Effect of a commercial seaweed extract (Kelpak®) and polyamines on nutrient-deprived (N, P and K) okra seedlings

In agriculture, nutrient depleted soil is a common problem, hence large amounts of applied fertilizer are required to maintain optimal nutrient levels. Nutrient-deficient plants are often vulnerable to pathogens and show a reduction in yield. In this study,the nutrient-stress-relieving effects of the seaweed concentrate, Kelpak (R) and a polyamine (PA) solution were investigated. Kelpak (R) is prepared from Ecklonia maxima (Osbeck) Papenfuss and recently shown to contain endogenous PAs. Okra seedlings [Abelmoschus esculentus (L.) Moench] deprived of nitrogen (N), phosphorous (P) and potassium (K) were treated with either a 0.4% Kelpak (R) solution or a 10(-4) M PA solution (a combination of putrescine, spermidine and spermine) three times a week under greenhouse conditions. Both Kelpak (R) and PA treatments significantly enhanced seedling vigor under nitrogen-deprived conditions. Kelpak (R) treatment was effective in significantly improving most of the seedling growth parameters under P and K deficiency compared to the respective controls. Although, the PA treatment resulted in some improvement in the growth of the seedlings in P and K deficient plants, these results were not significantly different from the control. The beneficial effect of Kelpak (R) in relieving nutrient deficiency, especially N deficiency, may in part be due to the PAs present in Kelpak (R) acting in synergy with other plant growth regulators such as auxin. The application of seaweed concentrate as part of a fertilizing regime could potentially help mitigate the detrimental effects of major nutrient deficiencies, minimizing the use of expensive chemical fertilizers. (C) 2012 Elsevier B.V. All rights reserved.