Liz Kimbrough

Ph.D. Student

25 June 2017

As you look around a forest or out into your garden, you may have noticed that leaves come in a variety of shapes, sizes, and textures. But have you ever stopped to ask yourself why leaves have these different traits?

In order to be successful, plants must both grow and survive. They grow by taking in water, nutrients, and sunlight and survive by defending themselves structurally and chemically from disease, herbivory, and stress. A plant has a limited amount of resources that it can invest into building a leaf, so it must invest wisely, striking a balance between traits that favor growth and traits that favor defense.

Imagine a scenario in which 1000 families are given the same amount of money to build a home (but are not allowed to spy on their neighbors’ designs). It is likely that all homes will share similarities (a roof, walls, an entrance) but, depending on the location of the home, each house will be unique. In a plot of land that neighbors an enemy, much of the money may be spent on a moat or a high fence. In a safer location perhaps a family chooses to make a house as large as possible with many windows to let in the light. These tradeoffs are what we see manifested in the leaves of plants.

One trait that interests our research group is leaf mass per area (LMA), which is a measure of leaf density. LMA is correlated with leaf age, meaning long-lived leaves are denser then short-lived leaves. And this makes sense. To return to the house metaphor, if you are building a shelter for a week, you pitch a tent, but if you are building a home to last a few decades, you may want to invest in brick. The leaves of some tropical trees can live over a decade. These leaves must be physically tough to withstand the elements and must also be well defended chemically. Other leaves are ephemeral, lasting only weeks or days. Plants invest fewer resources into reinforcing and defending these leaves and, instead, use them as a quick sugar making factory.

The Van Bael lab studies endophytes- the microscopic fungi and bacteria that live inside of plants without causing apparent harm. Like most organisms, endophytes are hyper diverse in the tropics. Researchers are still trying to figure out why certain endophytes live where they do and what explains this diversity. Our research asks the question: Do leaf traits play a role in endophyte community assembly? Do some endophytes prefer houses with windows? Can endophytes make it through the moat and over the fence? This is what we hope to find out.