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Are you growing a C4 crop? Maize, millet, Sorghum, Bermuda Grass etc · Hydroponics Daily

• 0:00
  Hello there and welcome back to Hydroponics Daily. Yesterday
• 0:03
  we were talking about cyanide in plants and we
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  said it was found in sorghum and I mentioned that that was a C4 plant and today
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  I'm going to talk about what C4 plants are because if you're growing one hydroponically
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  then you could be missing a trick if you're not doing some key things to maximize their growth.
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  They are a type of plant c4 plants
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  that have a different type of photosynthesis or
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  certainly a different way of capturing carbon to make
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  sugars and so we'll go into how that
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  is and why they do that and what impact that
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  has on your grow so first off
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  plants need co2 to make sugars by photosynthesis and
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  most plants use what's called the c3 pathway most
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  that's the vast majority of also known as
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  the calvin cycle where co2 is fixed by
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  an enzyme called rubisco and rubisco
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  is the most common enzyme in
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  the world there's more rubisco than any other type of enzyme in
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  the world it's that crucial it it can bind oxygen and it can bind co2 and it's
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  the first step in photosynthesis but it's reversible and so you get something
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  called photorespiration where it actually releases CO2 in stressful conditions.
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  Now, C4 metabolism, also known as the Hatch-Slack pathway, after the inventors, I assume.
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  That's evolved a new method, a new method, a different method,
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  for suppressing this photorespiration, this release of CO2 in really stressful conditions.
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  And it works by concentrating CO2 around this Rubisco enzyme,
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  so it's in really, really high concentrations, thereby reducing the enzyme's
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  ability to oxygenate in a reaction.
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  So to do this, it has specialized leaf anatomy.
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  Now the leaf anatomy is called cram's anatomy. You don't need to know that.
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  It's just got two distinct cell types in the leaf or in the stems.
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  And it's got mesophyll cells, normal cells that make up the spongy middle of
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  a cell, and it's got bundle sheath cells where the rubiscuit is.
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  And they have enzymes and metabolic pathways that push these C4,
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  these carbon-4 compounds through from the mesophil cells into the bundle sheaths
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  to prevent this photorespiration from occurring.
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  It's very clever and it results in far higher levels of photosynthesis in stressful
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  conditions, especially when it's really hot and dry and when there's lots of CO2 around.
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  Now C4 photosynthesis is not as energy efficient as C3.
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  So that's why in temperate climates like here in the UK, virtually no plants are put.
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  I don't think there's C4 plants in the British flora or any of the crops that
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  we grow really apart from maize.
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  And so because this extra energy cost of having this different bundle sheaves
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  and these different enzymes means that it's in low temperatures,
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  when there's plenty of water around.
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  Then it's actually beneficial to be C3 plants and not have this extra enzymes
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  and extra anatomy in the plant.
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  It's only when you get into those stressful, serious conditions that you need C4.
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  But as you can imagine, if you bump the temperature up and bump the CO2 levels
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  up, then if you're using a C4 plant, you can get really, really high levels of photosynthesis.
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  That's why plants like maize grow so fast and
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  sorghum can grow ridiculously fast in hot
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  dry conditions and other plants will just wither and die
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  c4 plants are also a lot more water use efficient and nitrogen use efficient
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  as well because they can concentrate that carbon dioxide around the enzyme and
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  they don't need to lose water through respiration so they can keep their stomata
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  closed for longer the pores in their leaves so there's something about the the
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  biochemistry involved.
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  So which plants are C4?
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  Well, the main crops are maize, sugarcane, sorghum, millets.
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  And certain tropical grasses, some of the sports turf species.
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  Is it zoysia, something like that? Bermuda grass.
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  If you're in America, you'd be familiar with that species of grass that's used
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  in lots of field sports, and it might even be used in fairways and golf.
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  They're all C4 plants so sugarcane, sorghum, millets, tropical grasses.
