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We started out this week by checking in on the trees to see if we had enough root growth to begin waterlogging. Some of the sugar maples and star magnolias are slow-pokes. Their root growth rates could be compared to the speed of our beloved lab pets seen on the left (on the right is Cater, followed by Pillar). To get the best results possible from the experiment, we want all of the trees to be well established with an abundance of roots before waterlogging. So, we wait! Nevertheless, there is always work to be done in the lab. Take a look at what we were up to this week:
Recorded photosynthesis measurements using Li-cor 6800
Let me introduce you to the spectacular machine that is the Li-cor 6800. Scientists use it for a wide variety of research questions. The environmental settings are adjustable which allows us to look at plant responses and performance in different conditions. For instance, how would photosynthesis rates be impacted by changes in temperature, light, and atmosphere composition (amounts of CO2)? These are questions we can answer using this technology.
Li-cor 6800
For our waterlogging project we are focused on three variables provided by the 6800: assimilation rate, intercellular CO2, and stomatal conductance to water vapor. Don’t worry if you aren’t familiar with those terms, not many people are (unless you spend your free time playing with Li-cor machines or reading plant physiology journals). Here’s a basic rundown of what is being measured:
Assimilation rate is looking at leaf size and how much CO2 can be “absorbed” in a given amount of time. We know that for photosynthesis to occur, plants have to take in carbon dioxide. This is part of that process!
Intercellular CO2 is telling us the amount of carbon dioxide inside the leaf.
Stomatal conductance to water vapor is measuring the amount of water leaving the leaf. Little pores on the underside of leaves, called “stomata,” act like doors that open and close. This determines how much water and carbon dioxide exit and enter the leaf.
Here I am taking photosynthesis measurements of a star magnolia. A single leaf is placed in the leaf chamber for analysis.
Imaged roots
From the examples below you’ll be able to see why we decided to hold off another week before waterlogging. Some of the windows show moderate-high root growth, while others are completely empty. Since we are using 4 different species in our experiment, the growth rate and total amount of roots will never be exactly the same for all of the trees. On top of that, trees are all unique individuals, just like us! You could have two sugar maples growing in your yard experiencing the same conditions, and one will be a little taller or better at playing the piano than the other.
This is a great example of the differences we are seeing in the rate of root growth between our trees. The top row shows 2 maples trees, the one on the left has no visible roots in that window, and the one on the right shows a good portion of roots. The magnolia trees on the bottom row are showcasing the same variability. Keep in mind that just because we are not seeing any roots in this window, it doesn’t mean the remaining 3 windows look the same. The rest of the windows are dedicated to tracing. I will continue updating the blog with the traced images as well to make sure we are getting the full story of these trees.
Watched as our caterpillars entered teenagerdom
Our little friends are growing up so fast! We have a small insect cage in the lab where we have been housing 3 caterpillars. Cater and Pillar, featured earlier in this week’s blog update, are around 3 weeks old. Butter, the black and white giant swallowtail (Papilio cresphontes) seen below, is a little younger. The green dude is an Eastern tiger swallowtail (Papilio glaucus).
Butter, making their root lab blog debut. Don’t let the small size fool you, Butter is a giant swallowtail, the largest species of butterfly in North America.
This is either Cater or Pillar. Can you blame us for not being able to tell them apart? The horn-like structures you see here are called osmeterium. When a caterpillar feels threatened, it sticks out this organ and releases a stinky smell to fend off predators.
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