A Dirty War | by Cheryl Farkas
The first impression is that plants, bushes and trees just sit in one place their whole life minding their own business, growing, shedding leaves, being subjected to the weather, bugs, animals and people right? Well, the one thing science has found for sure, is that some plants just won’t be subjected to another plant’s company. As a matter of fact, there’s a silent, violent, territorial and downright dirty war going on out there that science is learning more about daily. It’s basically ‘chemical warfare’ in the most natural state. Shocking but true!
Here’s The Dirt On It
There really is a term for this, it’s called Allelopathy, pronounced: al-uh-lop-uh-thee or uh-lee-lop-uh-thee. The word is derived from two words, allelon meaning “each other” and pathos meaning “to suffer.” And suffer an innocent plant will, if it tries to grow near a plant that releases Allelopathic chemicals.
A German professor, Hans Molisch created the term in 1937, even though botanists were aware of “pothos – suffering” as early as 300 B.C., first recorded by Theophrastius, then 1 C.E. by Gaius Plinius Secundus who noticed some effects causing scorching. Then Agustin Pyramus De Candolle in 1832 suggested soil sickness from chemicals from crops. Next, in 1907, Schreiner and Reed investigated phototoxic chemicals (the actual poisonous substances). Elroy Rice recreated the notion in 1974 and 1983 by writing a book. This subject has caught more attention in the past 10 years because of the positive effects allelopathic chemicals can be used for in science, such as a natural herbicide in agriculture, landscape maintenance and management.
Dirty Political Powers and Purpose
The primary purpose in this war is to reduce the competition or let your competition work for you. Some plants just plan to impose upon another by stealing vital nutrients from the soil, drinking up all the water and hogging up all the sunlight making it impossible for others to survive. Other plants are welcome because they bring something that is beneficial like a chemical that will kill an unwanted neighbor or a plant that attracts certain kinds of bugs or animals that eat their neighbors. Nothing like using each other for personal gain. So, vegetation ultimately has the ability to alter or control entire areas while summoning particular species. Like a parasite, disease, or animal that kills off certain kinds or amounts of organisms in an environment, therefore defining an entire ecosystem, which is powerful!
The Grit and Grime
There are three main ways in which trees, shrubs, and plants do things. Vegetation and microorganisms interplay and alternate roles depending on their means or intent. Allelopathy can be the interaction and mixture of chemicals too. One way is by means of exuding (discharging) allelopathic chemicals into the soil through their roots. An innocent bystander absorbs the chemicals and it’s simply over.
Another way is leaching, (drains away from) in this way a soluble chemical, which can be an oily or watery substance, is omitted from so many different possible parts of a plant or plant debris an enemy can accidentally intake these chemicals by as many different means and parts. This is a slower death. Some get the last dirt in after death and wait until they fall to the ground and decay and decompose to release. Here the parts these chemicals can be expelled from: Pollen, spores, lichen, mushrooms, flowers, buds, bulbs, berries, flower debris, seeds, nuts, nut hulls, leaves, leaf debris, leaf mulch, fruits, roots, bark, stems and branches.
This is a dirty poster tree that uses this last trick in the trunk, volatilization (gassing). They can release a chemical in a gas form through small openings in their leaves and can be carried a distance by the wind. Lethal!
Dirty Ways and Weapons
There are different reasons why they release warfare into the environment. Some can actually choose which weapon they want to use from their arsenal. This depends on the level of stress or type of threat vegetation is experiencing. It could be lack of water, sun or nutrients.
Here are just a few things that make a crabby tree. If environmental conditions are threatening they pick up the pace and their speed by inhibiting and controlling root or shoot growth, they can even inhibit and control nutrient uptake and starve their enemy. They can kill their neighbors’ interrelationship they have with other local plants, therefore destroying their food source and nutrients. Jealousy is poisonous! Soil sickness is a common dirty trick. Residue from allelochemicals can stay in soil long after a plant is gone making an area infertile, unable to produce anything for a long time. Mean!
Temperature extremes or other environmental punishments such as hail injury, wind, fire, or ice damage, infections from diseases, insect invasions or injury from an animal throws them into a panic, releasing chemicals implicating and impacting all species around an area even at the same time or just implicating certain parts of a tree or plant.
These nutty trees release an allelopathic chemical that changes the level or amount of chlorophyll, in another plant. If the level is off, it can’t produce food. (Chlorophyll is the molecule that absorbs sunlight and uses its energy to synthesize carbohydrates from carbon dioxide and water. The process is photosynthesis.)
While they are at it, they can also release a chemical that can stop or just slow down
photosynthesis, water intake and growth process just enough to torture, maim or kill. (Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar.)
Increasing or decreasing activity during a season is a choice they can make, like this choice. Active compounds are sometimes held in forms inside cells or kept in special sealed compartments with passage doors ready to be transported along main routes or oxidized (to combine with oxygen) when needed, injured or threatened. Wow, ectoplasmic!!!! (Ectoplasm is stuff that allegedly oozes from ghosts or spirits and makes it possible for them to materialize and perform super feats.)
Plants have had to live together and tolerate each other for so long they have learned how to evolve and co-exist. One way to make your enemy mad and get them out of your roots is to become immune to their assaults by building a resistance to their toxins or create your own chemical to make theirs biodegrade faster. Ah-huh!
There are different kinds of defenses and the use of materials. To prevent damage and decay of reproductive parts and materials like seeds, nuts or fruit, seems innocent enough, even parental in a way. But don’t get too mushy. In allelopathic terms autotoxicity is a term for killing your own children! Yep, that’s where a species purposely inhibits growth, prevents germination of its own children by causing roots to be swollen, plants to be puny, wilted, sickly and pale in color, whereby reducing nutrient intake. Ultimately reducing competition with their children/species. Selfish!
On the bright and berry side, allelopathic plants or plant parts like buds, roots, leaves and plant tissue, can prevent themselves or other plants from injury, reduce injury, lengthen survival time or inhibit consumption by insects, birds, animals or the environment. They can even release growth compounds from their roots into the ground. Other plants nearby are unable to handle all the sweet, excessive kindness and get sick of it and die.
A large majority of allelopathic substances – chemicals, have not been specifically identified, but there are many that have and the list grows yearly. Controversy surrounds allelopathy as science tries to distinguish the type of competition that is being displayed between plants. Not all plants have allelopathic tendencies though. Some just exhibit aggression and competition without using chemicals, just playing games. The characteristics of the plant world seem to encompass as many of the same characteristics as people possess, reckoning the fruit doesn’t fall far from the tree.
For more information on allelopathy visit the website: USDA National Library, National Invasive Species Information Center www.invasivespeciesinfo.gov/resources/lists.shtml
For an invasive plant list go to: http://fs.fed.us/database/feis/plants/weed/index.html