1224 GMT February 22, 2019
Nicholas Money, a professor of botany at Miami University in Ohio, said, "The short answer is no. Plants are not vegetarian. But the devil, as always, is in the details.
“Those details depend on how strictly vegetarianism is defined. Trees don't directly eat animals, but they do consume them with the help of fungi.”
It's well known that trees can make simple sugars through photosynthesis — that is, basically using sunlight to fuel a reaction between water and carbon dioxide, resulting in carbohydrates and oxygen.
Money added, “However, trees also need minerals such as potassium, calcium, sodium and certain metals. In order to get these nutrients, they need fungi's help.”
Fungi are literally everywhere in forests' soil, according to Money, as reported during a 2016 Radiolab episode that explored the relationship between trees and fungi.
This massive fungal network is composed of millions of microscopic filaments that run every which way.
The network constantly soaks up water from the soil and always looks for a new meal.
Money added, "The mushroom itself is just the most conspicuous part of this huge [fungal] organism that's pulsing away underground in the soil.”
The fungal network produces enzymes called proteases that can break down fats and proteins from dead organisms, such as tiny worms known as nematodes, that live in the soil.
However, because fungi can't photosynthesize, they can't make their own sugars.
Money added, “This need for sugar drives the fungi's relationship with trees.”
The fungi's filaments connect to the tree's roots — basically, covering the roots like a well-fitted glove — and send out structures that penetrate the roots, enabling a two-way nutrient exchange.
Once the exchange is established, the tree can give the fungi some of its sugar, and in return, the fungi give the tree minerals dissolved in water.
Money added, “It's a perfect symbiotic relationship: One partner is not gaining more in the relationship. It's mutually beneficial.
“In fact, the relationship has its own name: Mycorrhiza, which is Greek for fungus root.
“Thus, trees consume animal components through this mycorrhizal relationship.
"In this sense, depending on your definition of vegetarianism, perhaps we can't recognize trees as completely vegetarians, since some of the nutrients they absorb come from animal carcasses.”