Plant Growth: Auxins and Gibberellins | Plants | Biology | FuseSchool

Plant Growth: Auxins and Gibberellins | Plants | Biology | FuseSchool
If a plant has enough water, minerals and energy, it will grow, right? Well, sort of… but there is more to it - like why do plants bend towards the light and not just grow straight? And why does the stem grow up but the roots grow down? It isn’t as if a plant has eyes to tell it where the sun is.
Plants are packed full of hormones, sending messages around to its different parts. Where humans have the creatively named ‘growth hormone’, plants have hormones called auxins.
Auxin is produced in the stem tips and roots, and controls the direction of growth in response to different stimuli including light and gravity. Having been made in the tips of the stems and roots, auxin is moved in solution by diffusion to older parts of the plant. In the stem, the auxin causes the cells to change in elasticity. More elastic cells absorb more water, and can grow longer.
Strangely, though, stems and roots respond differently to high concentrations of auxins. Whilst the stem cells grow more, the root cells actually grow less. So auxins make plants grow, but why do they bend towards the light? How do they know to do this when they don’t have eyes?
The bending happens because the light hits the one side more and breaks down the auxins in that side of the stem. So then growth slows down on the ‘light’ side. The faster growth on the ‘dark’ side causes the shoots and leaves to turn towards the light - which is ideal for the plant for photosynthesis.
Auxin is produced in the tips of growing shoots. If the tips are cut off, then no auxin can be produced and so no plant growth. If the tips are covered, whilst auxin is still produced, light cannot break it down and so phototropism cannot occur: the plant just grows straight up and does not bend towards the light.
Auxins have the opposite effect on root cells. In roots, auxins cause less growth. The shaded side of roots contain more auxins, and so they grow less. This enables the ‘light’ side of the roots to grow more and bend away from the light.
And if that wasn’t weird enough, we have opposites happening with auxins and gravity too. In a horizontal root, the bottom side contains more auxins and grows less, so the root bends downwards in the direction of gravity. So positive geotropism. But of course, the stem responds differently.
In a horizontal stem, again the bottom side contains more auxins because it is less directly hit by sunlight. But because auxins cause growth in stems, the bottom side grows more causing the stem to bend upwards, against the direction of gravity, so negative geotropism.
But I am giving auxins too much credit; they don’t work alone. They have a partner in crime; cytokinins. You don’t need to know anything about these hormones other than the fact that they work alongside auxins. There is another plant hormone that you do need to be aware of… Gibberellins.
Once a seed germinates, the roots and shoots start to grow. But for this, the seed needs energy. Luckily, the seed releases a hormone called gibberellin which causes the starch in the seed to turn into sugars and provide the seed with energy to grow. As well as causing shoot growth, gibberellins can also stimulate flowering and fruits in some plants. And they also work with auxins to cause stem elongation.
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[@sv7379]

*watching and feeling as if i was a detective or an investigator cause of the music*

[@abhisheksrivastava3033]

I understand very nice

[@shynijose1020]

How plants are sensitive to their particular stimuli? Why auxin is break when the plant is kept in light? I didn't understand these two things.

[@elizamunday6933]

One thing I don't get: You say that the light breaks down the auxin on the side closest to the light, but my science book says simply that the 'hormone moves away from the light as it diffuses downwards'. Which one is right? Really helpful video otherwise - thank you so much!

[@fuseschool]

Good question Eliza - there are actually 5 (or more) different models proposed for the breakdown / loss of auxin on the light side of the plant. The main thing you need to know is that the side closest to the light has less auxin in the cells, thus the plant bends towards the light. The 5 models in basic terms are: 1) light deactivates auxin (as we say in our video) 2) light inhibits the synthesis of auxin on the light side of the plant 3) light causes the auxin flows from the light to the dark side 4) light inhibits auxin and the auxin flows downwards (as your video says) 5) combination of 3 and 4: main auxin flow is from top to bottom with some auxin travelling horizontally. Light then inhibits the horizontal flow and blocks the flow on the side closest to the light, leaving just the vertical flow on the dark side.

