Seasonal changes in the position of the shoot apex of winter wheat and spring barley in relation to the soil surface

In many field investigations of cereal growth, stages of crop development may be described adequately using the Feekes scale (Large, 1954) or the more recent decimal code (Zadoks, Chang & Konzak, 1974). For example, the onset of stem extension (Feekes stage 6; decimal code 31) is frequently taken as a field indication of the switch from vegetative to reproductive growth. However, in investigations of the influence of soil properties, especially temperature, on shoot apex and leaf growth, it is important to know ( a ) the position of the apex below the soil surface during the early stages of development and ( b ) the timing of the rise of the apex above the soil surface.