Grain development

Abstract

Developing grains are complex structures consisting of maternal and filial tissues. Waves of cell proliferation, differentiation, maturation and disintegration occur in the different grain parts in a sequential manner. Comprehensive molecular and biochemical analyses point to an interplay between hormones and metabolites, which orchestrates these processes but also influences endosperm endoreduplication. Maternal factors preferentially influence grain length and determine endosperm cell number. Storage product accumulation in the endosperm influences both grain width and depth in a process under filial control. Analyses of the transfer tissues nucellar projection and endosperm transfer cells at the micro-scale provided insights into cellular differentiation and maturation. During embryo maturation, high amounts of lipids and micronutrients are accumulated. However, knowledge about endosperm-embryo communication is scarce. Towards increasing seed sink strength, it is most important to analyse the processes that partition nutrients to the different parts of the caryopsis and to uncover mechanisms that allow accumulation of higher amounts of micronutrients within the starchy endosperm.