Contents lists available at ScienceDirect Ecotoxicology and Environmental Safety journal homepage: www.elsevier.com/locate/ecoenv Influence of biostimulants-seed-priming on Ceratotheca triloba germination and seedling growth under low temperatures, low osmotic potential and salinity stress Nqobile A. Masondo, Manoj G. Kulkarni, Jeffrey F. Finnie, Johannes Van Staden ⁎ Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg Campus, Private Bag X01, Scottsville 3209, South Africa ARTICLE INFO Keywords: Kelpak ® Osmotic potential Smoke-water Sodium chloride Traditional leafy vegetable ABSTRACT Extreme temperatures, drought and salinity stress adversely affect seed germination and seedling growth in crop species. Seed priming has been recognized as an indispensable technique in the production of stress-tolerant plants. Seed priming increases seed water content, improves protein synthesis using mRNA and DNA and repair mitochondria in seeds prior to germination. The current study aimed to determine the role of biostimulants-seed- priming during germination and seedling growth of Ceratotheca triloba (Bernh.) Hook.f. (an indigenous African leafy vegetable) under low temperature, low osmotic potential and salinity stress conditions. Ceratotheca triloba seeds were primed with biostimulants [smoke-water (SW), synthesized smoke-compound karrikinolide (KAR 1 ), Kelpak ® (commercial seaweed extract), phloroglucinol (PG) and distilled water (control)] for 48 h at 25 °C. Thereafter, primed seeds were germinated at low temperatures, low osmotic potential and high NaCl con- centrations. Low temperature (10 °C) completely inhibited seed germination. However, temperature shift to 15 °C improved germination. Smoke-water and KAR 1 enhanced seed germination with SW improving seedling growth under different stress conditions. Furthermore, priming seeds with Kelpak ® stimulated percentage ger- mination, while PG and the control treatment improved seedling growth at different PEG and NaCl con- centrations. Generally, high concentrations of PEG and NaCl brought about detrimental effects on seed germi- nation and seedling growth. Findings from this study show the potential role of seed priming with biostimulants in the alleviation of abiotic stress conditions during seed germination and seedling growth in C. triloba plants. 1. Introduction Seeds are constantly exposed to harsh environmental conditions throughout their germination and seedling growth stages. These en- vironmental factors include extreme temperatures, drought and salinity stress. Temperature is one of the most crucial climatic factors influen- cing seed germination. Changes in temperature significantly affect seed germination through the inhibition of radicle emergence and post- germination growth in seedlings (Probert, 2000). Successful seed ger- mination and seedling establishment are dependent on surrounding temperatures with each species having a particular set of requirements. Outside these, seed germination declines gradually. Furthermore, drought and salinity stress severely affect seed germination by pre- venting water uptake and through the toxic effect of sodium and chloride ions. These factors result in inhibited or delayed seed germi- nation and seedling growth (Ashraf and Foolad, 2005). In order to enhance seed germination under extreme temperatures, drought and salinity stress conditions, seed priming could be an indispensable technique in the production of stress tolerant plants (Jisha et al., 2012; Paparella et al., 2015). Seed priming agents including natural and synthetic compounds improve physiological processes in seeds prior to germination (Jisha et al., 2012). Priming is a process by which seeds are hydrated in different solu- tions for the initiation of certain metabolic processes (e.g. protein synthesis using mRNA and DNA as well as repairing or synthesizing new mitochondria), which permits preliminary germination but not the final stage (Jisha et al., 2012; Paparella et al., 2015). The technique also improves seedling shoot and rooting frequency, vigour index and ulti- mately crop yields. There are several priming approaches currently applied in seeds of various species including hydropriming, osmo- priming, chemical priming, hormonal priming, biological priming, redox priming and solid matrix priming. Seed germination after priming is dependent on the priming agent, severity of stress and crop species (Jisha et al., 2012). The use of biostimulants in order to http://dx.doi.org/10.1016/j.ecoenv.2017.08.017 Received 26 May 2017; Received in revised form 1 August 2017; Accepted 4 August 2017 ⁎ Corresponding author. E-mail address: rcpgd@ukzn.ac.za (J. Van Staden). Ecotoxicology and Environmental Safety 147 (2018) 43–48 0147-6513/ © 2017 Elsevier Inc. All rights reserved. MARK