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Plant Sciences, Zoology & Evolution / With seeds, does size matter?
« on: 04/10/2007 00:56:39 »
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.
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.