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Open the
Blinds,
Pinecones!

The pinecone reminds us of the holiday season with its spiral and scrubby outfits, a perfect ornament for a Christmas tree decoration. The beauty of this nature-based ornament comes from its kaleidoscopic 3D geometry. The spiral arrangement of woody seed scales constructs multi-layers, delivering different experiences from various viewpoints. But few people know that the pinecone can close and open its multi-layered structure in response to environmental humidity changes.

Pinecone

Seed scale!

A Characteristic of Pinecones

Pinecones
Can Open and Close

Repeatedly

Pinecones open and close depending on the weather
Scientists found that changes in the weather trigger the reversible transformation of the pinecone. Under cold and wet weather conditions, the seed scales of a pinecone close up to protect and bear the seed. On the contrary, when the weather is warm and dry, the pinecone opens up the structure and exposes the seed scales.

"Why do pinecones keep opening and closing following changes in weather?"

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Pinecones are waiting for the perfect weather conditions for seed dispersion

The seed is packaged inside of the scale for effective seed dispersion. These seed scales in a pinecone start their journey when enough force from wind detaches them from the pinecone.

At this time, warm and dry weather conditions help spread the seeds longer distances because there is greater likelihood of avoiding rain and experiencing streamlined wind flow, which can carry the seeds further. Pinecones may open and expose the seed scales on days that are warm and dry to take full advantage of this, so it can be understood that pine trees have evolved to avoid wet and rainy days for successful seed dispersal. On rainy days, the pinecone is closed to keep the seeds from being dispersed.

Humidity decides, not the tree

A fun fact is the pine tree does nothing special when it comes to the opening and closing of pinecones. And because this task is programmed to happen during the pine tree's preferred climatic conditions, it can achieve its goal with little effort and at the moment it desires.

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“The scales of pinecones react to changes in humidity. For example, if the humidity decreases, the scales bend and move from a straight to a curved shape—so the cone opens in dry weather. It is the cone’s structure that makes this possible because the scales consist of two connected layers that contract to different degrees as the humidity decreases.”

from https://www.futurity.org/pine-cone-shading-system-1844342-2/

"

If you look closely at the cross-section picture below, you can see that the pinecone opens as the scales bend.

It adjusts the degree of opening by varying the degree of deflection; consequently, it can be repeatedly opened and closed.
Interestingly, changes in ambient humidity cause this warpage.

"What does this discovery mean for us?"

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Click and Read
Pinecone's Opening Mechanism

Image:

The cones of conifers are closed when dry (left) and open by themselves when wet.

Image © C. Zollfrank, Technical University of Munich

Learning from Pinecones

Steel Awning on Modern House

Pinecones
inspired a thermostat system

Energy efficient thermostat with a nature-inspired shading system

This pinecone-inspired shading system reacts on its own according to weather changes. Unlike conventional blinds, this system does not require sensors, motors, or electrical energy.

As we know, a pinecone moves in response to changes in humidity. For example, when humidity decreases, it causes the bending of the scales, and the pinecone is simultaneously closed and, in dry weather vice versa. Engineers got an idea from this phenomenon and incorporated this opening and closing mechanism into a shading system.

The panels of the blinds are layered with different types of wood, and the fibers are also oriented vertically. Like a pinecone, the blinds move according to the humidity changes. And they adjust the amount of light entering the room. These blinds can be placed on the roof of a building or over a window on a building's facade.

Image:

Prototype of coupled bilayered planks. Image ©ETH Zurich

Image:

Adaptive shading system. Image ©ETH Zurich

Buildings consume 40% of the world's energy!

Up to 40%
    Energy Savings!

     Thank you

 pinecones!

During midsummer, it can be swelteringly hot in a building exposed to direct sunlight. On days like this, we use blinds to block direct sunlight and turn on the air conditioner to lower the room temperature.

According to the International Energy Agency, buildings are the world's largest energy consumer, accounting for more than 40% of energy consumption. Unfortunately, people rely on electricity-powered thermostat systems to help control room temperature. That's why buildings use most of their energy for heating and cooling.

Exploration

You can build a hygrometer utilizing the opening and closing principle of pinecones.
Follow the instructions, and try to create a pinecone hygrometer. Check the humidity level of your room.

Looking for Pinecones

Click and discover pinecones

Introduction

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Let's collect pinecones!

Let's find pinecones in our neighborhood and observe how they mobilize their seed scales. Is it really true that pinecones can respond to humidity changes?

Let's collect pinecones!

Are there pine trees in your area?

Collect pinecones                 in your neighborhood!

