The bioactivities of eckol-type phlorotannins, specifically eckol and EA6 (a fraction containing 2-phloroeckol and dibenzodioxin-fucodiphloroethol), extracted from Ecklonia maxima, and a commercial seaweed biostimulant (Kelpak®) were investigated in white lupin and cucumber seedlings under different phosphorus (P) supplies.
Lupin seedlings were grown with P-supplemented, P-free, or P-free media with either eckol or Kelpak. The cucumber seedlings were raised in hydroponic media with an insoluble salt of P as the sole P source and either supplemented with eckol, EA6, Kelpak, or no biostimulant. In the lupin seedlings, P starvation led to a reduction in root dry matter accumulation, which was reversed when eckol or Kelpak were applied. In cucumber seedlings, all the biostimulants significantly increased root dry matter, but only eckol and Kelpak induced total dry matter accumulation, with Kelpak also promoting shoot dry matter accumulation. In both lupin and cucumber seedlings, phlorotannins and Kelpak elicited an increase in dry matter allocation to the roots. Eckol and Kelpak elicited similar effects on cluster root development in lupin seedlings. All the biostimulants increased phosphatase activities in root exudates of lupin and cucumber seedlings. While tissue P contents were only augmented in Kelpak-treated lupins, eckol, EA6, and Kelpak treatments led to P-accumulation in the cucumber seedling leaves.
The results showed that eckols influenced physiological traits linked to P-acquisition, while Kelpak altered both morphological and physiological traits for coping with P-limitation in both plants. The data suggest that eckol and seaweed biostimulants like Kelpak may serve as sustainable tools for managing crops under P deprivation.
Omoarelojie, Luke & Stirk, Wendy & Kulkarni, Manoj & van Staden, Johannes. (2025). Eckols and seaweed-biostimulant (Kelpak) improve adaptative responses for phosphorus acquisition in white lupin and cucumber seedlings under phosphorus deficiency. Journal of Applied Phycology. 1-13. 10.1007/s10811-025-03485-1.
Source: Research Gate