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The role of Gibberellins in Hydroponics · Hydroponics Daily

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  Hello there, welcome back to
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  Hydroponics Daily, your go-to podcast for everything soilless cultivation.
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  I'm your host, Dr. Russell Sharp, and today we're talking about one of the most
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  powerful plant hormones, gibberellins.
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  Gibberellins is a plural because there are over 130 gibberellins that have so
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  far been discovered, probably a lot more.
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  So we'll talk about that later. So they are plant hormones that are involved
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  in everything from seed germination to flowering, stem elongation to fruit development.
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  So we'll explore their discovery, diversity and manipulation,
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  both natural and synthetically.
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  And what does that mean for the future of controlled environment agriculture or hydroponics?
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  So the history of gibberellians begins
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  in the early 20th century in japan
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  where rice farmers noticed noticed a
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  mysterious disease that caused rice plants to
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  grow excessively tall and then collapse just
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  lodge we call it in agriculture the cause was
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  a fungus called gibberella fuji kuroi
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  in 1935 researchers isolated the
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  substance responsible for causing the disease when.
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  This fungus was infected and named it gibberellin later
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  scientists discovered that plants themselves produce gibberellins and
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  what we call endogenously themselves and
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  it's not just this fungus and this launched a
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  new field of plant growth research so the
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  early researchers did something very fortunate they
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  named the gibberellins after a
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  number and this is good because other hormones
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  like auxin and ethylene they just have a chemical name
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  whereas they named the gibberellins with a number
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  and that's good because they didn't know there was going to be 130 of them at
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  the time so the most commonly studied ones though
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  are ga1 which is active on stem elongation ga3
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  and that's the one that is often referred to
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  as gibberellic acid and that's one
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  that's synthetic and you can you can buy gibberellic acid
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  and ga3 is that ga4 and ga7
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  are active in flowering and fruit development and each
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  plant species uses a different combination and ratio of gibberellins depending
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  on its life cycle and environmental conditions so i did my phd on flowering
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  in rhododendron and there i tested the the levels and the effects of different hormones,
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  different gibberellins, and I found GA5 and GA6 to be particularly active in
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  rhododendrons, and GA5 and GA6 are also particularly active in grasses.
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  Particularly lolium perenne.
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  And interestingly, in different plants, gibberellins can have the opposite effect
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  when it comes to flowering.
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  So in some plants, gibberellins promote flowering, and others,
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  they inhibit flowering. And then in other plants, they have no effect on flowering.
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  For a while, plant scientists thought the gibberellins might have been the flowering
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  hormone, but that's since been proven not to be the case, and that's been identified
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  elsewhere to be a protein.
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  So the endogenous role of gibberellins, if they're not the flowering hormone, what do they do?
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  Well, one of the key things that gibberellins do is they break seed dormancy
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  by stimulating enzyme release to break down food stores. They're really important.
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  So Well, not necessarily light, but water, oxygen, and warmth.
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  That's what they need, isn't it? Yeah, so they'll germinate,
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  and the gibberellins will be a key process of that.
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  In hydroponics, stem elongation is the main one.
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  It increases cell division, but also elongation, especially in young tissues
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  and stems, and that's where it can become problematic. And we'll talk about that in a minute.
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  It's also important in leaf expansion, pronounced new leaf growth and biomass accumulation.
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  As we said, flowering and fruiting, Some species gibberellins trigger flowering
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  in long day plants especially.
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  And sex determination. GAs influence the male to female ratio in many monaceous
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  plants like the cucumbers and squashes as well.
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  So gibberellins have an important role in horticultural manipulation.
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  We're going to talk about growth regulators that inhibit gibberellins in a second.
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  First we'll talk about what the effect of actually applying
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  gibberellins can be so when you actually want to apply gibberellins and the
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  main one they're used in is in grapes and that's to produce increased berry
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  size and loosen clusters and produce seedless grapes if you see a grape that
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  is particularly big and long in a supermarket it's probably had gibberellins applied to it.
