Agriculture Reference
In-Depth Information
5
GRAIN DEVELOPMENT
Agronomically, heading is usually defi ned as the time when 50%
of the panicles have exserted. Anthesis normally occurs between
0800 and 1300 hours in tropical environments. Fertilization is
completed within 5-6 hours later. Only a very few spikelets
have anthesis in the afternoon. When the temperature is low,
however, anthesis may start late in the morning and last until
late afternoon. Within the same panicle it takes 7-10 days for
all the spikelets to complete anthesis; most spikelets complete
anthesis within 5 days.
The length of ripening, largely affected by temperature,
ranges from about 30 days in the tropics to 65 days in cool,
temperate regions such as Hokkaido, Japan and New South
Wales, Australia.
Upon fertilization, female gametophyte expressed
genes control the initiation of seed development. During
seed development, female gametophyte expressed gene
products play a role in controlling embryo and endosperm
development.
The biosynthesis of starch is the major determinant of yield
in cereal grains. As ADPG is an activated sugar, the dependence
