Jay, Jim, 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) > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://www.pacificbulbsociety.org/list.php >