Leafsnap

A List of Plant Identification Resources

Start with Leafsnap, an electronic field guide.

Check your results using this book: New York City Trees

Then, if you are still in doubt, check any of these online resources:

The USDA Plants Database.

The University of Connecticut Horticultural Plant Database.

What is Leafsnap?

Preserving Plants

There are several alternative techniques for preserving leaves to use in the classroom.

• Pressed and dried leaves glued onto a sheet of paper. A collection of such leaves is known as "an herbarium." Instructions for creating an herbarium are here: Download Anderson's Herbarium Guide
  
• A plant press isn't required: use an old telephone book or catalog.
• Or place a single leaf between several sheets of newspaper, and put it in the microwave with a heavy dish to flatten it. Zap for 30 second intervals for about 2 minutes, until dry.
• Scan whole leaves on a flatbed scanner. This example was scanned at 300 dpi: Download Scan-001. 
• Immerse the cut end of a branch in a mixture of 1:3 glycerine:water for at least 3 days. (Glycerin(e) is available at Whole Foods.) This is especially good for colored leaves.

 

An article about the history of herbaria, from the American Biology Teacher. Download Herbaria

Plant specimens preserved in herbaria can become important research subjects many years after they were collected. Here are 3 examples:  Julius Bisky in Flushing, Xyris-a new species, Global Warming evidence found in herbarium specimens 

Some links to images in virtual herbaria:

http://www.tropicos.org/Image/1350

http://sweetgum.nybg.org/vh/specimen.php?irn=568357

http://linnean-online.org/view/collection/linnean=5Fherbarium/Acer.html

Plant Blindness

Some articles about plant blindness:

Download Plantblindnesswanderseeschussler1999

Download Krepsplantblindness

Download Hersheybotanyneglect1996

History of Botany Education

In the mid-1800s, nearly all high school students studied botany and learned to identify plants.

This is a link to the full text version of a popular text of the day. Written by pre-eminent botanist, Asa Gray, most of the text is still accurate and useful today.

Here's my article about the history of botany education.

 

And here's the Regents Exam in Botany:

 

Combatting Plant Blindness in K-12 Education

Here are links to K-12 resources provided by the two major professional societies for botanists,

     The Botanical Society of America and the American Society of Plant Biologists

Plant Vegetative Morphology

Here is my handout summarizing terms used in describing plant stems and leaves.

Download Vegetative morphology

Dichotomous Keys

This is the dichotomous key that goes with the leaf identification kit that we used in class. Download Leaf Identification key

The kit is available from Young Naturalist Company.

 

Other dichotomous keys for trees are available online. Try the Arbor Day Foundation Tree Key.

 

The only polyclave that I could find online is here. But it doesn't work very well.

New York City Street Tree Key

LINK HERE TO DOWNLOAD THIS FILE AS A PDF

Urban Forestry in Context

Two papers documenting the value of trees in the urban environment:

Download NYC Parks 12 page report

Download USDA summary statistics 3 pg

 

Links to urban forestry resources from US Forest Service, Alliance for Community Trees, New York State Urban & Community Forestry Council, Trees New York.

Interactive Map of Street Tree Species in NYC

This is the link to the interacitve map: http://stewardship.nycparks.org/add_trees.php

    (Zoom the map in all the way to see the location of trees in any NYC neighborhood.)

 

BONUS MATERIAL:

Take a walk to see the biggest (champion) trees in NYC. Download this 75 page guide. Download GreatTreeWalkGuide1990

 

Secondary Growth and Wood

Treesgrow in  girth throughout their lives, through the action of two "lateral meristems," the vascular cambium (which forms xylem and phloem) and the cork cambium (which forms the bark). Helpful references: this Wikipedia article and images from my slides.

Some FAQs:

• Annual rings appear because the wood that is created in the spring has larger cells that those created later in the season. Wood of most tropical trees do not have annual growth rings.
• When the bark of a tree is peeled all the way to the wood, the tree will die because
  • the phloem has been removed so sugars cannot be transported between leaves and roots.
  • the phloem will not be replaced since the entire cambium has been removed.
• The center of most trees is dead at maturity. Tannins are deposited there in the heart wood, to prevent fungal infections.
• In the spring, sap flows only in the outer, living band of wood, called the "sap wood."
• The wood of many trees have bands of living tissue, called rays, running from the center of the tree out to the bark. The rays store food (starch) to fuel the spring flush of growth and are valued for their figurative patterns in the stripes of tiger oak and other decorative woods.

 

Trees Grow Tall

 

Trees grow in height only through the growth from the tips of their branches. (If you carve your initials in a tree trunk and come back in 10 years, the carving will be at the same exact height above the ground.)

(from Pinterest) My attempt to spread reason: Trees do not grow taller from the ground up. If you carved your initials in a tree when you were 10 years old and come back when you're 75, those initials will still be at the same height you originally carved them. The tree would have grown in girth, but those initials would not have risen any higher than the day they were carved. And then there's the bike itself. This bike (or at least all the parts that are visible) are NOT 100 years old. I swear. So although this is a completely FABULOUS photograph and it is fantastic that this bike and tree inspired a wonderful story, that does not mean that the bike was chained there by a boy in 1914. Sorry to be a party pooper. :-)

See also: http://www.snopes.com/photos/natural/bicycle.asp

Leaf Arrangement

Objective: To learn to make accurate observations and then communicate these observations by drawing. We will do this by constructing a figure of how the leaves of two different types of plant are arranged on the stem from two different perspectives.

