The effect of parental environment on various aspects of seed biology in two species of Sorghum

Abstract

The effect of parental environment on dormancy, nutrient content and size in seeds of Sorghum bicolor and Sorghum halepense was investigated. The environmental factors assessed were water stress during the grain filling of both species, potassium nutrition during the life cycle of S.bicolor, and nutrient availability during the life cycle of both species. Water stress during grain filling increased the germinability of developing seeds of S.bicolor, so that they reached high termination rates earlier within the developing period than did control grains. The higher germinability of droughted developing grains was parallelled both by a lower endogenous content of abscisic acid (ABA) and by a lower embryonic sensitivity to the hormone. Water stress during grain filling also decreased dormancy of S.halepense mature seeds but through modifications in the glumes' properties that, apparently, result in a higher permeability of the glumes to the transport of oxygen to the caryopses enclosed within them. Water stress during grain filling decreased seed size in both species. A shortage in potassium availability increased germinability of developing seeds in S.bicolor, particularly when the deficiency was not extreme. This was also parallelled by a lower endogenous ABA content and by a lower sensitivity to ABA. Moderate potassium deficiency led to a shortening in the growing period of the grain and consequently seed size was reduced. Low nutrient availability to the parent plant reduced the concentration of minerals in S.halepense seeds, while the chemical composition was maintained stable in S.bicolor grains regardless of parental supply. In contrast, seed size was increased with decreasing nutrient availability in S.bicolor, while it was unaffected in S.halepense. These results are discussed in terms of differences and similarities in the reproductive strategy of both species.</p