Seed physiology and response to germination conditions

This chapter brings together knowledge of the germination and storage behaviour of quinoa seeds in relation to three general aspects: germination response to different factors and in situations of stress; tolerance to pre-harvest sprouting and dormancy control; and the dynamics of ageing and potential longevity of seeds in storage. Quinoa seeds demonstrate the capacity to germinate at temperatures around zero degrees and show tolerance to brief exposure to freezing in some cases. In general, accessions from saline and arid zones are more tolerant to water stress and salinity, as a result of their adaptation. Nonetheless, the distinctiveness of the ionic and osmotic components of salinity has revealed diverse responses and levels of tolerance in accessions of different origins. Pre-harvest sprouting limits the expansion of quinoa cultivation to humid regions. The study of the germination behaviour in accessions with dormancy made it possible to determine the effect of different factors: environmental (temperature and photoperiod), hormonal (ABA and GA3) and structural (coat thickness), on the level of dormancy of quinoa seeds during development, ripening and storage. Quinoa seeds have the capacity to tolerate water loss and maintain viability, recovering vital functions when rehydrated. The kinetics of the reactions of deterioration leading to a loss in viability are largely determined by the degree of water mobility in multilayers. The reactions of deterioration include lipid peroxidation and the formation of compounds from the Maillard reaction. There are references to the differences in storage tolerance for different cultivars, although these are inconclusive in terms of the link between longevity and the characteristics of the regions of origin.