The upside of Autumn rain
Rain, rain and more rain today. I’m a fair-weather walker, so haven’t braved it today, but I’m hoping that the upside of the rain will be that we’ll see some more fungi about. The mushrooms we see above ground are the fruit of the fungus; the ‘body’ of the fungus is underground, an often vast network called the mycelium, which is composed of tiny white strands called hyphae. The fungus will only produce fruit when conditions are optimal, and that means damp. This got me thinking about why fungi like it damp, so I did a little reading on the subject.
As I said above, the body of the fungus is a network of microscopic strands which exist within the substrate from which they feed; so that means soil, wood, leaf litter, dung. Because there is such a large surface area exposed to the substrate, the mycelium is very vulnerable to damage and dehydration. That’s why they need to be kept nice and moist. So to expend the energy that reproduction requires, the fungus wants to be in good condition itself, with good environmental conditions to match.
To produce a fruit body, areas of hyphae start to converge (rather than diverging as they would normally do). They bunch together and the cells begin to differentiate as they prepare to become something new. Amazingly, by the time the fruit body is less than 1mm long – a fraction of the size of a mature specimen – all of the main component parts of the mushroom, such as the stem and cap, are already formed and in place.
The structure and form of a plant, animal or fungus does not develop all at once. Cell differentiation takes place in stages, with each previous differentiation determining the next, as the cells follow certain morphogenetic pathways. Chemical signals – hormones, growth factors, morphogens – within the organism tell the cells what to do, where, and how much, in order to form specific tissues.
What is most surprising, is that once the fruit body is a ‘mushroom’ or ‘toadstool’ that we would recognise as such, its incredibly rapid growth to maturity is not down to cell proliferation, as it would be in a plant or animal. The cells actually inflate, allowing much faster growth. I’ve spent all evening reading, trying to find out what they inflate with. Air? Water, as suggested by one site (not a scientific one)? There is mind bending scientific detail about every other stage of the process, then they just say “the hyphae inflate”. Aaarrghh!