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  And barley and rice break dormancy and accelerate growth
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  potentially but more often than not in arable
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  crops you're going to be put gross regulators on that prevent gibberellins
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  you know in certain crops where you're
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  trying to produce seed so if you say you were a seed producer
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  breeder then you might apply gibberellins
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  to lettuce and celery to stimulate them to bolt to
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  flower but that's a very very niche use in
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  citrus and apples to delay fruit aging and increased size potentially
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  depends on the country where that's allowed and but
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  dosage and timing are critical too much gibberellins can
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  cause excessive elongation and probably could kill
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  your plants so you need to be really careful so where
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  would you might want to inhibit gibberellins so
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  in some cases you might want less gibberellin activity especially
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  in ornamentals and compact crops where growth
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  retardants come in the most common one that i've come across
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  is called paclobutrazole that goes under the trade name bonsai and that inhibits
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  gibberellin synthesis and it's used on bedding plants to keep them compact it's
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  also marketable size it's used on rhododendrons to promote flowering and keep
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  them short and squat and increase the number of flowers to them.
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  Comparative to the size. Chlormequot, chloride, CCC, reduces stem elongation
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  in cereals and ornamentals.
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  So cereals, that's going to be the one, and uniconazole, highly effective in flowering plants.
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  These products though, they're all applied in ornamental plants.
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  They're not applied on any food crops apart from, I think, oilseed rape.
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  And even then, if you speak to an oilseed rape grower none of them will actually
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  use it even though it's authorized for that so.
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  The only crops they're used they're actually
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  permitted on is ornamentals and
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  even then they're not great because you buy a rhododendron plant from the supermarket
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  it's had growth retardants applied to it and in the soil and they stick around
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  in the plant and in the soil for years for several years if not decades and
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  they impede the growth of your plant so people say I really struggle to grow
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  rhododendrons in my garden.
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  Could be due to the acidity of the soil, it needs to be acidic, the pH of the soil.
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  Could be that you've planted them too deep, but it could be that they've just
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  received too many growth regulators.
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  So the plant just stays stunted for years and years and years.
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  The other problem with growth regulators is that they are poisonous and they
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  can impede the growth of humans, especially developing fetuses.
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  So that is why you will not find them
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  authorized for use on edible crops and if
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  you are but they do find their way
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  into the hydroponic market it's the dirty secret that a
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  lot of people don't want to talk about but a lot of people do want to talk about you know
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  you speak to lewis at shogun
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  nutrients he'll he's prepared to stick his head above the parapet and talk about
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  the use of gross regulators and how it should be stopped me too i think there
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  are alternatives to using them they don't produce a good crop and they certainly
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  are not good for human consumption so.
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  How do they actually work? They often act by blocking an enzyme in gibberellin
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  synthesis called ent-courine oxidase.
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  There is one, another gibberellin inhibitor.
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  What's it called now? Produced by BASF, I think. Oh, what is it called?
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  Prohexadione. I just had to Google that, I'm afraid. It was on the tip of my tongue.
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  Prohexadione doesn't stop gibberellins being produced. It stops the plants from sensing them.
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  So again, it's a synthetic chemical and it's not authorized for
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  use on arable crops as farmers are aware yeah crop
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  suitability let's have a look here it might be used
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  on apple and cherries in some countries but yeah certainly not
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  going to be as bad as prohexid iron and things like that chloramacot so
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  there are other ways to modulate gibberellin activity
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  and i've talked about some of them in the past controlling the
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  red to far red ratio making sure you plants have got a
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  small amount of far red not completely eliminate it but
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  a very high red to far red ratio this prevents
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  excessive stem elongation making sure the light
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  intensity is high enough so the plants don't think they're shaded inducing the
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  stress hormone aba otherwise known as abscessic acid that and it's an antagonistic
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  to gibberellin acids it delays german well germination but also growth and stem
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  elongation so we talked in the past about partial root zone drying regulated
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  deficit irrigation there are other ways you can control.
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  If you can increase the ABA concentration by stressing the plant slightly in
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  a moderate way or tricking the plant into thinking it's stressed or there's
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  not enough water there, then you could potentially reduce the action of the gibberellins.
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  And then in the future, there is potential for using what's called CRISPR,
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  all capital letters, which is a way to modulate gibberellin synthesis in plants
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  like rice and tomatoes that people are looking at.
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  This is a way of using the RNA, the product of DNA. When a gene's expressed,
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  it produces something called RNA, CRISPR, CRISPR.
