Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2008
Publication Date: 8/1/2009
Citation: Jaradat, A.A., Rinke, J.L. 2009. Dynamics of Macro- and Micronutrients in Cuphea. Journal of Plant Nutrition. 32:1383-1406. Interpretive Summary: Improvement of seed oil content would enhance the competitiveness of cuphea as a potential oilseed crop for industrial uses. Little is known about the nutrient requirements of this potential crop and which nutrients may enhance or suppress its seed oil content. Fourteen macro- and micro-nutrients exhibited large variation in leaves and seeds of cuphea during the growing season, some nutrients (sulfur and zinc) were remobilized to the developing seed in large amounts, while others (barium and strontium) were almost totally excluded from the seed. We found that copper, iron, sulfur and zinc are accumulated in the embryo, whereas barium, calcium, magnesium, manganese and strontium are largely accumulated in the seed coat. Increasing nutrients of the first group in cuphea seeds would result in more seedling vigor and viability, thus enhancing the performance of seedlings upon germination. Nutrients with large densities in leaves at harvest (e.g., calcium, iron, phosphorus, potassium and sulfur) may constitute a resource potentially available for subsequent crops. This information would help plant breeders exploit genotypic variability in seed nutrient concentration and agronomists identify critical nutrients and plan fertilizer programs for this potential oilseed crop.
Technical Abstract: Understanding the homeostatic mechanisms that delineate nutrient accumulation and remobilization in cuphea will help toward its development as a competitive industrial oilseed crop. Temporal dynamics of 14 nutrient densities, their interrelationships and remobilization from leaves to seeds were quantified in growth chamber and field studies. Temporal nutrient densities in leaf samples exhibited large levels of variation (C.V. 15.0-55.0%), whether remobilized and largely accumulated in the seed (Cu, K, P, S and Zn), remobilized and accumulated, primarily in the seed coat, in low densities (B, Ca, Fe, Mg, Mn, and Na), or almost excluded from the seed (Ba, Se, and Sr). Differences between the embryo and the seed coat accounted for >80.0% of total variation in most nutrients, except Fe (37.3%) and Mn (7.6%), with significantly larger densities of Cu, Fe, Mg, P, S and Zn in the embryo. The temporal seed-to-leaf nutrient density [S]/[L] ratios and the proportion of variance unique to each nutrient (1-R**2) separated the nutrients into a group (Cu, Fe, S, and Zn) with large [S]/[L] ratios and large unique variances, and another group (B, Ca, Mg, Mn and Sr) with small [S]/[L] ratios and small unique variances; the first, but not the second group, was selectively remobilized and stored in the developing embryo. Nutrients with large densities in leaves at harvest (e.g., Ca, Fe, P, K, and S) may constitute a resource potentially available for subsequent crops. This information would help plant breeders exploit genotypic variability in seed nutrient density and agronomists identify critical nutrients and plan fertilizer programs for this potential oilseed crop.