Delicious, but hard to get?! Walnuts.
Nature hides the delicious walnut meat within not one but four consecutive layers of protection. One cannot help but wonder: How did our prehistoric ancestors deduce what was inside all those layers, which might make it worth banging away at them with rocks?
Scientists have discovered that walnuts have a uniquely tough shell, made of an intricately shaped and previously unknown type of cell.
All nuts have tough outer shells made of layers of thick-walled cells and separating fibers in a polygonal pattern. Walnut shells, however, are made of a dense tissue in which individual cells and their shapes are difficult to discern, even under high magnification.
Researchers found that walnut shells are composed of a previously unknown cell type—dubbed the “polylobate sclereid” cell—which sports irregular lobes with many different concave and convex contours. These fit together in an intricate and remarkably strong pattern, with each cell surrounded by an average of 14 neighbors. If the structure were a 3D wooden puzzle, it would be impossible to take apart without breaking it into pieces.
This property gives the walnut shell its higher tensile strength, making it much harder to crack. The findings could inspire artificial materials built on the same principle, the researchers say, or even ways to reuse discarded walnut shells—a development that would be great news for recycling “nuts.
The reason behind it all…
Walnuts have tough shells for reproductive reasons. If walnuts had no shells, if their delicious meats just hung on branches unprotected, they would all be gobbled up effortlessly by every passing creature. If that was the case, no walnut meats would survive long enough to reach the ground, germinate and sprout into new trees. If that was the case, walnuts would have become extinct long ago.
