Friday, January 25, 2013

The tara experiment continues.

In a previous post, I told you about planting tara trees with the students and staff at the technical college in my town. I went back today to have a look at the plants. The first group we planted are now 5 weeks old, the second group 4 weeks old.
It's vacation right now so no students were around today. The college secretary helped me record data. She also helped me weed the bags. Thanks, Ana!
We counted the number of trees that germinated in each treatment condition. I'll need to track down a way to run the statistics, but there's action for sure. First of all, there was a main effect of nicking. The germination rate was much higher for the seeds that we nicked open than for those we left alone. At this point, 93 of the 200 nicked seeds have popped up, but only 17 out of 200 of the un-nicked seeds.

I had hypothesized an interaction between nicking and soaking. There is one, but not what I expected. I thought that the nicked seeds that we soaked would do the best, but I was wrong. The best germination was for the nicked seeds that were planted dry. Soaking actually has hurt our germination rate. How weird!
Here's my data. (I love data.)
Here are photos of the different conditions, from the older group of trees. Condition 1 was dry, un-nicked seeds. Only 3 have germinated as of today.
But look at the difference--here's group 2, dry seeds that were nicked to help the seedling break out of the hull. 45 of 50 seeds germinated! We planted 2 seeds in each of 25 bags. Soon, we'll remove the weaker plant from each bag. I was planning to throw the culls away, but maybe I'll put them in their own bags.
Here's group 3, not nicked, and soaked. 7 germinated in this condition.

Finally, group 4, nicked and then soaked in warm water overnight. 13 of the 50 seeds have germinated, so far. I wonder if soaking really is a bad idea, or if the way we soaked them was a problem. Kristi (nearest Peace Corps volunteer, who helped with the project) and I talked about it. She reminded me that she had originally soaked the seeds for the day we thought we would be planting. However, when we showed up to plant, it turned out that it was a bad day for the institute, and planting was postponed a week. We poured out the water and left the damp seeds in a plastic bag for a week. Was that too long? Maybe a short soak is good and a long time damp is bad? Sounds like a question for another experiment!
That's the results from the first planting week. We got 100 bags (200 seeds) planted that first day, then it was time for lunch and everyone left. A week later I got a crew together and did it all again: 25 bags for each condition. The data for the second week is similar to the first week.

I'll collect data each month. What I want to know is whether the important outcome is in terms of how quickly the seeds germinate or how many germinate. Maybe the other conditions will catch up over time and it will turn out that the effect of nicking and soaking means nothing in the end. We shall see. Whatever the results, there's enough going on to justify a presentation at a conference. That will be a great resume-builder for the Peruvian college students I'm working with.
And the important thing is that we have baby tara trees for our community!

No comments:

Post a Comment