Repotting, Re-PCRing, and the War for the Greenhouse

Life has been hectic since returning to campus for summer research. I dove back into work with a massive repotting of my milkweed. My project requires two stems of milkweed in every pot—on one stem I will simulate insect herbivory, and I will measure cardenolide levels in both to determine whether chemical defense signals are shared through root systems. Splitting and repotting milkweed is an all-day event, mostly because by the end of it you’ll be too dirty and exhausted to want to do anything else. Milkweed naturally occurs in fields and prairies, where plants send out sprawling root networks that take up water and nutrients and anchor the plants so they can grow as tall as over two meters. Though our plants in the greenhouse never grow that tall, their roots still try, and milkweed pots are crammed with tangled and gnarled knots of them. My labmates pitched in to help me out on repotting day, which I will always be thankful for, considering what a huge and messy task it was! We shook out gallons of loose dirt and chisel away more from the roots, so we could trace roots to see which stems are closely collected and can become a pair in its own pot. We do all this while trying not to snap the delicate stems, which grow to about two to three feet in the ISC. By the end of the day, we were all covered head to toe in potting soil, as were the floors of the greenhouse, which we bleached and scrubbed.

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Milkweed Connectedness Update 1:

My original plan was to use common Milkweed as a study system to understand the impact of clonality and group survival. By intentionally adding a pathogen, such as an herbicide, the spread of the negative effects can be witnessed in a clonally connected plant. The goal of this experiment is to see how far the pathogens travel in a patch, how long it takes for other plants to die, and if there is any preferential sharing. For instance, sometimes younger plants are favored in sharing. Herbicide will be used as a proxy for connectedness and physiological integration. 

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Herbicide Transfer through Clonal Milkweed

In this study I propose to use common Milkweed as a study system to understand the impact of clonality and group survival. By intentionally adding a pathogen, such as an herbicide, the spread of the negative effects can be witnessed in a clonally connected plant. The goal of this experiment is to see how far the pathogens travel in a patch, how long it takes for other plants to die, and if there is any preferential sharing.

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The Effect of Novel Animal Models on the Sexual Reproductive Pathways of Asclepias syriaca

One of the most beloved insect species alive today is the Danaus plexippus, or the monarch butterfly.  Ominously, they have seen concerning population declines which have been strongly linked to a decline in milkweed, specifically Asclepias syriaca (Common Milkweed) populations, the host plant of the Monarch caterpillar.  Between 1999 and 2010, the milkweed and monarch populations decreased by 58% and 81% respectively (Pleasants and Oberhauser 2012), highlighting the need for conservation.  While we know a great deal about monarch and milkweed interactions, we know comparatively less about the milkweed interactions with other specialist insects.  In addition, much of the literature deals with the milkweed’s ability to propagate itself through asexual budding, while the sexual pathways necessary for long term survival remains receive less attention.  By learning more about the milkweed’s sexual pathways, conservation efforts can be more targeted to increasing genetic diversity more efficiently, raising the likelihood that milkweeds can make a comeback.

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They Heard It Through the Grapevine: How Asclepias syriaca Communicates

Asclepias syriaca, or common milkweed, is a tall, herbaceous plant that reproduces both sexually, through pollination, and asexually, through producing multiple shoots from a single root system. It has strong chemical and physical defenses against herbivory, and when the plant senses that tissue is being disrupted by insects, it accordingly increases its production of latex (a gummy liquid) and cardenolides (toxic compounds). Previous studies have shown that other clonal plants with shoot or root connections are able to share resources such as water and nutrients between stalks. My research will investigate whether stalks of A. syriaca experiencing herbivory can share the signals that induce increased defenses with their clonal relatives; in effect, can milkweed stems “talk” to their fellow clones to warn them about present dangers?

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