[@kingstauntonbiology]

Experiments have been done to show that light has very little effect on Auxin in terms of breaking it down. Instead the most likely explanation is that the increased light levels allow, via photophosphorylation, the increased production of ATP. This ATP can then be used to actively transport Auxin out of the illuminated cells towards the shaded side of the plant.

[@srilals.kumara4377]

This video really helped me , I loved the clear explanation , thank you so much

[@fuseschool]

Most welcome! Glad it helped!

[@fine1876]

Thank you so much for this😭😭 been struggling a lot for this 🤧 💜💜

[@fuseschool]

Most welcome! Glad it helped 🙂

[@thelibertymomma8304]

INK!!! Thank you fuse school!

[@goon6384]

Thanks for cool visualization

[@tuhina2310]

Is it just me or the term 'gibberellin' actually sounds Harry Potter-y Like some herbilogy term. Lol

[@farahangel517]

nice i get it really amazing work keep it up may god bless u with success ameen

[@fuseschool]

Many many thanks!

[@deepagaichari9546]

Nice video🙌🙌🙆🙆

[@wilsnet]

vry cool i show my class from africa dey ave neva seen plant before

[@shayemcee]

Thank you so much this helped a lot!

[@cooldiys3477]

wow thank you so much this was rlly helpful!!

[@ritamandal9726]

Thanks for your help 👍🏻

[@fuseschool]

No problem 👍

[@thandomathanda3201]

Thank you sir!🙂

[@ramyatxc9923]

Wow!!the video is really awesome😍😍Thank you very much for making this video🤗

[@fuseschool]

You are so welcome! Glad you liked it 🤗

[@kritisingh2217]

Thanks a lot for this vedio sir

[@mikayla4280]

Thank you so much!

[@fuseschool]

No worries!

[@laughbig3400]

I got a 9 in Biology because of FuseSchool

[@datboi1861]

Is that bad or good

[@shaunakn5881]

@@datboi1861 i think he meant 9/10

[@lillaczegledi9197]

Cool Thanks :)

[@user-qn1mi8ft6p]

Cool

[@ihtishamulabideentechnical484]

Excellent video

[@noelle4145]

How does spraying auxins in a wheat field only kill weeds and not wheat

[@sivabalu8873]

Really helpful fr studies thnk u guys..

[@AbdulHadi-pd9gq]

Nyc.......

[@follyjolly7833]

This is cool

[@PradeepKumar-rn1hq]

This is useful 👍🏾

[@alibinzaheer8098]

Convenient form 😉

[@indikahewapathirana2312]

Thank for made a video about auxin and gibberellin

[@GJRahul-rr3uk]

Very helpful

[@c9kit803]

This is a pretty helpful animation, just a small part on the tropism section though: 'The original theory was that auxins were destroyed by light but recent evidence suggests that levels of auxins in the shoot stays the same regardless of whether they are kept in the dark or in the light' (Fuller, Ann 2015 Edexel Biology B A level. Page 184 paragraph 3) just wondering your thoughts about that, can't see any other method of causing a phototropism

[@subtle7461]

Have a look at phototropin 1 & 2, they under go phosphorylation in the presence of blue light which somehow causes the lateral distribution of IAA to the dark side of the apical meristem then the IAA diffuses down the plant, causing more growth on the side not in the light. Interesting book for you might be plant physiology 3rd edition by Taiz (just google and you should find a pdf link) and chapter 19 is specifically about auxin and it's mechanisms. Although it is slightly outdated as the TIR1 receptor for auxins was discovered in 2005 and the book was written in 2003 i believe but sis still a good foundation for the subject

[@ammarali2880]

hi guys! i need help, i have searched whole internet but couldnt find the ans, i gave my Tomato plant (NAA) which has been recovering from transplant shock, kept under low LED/HPS lights, after NAA the plants started wilting & dropping badly, now seems like they are dying, i didnt overdose NAA, i follow the description mentioned in the bottle, what it might be? lack of light or wrong time to give auxin?

