Plants are frequently damaged by a range of animals, including by humans, yet plants generally continue to grow and reproduce despite substantial tissue loss. A new manuscript by Daniel Scholes, assistant professor in biology, Erika Rasnick ’17 (biology), and Ken Paige, professor at the University of Illinois, published in the journal Oecologia details their analysis of the factors that contribute to plant damage tolerance.
The new study, Characterization of Arabidopsis thaliana regrowth patterns suggests a trade-off between undamaged fitness and damage tolerance, sought to determine the traits and developmental strategies that plants use to tolerate stem damage typically caused by mammals such as rabbits and deer. Stem damage causes a change in plant architecture such that regrowth often looks very different than natural, undamaged growth. This effect can commonly be seen on pruned trees and hedges, where cut branches sprout many new stems.
Using the model plant Arabidopsis thaliana, a mustard species commonly studied by plant biology laboratories worldwide, Scholes, Rasnick, and Paige determined that some individuals, based on their genetics, will invest immediately in growth and reproduction, becoming very large and producing lots of seeds. Other individuals with a different genetic makeup will grow relatively small and with relatively few seeds.
The magnitude of their growth and reproduction reverses upon damage, however; plants that naturally grow small and with low reproduction become large with high levels of seed production when damaged while the naturally large and highly reproductive individuals regrow smaller and with reduced seed production when damaged.
The comparison of plants natural, undamaged patterns of growth and reproduction to their damaged patterns of regrowth and reproduction therefore provides evidence of a bet-hedging strategy to maximize reproductive success. Due to limited environmental resources, like nitrogen and sunlight, plants can invest into growth and reproduction only once: either early in their lives, growing large quickly which is advantageous if animals do not eat them at a later time, or late in life which allows plants to save their resources for growth and reproduction until after damage occurs.
But how can plants predict whether they will be damaged or not? They cannot, but instead they carry a genetic makeup that will cause them to invest in growth and reproduction either early or late in life. Individuals with genetics that do not match the behavior of the local animals (for example, plants that invest in reproduction late in life waiting for damage that never comes) will have low reproduction and few offspring. If animals behave similarly generation-after-generation, such as the regular timing of damage by seasonal migrations of deer, plants with the best investment strategy should reproduce the most each generation and over time the plant population should be composed of an increasing proportion of individuals with the most advantageous growth and reproductive strategy. When Scholes, Rasnick, and Paige surveyed the growth and reproductive strategies of mustard plants from different locations around the world, they found a variety of plant investment strategies that may be reflective of the particular set of animal species, behavior, and environmental resource conditions found in those regions. Looking across strategies, the trade-off between investment early in life vs. late in life in relation to the risk of damage by animals became clear.
Rasnick presented this study at the 2017 Midwest Ecology and Evolution Conference in Urbana, IL in March and Scholes will present it at the 2017 Ecological Society of America annual meeting in Portland, OR in August. This study and these presentations were supported by the National Science Foundation, the University of Illinois Campus Research Board, and the University of Indianapolis Biology Department, Shaheen College of Arts and Sciences, and the Provost.
Daniel Scholes has authored two other published manuscripts this year on related studies in the journals Ecology and Plant Ecology.
Citation: Scholes DR, EN Rasnick, KN Paige (2017) Characterization of Arabidopsis thaliana regrowth patterns suggests a trade-off between undamaged fitness and damage tolerance. Oecologia Online First 24 Jun 2017. doi: 10.1007/s00442-017-3897-1