Submitted to: Seed Science and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2010
Publication Date: 12/20/2010
Citation: Jaradat, A.A., Rinke, J.L. 2010. Nutrient homeostasis, C:N:S ratios, protein, and oil content in Cuphea seed. Seed Science and Biotechnology. 4(1)1-9.
Interpretive Summary: Oil is the economically valuable component in seed of indeterminate Cuphea plants; however, protein in the seed meal is of potential value as animal feed. Oil content depends, among other factors, on seed weight, which in turn, depends not only on the source of assimilates during the seed-filling period but also on total mass of nutrients per seed and on seed number per plant. The relationships between densities of 14 nutrients, C:N and N:S ratios, and oil and protein contents were assessed in seeds of indeterminate Cuphea plants subjected to source-sink manipulation after flower initiation. Oil and protein contents in Cuphea seed, being positively and negatively correlated with C:N ratio, respectively, may not be easily and concomitantly improved unless the currently large N:S ratio can be reduced through proper plant nutrition. Oil content can be improved by removing the top ~25% of plant foliage no later than 10-15 days after flower initiation to help synchronize flower production, allocations of dry mass and nutrients to the developing seed and seed maturation. This information would help agronomists design nutrition studies and farmers obtain larger seed and oil yields from this indeterminate potential oilseed crop.
Technical Abstract: Macro- and micro-nutrient densities, carbon:nitrogen (C:N), nitrogen:sulphur (N:S), protein, and oil contents and interrelationships were assessed during a 3-year study in seeds of the indeterminate Cuphea germplasm line PSR23 selected from an inter-specific cross between two species of the Lythraceae: Cuphea lanceolata and C. viscosissima. In order to mitigate the effect of indeterminacy on seed quality, plants were subjected to source-sink manipulation by removing the top 25% of biomass at 100 and 200 growing degree days (GDD1 and GDD2, respectively) after flower initiation, as compared to no treatment (GDD0). Most seed traits were impacted by treatments and their interaction with years; number of seeds per capsule by single seed weight or the seed packaging cost (i.e., ratio of capsule tissue weight to seed weight) impacted seed traits to an even greater degree. Carbon and N allocations responded in different quantitative manners to treatments over years; nevertheless, large variances in C, and N contents and C:N ratio (R2=0.70, 0.73, and 0.82, respectively), but not in N:S ratio (R2=0.21) were explained by all factors. C:N ratio and oil content, but not protein content, can be predicted as functions of nutrient densities in the seed with acceptable, but wide range of reliabilities (R2). Removing the top 25% of biomass 100 GDD after flower initiation consistently resulted in slightly increased oil content and in marked improvements in the reliability of its estimates. Oil and protein contents in Cuphea seed, being positively (r=0.83; p<0.01) and negatively (r=-0.86; p<0.01) correlated with C:N ratio, respectively, may not be easily and concomitantly improved. An improved N:S ratio (<12:1), which ranged from 10.4:1 to 19.8:1 in this study, is negatively correlated with total nutrient density in the seed and could lead to larger oil content.