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  Takes advantage of that and i'm not an expert when it
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  comes to crisper but there must be potential of modulating
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  gibberellins in plants with that and it could be a less
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  toxic way of you than using synthetic growth
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  regulators a lot of my arable farming
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  customers who are in the regenerative space
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  they also use our potassium silicate and
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  our organic c silica products as an
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  alternative to growth regulators because they find
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  that it produces a squatter plant and also crucially the
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  increase in the stem strength means they don't need
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  to use growth regulators because in arable crops they're really
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  using the growth regulators to prevent lodging and keep the plants strong and
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  so there is a potential of using things like that and also if you are increasing
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  the pH of the xylem sap you can increase the flush of ABA around the systems
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  and potassium silicate based
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  silicon products are really good for that because they're also alkaline if
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  you're using a um sort of one based on an
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  organic solvent silicon product then that won't obviously flush aba into the
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  system so you probably want to look for something based on potassium silicate
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  gibberon research is far from finished as i said there's about 130 have been
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  identified so far i'd say gibberon research has been stunted in the last 20
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  years because there's been about 130 for the.
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  There was about 130 20 years ago and there's
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  still 130 identified i used to work in a lab in east morling in kent famous
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  for its apple research and there was a guy there called patrick blake and he
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  discovered loads of gibberellins i don't think he even had a phd he was just
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  a really good biochemist and chemist and he was really good at gas chromatography mass spectroscopy,
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  and he discovered loads of them in strawberries and since then it doesn't seem
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  to be that more have been discovered because that sort of science isn't sexy
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  as much as it used to be but you know there's,
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  There's potential for using sensors. If we could look at real-time gibberellin
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  levels, then that would be really interesting.
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  Gibberellins are extremely active and only in very low doses.
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  So compared to other plant hormones, they're really difficult to measure.
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  So you have to be really good at that. Potentially, there's tailored breeding
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  to lower GA cultivars in vertical farming, especially things like legal cannabis,
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  strawberries, cucumbers, and things like this.
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  Sustainable intensification balancing GA application
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  with nutrient use and light conditions and potentially
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  there's biostimulants out there natural or microbial products that can
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  modulate gibberonis synthesis or receptor activity so
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  there are biostimulants out there that can
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  mop up ethylene and and
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  do other things with plant hormones feed cytokinins and
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  things like this so it's not beyond the way to manage some
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  sort of microbial or non-microbial biostimulant to activate gibberellin
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  biosynthesis or modulate it so closing
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  thoughts gibberellins are key for the architecture of
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  your plants and your things like that just like auxin
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  is whether you're pushing the lettuce crop to bolt you
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  want compacted compacted ornamentals or you're just trying to get some seeds
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  to germinate gibberellins you should definitely look at gibberellins as a not
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  just as a tool but also to to improve your knowledge how how plants grow led
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  lighting is allowing us now to
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  manipulate spectrums and intensities much more than we could in the past,
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  and things like crisp bar technology could mean that ga management becomes much
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  more precise and much more talked about in hydroponics and vertical farming
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  and horticulture in general so that's been hydroponics daily for today gibberellins
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  it's been really good to revisit this because i've not looked at gibberellins for a good.
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  20 years so yeah
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  if you know more than me if you think there's been some big breakthrough
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  in gibberellin technology in the last 20 years then
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  let me know and if you think i've got anything wrong then i'm always
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  happy to clarify if you've been shared this episode because
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  you are interested in gibberellins then you owe
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  the person who shared it with you a pint and if you could do me a favor and
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  just screenshot your podcast provider here
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  on your phone and and share it to social media
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  and say i listened to this episode of hydroponics daily and it was
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  blooming brilliant check it out now that would
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  mean the world to me because it would help share the podcast and grow my
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  listener figures which i'm a bit obsessed with i'm
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  trying to get some listeners in madagascar today um i
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  got listeners in where was i after idaho i'm really
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  happy i've got listeners in idaho still no one in north or
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  south dakota nowhere in west virginia no one
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  in greenland or iceland i poked my friends
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  in macedonia i've got a few friends in macedonia didn't have any listeners in macedonia
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  don't have any listeners in the Czech Republic but yeah the map
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  of the world is is slowly slowly filling
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  up still no listeners in the northern territories of Australia if you know anyone
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  who lives out there or lives in the far north of Canada I'd be really interested
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  in getting some listeners there anyway that's enough waffling for today until
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  tomorrow that's been hydroponics daily thank you ever so much for listening goodbye.