[paul.fr]

Weeds have small seeds and don't grow too big, yet horse chestnuts have big seeds and grow tall. So does seed size equate to eventual height?

[WylieE]

There is a basic correlation that a bigger seed will produce a bigger plant.

 However, unlike in mammals, this is not a great predictor of adult plant size.  In mammals, there is a fairly tight correlation between the size of the offspring and the size of the adult.  However in plants, this correlation is much weaker,especially with the largest plants. 

I think that this lack of correlation is likely due to two reasons, first is the fact that plants don't provide much paternal care.  Most of the correlation probably comes from the fact that the plant would like to produce a seed large enough to give the offspring the best chance possible, but there is some limit on the size of seed that a plant can produce.  For example, a pansy would have a hard time producing a seed the size of an avacado. While at the top end, sometimes it is a better reproductive strategy to spend the energy available producing lots and lots of small seeds in the hopes that some will survive rather than investing a lot of energy into a few large seeds.

 Secondly, larger plants (think trees) tend to be longer lived and therefore it is an important consideration for offspring to be able to disperse away from the parent so they aren't competing for the same resources with their already established parent.  For example, pine trees and maples produce small seeds that can be carried on the wind, yet these small seeds grow into large trees. 

Another consideration is the plants that we have bred for seed size- corn, soybean- won't accurately reflect this trend.

A few years ago there was a paper in Science suggesting that there was a straightforward correlation between seed size and plant size in angiosperms.  There was a lot of debate about that paper, but I can't find anything since then either supporting or disproving it.  So I guess its still a somewhat open question that hasn't been fully answered yet.

[Alandriel]

Seed size, IMO, does not equate to height and I'm really astonished to hear that there was a paper suggesting such a correlation... but then I'm not a scientist.  []

Just think of the largest seed, coco-de-mer and the tree it produces vs. e.g. seeds of the giant redwood (and the tree that produces).

Lodoicea maldivica
Sequoia sempervirens

No, no correlation there.  If anything, there is perhaps rather an environmental co-relation to be found - but even then, I don't think matters are that simple...

[dkv]

There is no co-relation between size of the seed and size of the tree.
From gene replication point of view it would have been more beneficial to start reproducing at a young age with small seeds but this doesnt happen.
And in a random space with gene oriented selection this strategy would have led to the creation of lilliputians. But we dont find them.
Why?

[Karen W.]

Seed size, IMO, does not equate to height and I'm really astonished to hear that there was a paper suggesting such a correlation... but then I'm not a scientist.  []

Just think of the largest seed, coco-de-mer and the tree it produces vs. e.g. seeds of the giant redwood (and the tree that produces).

Lodoicea maldivica
Sequoia sempervirens

No, no correlation there.  If anything, there is perhaps rather an environmental co-relation to be found - but even then, I don't think matters are that simple...

That is the biggest tree seed I have ever seen!

[Alandriel]

That is the biggest tree seed I have ever seen!

It is!! Coco-de-mer has the largest seed of all plants known so far. Cool, aye? Only comes from the Isle of Praslin (Seychelles) in the Indian Ocean - though I think now they grow them also in east Africa and possibly Mauritius.
And the folks here at Kew Botanical Gardens have a few too  []

[WylieE]

The paper suggests a general correlation if you look across 4,000 species of plants- they did include plants such as redwood and other large trees with even tinier seeds and small plants with large seeds (although I can't search the list to see if the Coco-de-mer is in there). 
It does seem like there are a lot of exceptions to the rule.  I guess it will just take a look at even more plants to see if the correlation is true- I'll bet with all the controversy that the last paper caused that there are some out there doing this now.

[JimBob]

A mustard seed produces a tree, as do pepper seeds, etc. I do not think there is a correlation per se.