This 'smart plant' factor could lead to stronger crops
April 20, 2017
Plants may be smarter than we give them credit for. They do not have brains, and therefore do not think in the same way that humans and other animals do, but they have intricate systems in place that compute the best response to the challenges of daily life.
Deciduous trees drop their leaves every fall in order to preserve water, and when many fruiting plants lose branches, the remaining branches will make more fruit more quickly to compensate.
Researchers from UNC-Chapel Hill have discovered that many plants can make up-to-the-minute adjustments in their metabolism to compensate for shadows and flickering light.
UNC biology professor Alan Jones found that sugars in the plant leaves and a protein called RGS1 can detect the intensity of sunlight hitting the plant and tune how efficiently they photosynthesize to make the best of their current light situation.
The research paper, published in the Journal of Theoretical Biology, describes a never-before-seen control that plants have over their metabolism and is the first to describe that mechanism.
Plants require sunlight to convert carbon dioxide and water into sugar and oxygen. Plants that thrive in the shade adjust the position of their chloroplasts, the tiny organelles that do photosynthesis, and their internal chemistry to take advantage of any light they can get. When these types of plants get too much direct sun, their efficient photosynthesis runs out of control until they dry out.
Many plants make photosynthesis adjustments on a daily basis: turning down their efficiency after the sun is raised high in the sky and turning it up when the sun sinks in the afternoon and light gets dimmer. If a plant were to mistake a passing shadow for nightfall, it could turn its efficiency way up and fry as soon as the shadow cleared.
Jones and colleagues from Michigan State University found that plants with RGS1—which is also a protein in humans that regulates signaling pathways—can actually tell the difference between those passing shadows and a real sunset. The discovery was made using a light-box chamber that mimics the changes in natural light over the course of a day.
Plants genetically engineered to lack RGS1 did well when the light mimicked that of a prairie: sun up in the morning and sun down at night without any other shadows or flickers in the light. When the box mimicked clouds and shadows with dark periods, the RGS1-lacking plants overcompensated for the darkness and when the lights came back on, they dried out.
Plants with RGS1 on the other hand are able to deal with those changes. Sunlight causes molecules in plant leaves to decay, and mathematical models created by the researchers show that RGS1 is able to detect the rate at which those molecules decay and then signals the plant to adjust the rate at which it can photosynthesize. Tests in the light-box showed that the plants did not react to any shadow lasting less than four minutes, but after that time, they will make an adjustment.
This knowledge is important because it can help with agriculture development. Greenhouse farmers can precisely time the light in the greenhouse to enable the best growth. Since nearly all plants except grasses have the RGS1 protein, this one finding could help grow pretty much everything.
Those smart plants have done the hard work for us, and by playing into their computations we could potentially grow more of the food crops and other plants that we rely on.
Daniel Lane covers science, medicine, engineering and the environment in North Carolina.