Screenshot 2023-01-12 at 3.12.53 PM.png

Image:

from GBIF.org (2020), GBIF Home Page. Available from: https://www.gbif.org [13 January 2020].

Many coniferous trees, such as pine trees, spruce, and larch etc., form pinecones to safely grow seeds until those are mature and no longer need protection. In particular, heavy rain, wind, or hot sunlight over the summer season can damage the seeds, so these must be avoided. During this potentially harmful season, pinecones stay closed to protect the seeds inside and ensure that the seeds grow safely.

Let's find pinecones in our neighborhood and observe how they mobilize their seed scales. Is it really the case that pinecones can respond to humidity changes?

Meet different pinecones among the coniferous tree family!

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Pine

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Cedar

spruce.jpg

Spruce

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Cypress

Click and learn about this plant

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Redcedar

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Fir

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Larch

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Hemlock

Making a Pinecone Hygrometer

Click and see how to make it

Introduction

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Difficulty: Easy
Time taken: 10-20min
Components:

  • pinecone

  • water tray with water

  • graph paper

  • aluminum foil

  • thin pin

  • PET bottle or PET cup

  • marker

  • glue

  • thermo-hygrometer (optional)

Step 1: Cut a plastic bottle or cup to make a pinecone hygrometer

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Cut a plastic bottle or cup in the way shown.

It will become the body of the hygrometer.

Step 2: Soak a pinecone in water

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Soak a pinecone in water to close the scales.

Step 3: Insert a needle into the pinecone

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Lightly insert a needle into the tip of the prepared wet pinecone in the direction the scale is facing.

Step 4: Fix the pinecone to the bottom of the bottle

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Attach the pinecone to the bottom of the bottle or cup using glue.

Step 5: Attach graph paper to the body of the hygrometer

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Cut and attach a piece of graph paper to the body of the hygrometer.

Mark the initial height of the needle with a marker on the graph paper.

Step 6: Record and compare the needle height that changes as the pinecone opens

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Observe the changes in the pinecone while it dries.
 

Check how the height of the needle changes while the pinecone opens.

Record the height on the graph paper.

Expand Your Vision

Close the blind, pinecones!

Various strategies to gain the upper hand in reproduction

As we have seen above, the reason the pinecone opens at the right moment is to achieve successful reproduction of the species. The pine tree launches seed dispersion when the day is warm and dry. The pine tree prefers warm and windy days to disperse the seed scales with enough force from the wind. It might help the pine trees to reproduce. This characteristic is known as being quite common among coniferous trees.

However, even in the same coniferous tree family, there are distinctive trees that have novel strategies. Some pinecones do not usually open in warm and dry weather, unlike what we've seen above. These pinecones open and release seeds in extreme conditions such as wildfires, extreme heat, or drought. These unique traits can lead to an explosive spread of seeds in extreme conditions, where competitors are eliminated, and seedlings can grow in empty, fertile ground.

It is interesting to note that even plants that seem to live passively can actively perceive and respond to changes in their surroundings.

 

Let's investigate active plants that can act in response to specific conditions, such as pinecones.

What plants can act in response to environmental changes like pinecones?

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Plants can move?!

Surprisingly, many plants can move in response to certain conditions or energies. It's just that we don't notice the movement because it is too slow or not as dynamic as human movement. Listed here are the series of plants that can move in response to certain conditions. Check out how these plants can move!

"

Pinweed

In response to humidity, the coils behind the seeds can be uncoiled. This rotational force is used for drilling and planting in the ground.

Create inventions!

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Click and learn about this plant

Reference and Further Readings

  • Dawson, C., Vincent, J. F., & Rocca, A. M. (1997). How pine cones open. Nature , 390(6661), 668-668.

  • Vailati, C., Bachtiar, E., Hass, P., Burgert, I., & Rüggeberg, M. (2018). An autonomous shading system based on coupled wood bilayer elements. Energy and Buildings, 158, 1013-1022.ISO 690.

  • Quan, H., Pirosa, A., Yang, W., Ritchie, R. O., & Meyers, M. A. (2021). Hydration-induced reversible deformation of the pine cone. Acta Biomaterialia, 128, 370-383.ISO 690.

  • Poppinga, S., Zollfrank, C., Prucker, O., Rühe, J., Menges, A., Cheng, T., & Speck, T. (2018). Toward a new generation of smart biomimetic actuators for architecture. Advanced Materials , 30(19), 1703653.

  • Vailati, C., Hass, P., Burgert, I., & Rüggeberg, M. (2017). Upscaling of wood bilayers: design principles for controlling shape change and increasing moisture change rate. Materials and Structures, 50(6), 1-12.

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