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Plant Matter

Blue OnionBlue Onion Posts: 2,995
in Plants
We just got new Science standards in Utah this year, and today I started researching the basis of a new Art/Science lesson using the school garden. 

Here is what it says:
Standard 5.3.1 
Construct an explanation that plants use air, water, and energy from sunlight to produce plant matter needed for growth. Emphasize photosynthesis at a conceptual level and that plant matter comes mostly from air and water, not from the soil.

I had always understood/assumed that the cells making up the leaves, plants, and fruit were materials/chemicals taken up from the soil - not CO2 and H2O.  It sort of blew my mind.  This explains it.

Suppose I never stopped to wonder why there weren't big holes around trees.. 
Utah, USA.

Posts

  • PosyPosy Posts: 3,601
    The science bit will doubtless follow, but plants DO need chemicals from the soil. If they didn't, there would be no need to feed and mulch them. I imagine that it is much the same as other living things: we absorb nutrients from what we eat to grow the cells that make up our bodies. 
  • Joyce GoldenlilyJoyce Goldenlily Posts: 2,933
    Are they hinting at permculture where plants are grown in water? The plants still need to be fed nutrients through their root systems
  • strelitzia32strelitzia32 Posts: 758
    That's an unusual aspect to start from, is that quote referring to science for very young children? It's kind of missing the point that all growth comes from chemical reactions. Here's how I understand it from school biology...

    Plant matter doesn't "come from" air, water, soil, sunlight or anything else. It comes from chemical reactions with the components and the elements of those things, just like how humans grow through consuming food and converting it to potential energy. Scientifically there's no such thing as "soil" - there's a collection of sequestered carbon, elements, complex nutrients, excretion from organisms etc etc, in different ratios. We just see the honeycomb structure at a macro level. Roots take up water and nutrients from the soil using osmosis, which are then transported to the leaves. That water is combined with co2 absorbed by leaf stomata to produce complex sugars. That process uses sunlight as the source of energy for the endothermic chemical reaction and is what everyone knows as photosynthesis. The resulting sugar feeds the plants, and excess sugar is converted to starch and is stored. That's how plants grow.

    But photosynthesis can only happen efficiently if the supporting structures and processes are functioning correctly in the plant. For example, sunlight can only be converted to potential energy and used in photosynthesis if there is enough chlorophyll in the leaves to do it. Chlorophyll is "made" (let's skip how that works) using chelated iron, which is why nutrients are important and why we feed plants in pots because they will consume all the available nutrients in that closed biome. Chlorophyll is green, and that is why sickly plants have yellow leaves and don't grow (gross generalization there!).

    I doubt that's of much use, but maybe helps explain a bit? Also I'm a little hazy on the exact process that transports iron and other chemicals, and then reacts to produce chlorophyll etc, but Google will probably answer that better than I can.
  • Blue OnionBlue Onion Posts: 2,995
    @strelitzia32. Thanks for the detailed explanation. It's the standard for 5th grade students (Year 6).. so not too simplistic, but leaving out the actual chemistry or any explanation. I feel like they are trying to teach that the physical building blocks of plants come from air/water.  But ignore all the effects of the soil, because that part is 'complicated'.  

    Still crazy.  
    Utah, USA.
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