Transcript The Dandelion - schallesbiology

The Dandelion
References:
The Amazing Dandelion by Selsam & Wexler
http://en.wikipedia.org/wiki/Dandelion
http://www.botanical.com/botanical/mgmh/d/dandel08.html
They are not native to America
• Dandelions evolved about thirty million years ago
in Eurasia
• North Americans are just about the only people
who look on the dandelion as a problem. Most of
the world thinks of it as a food crop.
• The theory is the dandelion - was brought over
from Europe originally as a garden crop and then
went native.
Scientific classification
• Kingdom:Plantae
• Division:Magnoliophyta
• Class:Magnoliopsida
• Order:Asterales
• Family:Asteraceae
• Genus:Taraxacum
The English plant name is from
the French phrase “dent-de-lion”
• Which means “Lion’s
tooth”
• Because the leaves have jagged teeth
• In Spanish diente de león,
Some other names for Dandelion:
• In modern French the plant is named pissenlit, which
means "urinate in bed", apparently referring to its
diuretic properties
• Also, in the dialect of Veneto, Italy, it is known as
pisacan, which translates to "dog pisses",
referring to how common they are found at the side of
pavements (source: Giulia Zanetti, native of Veneto),
• In Polish it is called "dmuchawiec" which comes
from "dmuchać", "to blow" when in its seed state.
• Hungarian is “kutyatej” ("dog milk", referring to
the white sap found in the stem)
Dandelion flower
• A bright yellow flower head
• is open in the daytime but closes at night & in
the rain
When picking the flowers,
a bitter, milky juice exudes
from the broken edges of
the stem, which is present
throughout the plant, and
which when it comes into
contact with the hand, turns
to a brown stain that is rather
difficult to remove.
The flower is actually
many tiny flowers
• In the family Asteraceae the "flowers" are
morphologically a composite flower head
consisting of many tiny flowers called florets.
• Try counting the florets in a dandelion flower.
• How many do you get?
(there should be between 150 & 200 flowers in
each cluster that is the dandelion head)
Also members of the family
Asteraceae:
• Daisy
• Thistle
• Lettuce
• Chicory
• Escarole
• Endive
A closer look
Look at an individual dandelion floret
• The ovary is at the bottom
• The flower head matures to contain many singleseeded fruits (achenes).
• Above, a circle of fin, silky hairs called a
“pappus”
• Each achene is attached to a pappus of fine hairs
(which enables wind-aided dispersal)
A flower beginning to open
• A single petal moves away from the central
tube
• The tube is made up of five anthers (sacs of
pollen) joined together
• Out of the anther tube a part called the style
emerges
• It comes out of the ovary, & the tip of the
style is the stigma
New dandelions: many ways
• Insect pollination
• Self pollination
• No pollination- just produces seeds without any
pollination!!! (produce seeds asexually by apomixis,
resulting in offspring that are genetically identical to
the parent plant)
• Roots divide & produce more plants
What is a dandelion seed is
actually fruit
The puffy ball
• The pappuses (the silky hairs) grow together
• A breeze carries away the parachutes
• The pappus opens fluffy in dry air, stays tight
in humid air.
• When it hits the ground, the pappus may fall
off & the achene (the fruit with the seed in it),
which has hooks on it will grow into a new
plant.
Length of stem
• Depends on where it grows• In a mowed lawn- it may be 3 inched long
• In weeds, the stem may be 2-3 feet tall!!!
Tap roots
• A dandelion is hard to get rid of
• The tap root with the smaller side branches
coming out of it goes down about a foot into
the ground
Why it’s a weed to Americans
• As the leaves grow outward they push down the
surrounding vegetation, such as grass in a lawn,
which kills those plants by cutting off their access
to sunlight.
• When lawns are dying all around them, dandelions
will be green and vigorous. Dandelions can
regenerate from a root or stem, so when the plant
is mowed, an individual plant doesn't lose its hold
on an area of turf."
Perennial Plants
• Means it lives on from year to year
• The top leaves & stem dies off but the stem
lives underground.
• The tap root divides & produces new plants,
• Additionally, one root may get big enough
to support several plants instead of just one.
Useful Dandelions
• Fleshy roots are used as food:
– Scraped, sliced roots can boiled in salt water like
potatoes
– Can be cleaned, baked, ground up & used as a coffee
substitute
– Young leaves considered a tasty vegetable & mixed in
salad greens (older leaves are tough & bitter)
– Can be cooked like spinach
Interesting stories
• Seed houses are developing better tasting dandelions
for consumers- You can buy these in the produce
section at the grocery store.
• "Nutritionally, it puts almost all greens to shame,"
"Capsicums (chili peppers) come close in terms of
vitamin A, but those aren't really greens. If you
compare dandelion greens to something like spinach,
they have twice the vitamin A, twice the calcium,
more vitamin C and as much iron.
• It's interesting that one of the greatest nutritional
plants is viewed as the lawn's public enemy No. 1."
Interesting stories
• American Indians considered dandelions a
medicine
• Dandelion root is a registered drug in Canada, sold
principally as a diuretic.
• A leaf decoction can be drunk to "purify the
blood", for the treatment of anemia, jaundice, and
also for nervousness.
• Drunk before meals, dandelion root coffee is
claimed to stimulate digestive functions and
function as a liver tonic
Interesting stories
• After a swarm of locusts ate all of the other
plants on the island, the people of Minorca,
Spain were able to stay alive eating
dandelion roots.
Interesting stories
• Scientists tried to use the white sap (latex)
that comes out of the stem to make rubber
– unsuccessfully with our local species
• But a Russian variety, kok-saghyz, does
make rubber.
Interesting stories
• Dandelion flowers can be used to make
dandelion wine, for which there are many
recipes.[9]
• It has also been used in a saison ale called
Pissenlit (literally "wet the bed" in French)
made by Brasserie Fantôme in Belgium.
• Another recipe using the plant is dandelion
flower jam.
Interesting stories
• The milky latex has been used as a
mosquito repellent
• the milk has also been used to treat warts, as
a folk remedy
Besides being useful, dandelions
are fun
• You can pick a bouquet of flowers
• You can blow the puff ball
• They make lovely flower necklaces