flowering Plants
DNA, biochemistry, and anatomy used to propose phyolgenies
two widely reference books used are Plant Systematics and A Phylogenetic Approach
flowering plants began to follow two distinct lines of evolution
all angiosperms classified as either monocot or eudicot
monocots have 1 cotyledon on their embryo
leaves also have parallel veins, vascular bundles throughout the stem, and never have ordinary secondary growth and wood
flowers arranged into multiples of three: 3 petals, 3 sepals, 3 stamen, and 3 carpels
eudicots are more diverse and have 2 cotyledon on the embryo
reticulated venation in leaves
vascular bundles in only one ring in the stem
can be woody, herbaceous, or succulent
flower parts are in sets of 5
early angiosperms divided into basal angiosperm clades first
DNA sequences showed that they had become reproductively separate from the angiosperms
Basal angiosperms
contain living descendants of several groups that originated while angiosperms were still a young clade
3 groups of these extant descendants are the Amborellaceae, Nymphaeaceae, and the Austrobaileyales
the Nymphaeaceae= water lilies
Austrobaileyales have woody trees with bisexual flowers, with stamens and carpels similar to Amborella
DNA evidence-morphologically, shows magnoliid diverged from earlier angiosperms
does not differ from the other two clades
wood similar to to that of gymnosperms, which lacks vessels, fibers, and axial parenchyma
pollen have single germination pore= they are uniaperature as are all basal angiosperms and monocots
Monocots
arisen from early angiosperms 80-120 million years ago
ancestors lacked vascular cambium or little cambial activity because they most likely herbs
gynocecia are composed of several carpels
perianth composed of three inner membranes and perianth members= tepals
water lilies have similar features
Nymphaeales gave rise to lilies and monocots
ancestors had broad leaves and lived as aquatic plants
leaves have since evolved to be adapted to land
Alismatales
contain many aquatic herbs and aquarium plants
found in swamps and marshes and are partially or entirely submerged
sea grasses with no transpiration have mutations that result in loss of stomata
have air chambers for buoyancy
plants do not waste carbon and energy
tend to be thin and delicate then with loss of tissues or that have become simplified
flowers are large and showy
some species have inflorescence: tiny flowers
Liliales
large colorful flowers
spots or lines on the petals and ordinary nectaries formed at bases of tepals or stamens
Asparagales
nectaries formed in an unusual way
carpels fuse side by side and the sides= septa
open areas= septal nectaries
very diverse in morphology
small delicate bulbs to vining epiphytes
very diverse in biochemistry as well
groups having distinct chemical compounds
flowers are large and showy for the most part with distinct aromas
Dioscoreales
form important food crop= yams
major source of carbs
Commelinoid Monocots
unique type of epicuticular wax, walls have unusual hemicellulose and UV fluorescent compounds and pollen and DNA contain starch
Arecales
Palms
scattered vascular bundles
leaves always occur near shoot apex
trunks are prostate
coconuts and dates
flowers very tiny
Poales
Poaceae, cattails, bromeliads, and sedges
Poaceae= wheat, oats, rye, corn, rice, and sugar cane
wind pollinated so sepals and petals are of little importance and reduced to bristle-like structures
Zingiberales
most familiar house plants: canna lilies, gingers, banana =, and bird of paradise
large showy flowers pollinated by insects, birds, or bats
Eudicots
far numerous then the monocots
multiple variations of tissues, organs, and metabolism
pollen grains have 3 germination pores= tricolpate
flower parts arranged in whorls and stamens have a well defined filament/stalk and anther
Basal Eudicots
Ranunculaceae
flowers have few fusion of parts
buttercups, windflower, and clematis
numerous free parts
also poppy family
=herbs or shrubs with a very soft wood
several hamamelid families are also eudicot
Caryophyllales
DNA based studies put certain families into the group Caryophyllales
cacti, iceplant, portulaca, spinach, beets, and Russian thistle
flowering plants have anthyocyanin pigments in their leaves, but Caryophyllales have betalain pigments
endosperm develops only a little, and nucleus cells develop nutritive tissue called the perisperm that surrounds the embryo
the nature of sieve tube plastids contains deposits of fibrous proteins located as rings just interior to plastid membrane
most members are herbaceous with either no wood, or very little wood
Santalales
most are parasitic
Santalum tree used as sandalwood incense, uses its roots to parasitize nearby roots
Mistletoes are also parasitic
Rosid Clade
diverse vegetative bodies, flowers, chemistry, and ecology makes it hard to see how they are related, but some do share enough characteristics to show a relationship
DNA analysis also adds a great deal of info on the relationships
rosids contain several small orders and two large groups
Vitis= genus of grapes that gives juices and raisins and Vitis vinifera= wine grape
another small order is the Geraniales
two large groups are the fabids and the malvids
important character of rosids is pinnately compound leaves
also contains Rosales, Sapindales, Fabales, and Mrytrales
Asterid Clade
sunflowers, periwinkle, petunia, and morning glory
distinguished on the basis of 1. have sympetalous flowers 2. just a few stamen 3. stamens alternate with petals
exploit very specialized pollinators with complex floral patterns
many chemical differences from other clades
iridoid compounds found only in this group
certain families make poisons or deterrent chemicals
grouped into two orders
lamiids
campanulids
many asterids are important medically
Apocynaceae contains periwinkle which vinblastine and vincrstine are extracted from
anticancer drugs
