Sugars transport to maize endosperm

​Sugar manufactured via photosynthesis in leaves begin as 6-carbon structures (hexoses), primarily as glucose and fructose.  These two may be combined to form sucrose. These are the primary sugars transported through the phloem to the developing kernels. Transportation is driven by energy and osmotic pressure and influenced by the cytokinins produced by the new kernel embryos.
 
Studies concerning the entrance of these sugars into the embryos is usually done with only a few genotypes and probably represent only general principles. Sucrose tends to accumulate more in the embryo but glucose and fructose molecules tend to be more dominant in absorption in the corn endosperm. There are indications that the sucrose is broken into its two components, glucose and fructose, before entering the endosperm cells.
 
It is difficult to imagine all the genetics that got this human-derived species to this point.  Genes affected root efficiency in absorbing minerals and water, leaf size and structure, photosynthetic efficiency, flowering timing, disease resistance and movement of the energy captured by photosynthesis to allow all of this to happen.  And now the human objective of capturing excess sugars in the grain involving more genes for the final deposition. It is estimated that corn may have 40,000 genes. The complexity of reaching this point, and the variability for all the parts of this process that is visible to us plus those invisible physiological steps that gets the plant to this point is supportive of this estimation.