Sorry if this is a stupid question, but I started thinking about it today. Trees spend their whole lives outside where they are bound to get bombarded by the sun. Why do I never hear about trees getting cancer? Is it not possible, or just one of those things thats been going on for so long its natural and no one talks about it?
Trees can get several types of growth disorders, among them Witches’ Broom, Crown gall, and Burls.
Thanks. All of those are caused by microorganisms though. Are there any that are caused by a DNA mutation?
This site says that burls in some trees can be considered the same thing as cancer:
The problem is defining cancer in a way that’s meaningful when applied to plants. Cancer in animals is essentially a runaway cell division process. That’s easy enough to understand and define because in (most) animals) there is a specific structure to the animal and the organs within the animal. When a liver or the skin devlops irregular lumps it’s easy to define it as cancer. However most plants have irregular growth anyway. There’s no fixed number or shape of leaves or branches or roots in a plant. As such it’s very hard to even define what cancer is when applied ot plants.
There’s no doubt that plants regularly produce genetic mutations that continue to grow on the parent plant. These changes are so common that it’s often claimed that most individual plants are composed of two or more genetically distinct strains. So in that sense you could say that most plants contain cancerous growths.
Well, in animals, cancer kills. Do trees get irregular growths that end up killing them?
Well cancer kills somebody by spreading (through the bloodstream) all over a vital organ and destroying it. Plants don’t have any vital organs that are connected by passageways able to carry diseased cells.
Well cancer kills somebody by spreading (through the bloodstream) all over a vital organ and destroying it. Plants don’t have any vital organs that are connected by passageways able to carry diseased cells.
As I understand it, all multicelled creatures get cancer; it’s a fundamental weakness in the design.
So amoebas are safe? This may sound like an unusually dumb question, but bear with me. Cancer starts in a single cell and spreads from there, right? Why can’t that happen to an amoeba?
Because it is a single cell. Ultimately, muticelled creatures are a collection of clones; being genetically identical, they have no genetic self interest and work selflessly for each other. When cells mutate, they evolve. They can then begin evolving into independent cells, instead of parts of a greater body - cancer, in other words.
This can’t happen in single celled creatures, as they have no subunits that can do that. They can have problems with genes/chromosomes subverting the whole, which is sort of a distant relative of cancer I suppose.
Note : I’m an interested layman, not a biologist, so don’t take this as holy writ.
But a cancerous tumor wouldn’t have larger-scale structures like leaves or roots - cancer cells are undifferentiated, and they just sorta grow in globs. It’d be easy to distinguish a glob growing on the stem of a plant from a leaf.
However, plants don’t have much in the way of a circulatory system, so it wouldn’t metastasize, and the lack of individual “organs” means that a cancer would only kill a plant if it completely blocked its main stem or something.
Yes, but not all cancers are fatal. In fact I doubt that most cancers are fatal to most people.
This gets into the nitty-gritty of why cancer is hard to define in a way that can be applied to plants. But the first point to realise is that tumours can indeed produce large-scale structures analogous to leaves or roots. If you want to be sick use the Google image search to find some good pictures of teratomas, complete with teeth, hair, working muscle tissue and so on.
The reason why teratomas can do that is because they are derived from reproductive cells, which retain the ability to generate all the different tissue types. That ability to produce multiple tissues is called totipotency. The reasons why plant ‘cancers’ won’t normally produce undifferentiated masses of cells is because all plant cells are totipotent, so any leaf cell or root cell or even pollen grain can produce all the cells needed to contruct a new shoot or a whole new plant if it is able to divide.
Which is why it’s hard to apply a meaningful definiton of cancer to a plant. In animals it requires an unusual mutation in an unusual cell type to produce differentiated tissues when a cell divides. In plants excatly the oposite is true. It requires an unusual mutation in an unusual cell type not to produce all the required tissues when a cell divides. As a result any uncontrolled growth in a plant will normally reuslt in more plant growth with all the normal organs and tissues. That growth can and often does overwhelm the parent tissue and kills it, but it does so by outcompeting it, not by choking it as is usually the case with animal cancerts.
True, but it can spread simply because of the apical growth mechanimns of most plants. In that respect a genetic mutant can be more vigorous and spread more rapidly than cancers in humans. A cancerous cell in a human has to spread thorugh the circulatory system and hope to lodge somewhere it can take hold. In plants they stay put and simply grow new limbs, all composed of ‘cancerous’ tissue.
Thanks, Blake for that info. I’m not sure I understand it completely well, but , what an amazing difference between plants and animals as to cellular growth modes.
Plants also produce many chemicals for their own protection, many under intense scrutiny for cancer prevention in humans, most notable in Brassicas (Broccoli, Kale, Cabbage) and polyphenols (Green Tea, grapes). Any insight into this, Blake.
It should be noted that many cancers are a result of modern human lifestyle, mostly intake of bad substances. Trees, by the OP, and plants, generally haven’t changed their diet and recreational substance use much, so probably aren’t susceptable to those type of cancers. I would think they are as vulnerable as the rest of us to environmentally based cancer though.