# What makes up new plant growth? Is it dirt? **URL:** \ **Category:** Factual Questions\ **Created:** [June 27, 2005, 6:46am UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009 "2005-06-27T06:46:03Z")\ **Posts on this page:** 9\ **Page:** 2
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [June 27, 2005, 4:20pm UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009/21 "2005-06-27T16:20:15Z")
Upon reflction, that thimble full probably refers to mineral ash. Still seems low though. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [June 27, 2005, 11:18pm UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009/22 "2005-06-27T23:18:27Z")
> [@fishquail](#): > > That seems impossible to me. Matter is never created but only changes form. But of course air is made up of matter - molecules of nitrogen, oxygen, and carbon dioxide. These particular molecules are gaseous at normal temperatures, but the elements they contain can be used to form other molecules that are solids or liquids. Think of the process in reverse - when you burn wood, most of its weight is converted from solids into gases. ---
**Author:** ![elelle](https://avatars.discourse-cdn.com/v4/letter/e/f0a364/32.png) [@elelle](https://boards.straightdope.com/u/elelle)\ **Post date:** [June 28, 2005, 12:53am UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009/23 "2005-06-28T00:53:01Z")
Much of the good information here deals with the specifics of photosynthesis and basic soil components. Plants are fine, adaptable subjects to human-aided growth, and you can grow them with basic chemical knowledge, without soil. Soil science, like so many others, is currently exploring the complexity of it’s domain. In forestry and horticulture, there is research exploring the interaction of soil microbes and mycorhyzzia (fungus), and how that aids in plant growth. Basically, it is a symbiotic relationship, with benefits to both. Here’s a link: [http://www.ffp.csiro.au/research/mycorrhiza/intro.html](http://www.ffp.csiro.au/research/mycorrhiza/intro.html) for more detail. You can grow plants through simple chemistry, but the way plants compose themselves for optimum survival is quite complex. We tend to focus on the easily observable, and use for us, but note that at least half of any plant’s existence is underground. It’s an unseen world we’re just beginning to understand. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [June 28, 2005, 1:30am UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009/24 "2005-06-28T01:30:22Z")
Doesn’t it depend a lot on the plant? I would expect that the amount of water in plants varies considerably. Anyone have some info on how much of the mass of various plancts is made up of water? ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [June 28, 2005, 2:21am UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009/25 "2005-06-28T02:21:45Z")
Plants are usually described as being about 70% water, but in reality that number varies all over depending on climate, time of year etc. [Here’s some numbers for wheat](http://agron.scijournals.org/cgi/content/full/94/3/585) (techy article, click on at own risk) > [@](#): > > seedling water content decreased from 80% to 45 to 55% in both NT and CT (Fig. 5A). The water content of plants that germinated late in winter decreased from 80% in January to 20 to 35% by mid-April, irrespective of cultural management Obviously, the water content of corn plants, elm trees, bristlcone pine, sujuaro, and [welwitschia](http://www.plantzafrica.com/plantwxyz/welwitschia.htm) will vary across species as well. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [June 28, 2005, 5:45am UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009/26 "2005-06-28T05:45:47Z")
It’s usually assumed int hese sorts of discussion that it’s dry weight, not wet weight. Obviously most of the wet wieght will come from water, but that’s just as true of people as it is of plants. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [June 28, 2005, 6:16am UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009/27 "2005-06-28T06:16:02Z")
Right- the bulk of the mass of a plant is from water, then air. The 'drit" adds very little mass- but very critical elements. ---
**Author:** ![OliverTwistofLime](https://avatars.discourse-cdn.com/v4/letter/o/b487fb/32.png) [@OliverTwistofLime](https://boards.straightdope.com/u/OliverTwistofLime)\ **Post date:** [June 28, 2005, 9:11am UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009/28 "2005-06-28T09:11:02Z")
Has it been determined how hardwoods or tree matter in general can combine co2, water, nitrogen, potassium and other minerals to create the hard material that comprise the trunk or roots of trees? or to put it more simply, how does the tree do it? ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [June 28, 2005, 1:09pm UTC](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009/29 "2005-06-28T13:09:28Z")
yes and no - [How Plants Make Lignin — Researchers Begin to Count the Ways](http://www.ars.usda.gov/is/pr/1998/980113.htm) [Previous page](https://boards.straightdope.com/t/what-makes-up-new-plant-growth-is-it-dirt/310009.md?page=1)