Friday, November 5, 2010
I was out talking photos of different pecan cultivars when I spotted a Pawnee nut suspended from the shuck (photo at left). I like this kind of photo because it portraits the action of nuts falling out of the husk when the nuts are fully ripe. But this photo also tells the story of the importance the shuck to nut development. Look carefully at the fibers than are holding this Pawnee nut suspended from the shuck. These fibers are part of the vascular system that lines the inside of the shuck and are attached to the base of the nut. A healthy vascular system is critical for nutrients (minerals and carbohydrates) to be transported from the tree to the developing seed (pecan). The fibers you see in this photo represent only 1/2 of the shuck's vascular system. A networks of vascular bundles also covers the outside of the husk. When visualizing the vascular system of the shuck as a whole, start at the base of the nut where it is attached to the tree. The flow of nutrients from the tree into the nut starts through the outer vascular bundles towards the tip of the nut. Once the nutrients arrive at the tip of the nut they travel through the inner vascular bundles to the base of the shell. All the water, minerals, and carbohydrates needed to build pecan kernel enter the nut through vascular connections at the base on the shell. So it is easy to see that any pest that damages the husk of the nut will reduce kernel fill.