Prerequisite Process Skills: Observation, Measurement, and Communication

Materials: Chrysanthemum plant (alternate) 1 Vinca plant (opposite) 1 Styrofoam cup marking pen, tape, rulers

Procedure

1. Tape the cup upside down on the table. Punch a small hole in the center of the cup with a pencil. Make marks in a "clock-like" manner at 12, 3, 6, and 9 around the cup with the pen. Remove about a 4 inch piece of one of the plants and place it in the hole.

2. Side View. Look carefully at the stem in the cup. Draw a horizontal line to represent the top of the cup. Measure the length of the stem from the cup to the top. Draw a line coming from the "cup" that long to represent the stem. Measure the distance from the cup to the first leaf. Draw a line at a right angle to the "stem" at this distance to represent the leaf. Just draw the lines at right angles to the stem and do not worry about whether they go forward or back. Measure to the next set of leaves and then draw them. Repeat this until you can't measure any more.

3. Questions. How does it look? Does this accurately represent the stem? How are the leaves arranged? Are they always the same? Look at some other people's drawings. Are the leaves always the same distance apart? Can you see any pattern? Can you attempt to explain this pattern?

4. Top View. Don't remove the stem from the cup. Look down on the stem from above. Using another cup draw a circle to represent the bottom of the cup. Place marks around the circle in the clock positions the same as on the cup. In the center of the circle place a dot to represent the stem. Looking from position coming off the stem with a "lollipop" to represent the leaf. Number the leaves starting with the 1 to help keep track. Move up the stem and draw the position of as many leaves as possible before it gets too confusing. Can you see a pattern?

5. Repeat parts 2 and 4 using the other plant.

6. Compare the two patterns. What is different? Which type of leaf arrangement do you think might work better? Think about shade.

(This activity is from a seminar presented in Central Illinois Saturday Science Education Seminars for Elementary Teachers, 1993, by Donald Schmidt, Horticulturist, Illinois State Univ. Normal, IL. http://www.bio.ilstu.edu/armstrong/biolab/eled/leaves.htm )

Primary Growth

In plants, growth in length is accomplished primarly through the activity of apical meristems.

New leaves start out as just a few cells: the leaf primordia.

Mitosis (cell division) occurs continuously in the apical meristems and cell enlargement then results in the increase in size of the leaf primoridia.

Download Primary growth

Winter Botany

Twigs and Buds, Kirigami leaves, etc.

Download Winter botany slides

Download Adopt a bud (a year-round activity to do with your students.)

 

Why do leaves turn color in the fall? How do trees survive in winter?

Science made simple has a good answer, written at a student's level.

 

Plants respond to the environment (just very very slowly)

See for yourself at Plants In Motion, where time-lapse photography demonstrates plant responses to light, gravity, and other stimuli.

Leaf vein patterns have a purpose

Science Friday video -- leaf venation

 

Plant Growth Regulators (hormones)

Auxin is important in apical dominance:

Apical buds produce auxin, which is trasported to the lateral buds where it prevents them from growing out (makes them dormant).

When an apical bud is removed or dies (or grows far enough away from the lateral buds), the source of auxin is lost, and the lateral buds are released from dormancy and begin to grow.

Plant Growth Regulators (hormones): Ethylene

Ethylene is a gas emitted by ripening fruits and stressed plants. There are also artificial sources: at the turn of the century street lights were lit with coal gas that released ethylene and inhibited growth of street trees.

Ethylene can have the following effects:

• Stimulates the release of dormancy
• Stimulates shoot and root growth and differentiation (triple response)
• Stimulates leaf and fruit abscission.
• Stimulates flower opening.
• Stimulates flower and leaf senescence.
• Stimulates fruit ripening

Two effects of light intensity

Plants that receive insuffient light may be "etiolated." Etiolated plants lack chlorophyll and have relatively long internodes and undeveloped leaves like the pea seedling on the left.

In many tree species, leaves in the top part of the canopy are adapted to higher intesity light than are leaves of the lower branches.

Compared to sun leaves, shade leaves have a greater ratio of area to perimeter (are not so deeply lobed). They are often larger and have a thinner cuticle than sun leaves.

 

Flowering Plant Phylogeny

We ran out of time and I didn't get to present this piece.

Download Flowering Plant Phylogeny

The main points are:

• Flowering plants have been around since the Cretaceous Period, 125 Million yrs. bp.
• Before that time, during the Carboniferous, trees were mostly spore-bearing, and related to ferns.
• Trees do not form a synapomorphic group. They occur in nearly all plant orders.

Recommended Books

Which Mulberry?

Did you know that the white mulberry plant actually has red berries?

 

Perhaps all the mulberries we are seeing are actually the invasive species.

Read more about mulberries here: Download Which mulberry