Gioia Massa, a former Purdue postdoctoral researcher, measures the length of a sweet potato plant. In the background, other plants are climbing cages that minimize their area requirements, making them a possible crop that could be grown in space. Photo: Mitchell Laboratory |
Future astronauts spending Thanksgiving in space may not
have to forgo one of the most traditional parts of the day’s feast: fresh sweet
potatoes.
Cary Mitchell, a Purdue University
professor of horticulture, and Gioia Massa, a former postdoctoral researcher at
Purdue, developed methods for growing sweet potatoes that reduce the required
growing space while not decreasing the amount of food that each plant produces.
Their findings were published in Advances
in Space Research.
Sweet potato plants have main vines with many shoots that
branch out to the sides. Mitchell said it was common for one plant to cover the
entire surface of a 15-by-5-ft greenhouse bench.
“Sweet potato is like an invasive plant. It will take
over everything,” says Mitchell, who studies the selection of crops that
could be grown in space. “That’s not acceptable if you’re going to grow it
in space.”
Knowing they needed to contain the plant’s horizontal
spread, Mitchell and Massa
decided to force it to grow vertically. Using cones or cylindrically shaped
wire cages, they trained plants’ main vines to wrap around the structures while
removing the space-consuming side shoots.
“It turns out the vines are not really picky about
what you do with them,” Massa
says. “As long as you leave the main shoot tip alone, you can remove the
side shoots and trim them away without any yield loss.”
The main shoot tip, or the end of the main vine, is the
only really sensitive part. It sends hormones throughout the plant that
stimulate root development, which is important since it is the roots that
become the sweet potatoes.
The side shoots, if picked when still young, are tender
and can be eaten in salads, improving the plant’s usefulness, Mitchell says.
On Earth, scientists might want to find ways to get crops
to take up less area, focusing on only two dimensions. A tall, skinny corn
stalk, for instance, takes up little space in a farm field.
In space, however, that third dimension—height—is
important because plants may need to be stacked to use all available space.
Using a cone or cylinder is what might make sweet potato a viable space crop.
Since the area inside the cages is empty, astronauts could put other plants
inside and keep them alive with LED lighting.
The sweet potato plants also weren’t particular about
lighting or temperature. Mitchell and Massa
grew sweet potatoes in greenhouses during different seasons and saw no
difference in yield.
“Sweet potato doesn’t seem to care what season it is
or what conditions it’s in,” Mitchell says.
Massa
says that’s important because many different types of crops may have to be
grown in the same rooms in space. Picky plants won’t fare well with other picky
plants having temperature or lighting requirements much different from their
own.
“We call it a generalized-growth environment,” Massa says. “We’re
finding the optimum, not the maximum.”
Mitchell and Massa
say they’d next like to study LED lighting’s effect on sweet potato and other
crops. NASA funded their research.
