Plant embryo

The seed surely does not contain the entire future plant within its embryo? I can accept the plumule containing the first true leaves, and the embryo overall containing the precursor tissues for future growth - so this must mean that the embryo is the equivalent to a human being's DNA, ie the potential for its physical development.

Surely you're not telling me the seed actually contains the whole plant in miniature, waiting to be "unfurled" as it were?

And if we accept that the embryo contains the future tissue for the plant, then this must mean each plant has only a finite potential for growth and stature - so activities like pruning and so on only stimulate whatever growth is already in store. In short, every time I see a new shoot emerge from a pruning cut, this shoot and its emerging leaves were always there, waiting to be released.

I have nearly finished my current course and will always be grateful to the copious help I have received on these pages.

 

Hi Simon

I would agree with JWK. I think a plant embryo contains enough physical material to get the young plant started, and then DNA to instruct it how to develop later on. Its a sort of starter kit. It certainly doesn't contain a minature version of the whole plant - though they used to think that in the mid 1800s under the name of preformation.

As I understand it there are the cotyledons, which are preformed virtually fully functional leaves to give the seedling an immediate boost. Then the plumule is the embryonic shoot with two or more tiny leaves and a growing point between them. Once the plant starts to grow the direction of growth is determined by the DNA which makes new cells decide to be part of a stem or a leaf etc. The exact mechanism for this is not understood in humans and animals, and probably not in plants either.

 

Thanks for both those answers, which pretty much hit the nail on the head, I think.

 

Hi Simon,

Yep, all of the above.

The dna contains the blueprints of what to do if someting happens. Like which chemical to send wherever. Cut the leading shoot off a plant & growth suppressing hormones stop being transmitted down to the secondary shoots so that they all try to become the leader.

Insects have learned to disrupt the program with chemicals that make the plants produce galls.

What course are you doing then ? :flwsml:

 

Thanks for that.

If the embryo contains the genetics of the future plant, does each plant in theory have the possibility to produce only a finite number of leaves and branches, regardless of how it is pruned, how favourable its environment, etc?

The course I'm doing is a Certificate in Horticulture, via the Australian Correspondence School (ACS).

 

Simon Z

The seed basicaly contains 3 things.
1) genetic instructions, telling the plant how to grow, what its flowers and leaves etc will be like

2) baby leaves and roots, ready to sprout

3) a little bit of food to get the baby roots and leaves going until they can look after themselves

If the embryo contains the genetics of the future plant, does each plant in theory have the possibility to produce only a finite number of leaves and branches, regardless of how it is pruned, how favourable its environment, etc

Yep. You will never grow a 10 foot lettuce. And you will never produce an Oak tree out of a Bizzy Lizzy seed!

It's sexual reproduction, and evolution. Just like animals, plants 'try' to recreate the characteristics of their parents to give them the best chance of survival.

 

Simon

As I see it the DNA is a set of instructions. The DNA doesn't actually set the maximum size or maximum number of leaves that a plant can have, it just gives instructions on how to build it. However the limits tend to arise from the way in which a plant is built.

Consider a building in ancient Egypt, the DNA equivalent instructions would be to make it out of mud bricks. And you can make a taller building with more layers of mud bricks. But by the time the building reaches about three or four stories the mud bricks at the bottom will start to crumble under the weigh, because they are not very strong. Consequently Egyptian mud brick buildings only tended to be a certain height. The DNA instructions didn't set a specific limit to the number of stories, but the use of mud bricks did. A very skilled builder might make harder bricks than average, perhaps using a better local clay, and so be able to produce a taller building than average. In a similar way a plant under the right conditions may be able to live longer and grow taller than the average even though it has the same DNA instructions.

If the DNA instructions tell the builder to use kiln fired bricks, he will be able to build taller buildings, and if he uses steel girders he can build even taller.

The reason an oak tree grows taller than a lettuce is that they are a different design. Their height is limited by their DNA in so far as the DNA dictates the design, and the design dictates their final height and age etc.

 

Very well put Peter.:gnthb:.

Hi Simon, they jury is still out on the finite. By coppicing hazel bushes we have extended their lifespan way beyond normal, and the truth is, we don't know how long they will go on for.

And take potato varieties. The oldest one in the uk is called the yam. That was first grown in 1771 and as you know, the ones being grown today are clones of the 1771 plant, genetically its the same plant as are all the other yam potatoes.

Hope this is of some help & not just me woffling on :tnp:

 

:rotfl::rotfl::rotfl::hehe::thumb:

 

Thanks Ziggy.

I think coppicing is a good example of preventing a plant reaching its full potential - so it just goes on trying and trying. In a similar vein to deadheading. Christopher Lloyd wrote that it was many years before he realised that if you remove the flowers before they can make seed, you can make many biennials much more perennial. In both cases the plant is trying to complete the plan that its DNA has laid down for it - but is having problems.

On the subject of clones. There is one creature - I think its a slug - but I can't find any reference to it by Googling, where below a certain latitude they reproduce sexually. ie You need two parents and the offspring are all slightly different, but above that latitude its so cold and perhaps there are so few that they reproduce by themselves producing exact clones.

 

Very good point to bring up Peter, well explained.

Wasn't he just great in Back to the Future & Taxi though.:hehe: