Crinum self-fertility

you both have the right hit on apomixis vs self-compatable. Although I've
never studied this area closely, apomixis is common among many berry-bearing
trees and shrubs, such as mountain ashes (Sorbus) and Cotoneaster, as well
as grasses. Presumably, the production of fruit is advantageous for the
plants, regardless of cross-fertilization. I suppose it's a bit of hen vs
egg, as to which developed first and lead to the other. Is it necessary to
develope apomixis to assure a goodly crop of fruit? Or was the species at a
point of evolution that is so advantageous, further evolution would be a
disadvantage? Why would nature find an advantage to what is essentially
cloning?

Self-compatability is very common, as most plants can be selfed, but many
use self-incompatability as a method to assure cross pollination with a
different clone. Many Hemerocallis are self-incompatable, but occaisionally
produce the odd selfing seed. They are not apomixic! Apparently the
mechanism to prevent selfing is not 100% effective. Many plants simply have
different ripening times between pollen and ovum, preventing selfing, others
have long anthers to hold the pollen well away from the stigma. In any
case, as pollen and egg cells are both haploid, you will always have some
variation in the chromosome sets and thus variation in the off-spring.

In apomixis, the ovums set of chromosomes does not split and holds an
identical set to the parent. The only variation would be through mutation.

here is a basic layout of apomixis
http://www.apomixis.de/back.htm

Ciao,

Jamie V.
Cologne

----- Original Message -----
From: "James Yourch" <yourch@nortelnetworks.com>
To: <pbs@lists.ibiblio.org>
Sent: Friday, June 11, 2004 3:47 PM
Subject: [pbs] Crinum self-fertility

Jim McKenney wrote:

How does one distinguish between apomixis and self-compatibility? The
concepts are clear enough, I think: apomixis is seed production without
fertilization -presumably involving unreduced gametes which preserve
the diploid ploidy level for basically diploid species;
self-compatibility on the other hand is the ability of a clone to
produce pollen which fertilizes the ovules of the same clone.

Do we agree on the basics, or have I got the basics wrong?

In either case, aren't the resulting "progeny" simply clones of the
parent? The resulting "seeds" are not really seeds, they are just
neatly packaged bits of the original plant. In the case of apomixis,
the tissue is all derived from the maternal line. In the case of
self-compatibility, the tissue is derived from both the maternal and
paternal lines, so-to-speak. Except that since the maternal and
paternal lines are the same clone, there is no significant difference.

I was hoping someone with a biology background would step forward to

answer

this, but not yet. So here is the Software Engineer's answer.

In the case of apomixis, they are seeds, they just happen to contain the
identical DNA as the mother plant, a clone.

In the self-compatible case, they are not clones of the mother plant

because

there is still a mixing of genetic material during gamete formation and
fertilization. I think that every gamete produced
by an individual is unique and therefore every seed produced would also be
unique, even if the mother and father of it is the same individual.
Remember Monty Python's "Every sperm is significant"?

With regards to your Hymenocallis seed question, they look just like

Crinum

seeds. Crinum mostly produce one to a few seeds per flower, but the seeds
are very large. C. bulbispermum, maybe others too, can produce many seeds
per flower and the seeds are still large.

Hope this helps,

Jay Yourch

Central North Carolina, USA (USDA Zone 7)
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