The starch formation needs CO2 assimilation. Staygreen keeps it empowered by a core part of the plant, until physiological maturity is reached.

• Drought tolerant hybrids show a certain staygreen form flowering to black layer stage.

The Grainfill must start immediately after fecundation

• Drought tolerant hybrids show a short lag phase, from fecundation, to start of grainfill.

Moisture losses from the growing ear must be minimized

• Drought tolerant hybrids cover their ear well by husks, opening at black layer stage.

At terminal drought stress, kernel weight as the last yield component, needs to be reinforced

• Drought tolerant hybrids show less reductions of kernel weight, as reaction to drought stress