Wings on Seeds

Engage

As a formative assessment, ask students: Why is it important for seeds to move away from the parent plant? What are some ways that seeds move? Split students up into groups and give each group a bag of various different types of seeds and fruit. Give students time to sort the seeds based on dispersal method.  After the allotted time, have groups share with each other their criteria for sorting the seeds and the dispersal methods they came up with.  Encourage students to identify the seed itself as distinct from other parts of the fruiting structure that aid in dispersal. Seed Dispersal – The Great Escape shows a variety of seed dispersal strategies. 

Show students a maple seed and ask: What do you know about maple seeds?  Give each student a “helicopter” and allow time for observation and testing.  Ask for observations about the seeds and their movements and record these on the board. Ask students how the movement of maples seeds allows them to disperse away from the parent tree. Two short videos you may want to show are Maple Copters and a Maple Seed Falling in Slow Motion.

 Explore

• Tell students that they will be going outside to investigate maple seeds and the characteristics that affect how far they can travel.  Record student observations on the board.
   
• Establish or review rules for working outside before leaving the classroom, including the signal you will use to gather them together as a group.
   
• Once outside, ask students to collect maple seeds (samaras) and look for variations in characteristics of the samaras. (Characteristics that may vary from seed to seed: overall size, wing length, wingspan, seed size, angle between samaras, and weight.)  After a few minutes, call students together. Have students share what they discovered about seeds. They may have even found young maple trees just a few inches tall.
   
• Discuss seed characteristics students noticed, and consider questions they might investigate. Perhaps your students will want to compare dispersal distance of small and large winged seeds from the same tree. Or perhaps you will want to compare the dispersal distance of different types of maple if more than one species is available on your schoolyard.  With the class, decide what question you will test, or have students decide with groups what question to investigate.
   
• If you are using size as a dispersal factor, you and your students will need to determine how to measure size. Here are some suggestions: a) Younger children might collect maple seeds and then make two piles - large and small. b) Students can measure the surface area of each samara to be tested by tracing outlines on graph paper and then counting squares c) If you have a balance available, students can use the weight of the seed or samara as an indicator of size, or d) Older students might use the ratio between seed size and samara length to determine size. 
   
• Before testing maple seed characteristics, ask students to predict which will help the seeds travel farther.  Have them explain their thinking behind their predictions.  Depending on your students, you may want to determine how data will be recorded, or have students design their own data collection sheet.
   
• One way to investigate how far maple seeds go is for the students to drop one at a time from a spot that is at least 2 meters (about 6 feet) high.  Outdoor playgrounds often provide prime drop sites.  Dropping samaras from greater heights gives more dramatic results. Stairwells might be exciting indoor possibilities for rainy days. Make sure students are comparing their seeds from the same drop point.
   
• For each seed dropped, students should record either the distance traveled from the drop site or the time aloft. More advanced students, however, can measure distance AND time aloft. In this case, ask students to predict how or if the two variables of time aloft and distance are related, and if either or both is related to particular seed characteristics.
   
• Discuss students predictions and their actual results?  Were their predictions correct – why or why not? Have students create a hypothesis that describes what makes a maple seed disperse farther based on the results of their experiment.  How could they refine their experiment to test their new hypothesis
   
• Discuss experimental results in relation to plant survival and reproduction.  How did different characteristics affect distance traveled? What other factors might affect maple seed dispersal?
    
• Of all those maple seeds, the vast majority will never germinate. (Why not?) Of the seeds that germinate, the vast majority will never become mature trees (why not?)

Explain 

Most of us have, at one time or another, aided the dispersal of dandelion seeds and are familiar with the hair-like structures on dandelion seeds that catch the breeze, enhancing the distance that dandelion seeds travel.Wind also carries maples seeds, though the structure of the wings causes them to move in very different ways. 

What we commonly call a maple seed is actually a maple fruit made up of two samaras.  Each samara contains one seed with a wing-like extension. (Other trees such as ashes, elms, and hoptrees produce single samaras.) There is natural genetic variation in maple seeds even within the same species as students will see when they examine, measure, and test maple seeds. 

The vast majority of familiar flowering plants, including trees, form structures called fruits that protect the developing plant embryo (contained within the seed) and to help disperse the seeds to new locations. Most fruits and seeds are adapted for dispersing seeds away from the parent plant, where young plants will not encounter as much competition for nutrients, water, and sun as they would if they remained under the parent with hundreds or thousands of other young plants. In addition, seedeaters (squirrels, mice, birds, some insects) and pathogens (bacteria, viruses, fungi) may be more successful in eating or destroying seeds if they occur in large clusters. 

The seeds of fleshy fruits such as those of cherries and blueberries are tasty to many animals and are well adapted for passing through an animal gut intact. Others have hooks, spines, hairs, or sticky surfaces and adhere to the feathers or fur of animals that brush against them; thus, they are eventually transported to new locations. One of the most common means for dispersal used by New York’s native trees is wind dispersal.

The vast majority of seeds never germinate and fewer still become mature trees.  Seeds may be eaten, damaged by a pathogen, land on inhospitable terrain, succumb to heat or freezing. 

 Extend:

1. Based on the study they just preformed have students develop their own testable questions and hypotheses about maple seeds, then design and conduct an experiment to investigate their question.  Students might investigate drop height, air currents, or time aloft. Characteristics such as shape, size, and angle between “wings” of different maple species can be compared.  Students may be able to find evidence of seed predators (munched seeds!) and investigate whether seed size or distance from parent tree seems to effect predation.  

2. Find out how many seeds have fallen various distances from the parent tree and construct a graph showing how many seeds are dispersed out to various distances. 

3. Investigate travel distances of other wind-borne seeds, such as those from dandelions, milkweed, or elm.

Evaluate

• Have students sketch and label a maple seed with characteristics that help it travel far from the parent tree.  Then ask them to sketch and label one that probably won’t be able to travel far.  Students should give their work a title, and write an informational caption explaining their drawings.
• Assign a written summary or lab report.