‘A cauliflower has fractal architecture — its ‘curds’ repeat via gene mutation and memory’

What is the core of your research?We are a group of mathematicians, statisticians and physicists studying the development of plants, looking at how genes control this process. Our work focuses on the meristem, a region of plant tissue at the tip of each stem. This has a population of actively dividing cells — these produce all the organs a plant has, from internal ones to leaves, branches, tendrils, flowers, etc. This happens in a tiny space.

What is a fractal property here?
The term ‘fractal’ was coined by Benoit Mandelbrot, a mathematician. It means an object with geometric properties and a mathematical quality — it occurs with many details, repeated at different scales. A tree, for instance, has a complicated architecture with branches that repeat, many branching patterns and consecutive orders — it thus has a fractal shape. In plants, one of the most iconic fractal shapes is produced when all the branching elements are tightly compacted with each other — this occurs in cauliflowers and broccoli Romanesco. Their compactness, with many organs operating very close to each other, shows an extremely strong fractal property.

What explains a cauliflower’s shape?Consider a cabbage — it would normally produce a bunch of plant axes going upto a third order. That’s a branching structure but the number of branching events or orders — one stem means one order and so on — are limited to three or four here. In a cauliflower, there are eight to nine such orders. When I researched this with Francois Parcy, a biologist who has specialised in inflorescences or genes which control the development of flowers, we discovered that in wild plants, the possibility to produce a higher order was blocked genetically — it could have two to three orders after which its genes would stop any more.


In a cauliflower, this was unlocked by a double mutation. We tried this in a model plant and obtained a vegetable resembling the cauliflower on an Arabidopsis thaliana weed. We felt making the meristem larger could increase the shoots the plant produced but we didn’t know which gene controlled the meristem’s rate of shoot creation. Finally, we found a gene which changed the size of the meristem’s central zone. We altered the plant genetically — and cauliflowers emerged.
Why does your research mention a ‘memory’ that cauliflowers have?
This isn’t a memory in that it doesn’t use a neural network but it functions in the sense of events occurring. The first event we found was that higher-order branches were unlocked in a cauliflower, which causes a chain reaction of branches proliferating — that produces what scientists term ‘curds’, the edible part with internodes, bracts and branches. Cauliflower curds are actually buds which were designed to become flowers but didn’t succeed — instead, they formed shoot upon shoot, growing rapidly, without leaves and proliferating almost infinitely, each floret taking on a triangular shape. In a wild plant, lateral meristems are transformed at order two or three into flowers — that stops its growth. In the cauliflower, a floral architect genetries to rise but because there is a mutation, it can’t sustain its progress and falls into no activity, leaving a ‘memory’ of floral patterns. The cauliflower then produces more axes as the floral gene can’t stop this.


What are the technologies you use?
We utilise genetic technologies with imaging, microscopy and the fluorescent marking of cells and genes — that means attaching fluorescent markers to the proteins produced by genes and observing thus-marked molecules in the tissue at the level of different cells. So, if you want to see one gene being active at any moment during a plant’s development, you attach these and see where and when the gene functions. We also use computational modelling to understand the many plant processes working at different scales and how these synchronise and interact with each other. Quantitative methodology helps us assemble all the pieces of this jigsaw puzzle.

Why is plant architecture important?
A key reason is that plants make flowers which lead to fruit. Understanding how this happens — and why it sometimes fails — needs a study of plant development, gene control, etc. This lets us understand how crops produce yield. By studying plant architecture, we can breed resilient varieties.


Could climate change impact such genetic movements within plants?
Yes — we are already finding evidence of this. Plants are reacting to environmental stresses which link to plant control systems. Researchers are trying to understand this, looking, for instance, at how water stress is changing how plants grow, particularly through impacts on root systems, how these sense water scarcities and transmit such information to the aerial plant, the two parts then synchronising.