Pine Cone Wet and Dry
I am a Literacy Teacher and read a story about a
boy and his father buying a tree to plant in their yard. They ended
up buying a pine tree. I have several pines cones and one that I
have is inside a mason jar. I asked my students how they think it
got in the jar and how can we get it out? So, I filled the jar with
water and told my students that they will observe and see what will
happen. By the end of the day it was closing up. The next day I was
able to remove it from the jar. The question we have is,"Is a pine
cone that is not attached to a tree living or dead? They we
amazed!It has movement by closing up. I have emptied the water out
of the jar and we are watching it dry up and begin opening up again.
Once the pine cones are dried out by the tree cutting off the water
supply to it, it is no longer alive. Pines cones develop, in most
species, over a two year period. Pine cones have a structural
mechanism at the base of each seed petal (that houses the developing
seed) that, when it dries, it automatically opens up by moving away
from the center of the cone. This opening allows for the seed to
drop (it is also dried due to lack of water) and blow away in the
wind or just drop out by gravity. After a time that has allowed for
seed dispersal, the cone will break off its attachment to the tree
and fall. As long as the pine cone is intact, it will open and
close depending upon the water it receives or loses. Place the cone
in a glass of water, it will close as it did when it was keep moist
as the seeds were developing in the first year. These first year
cones are usually green and tightly closed.
A fun, but soon to be boring, activity is to see how many times the
cone will close and open with drying and placing it into water. It
is not alive.
Up-date: Summer, 2012
I read a your response to "Pine cone Wet and Dry". You indicate once a pine cone is disconnected from its host tree that it no longer is a live organism and it is not receiving any water from the tree any longer therefore concluding the pine cone will stop opening and closing when exposed to moisture. How long would you say this process would continue until it would no longer open and close?
I ask, because I have a couple of pine cones sitting on my patio table for decoration and it never ceases to amaze me that every time it rains they close up and open again when they dry out. My amazement may be caused by the very infrequent times it rains in the desert southwest. However, I have had these pine cones on my table for 4-5 years and they still close every time it rains and open again when they dry out.
Could you explain this phenomenon further and how long they would continue to do this if they are no longer alive? What drives them to do this?
I have never test the longevity of this pine cone phenomenon. As long as they are not kept in a moist environment where the cone can not completely dry out thus allowing the cellulose matrix of the cone to begin to decompose, I would predict it would take a very long time before the process would stop. I have used cones that were over 10 years old, used them several times a year and they continued to function well.
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Update: June 2012