Friday, September 5, 2014

Water makes pecan kernels fill

   After an extended period of dry and hot weather in August, we received 5 inches of rain at the Pecan Experiment Field on September 1st. Up until that big rain storm, the dry weather had inhibited kernel fill and it was looking like kernel quality would ultimately suffer. I was curious to see how our pecans would react to the sudden resupply of soil moisture, so I decided to collect some nut samples.

   On the day following the rain (Sept. 2) and for the next two days, I harvested some Kanza nuts from trees growing at the research station. I then stored the nuts in the refrigerator until all samples were collected, then cut open nuts just before taking the photo above.
   From the three nut samples pictured above, we can learn a lot about how pecans fill kernel and which portions of the kernels are most affected by drought stress. In a previous post, I described how pecan kernel forms inside the nut--kernel tissue is first deposited just inside the seed coat then grows inward to eventually fill the inside of the shell. However, close inspection of the nut collected on Sept. 2 you will note recently formed translucent kernel material on each kernel half closest to the inner wall partition (red arrows). The rain had already stimulated new kernel deposition in an area that had suffered from drought stress. If the weather had remained dry, the under side of each kernel half would have remained undeveloped and the kernels at harvest would have appeared to have a "hollow back" side.
   Two days after the rain, solid kernel had developed all the way around the inside of each kernel half. By Sept. 4, the kernel inside the Kanza nut had expanded to the point of almost eliminating all air spaces inside the shell. It is truly amazing how quickly a pecan can fill its kernel when given a plentiful supply of water. It will be interesting to see how Kanza turns out this year in terms of percent kernel.