We already know quite a bit about plant architecture, so it’s somewhat surprising that a new natural organ was discovered in the most well-researched plant in the world.
Timothy Gookin and Sarah Assmann of Pennsylvania State University, US, discovered the new organ in Arabidopsis thaliana (the thale, or mouse-ear, cress) – the ‘mouse’ of plant research – and called it a cantil, because it connects to the stem at one end and hangs in the air to hold up the flower-bearing stalk, much like the cantilever used in engineering.
It grows in a structure similar to a horizontal humerus when somebody is showing off their muscles – where the forearm is like the normal stem and the hand is a flower.
“I first observed the cantils in 2008,” says Gookin. “I initially didn’t trust any of the results; I thought it must be an artefact of genetic contamination, perhaps combined with environmental contamination of the water, soil, fertilizer or even the building air supply.”
It might seem a little strange that an organ could go undiscovered for so long, but that is because cantils only grow under certain conditions and at a very specific time – at flowering time, when the days are short.
Gookin had to grow a lot of plants for over a decade to prove that these were a condition-specific, but natural, organ that wasn’t the result of a mutation.
“It took over 12 years of experimentation to really get a grasp on what we were seeing and to understand how cantils were regulated. This study required the growth of 3,782 plants to full maturity and the manual inspection of over 20,000 flower-bearing stalks in 34 unique plant lines,” explains Gookin.
“I finally deemed the cantils a natural phenomenon after identifying them in wild-type (non-mutant) plants from different sources, which were growing in independent locations and diverse conditions.”
In the paper, published in Development, they also show that some genetic mutations prevent the plants from growing cantils, and together with their other data this could point to some important traits of conditional plant structures as a response to the environment.
“One speculative interpretation is that the cantil represents a highly repressed ancestral linkage between different types of flowering plant architectures; the multiple layers of genetic and environmental factors that regulate cantil development are certainly quite striking,” says Gookin.