The Planetary Society of Japan : Column

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YM COLUMN ARCHIVE

November 11, 2009

The veins of a leaf and life-----a conversation with a girl-----

In the event program to enjoy together with children is, “To make a pretty bookmark by vein skeleton”.

The process is to first cleanse a leaf with water and then boil it with alkaline solution (solution of sodium hydroxide or sodium carbonate), which is further followed by careful cleansing of a leaf with water again to get rid of mesophyll off a leaf by toothbrush or ink brush. Sometimes you may give it the last treatment of water cleansing again or make it whitened by bleaching agent, and then you can have a really beautiful vein skeleton.

You must be only careful not to let children handle alkaline solution by them alone, though. Children heave sighs to be impressed with the beauty of vein skeleton made by themselves. You can color it or draw letters or patterns of your own liking to complete vein skeleton by laminating it.

We often see leaves only left with veins afloat on pond. Some of you may remember to have seen the fossils of leaves in veins; whose reason are perhaps the veins are much harder than the rest of the tissues. If you have a plenty of time, the best way to make the vein skeleton is to leave a leaf in water for a long time until it gets decayed. In playing with children, however, we just can’t wait that long, so we use alkaline solution and heat to quicken reaction to get rid of the tissues other than veins.

The other day, I played with children to make the vein skeleton by using sodium bicarbonate. We heated up sodium bicarbonate by frying pan to make sodium carbonate, by which watery solution we treated the leaves. It’s really a happy fun to look at children’s faces excited with expectations. At that time we used a leaf of gardenia. Children’s joyful expressions with bleached veins in their hands appeared as if they were in heaven.

After a while, a girl said, “Why are only the veins left?” I expected this question and answer would soon end. I answered, “Maybe because the veins are harder than the rest of the leaf, I suppose” to which she didn’t say, “I see” as I expected she would. Instead, she said “Why are the only veins hard?” still further said, “What are the veins for?”

It was when I was given a start. Magnifying a section of the vein shows that in its interior runs the phloem to carry nutriment and the trachea to carry water. Needless to say, water is siphoned off from the roots and nutriment is made by leaves. The veins to carry water and nutriment are highways vital for vegetables. Therefore, there run tough strings through the veins in order to protect the highways so that they would not be so much damaged, even if the other parts were given strains. It is a lifeline in a true sense of the word.

I answered the girl, looking at her in face, by warning myself of my frivolity in prudently choosing the words, “I suppose these veins must be very important pipes to carry water and nutriment vital for vegetables to live on. This is why, I think, the veins were left to the end unbeatable from any kind of damage to protect the very “life” of gardenia.”

The girl was moved to tears. I wondered if I said something pitiful.

I welcome your comments on this column to the following E-mail address.
matogawa@planetary.or.jp

(Translated by The Planetary Society of Japan)