Science in your summer garden

Flowers that form fractals

Romanesco cauliflower is mesmerizing. Unlike the boring old regular white cauliflower, romanesco’s buds spiral out in a distinctive fractal pattern. But how this pattern comes about is something biologists have been asking for a long time. A recent study suggests that the pattern may be related to the dynamics of how the florets grow (Science 2021, DOI: 10.1126/science.abg5999).

Through a combination of computer modeling and genetic experiments, Christophe Godin, a computational scientist at France’s National Institute for Research in Digital Science and Technology and the University of Lyon, and François Parcy, a plant geneticist at the French National Center for Scientific Research and Grenoble Alpes University, mutated the model plant Arabidopsis thaliana to grow in a romanesco-esque flowering pattern.

The team found that this change in flowering shape was caused by only one genetic tweak to a cauliflower mutant of the Arabidopsis plant. This gene controls the meristems, the cells in plants akin to stem cells. The meristems can develop into multiple kinds of parts of a plant. These cells are at the tip of each flowering part and are responsible for growth, Godin says.

“What is exceptional in the romanesco [flowering pattern] is not so much the fact that they are spirals but the fact that the spirals are nested within each other,” he tells Newscripts. To replicate this, Godin and Parcy introduced a mutation to the gene known for keeping the meristem the same size through the life of the plant, Parcy says. “If you perturb this part of the plant, instead of always staying the same size, it starts to grow and grow and grow. And then it gets crazy at the end,” he says. Their mutated Arabidopsis was pointy and fractal-like at the flowering parts, much like romanesco, Parcy says.

“We found a possible mutation that does the right thing,” Parcy says, but the researchers aren’t sure yet that an equivalent gene is responsible for this pattern in romanesco. “Of course, it’s a super good candidate,” he says. Scientists don’t have enough information about the genetic code of any cauliflower, much less romanesco, to figure that out yet.

Godin and Parcy dissected and examined a lot of the vegetable in this research and ate it with fancy dipping sauces whenever they got together. Their next project might even be a cauliflower cookbook.

Underripe is underrated

In many parts of the world, summer means tomatoes: red, yellow, orange, purple, green, and all kinds of delicious. But just how delicious might be related to the tomato’s color. To determine if that’s true, Miyako Kusano and coworkers at the University of Tsukuba analyzed the pigment molecules in 157 kinds of tomatoes (Metabolites 2021, DOI: 10.3390/metabo11060398). They found that tomato varieties with underripe-looking green parts might actually be sweeter than those perfectly red tomato varieties.

The pigment molecules in tomatoes are called carotenoids and are usually red, yellow, or orange, Kusano says. These compounds don’t have a flavor. However, the carotenoids degrade into compounds called apocarotenoids, which do. “Some apocarotenoids are released from the fruit as flavor compounds and have a fruity or floral scent,” Kusano tells Newscripts.

The team measured amounts of chlorophyll, responsible for green color, and prolycopene, a type of carotenoid that makes tomatoes orange. Overall, tomato varieties with high amounts of chlorophyll also had higher sugar content. Tomatoes with a lot of prolycopene had higher amounts of the volatile compound 6-methyl-5-hepten-2-one, which is partly responsible for that distinct sweet-tomato smell and can also affect flavor. Taking all these chemical components into consideration, the researchers concluded that the tastiest tomatoes strike a balance between chlorophyll and prolycopene content, and aren’t necessarily the ripest ones.

Unfortunately, the team used instrument-measured sweetness parameters only and didn’t taste test any of these tomatoes. But for your at-home eating pleasure, Kusano recommends the Maglia Rosa cherry tomato, and the Japanese variety Aiko.

Please send comments and suggestions to newscripts@acs.org.