Abstract
In this study, the effect of seaweed on the growth of Zea mays L. and Helianthus annuus L. was investigated. Seeds of the plants have been soaked for 6 hours in 0.5% Gracilaria corticata and 1.0% Enteromorpha flexuosa aqueous extract. The presoaked seeds were sown both in soil irrigated monthly with aqueous extract and in soil mixed with powdered seaweeds. Growth parameters of plants were studied after 60 days of growth. The results revealed that both applications of G. corticata and E. flexuosa enhance shoot length, root length, shoot and root dry weights, photosynthetic pigments, carbohydrate and protein contents, and nutrient uptake. The maximum growth was observed with irrigation by E. flexuosa extract. The element constituent [nitrogen (N), phosphorus (P), potassium (K
+
), calcium (Ca
2+
), magnesium (Mg
2+
), iron (Fe
3+
), manganese (Mn
2+
), and zinc (Zn
2+
)] and phytohormones [Indole-3-acetic acid (IAA), gibberellins, and cytokinins] of E. flexuosa extract and powder was higher that of G. corticata. Of the two seaweeds tested, E. flexuosa exhibited better responses.