Molybdenum as an essential element for improving total yield in seawater-grown Salicornia europaea L

The growth of crop plants on full-strength seawater constitutes a major challenge because of the high salt content and the limited availability of essential microelements such as molybdenum. For cultivation of the halophyte Salicornia as seawater-grown crop, the effect of molybdate application on total yield production and the activities of the two molybdenum containing enzymes, nitrate reductase (NR) and xanthine dehydrogenase (XDH) was investigated. Increasing molybdate levels in the growth medium supplemented with nitrate or ammonium enhanced yield during multiple shoot removal. Similarly, NR and XDH activities were enhanced with increasing molybdate, indicating that the activity of both enzymes may play an important role in facilitating yield accumulation. Notably, XDH activity in the roots was high and the levels of ureides were low, whereas in the shoot tips ureides were higher and XDH activity was lower. Considering that XDH is a key enzyme in the biosynthesis of the low C/N ratio ureides, these suggest a source–sink relationship between the roots and shoot tips for efficient transport of root-generated ureides to the young growing shoot tips. Our results imply that the supply of molybdenum to Salicornia grown in seawater enhances plant biomass accumulation by increasing the activities of NR and XDH, thereby stimulating a more efficient remobilization of ureides to the newly grown shoot tips after periodic shoot removal.