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We are in 1st grade. We are doing an experiment. We are growing rye grass and alfalfa in the dark without any sunlight. Our classroom has no idea how it is growing. It is growing faster than the grass in the window. The grass getting sunlight is a darker green, and the one in the dark is a very light green, but it is taller. How come it is growing without sunlight? We are going to keep watering it and keep it in the dark to see what happens. Will it keep growing? Please write back or come visit us in room 8. We have lots of other stuff growing too, like a sweet potato. Thank you! P.S. Daphne helped type.
Question Date: 2015-05-05
Answer 1:

We don’t usually think of plants as parents, but when they make a seed, they put in a lot of energy and nutrients. This gives the new plant a good start in life. The new sprout may be buried deep underground, so it needs a good food supply until it can start collecting light and carbon dioxide from its leaves and nutrients from its roots. People have bred plants like rye for hundreds of years to get seeds that are packed with food. We usually collect the seeds and grind them for flour, so we want them to be full of energy and nutrients.

So those young plants are doing fine now, even in the dark because they are using the stored food. They are a pale green and tall because they are putting most of their energy into growing up instead of making green chlorophyll. Why? Because they aren’t getting any light. This usually means that a seed is too far underground and its only chance for survival is to grow as fast as it can so that it can get some light before the food in the seed runs out.

Which plant do you think will last longer in the dark, the sweet potato or the rye grass?
Keep experimenting and wondering!

Thanks for asking,

Answer 2:

My guess is that the plants in the dark are growing using energy they have stored up either in seeds or in their roots. If this is true, then they will one day run out and stop growing, while the plants in the light will keep growing.

Answer 3:

I have a feeling that the grass growing without sunlight is still receiving indirect light from your classroom. Sunlight is best for plants but they will photosynthesize (produce sugars for energy) with any light they can get. If you grew a plant in complete darkness it would not survive, although it would try to grow upward as fast as possible to reach sunlight (which is why the "shade" grass is so tall). Your "shade" grass is trying to access sunlight through the "dark forest" that you've created.

The color of the plants is really interesting too! Plants produce colored stuff that catches sunlight. The more sun they receive the more green pigment (the colored stuff) the plant produces to catch the light. It's just like when we get freckles from being in the sun too long! The darker green the plant, the more freckles the plant has to catch sunlight!

I would be happy to visit and say hi. I'll let the organizer contact me about this great opportunity.

Happy growing!

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