Archaeological research indicates that Wheat was being farmed in Egypt's Nile Valley since before 5,000 B.C. The Wheat plant is shown at different stages of maturity to indicate the different energy densities of the Aether. The Fields of the Duat or Aaru depict Wheat fields being harvested showing how energy is supplied to celestial bodies powering planets, stars and galaxies.
Tesla said that the Aether could be "conceived as lines or tubes of force", creating greater ease of movement in one direction than the other. This is analogous to the tubular stem of the Wheat Plant, whereby if you run your hand up and down the plant you will experience a friction to movement in one direction greater than the other. Tesla also said that the Aether "behaves as a fluid to solid bodies, and as a solid to light and heat". Again this would be analogous to a field of Wheat, behaving like a fluid to solid bodies that brush through the field, and as a solid to light which are absorbed by the Wheat plant.
For this reason the Wheat plant hieroglyph symbolizes the Aether and its different energy densities.