Coconuts and corn

David Starrett dstarret at BIOLOGY.SEMO.EDU
Fri Aug 13 08:08:41 EST 1999

At 03:18 AM 8/13/99 -0700, Steve Hinkson wrote:
>Yes john, you're right.  The corn you eat off the cob is also a seed that is
>eaten unripe.  The sweetness is in the liquid endosperm, just as in a
>coconut.  When corn's ripe, it's starchy.
>Thought the starch was the corn's cotyledon, and the endosperm was enclosed.
>Guess Bill Purves thinks that's the wrong anatomy of monocot seeds.  I still
>want to know where the  cotyledon is in a Mono - cotyledonus plant.
>John T. Barber wrote:
>> I believe that corn goes through a similar (to coconuts) "milk stage" - an
>> immature stage at which the unripe corn has a "squishy" kernel that
>> subsequently hardens as the liquid endosperm solidifies.  Doesn't answer
>> many of the questions that have been asked but at least corn is more
>> familiar to most of us.  There are probably many plants whose seeds go
>> through the same developmental sequence (but if so, I don't know what they
>> are).

I DO know the answer as to where corn's cotyledon is.  It is a small
structure called the scutellum.  It projects into the starchy/liquidy
endosperm.  Dicots convert most of their endosperm into cotyledon material.
 In corn, the cotyledon never gains much "weight" but rather transfers the
nutrients directly to the developing embryo proper.  This is true of many
of the grains familiar to us.  I make a big deal in botany about endosperm
vs cotyledon, one is embryonic, the other not, one triploid, one diploid,
etc.  By the way, the little slivers that come out of a corn kernal when we
bite into it are the embryo, with most all the sliver being the cotyledon.

One of my earlier coconut queries was whether coconut has a scutellum like
structure as well, something suggested on a recent posting.

Thanx for the postings on these questions, seems most are answered, but
would like a more difinitive answer on the cotyledon.  Anyone?

Dave Starrett

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