[@shabnamparween6893]

Ammar Ali good evening

[@safa9605]

Ammar Ali it’s time to eat it bro

[@tiana9200]

did you find the answer?

[@marlenemortler3620]

thats interesting

[@sunrisefarm5489]

Please do I apply directly to the root or by spraying, thanks

[@Asif3627]

could anyone please share the reference of any research article for the lines aforesaid ''In the stem, the auxin causes the cells to change in elasticity. More elastic cells absorb more water, and can grow longer''.

[@waryotofajar8075]

how,,,we can get auksin and giberlin in the plant

[@antalenej3885]

Thank you so much this helped a lot

[@fuseschool]

You're welcome! Glad it helped!

[@thobekamsibi8045]

that great thank you

[@trixieso4144]

so which type of growth do stems have?

[@yashugarg9586]

mam i really undersyand it but jin plamts k leaves baad me yellow ho jate h to unkabchlorophyl ka kya hota h

[@rodelpaculba8482]

What is the relationship between precipitation and plant growth??help me plsss

[@ruthvickraj2037]

Super 😊

[@wishnusatrya7946]

is there no reference to this explaination in the video?

[@pam9451]

Thanks so muchhhh

[@johny69]

Cleared mu doubts 👍👍

[@srilals.kumara4377]

But please can I know some functions of gibberellins...

[@mohmaya4796]

What types of software are use

[@fuseschool]

We use After Effects.

[@amayarandeniya6692]

Can you please speak a little slower? I merely can't understand anything because of your fast speaking. However, the lesson was perfect. Thank you and nice presentation.

[@fuseschool]

Thank you! And noted!

[@bryanu1737]

1:25 Cell Élongation :D

[@rosieosabutey6579]

Lovely video. Please make more :)

[@rugvedpawar7114]

1:58 What do you mean by 'shaded' side of roots. Also the root was kinda moving towards the light just like the horizontal shoot in the video at the 1:58 mark. If you could explain, that'd be awesome. Cheers!

[@vivekar.164]

i believe shaded side means the part of the plant that does not receive the sunlight, or as in shade. i might be wrong, but the root was moving towards the area with more concentration of water (a stimulus) which coincidentally happens to be in the same direction as the source of light, or sun.

[@1dogissky]

Thank you!!!!!

[@RadhaKrishna-ee6ge]

awesome.

[@gamingstupid2006.]

👍👍👍👍👍👍😎😎😎😎😎

[@fuseschool]

👍👍👍👍

[@pranoyde2028]

That's not the structure of a gibberellin, shown at 3:12...

[@AyeshaAht]

the music in the background is creepy. Can you try not putting music in you future videos? its distracting

[@ashvini192]

i didnt get why the plants needs oxygen part

[@callumj2003]

fuse school hit 100k XD

[@RadhaKrishna-ee6ge]

😮😇

[@abubakr7304]

1:40 wouldn't the plant not grow anywhere because it has no light for photosynthesis.

[@WilliamReddingGuitar]

No i dont think so, as auxin can still be produced

[@itsdizazzle3293]

the background music is creepy

[@shaneelakhan2480]

Hi Main Ek bachi hoon mujhe mere School Mein Ek Sawaal aaya hai ki the direction in which fruits grow mujhe laga is yoga for fruits fruits fruits aagaya aa o o t s uski spelling hair roots roots Kaha konsi direction Bagrodia

[@aimeethomson7806]

Might be here forever...mightened we

[@rio5339]

hey bio class

[@zahricade3401]

this guy was really hard to understand. i mean, the video said gibberellens and he said give or Ellen's. ?????????

[@yashugarg9586]

plej reply

[@lucasburnett4422]

Bro you talk to fast ffs

[@mrmanbd982]

U r too much fast, talk slowly.Thank u

[@ranasayed5179]

You can always change the speed. When I read your comment I changed the speed to 0.75 and it works nicely!