In terms of flavor, broccoli is a vegetable that divides. But visually, you would have a hard time finding someone who didn’t find Romanesco broccoli aesthetically beautiful.
You’ve probably stopped to gawk in the produce aisle before: Romanesco broccoli – or “Romanesco” for short – is a breed of broccoli that looks like a giant green flower, with flowers in strangely perfect geometric patterns that repeat like you zooms in. It is the peel of vegetable nautilus: a perfect and always repeated spiral that resurfaces continuously. As a late autumn and winter vegetable, it is found in most supermarkets in the United States at this time of year, mesmerizing shoppers with its impressive patterns.
These patterns are called fractals and are essential for understanding Romanesco broccoli.
“A fractal is a shape or structure equal to itself at different scales,” wrote Edmund O. Harriss, professor of mathematics at the University of Arkansas, at Salon. “In other words, as you zoom in, you see the same (or sometimes related) structure.”
In the natural world, plants sometimes approach these repeating structures. Many ferns, for example, have leaves that exhibit fractal architecture. Pine cones, spiral nautilus shells and ice crystals also have repeating patterns.
But among the recursive patterns that appear in living beings, Romanesco broccoli is a fractal for excellence, looks.
“Romanesco is considered the quintessential model of fractal architecture in biology”, Zachary Stansell, a professor at the Cornell University School of Plant Integrative Sciences, told Salon by email. “We know that it exhibits a very unusual and recursive growth pattern compared to ‘normal’ (or Calabrian) broccoli. Almost paradoxically, some of the rules that govern normal broccoli branching and development appear to be ‘relaxed’ in Romanesco – allowing you to repeat the branching process … repeatedly. This iterative branching pattern corresponds to some interesting mathematics like the Golden Ratio, a common theme in classical architecture. “
One of the oldest mathematical concepts, the Golden Ratio, whose value is around 1.618, is the ratio between two objects of different sizes where the smallest is for the largest and the largest is for the sum of both. As John Edmark, professor of design and mechanical engineering at Stanford University, told Salon, the Golden Ratio occurs “if you take a line and divide it into two segments so that the ratio of the entire line to the segment longest is the same as the ratio of the longest segment to the shortest segment. “Edmark noted that” there is only one proportion that can meet this requirement – the Golden Ratio – and its value is approximately 1.618. “
The Golden Ratio has a remarkable history, dating back to the ancient Greek mathematician Euclid. It has been used by artists, architects, engineers and musicians, incorporated in their respective crafts. Some even believe it can be used to explain beauty and understand how life is designed in nature.
This brings us back to Romanesco broccoli. The spiral pattern in broccoli displays the golden ratio, in which each small bud that grows out of the main has the same size ratio as its predecessor, specifically the golden ratio. In other words, the same formula that governs the appearance of Romanesco broccoli was explored by Leonardo Da Vinci and Piet Mondrian on their canvases.
That’s the math behind broccoli. But what about biology? And does Romanesco’s genetics make it so … spiral?
Interestingly, the reason why Romanesco looks different from its almost genetically identical cousins - broccoli and cauliflower (normal) – remains a genomic mystery.
“As far as I know, no one has fully proven the genetic control of the patterns seen in Romanesco,” Stansell told Salon. “There are some known genes in the ‘laboratory rat’ of plants (Arabidopsis thaliana) that seem to cause somewhat analogous behavior, but genetic control remains a permanent issue. “
Cornell’s Stansell colleague Thomas Björkman added to these observations when writing to Salon that “broccoli (like cauliflower) is built by the growth spike that makes branches and flowers in a consistent repetition pattern. On the other hand , the more regular appearance of Romanesco is caused by the growth point forming branches and flowers in a pattern of constant change. In Romanesco, the time and distance between the new branches gets longer and longer. If you look at the tip of a Romanesco head, you will see that the growth point is really big, easily visible to the naked eye. “
Stansell and Björkman know what they are talking about when it comes to broccoli, as the two scientists published a paper in October about the genetics behind broccoli. They studied the genomes of broccoli and found that the iconic plant retained about half of the genetic diversity that existed in the original broccoli cultivated by Italians for centuries and centuries – information that can be used to change its flavor.
“Although modern broccoli is extremely uniform, it retains about half of the genetic diversity found in its Italian ancestors,” explained Björkman. “This diversity is valuable for resilience and continuous improvement.”
He added that he and his co-author, Stansell, “also found parts of the genome (the complete set of genetic instructions for the organism) where genetic diversity is very low. This uniformity is a sign that a gene in that part of the genome is very important for making good broccoli and other versions have been eliminated. “This reveals that people who grew broccoli deliberately knew which characteristics to encourage and which to minimize. Interestingly, this happened through the creation of vegetables by farmers, long before human beings even understood that genes existed.
The “characteristic flavor” of brassica vegetables, the cabbage and mustard family in which broccoli is also found, is related to a class of compounds called “glucosinolates”, Stansell told Salon. “Certain glucosinolates contribute to the spicy or bitter flavors that people love (or hate) in broccoli,” he noted.
Stansell also noted that human genetics can play a role in how we understand the relevance of broccoli genetics; some people have genes that make them more sensitive to glucosinolates.
“It is possible to create brassica vegetables to have less of these bitter compounds, as Dutch plant breeder Hans van Doorn did when creating Brussels sprouts,” explained Stansell. “Greater knowledge of the genetic diversity in broccoli may allow plant breeders to select or pollinate new varieties of broccoli with different or even new flavor profiles.”
Perhaps, eventually, such genetic knowledge could allow breeders to select mathematically stunning broccoli as well.