In vitro Degradation of Starch Granules by α‐Amylase Isomers from Mature Triticale

Starch granules and α‐amylases (green, α‐I, and germination, α‐II) were isolated from a triticale line with a high frequency of kernel shrivelling. The isolated starch granules were treated with the α‐amylase ismomers for different periods of time. Degradation of the starch granules was followed by analyses of reducing sugar produced, and by scanning electron microscopy. About similar degrees of starch degradation were observed after treatment with α‐I‐ and α‐II‐amylases. After a few hours, the degrading effects of the enzymes were manifested as holes or craters on the surface of starch granules and as erosion and dilation of the equatorial groove. These features were also characteristic of starch granules present in shrivelled kernels. Amylase treatments for a longer time caused more profound degradation, leading to collapse and fragmentation of the starch granules. The lack of such effects in shrivelled kernels means that amylases are not the sole factor in the formation of kernel cavities associated with shrivelling. The occurrence of mitotically aberrant and degenerating cells, already existing at early stages of endosperm development, and disparity between the processes that determine kernel size and kernel filling potential are also of relevance in this connection.