Presentation on theme: "FLOWERS Notes for Biology 2410* at Utah State University"— Presentation transcript:
1 FLOWERS Notes for Biology 2410* at Utah State University *Plants and fungi: ecosystem essentials
2 Flowers: A Marvelous Innovation Flowering plants first appeared around 140 million years ago (Upper Jurassic).Oldest flower fossil is 125 million years old.The dominant forms of plant life were gymnosperms, cycads, and ferns.
3 TodayFlowering plants are now the dominant form of plant life over most of the earth’s land surface.Ferns are rarely dominant and gymnosperms are dominant only in cold, or seasonally cold locations. Cycads are hanging on by a thread.Why have flowering plants been so successful?
4 Flowers Double fertilization: saves energy Ovaries protect ovules and developing seeds; mature into fruits that promote seed dispersalFloral structure encourages pollinator fidelity; nectar and pollen to reward pollinatorsFast reproductive cycle compared to gymnospermsShorter haploid phase (a genetically risky phase) than all other plants
5 Origin of benefits Some benefits derive from structure of flower Some benefits derive from short reproductive cycleSome benefits from double fertilizationMany benefits derive from evolutionary modifications within the flowering plant lineage
6 Structure of flowersFlowers are composed of four whorls. From the outside in, they are:Calyx (sepals)Corolla (petals)Androecium (stamens)Gynoecium (pistils)
7 Calyx Outermost whorl Usually green Protects developing flower PhysicallyChemicallyMade up of SEPALSSepals free or notCalyx radially or bilaterally symmetric
8 Corolla Is usually colorful and showy; Attracts pollinators Guides pollinators;Is composed of petalsPetals may be united or separate;Corolla may be radially or bilaterally symmetric.
9 Androecium Is composed of stamens Stamens have filaments and anthers Pollen is produced in anthersStamens can be free or united
10 Gynoecium Is composed of pistils A pistil is composed of an ovary, style, and stigma.Styles may be separate, branched, or unitedPistils have a slide of their own – just wait
11 HypanthiumIf the corolla and calyx are attached to a cup or tube that is then attached to the receptacle, the cup or tube is called a hypanthium.If a hypanthium is present, the perianth may behypogynousperigynousepigynous
12 Flower structure (2)Perianth refers to the combination of the calyx and corolla.Usedwhen the two are very similar (tulips)to refer to both structures at the same time
13 ReceptacleThe top floral whorls are attached to the receptacle – the tissue where the stalk to the flower changes to being part of the flower
14 Pedicels Flowers are borne on pedicels Think of a pedicel as the stalk to a flower
15 PistilsComposed ofStigma – landing platform for the pollen grains, first selection pointStyle – helps select among pollen tubes; may be branchedOvary – contains ovules; matures into fruit
16 Ovaries (and fruits) Ovaries protect the ovules and developing seed Become fruits, modified for seed dispersal.Fruits may have other parts of flower attached.
17 Identifying Flowering Plants To survive, species must reproducePollination is the first major step in the reproduction of seed plants like gymnosperms and flowering plantsFlowers persuade animals to serve as pollinators, preferably faithful pollinatorsTo get the right pollen, flowers need to be memorable so …
18 Start thinking like a pollinator Is there a reward?How can I find another like this one?Symmetry – radial or bilateralColor patternOdorWill it be safe for me?Corolla – united or separate petalsCorolla more important than calyx – why?Can I reach the reward and is it adequate?nectaries and androecium
20 Then look at the ovary position Above the calyx and corolla (ovary superior; perianth hypogynous)Below the calyx and corolla (ovary inferior; perianth epigynous)One more possibility exists …
21 And that possibility is … Ovary partially inferiorOvary partially inferior; perianth perigynousPerianthperigynous
22 And finally, the glories of the gynoecium … How many pistils are there?How many styles or style branches?How many chambers are there in the ovary (need a cross-section)Where are the seeds attached?
23 Still part of the ‘little more’ Each theoretical leaf unit is termed a carpelA pea pod is a mature pistil made up of 1 carpelPistils with 2 style branches and/or chambers in the ovary are said to have 2 carpelsPistils with 3 style branches and/or chambers are said to have 3 carpels etc. etc.
24 And that is enough to start … Assignment:Pick 4 non-cultivated plants and carefully examine their flowers. Show you understand its structure by completing the handouts.
25 Why a non-cultivated plant? Many cultivated plants have been selected for their abnormalities, which often makes it difficult for beginners (and even old-timers) to identify them.Most identification keys include a very few purely cultivated plants so the chances are good that a cultivated plant is not in the key.