seed vitality after storage

marc meyer mmeyer at csun.edu
Wed Nov 1 18:17:13 EST 1995


Mary Anne Lynch (mal at postoffice.ptd.net) wrote:

> My question is:  Will the seed that was stored
> produce a plant that is as healthy as, *or* not quite as healthy as,
> the plant produced by the fresh seed?  If both are quite healthy,
> is this because once they emerge from the ground, photosynthesis
> takes over, and it doesn't matter how much 'energy' was left in the
> seed, just as long as it had enough to germinate?  Or, will this
> stored seed produce a plant that will forever be inferior to the fresh
> seed?

I think the answer to this question can be explained by the multitude of
seed size experiments which have examined the relationship between seed
size, which correlates with the amount of stored energy in a seed, and
adult plant characteristics.  In these experiments it was shown that small
seeds produced smaller seedlings and larger seeds (within the same
species) produced larger seedlings, but that this correlation dimished
rather quickly with time.  Thus, by the first or second week of growth,
the seedlings and subsequent adult plants produced from small and large
seeds were indistiguishable from one another with respect to all
externally measureable characters (i.e. plant height, plant dry weigth,
reproductive output, etc.).  Nevertheless, in some follow-up experiments
that examined this relationship in a more competitive environment (=higher
density of plants), it was found that seedlings from larger seeds did
significantly better than seedlings from smaller seeds (within the same
population).  More specifically, large seeded species produced adult
plants with higher survivorship, greater height, more leaves and more 
flowers than their small-seeded counterparts. 

So how does this relate to stored vs. fresh seeds?  Well, *assuming* the
relationship between stored vs. fresh seeds to be equivalent to that of
small vs. large seeds (in terms of stored energy reserves within the
seed), we could conclude that stored seeds, like small seeds, are just as
"healthy" as their fresh (or large) seed counterparts.  This is likely
because, as you stated, photosynthesis takes over and the amount of
initial stored energy in the seed becomes unimportant after the first week
or two of growth.  However, if this newly-germinated seedling finds itself
in a high-density, highly competitive environment, then the amount of
stored energy in the seed is going to be of crucial importance to the
growth and survival of that seedling.  Thus, a stored seed may be at a
competitive disadvantage to a fresh seed and may remain competitively
inferior (i.e. fewer roots to take up water and nutrients or a shorter
stature that allows it to be shaded out by taller intraspecific
competitors) throughout it's life.  So, in answer to your last question as
to whether a stored seed (with fewer energy reserves) will produce a plant
that is forever inferior to the fresh seed plant (with greater energy
reserves), I would probably say yes, but only if there is relatively
intense intraspecific competition going on between these two seed types. 

Cheers,
Marc Meyer
mmeyer at huey.csun.edu



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