Juniper2007OriginSweetApple (dragged) 4

Juniper2007OriginSweetApple (dragged) 4 - endocarp pips...

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48 American Scientist, Volume 95 © 2007 Sigma Xi, The Scientific Research Society. Reproduction with permission only. Contact perms@amsci.org. part in ornamental plant breeding— but the fruits are sour, sometimes even intolerably bitter and astringent. Thus they are of scant culinary value and, as we shall see later, seem to have con- tributed little if anything to the gene pool of the sweet apple. What natural features of the unique Tian Shan might have contributed to this rigorous selection program? Time is, as we have seen, not a problem. The turnover of individual trees is likewise conducive to the rapid evolution of a tree species, as is the fact that sweet apples are now, at least for all practi- cal purposes, self-incompatible—that is, they cannot pollinate themselves. Therefore each apple tree within the forest and even each pip, usually five, within each individual fruit will be different. There are many apples on a mature tree, so natural selection has a rich and diverse population upon which to work. Birds, of course, eat all manner of fruit. But most birds eat seeds—a di- etary feature not conducive either to the selection or spread of a fruit tree. Sweet apples are often eviscerated
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This note was uploaded on 11/18/2011 for the course HIST 302 taught by Professor Jensic during the Summer '10 term at Purdue University-West Lafayette.

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