Silk

I have always been fascinated to learn about what people don’t understand about the world around them. In my capacity as a biologist I have had ample opportunity to learn about the sorts of things folks simply get wrong. I have quite a number of stories I could tell to make my point but I’ll spare you and recount just one. Several years ago I was driving a group of students through the countryside on our way to a small nature preserve. These were biology students and, if I remember correctly, the intent of the field trip was to learn something about plant community structure. Along the way we drove past a farm and along the side of the road there was a bull standing in a paddock. For those acquainted with bull anatomy you’ll know what I mean when I say that this was very obviously a bull. The students all took in the massive specimen and as we passed one student remarked, “Gee, I wouldn’t want to milk that cow.” Each academic year a whole new crop of misunderstandings arise, thereby giving me fodder for explanation. During genetics laboratory we make use of specially cultivated ears of corn in discussions and demonstrations of genetics. I am always surprised by how much students do not know about corn. First, they do not know that corn plants are monoecious and each has both male and female reproductive parts. Second, although they are vaguely aware that the ear has something to do with female reproduction, they have no idea where the male structures are. [Every once in a while a farm kid will raise his or her hand to set the record straight.] The tassel, at the very top of the plant, is responsible for the production of pollen and is therefore part of the male reproductive system. Fine. Then I ask my students if corn plants have sex. After their initial shock at the way in which the question is phrased they think about it and immediately become confused. Sure the tassel produces pollen which carries sperm to fertilize the egg which resides within the kernel but how does the former reach the latter which is sequestered deep within the ear? The fact is that each developing egg grows, from within its protective and nourishing kernel, silk. The silk is a tube connecting the egg to the outside world. When a pollen grain lands on the tip of a piece of silk it will germinate and grow a pollen tube which will allow the male reproductive nucleus access to the egg and voilá … fertilization is achieved. I was watching straw being baled down by the river. During a lull in the action I noticed that the corn was in silk. I thought this made for a nice image – I hope you will agree. You may click the image for a view with higher resolution.

Silk

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