Tuesday, October 18, 2011

Drought effects pecan nut shape

    Its interesting how our different cultivars react to drought stress in terms of nut shape. To document these changes in nut shape, I've collected nuts from several cultivars then arranged them in order of increasing drought stress.
  As drought stress increases, all pecan cultivars produce smaller nuts. However, there can be other changes as well. Note that the base of Giles and Maramec nuts get narrow as compared apex of the pecan. A nut with a strongly tapered base means that the kernels inside will also be strongly tapered. In comparison,  Kanza and Major nuts just seem to  shrink, turning into smaller, rounder pecans.  
     Kanza looses its distinctive "tear drop" shape as the prominent nut apex disappears in nuts made smaller by drought. In contrast, the "pinched" apex of Lakota can be recognized regardless of nut size or shape. Interestingly, I found Lakota nuts that had narrow bases and nuts that turned shorter and rounder all on the same tree.
    Because Major is a small nut to start with, this year's drought seems to have caused minimal changes in nut shape. Maramec, on the other hand, is a large pecan that suffers greatly from water stress. It is easy to see that Maramec nut size and shape are greatly impacted by lack of  soil moisture.