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Beni Meier with his 2323.7 pound world record pumpkin in 2014.

Beni Meier and his world record pumpkin (2014).

Size Does Matter (If You’re Growing Giant Pumpkins)

Question: What does a 1968 Volkswagen Beetle and the current World Record Giant Pumpkin have in common?

Answer: They each weigh about 1 ton (US) or about 2000 pounds (907 kilograms).

Indeed, the current world record heaviest pumpkin (see the photo on the left) weighed in at a massive 2,323 pounds (1,054 kilograms).

Of course, the obvious question is: How are these pumpkins able to grow so huge?

First, it’s important to note that a pumpkin is NOT a vegetable. It’s a fruit.

So, basically, what we’re talking about here is unfettered fruit growth. Seemingly, as long as the pumpkin is provided with sufficient water and resources (primarily in the form of carbohydrates from the leaves), it will continue to grow – until winter sets in.

I found that good basic resource about the physiology and genetics of giant pumpkins has been provided by Prof. Jules Janick of Purdue University. (See Ref. 1 below)

From this article (and references therein): “The accumulation of fruit size is a combination of physiology, environment, and genetics. The water content of pumpkin is about 88% and may be as high as 91 to 94% in giant pumpkins (Culpepper and Moon, 1945). The fruit acts as a physiological sink and the combination of cell size and cell number determines final fruit size. In large-fruited pumpkin as compared to fruits of smaller cucurbits there is a more extended period of cell division and greater cells expansion after cell division ceases (Sinnott, 1939).

As noted by Prof. Janice, there has not been very much research done on giant pumpkins. I did, however, find a few recent papers (listed below) regarding giant pumpkins, which have shed a bit more light on their nature.

Nakata, et al. (Ref. 2 below) “…found that both the cell number and cell sizes were increased in a large fruit while DNA content of the cell did not change significantly.” Interestingly, giant pumpkins apparently do not exhibit higher ploidy in their vegetative material or fruit, as do many large agricultural fruits. These researchers do, however, provide some evidence for enhanced photosynthesis in the leaves of giant pumpkins.

Several investigators in Prof. Holbrook’s lab at Harvard University have also recently been studying the growth of giant pumpkins. Briefly, they found that “There was no evidence that changes in leaf area or photosynthetic capacity impacted fruit size. Instead, giant varieties differed in their ovary morphology and contained more phloem on a cross-sectional area basis in their petioles and pedicels than the ancestral variety. These results suggest that sink activity is important in determining fruit size and that giant pumpkins have an enhanced capacity to transport carbon.” (from Ref. 3 below)

Finally, even some mechanical engineers have been fascinated by giant pumpkins. Hu, et al. (Ref. 4 below) reported: “Using time-lapse photography and measurements collected by volunteer farmers, we show that as pumpkins grow, they morph from spherical to pancake shapes, flattening up to 50% in height-to-width aspect ratio.” From these observations, as well as theoretical calculations, they concluded that “The observed growth plasticity allows the fruit to redistribute internal stresses, thereby growing to extreme sizes without breaking.

References

1. Janick, J. (2008) “Giant pumpkins: genetic and cultural breakthroughs.” Chronica Horticulturae, Vol. 48, pp. 16-17. (Full Text – PDF)

2. Nakata, Y. et al. (2012) “Comparative analysis of cells and proteins of pumpkin plants for the control of fruit size.” Journal of Bioscience and Bioengineering, Vol. 114, pp. 334–341. (Abstract)

3. Savage, J. A., D. F. Haines, and N. M. Holbrook (2015) “The making of giant pumpkins: how selective breeding changed the phloem of Cucurbita maxima from source to sink.” Plant, Cell & Environment, Vol. 38, pp. 1543–1554. (Abstract)

4. Hu, D. L., P. Richards, and A. Alexeeva (2011) “The growth of giant pumpkins: How extreme weight influences shape.” International Journal of Non-Linear Mechanics, Vol. 46, pp. 637-647. (Abstract)

“BIG Time” by Peter Gabriel (1986)

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