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.