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  If you're growing one of those hydroponically then you can bump up the lights
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  a lot more than you could normally and you'd optimize photosynthesis,
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  a lot higher temperatures.
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  Increase the CO2 even more and you might want to increase nitrogen and magnesium
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  to support chlorophyll and the enzyme regeneration.
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  So these plants can really grow rapidly at those higher conditions as opposed
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  to the C3 plants which would start to struggle.
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  And then recently there's been a study that shows that if you feed plants humic acids,
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  C4 plants especially, then that can upregulate genes related to light capture
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  and chlorophyll photosynthesis in maize and improve net photosynthesis rates really high.
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  So saying here, 46.5% increase in net photosynthesis rate, that seems ridiculously
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  high by the addition of just a simple humic acid biostimulant.
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  So I'd really want to look into that more before I started putting humic acid.
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  But certainly I'd look into it if I was growing something like maize,
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  just to see if adding humic acids could really improve my photosynthetic rates.
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  What else could we say? What other interesting developments have there been on C4 plants?
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  Well, not many. But basically, yeah, if you're growing hydroponically,
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  you're not going to be limited by water availability, which is one of the key benefits of C4 plants.
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  But certainly the high temperatures you don't need
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  to vent your grow room as much you can bump
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  the light a lot higher and you can massively increase
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  because you're not venting as much your co2 levels can go
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  higher so potentially you could get massive growth if you're growing a c4 plant
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  so interestingly cacti don't use c4 necessarily they use something called cam
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  for disynthesis or crassulaic acid metabolism where they actually open their
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  stomata their pores at night and capture carbon dioxide as acid.
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  A bit like, you know, distilled water is slightly acidic because of the carbon
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  dioxide dissolved in it.
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  Well, they dissolve carbon dioxide as acid in cacti during the night,
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  and then they can keep all their pores closed during the day,
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  and they turn those acids into sugars during the day.
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  So that's what a cactus does, whereas a C4 plant is
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  just like a C3 plant in that it opens its stomach during the day
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  and closes them at night it just has
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  this separation and of of the
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  two different types of cells and captures them
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  as c4 captures carbon dioxide as a c4
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  carbon4 molecule that then then goes on to feed the robisco enzyme to make sugars
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  the key thing is if you if you know that you're growing one of these then it's
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  those ability to ramp up those environmental conditions to supercharged growth
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  that's what you need to really be looking at.
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  So if maybe you're one of these scientists who's looking to grow food staple
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  crops in hydroponics or NASA looking at growing crops on Mars or in space,
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  then if you're growing a C4 plant, this is what you need to consider.
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  And then obviously look into that humic acid study as well, because an increase
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  in photosynthetic rates of 46.5% is not to be sniffed at, and that's massive.
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  I doubt many people are growing millet hydroponically it's a very much a subsistence
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  crop isn't it from african places like that ruckus and really really dry arid conditions,
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  it's mainly for bird food as well isn't it millet but it's very good for you
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  so maybe you're growing millet maybe you're a health-conscious hydroponic grow
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  who knows so yeah check it out if you want to know this humic acid study and
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  i'll just get up here it's by some chinese scientists.
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  And it's photosynthesis promotion mechanisms
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  of artificial humic acid depending on
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  plant type a hydroponic study of c3 and c4
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  plants sounds like a good study this one so yeah
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  check it out it's published by the i don't
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  know this journal psi total environment in 2024
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  so you know
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  i've never heard of that journal before but it's not
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  coming up anyway full name of
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  the journal is the science of the total environment so
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  check it out if you want to know about humic acids and your growing maize i
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  definitely would check that out and that's been hydroponics daily for today
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  c3 and c4 plants no idea what we're talking about tomorrow but it will be on
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  the podcast at some point during the day thank you very much for listening and
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  as always if you could leave us an apple podcast review it would help out tremendously
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  thank you very much goodbye.