The farm I'm working on grows a variety of melons. Here is what I harvested one day this week:
|Genetic diversity in melons on our farm.|
Have you ever noticed the netting on the rind of cantaloupes? If not, take a look at the cantaloupe below. If you did notice the netting, did you ever wonder what it was doing there? Not me, but when I started reading about cantaloupes for this post, I found out the most fascinating thing about that netting.
|Netting on cantaloupe rind.|
But back to suberins. You may already know suberins from their most famous location. Cork is pretty much solid suberin. Cork is the almost-outmost layer of bark of the cork oak (Quercus suber). It provides waterproofing for the cork oak, enabling the cork oak to survive in the very dry areas around the Mediterranean Sea. It provides the same function when humans peel it from those trees, cut it into cylinders and cram it into wine bottles.
You will probably be surprised to learn that roots of almost all plants contain microscopic layers of suberin under their surfaces. This seems ludicrous at first, since roots are supposed to absorb water. You'd think the last thing a plant would want is a layer of waterproofing around their roots. In roots, suberin helps the plant regulate what can get into the plant. There are doors and windows in the suberin layer, and those openings let in water plus the minerals the plant needs. The openings keep out anything the plant doesn't need, such as too much salt, harmful bacteria or lots of other things that could be dissolved in groundwater. Mangrove roots are highly suberized to keep out the salt of the ocean water in which they grow.
Suberins are actually a group of complicated molecules. All suberins have a similar structure, but they can vary slightly in their components. Suberins are long polymers of smaller molecules, arranged variously but allowing crosslinks. These molecules have a lot in common with oils, which makes them hydrophobic and water-repellent. A little-known fact about suberins is that they have their own facebook page.
Many varieties of melons don't have suberin netting, including most honeydew melons. Their rind is smooth and net-free. The lack of suberin is not due to an inability to make suberin or an absence of the gene for suberin. In melons lacking netting do not express the gene for suberin in their rinds. The difference between netted and non-netted melons is a genetic difference, but not in what the DNA says. The difference is in how the DNA is read. Imagine the DNA for melons as a book. If you read the pages in a different order, you get a different story. For honeydews, the suberin chapter is skipped over altogether, except in the root cells. (Source) I don't know why honeydew melons don't have cracks on them. Their rind must be able to expand around the fruit without cracking.
I'll leave you with this picture of last week's melon harvest.
|Nice melons! Ready for the market.|