Germination Experiments

Investigations in Germination

by Sci 4 Oppy & Spirit

We have been studying germination. Germination is the stage when the seed sprouts - the seed coat splits and the radicle comes out. We were trying to find out what would work best for alfalfa seeds to germinate.

We had these hypotheses, seeds need:

• need water to germinate (wwc)
• need light to germinate (ds)
• need soil to germinate (es)
• need carbon dioxide to germinate (al)
• need nitrogen to germinate (al)
• need potassium to germinate (ar)
• need phosphorous to germinate (jrs)
• need oxygen to germinate (lt)
• needs proper temperature (ar)
• needs bacteria to germinate (es)
• needs proper pH (es)

*“proper” amount may vary by species of plants

To test our hypotheses we glued 5 seeds to a piece of circular filter paper and put that in a petri dish. The petri dishes went into a container with water about 1 cm deep.

In our first trial, we put seeds in water and under constant light. We also put seeds under the light without water. The seeds that were dry did not germinate. The seeds that were wet germinated in two days. From this we concluded that seeds need water to trigger germination.

In our second trial, we asked, do they need light. We put the seeds in a dark cupboard to test this. The seeds germinated without light, but the cotyledons didn’t turn green, they were a pale yellow instead. The hypocotyls were white and very long. This tells us that seeds don’t need light to trigger germination. We think the hypocotyls were so long because they were trying to reach light.

In the third trial, we tested how temperature would affect germination. We put one set of seeds in an incubator at 35°C and another set in the refrigerator at 18°C. The seeds in the incubator germinated faster than at room temperature. Most of the seeds in the refrigerator did not germinate at all. The ones that did, grew v-e-r-y s-l-o-w-l-y. So, seeds like warmer temperatures to germinate. We wondered if the embryos in the cold seeds were still alive. We moved them to the room temperature and they germinated. The embryos were still alive.

Our fourth trial tested if the seeds could germinate in salt water. We made salt water solutions of 10 g/L, 5 g/L, 2 ½ g/L and 1 ¼ g/L. Only 7 of 40 seeds germinated at 5 or 10 g/L after 5 days. We moved these seeds to freshwater to see if the embryos were still alive. After 2 days, 6 more seeds germinated when moved to the fresh water for a total of 13 of 40 seeds. In 2 ½ and 1 ¼ g/L, most of the seeds germinated after two days. So that means the embryos can tolerate salt water at a low level. Less than 2 ½ g/L.

Our fifth experiment was to see if seeds needed air to germinate. We put seeds in a test tube completely filled with water and no air bubbles and put a rubber stopper to seal the test tube. After 5 days, the seeds had swelled up and the seed coats had lost color, but no germination. We put these seeds in petri dishes to see if the embryos had drowned or suffocated. We found that some of them were still able to germinate.

Doing these experiments, we learned that seeds need certain things to trigger germination. We also learned that science takes time. You can’t rush an experiment or you will mess things up. Sometimes you have to wait a few days to get your data. Experiments have to be carefully planned out. You can’t just say, “Let’s go!” and jump into action. You have to plan before you can do science. We also learned that the most important part of an experiment is the control. We have to have a control to see if there is any difference in the experiments. Our control was seeds germinated in “regular” conditions: room temperature, water and constant light.

Make Way for the Wintermaker - Sky & Telescope

Make Way for the Wintermaker - Sky & Telescope

Maths Likes

Math5 asked mathematicians on Twitter, "What do you like about math(s)?" We got some great responses. You can see the responses by clicking this link: https://storify.com/mwilkinson3/maths-likes?utm_content=storify-pingback&utm_medium=sfy.co-twitter&utm_campaign=&utm_source=t.co&awesm=sfy.co_bzd6

Soil Nutrient Lab

Soil Nutrient Lab

Our work in Michael’s 4th Grade Science class this year started with looking at the needs of living things. We came up with all kinds of things we thought we needed, but narrowed down to the basic needs of living things: food, water, air, habitat. We’ve been told that the plants bring the nutrients into the ecosystem by absorbing them from the soil. We wanted to see if we could find those nutrients ourselves. We learned that there are three main nutrients for life: nitrogen, potassium, and phosphorous. So we decided to test for these in the garden. Shouldn’t there be plenty of nutrients there since we were growing things to eat?

Collecting Soil Samples

We collected soil samples from the garden beds, the pond, the area outside the garden beds under the woodchips, and in the runoff from the playground by the bridge. We tested each of these soils for the three nutrients and found that while there was sufficient phosphorous and potassium in the soil, there was very little nitrogen. When we went back to the garden, we could see the effect on the squash plants. Their leaves were yellow-green with yellow and brown spots and the edges of the leaves were dry brown. These were signs of not enough nitrogen.

These leaves don't look healthy.

How can we grow healthy plants to eat in a garden without enough nitrogen? We wanted to find a way to improve the soil, so we brainstormed some solutions. We thought adding compost or fertilizer might help. We also remembered that there are some plants that help put nitrogen into the soil. We remembered from our “Three-Sisters” study last year (corn-beans-squash) that one of the things the beans did was help with nitrogen, we thought planting beans might help. We also wanted to try alfalfa. So we took some small pots and prepared the soil five different ways: control soil with no change, soil mixed with osmocote pellets, soil mixed with compost, soil planted with beans, soil planted with alfalfa. We put these under constant light and water and will test the soil nitrogen levels in a few weeks.

In the meantime, we learned that bacteria helped convert nitrogen from the air into nitrogen that plant roots could absorb. Maybe there wasn’t enough bacteria in the soil from the garden. Upperschool Science Teacher (and class parent) Howie Waldman came to class to help us grow some bacteria from the soil and compost. It only took a day for there to be a lot of growth. Howie is going to help us to try to make microscope slides of the bacteria next, so we can see individual cells.

We also noticed a lot of living things in the compost - macroinvertibrate decomposers. We found nematodes, earthworms, pseudoscorpions, weevils, isopods, and others we haven’t yet identified.

We’re learning a lot about soil, how it works and how it helps us to be healthy. Like the song says, dirt really did make our lunch. We can’t live without healthy soil.

DATA UPDATE 10/21/14

After one month, we tested our soil treatments for nitrogen levels with Rapitest kits:

Soil Treatment	Nitrogen Level after 1 month
Control	Depleted (N0)
Osmocote	Surplus (N4+)
Compost	Surplus (N4+)
Beans	Deficient (N1)
Alfalfa	Deficient (N1)

Conclusions

We can improve the nitrogen in the soil using compost and Osmocote. It only takes a little of these to raise the nitrogen in the soil. Planting beans and alfalfa changed the nitrogen a little bit, we need a lot more bean and alfalfa or more time to bring the nitrogen up enough. So, if we want healthy garden soil, we need to add a little compost to the soil.