Cinderella has to get to the ball. How to reach the palace on time? Her fairy godmother waves a wand, and poof! A nearby pumpkin morphs into a beautiful carriage.
The fairy godmother is a magical stretch, but massive pumpkins are very real. The huge ones you might see at your local fall fair are Atlantic giant pumpkins (Cucurbita maxima). It’s not the species that we eat and carve, says Jessica Savage. A botanist at the University of Minnesota, in Duluth, she’s someone who studies plants.
The Atlantic giant truly is a goliath. People compete every year to produce the largest. One grower in Germany set the record for the world’s heaviest in 2016 with a squash that tipped the scales at 1,190.49 kilograms (2,624.6 pounds). It weighed more than some small cars.
What’s really astonishing, Savage says, is that pumpkins can get that big in the first place. After seeing photos of giant pumpkins at the Topsfield Fair in Topsfield, Mass., she became fascinated by a problem. A transport problem.
A pumpkin has to transport water, sugar and other nutrients to swell up the fruit. (Yes, a pumpkin is a fruit.) Water needs to move up from the roots. Sugars produced by photosynthesis in the leaves need to go down to the fruit and roots. To do this, plants use xylem and phloem. Xylems are vessels that transport water from roots to a plant’s stems, fruits and leaves. Phloems are vessels that transport sugars from leaves to the fruit and roots.
Giant pumpkins need a lot of water and sugar, and they need it fast. A typical giant pumpkin grows from seed to huge orange squash in only 120 to 160 days. At peak growth, it’s putting on 15 kilograms (33 pounds) every day. That’s like daily adding a two-year-old child to its mass. And all of that mass must move through the stem, Savage notes. Most of the time, the stem is so narrow that you can still easily get your hands around it.
To study how pumpkin stems transport so much food and water, she asked growers of giant pumpkins to donate small slivers of their competition fruits. She also got any pumpkins that burst before they could be judged. She even got small pumpkins that farmers had rejected before they plumped up. (To grow a massive pumpkin, farmers will only let one pumpkin on each plant reach full size.) She also grew a few of her own.
Savage took a close look at the stems, leaves and pumpkins and then compared them to those from other large squashes. Giant pumpkins don’t produce more sugars, she found. And their xylems and phloems don’t work differently. The titans just have more transport tissue. “It’s almost like there’s this mass growth of the vascular tissue in [the] stem,” she says. Extra xylem and phloem help the stem pump more food and water into the fruit, leaving less for the rest of the plant.
Savage and her colleagues shared their findings five years ago in the journal Plant, Cell & Environment.
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Pumpkin or pancake?
The giant pumpkins in competition don’t have the nice round shape you’d expect. “They’re not beautiful,” says David Hu. “They’re saggy.” Hu works at the Georgia Institute of Technology in Atlanta. A mechanical engineer, he studies how things move and grow.
Giant pumpkins get flatter and flatter as they expand in size. Gravity just weighs them down, Hu explains. “They’re elastic. They’re springy. But as they get bigger, they get heavier, and the spring isn’t strong enough,” he says. Pumpkins end up squashed under their own weight. And if they grow large enough, they will even grow a small arch underneath. “It’s like a little dome in the middle,” Hu says.
The wall of a pumpkin doesn’t thicken much as the fruit gets really big. Small pumpkins can support up to 50 times their own weight without breaking, Hu says. But “big ones can barely support their own weight,” he notes. “They’re at their limit.”
By taking giant pumpkin samples and squashing normal-sized pumpkins to see how much weight they could take, Hu came up with a model for how a giant pumpkin spreads as it grows. One big enough for Cinderella, he says, would never be a good vehicle. Even if growers were to double the current weight of giant pumpkins, those fruits would just get flat.
“She’d have to lie down,” Hu says of Cinderella. And her ride, he points out, “definitely wouldn’t be super elegant.” The pumpkin would probably also need much longer to grow. “If we wanted it eight times bigger,” he says, “we’d need an eight times longer season — about eight years.”
If you could grow a pumpkin in outer space or under water, it’s height would no longer be a problem, Hu notes. “Ultimately all the [flattening] forces are due to [Earth’s] gravity.” Hu and his colleagues published their results in 2011 in the International Journal of Non-Linear Mechanics.
But while a pumpkin carriage might not be a realistic way to travel, Savage notes that Cinderella might have had other options.
Giant pumpkins, after all, can be hollowed out to make pretty good canoes. In fact, there’s a yearly boat race in Windsor, Canada, open to giant pumpkins only. So if the prince’s castle has a moat, Cinderella might be able to make a grand entrance from a pumpkin after all.
Power Words
More About Power Wordsblood vessel: A tubular structure that carries blood through the tissues and organs.
cell: The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Mostorganisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
colleague: Someone who works with another; a co-worker or team member.
engineer: A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need. (v.) To perform these tasks, or the name for a person who performs such tasks.
environment: The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature andhumidity (or even theplacement of things in the vicinity of an item of interest).
force: Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.
gravity: The force that attracts anything with mass, or bulk, toward any other thing with mass. The more mass that something has, the greater its gravity.
greenhouse: A light-filled structure, often with windows serving as walls and ceiling materials, in which plants are grown. It provides a controlled environment in which set amounts of water, humidity and nutrients can be applied — and pests can be prevented entry.
journal: (in science) A publication in which scientists share their research findings with experts (and sometimes even the public). Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.
mass: A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.
mechanical engineer: Someone trained in a research field that uses physics to study motion and the properties of materials to design, build and/or test devices.
mechanics: The study of how things move.
model: A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes.Or an individual that is meant to display how something would work in or look on others.
nutrient: A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.
phloem: The part of a plant that carries sugars and other products of photosynthesis from where they are made in the leaves to where they are needed.
photosynthesis: (verb: photosynthesize) The process by which green plants and some other organisms use sunlight to produce foods from carbon dioxide and water.
species: A group of similar organisms capable of producing offspring that can survive and reproduce.
STEM: An acronym (abbreviation made using the first letters of a term) for science, technology, engineering and math.
taste: One of the basic properties the body uses to sense its environment, especially foods, using receptors (taste buds) on the tongue (and some other organs).
tissue: Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
unique: Something that is unlike anything else; the only one of its kind.
xylem: The part of a plant that conducts water, nutrients and sap.
Citations
Journal: J.A. Savage et al. The making of giant pumpkins: how selective breeding changed the phloem of Cucurbita maxima from source to sink. Plant, Cell & Environment. Vol. 36, August, 2015. doi: 10.1111/pce.12502.
Journal: D.L. Hu et al. The growth of giant pumpkins: How extreme weight influences shape. International Journal of Non-Linear Mechanics. Vol. 46, May, 2011. doi: 10.1016/j.ijnonlinmec.2010.12.013.
About Bethany Brookshire
Bethany Brookshire was a longtime staff writer atScience News Exploresand is the author of the bookPests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.
