Science and I had started to drift apart. It was all my doing, or lack of doing, as the case was. It wasn’t that I’d intentionally turned my back on her, I’d just been spending more time with someone else, Social Media. While he was demanding, Science patiently waited. She knew that I’d come back to her, that there is only so much opinion supporting opinion on opinion that anyone can bear. So, on Friday afternoon, I reached out and reconnected, and I was rewarded with wonderful things. Oh, how I had missed Science. Then, on Saturday morning while still rekindling the relationship, I was introduced to negative time*. Negative time was not the reintroduction to Science that I was looking for. I wanted more time, not less time. I wanted a comfortable chair in the sun, and fish-n-chips for dinner. I wanted four pints of beer in a garden bar. I wanted to relax and contemplate things that didn’t quite fit, to ease the boundaries of familiarity. I wanted gentle, warm Science, in a safe environment. But no, in search of the perfect couch to ponder upon, I had flicked a lazy glance at quantum mechanics. I had caught a glimpse of Science at her most terrifying, and I was afraid. Where botany is graceful, quantum mechanics is frenetic. How can one hope to understand concepts like Uncertainty, Entanglement, and Dual particle density? In quantum mechanics ‘Everything not forbidden is mandatory’. That arm of Science is bonkers, what goes up… may or may not come down, it might do both at the same time. And now it seems, it might do one or the other even before it started doing either – negative time.

So desperate was I to distance myself from the quantum realm, that I spent the rest of the weekend thinking about things larger than particles and atoms – which strangely enough wasn’t that hard to do. I drew the line at organelles, which being sub-cellular are still quite small, but at least they make sense. And so, my story begins, and it begins with the organelle of choice, the statolith.

Statoliths are gravity-sensing organelles, or so the long-held belief has been. They are found in specialised cells called statocytes, which occur mainly in the root cap and shoots. Not being one for chemistry, I find them wonderfully mechanical; they have little lumps of starch in them. These lumps being heavier than the rest of the fluid in the cell settle at the bottom (visualise sand moving through an hourglass if you wish). Having a heap of starch at the bottom enables the cell to work out which way is up, and by default, which way is down. In humans, we have little carbonate crystals stuck on the end of tiny hairs deep inside our inner ear. These weighted hairs are affected by gravity and tell us which way is up – it’s kind of the same thing (at least mechanically).

Perhaps because statoliths are so wonderfully mechanical, scientists haven’t invested a great deal of time on them. Starch settles, a bunch of growth hormones (auxins) are stimulated, and directional growth occurs (positive and negative gravitropism). The starch is just a trigger, boring. Statolith actually means, motionless stone – who would wish to study motionless stones? But it turns out that the starch only settles in the roots. Elsewhere, our stones dance (or at least slosh about), and dancing stones are far more interesting. Particularly if you are an arborist. And why, I can hear you think, is this only particularly interesting to arborists, surely tiny lumps of moving starch have a much wider appeal…

It seems that statoliths do more than just sense gravity. The moving lumps of starch enable the plant to respond to movement and sense physical strain. Sensing strain is the weird bit. Not to be outdone by quantum mechanics, it seems that statoliths can sense strain even before it happens. Auxin redistribution occurs immediately before bending begins. How cool is that?

So, why might this be interesting? The ability of a tree to sense strain and movement challenges a long-held belief about how trees respond to physical stress. Unlike buildings, the proportions of trees change over time. They get taller, wider, and heavier. The bigger they get, the greater the load on their supporting structures (trunks, stems, and branches) becomes. To manage the changing load, they reinforce themselves. They grow additional material (wood). The additional wood that is set down is directly proportional to the load the tree part experiences. The term for this is response growth. It was thought (and taught) that response growth occurred due to microscopic damage caused by forces like wind or gravity (load). However, the research suggests that trees initiate this growth to prevent damage, not as a result of damage, that trees can sense movement and strain and respond to it. So… is the trigger for response growth tiny dancing stones that detect physical strain?

We know that statoliths are found in the growing tips of roots and shoots, and the statoliths influence growth in response to strain and movement. Cell division and secondary thickening (growth) occur in meristems, and meristematic tissue is found in the growing tips of roots and shoots, and in the cambium – and also in fruit, for some reason, we always forget fruit. Response growth is growth in response to strain and movement. So, my question to Science was, are statoliths also found in cambium? To this, she did not reply. Perhaps my question was too convenient, or perhaps I was being punished for not neglecting our relationship.

It makes sense that statoliths are the trigger for response growth and that statocytes exist in the cambium. But just because it makes sense to me doesn’t mean it makes sense to a tree. I could not find definitive literature to confirm the presence of statoliths in the cambium, but I also didn’t find anything to say that they weren’t. I’m sure this would be more than enough for Social Media, but I’m not that bold. Whatever the case, my weekend with Science has left me knowing more yet feeling less wise. An odd relationship, but one I’m happy to continue with.

* Negative time is a quirk of quantum mechanics, where particles appear to exit a location before they have arrived