Concernshave been raised over the hazardous effects of chemical fertilizers on thehuman health and environment directly or indirectly (Dubey 2010). Consequently, farmers began to shift fromconventional chemical-based farming systems to organic, alternative, orlow-input sustainable agriculture.
Seaweed extracts (SWE) as foliar sprays forseveral crops have gained significant importance as they contain growthpromoting hormones (IAA and IBA), cytokinins, minerals (Fe, Cu, Zn, Co, Mo, Mn, Ni), vitamins, and amino acids (Sivasankari2006). Seaweed extracts have been suggestedto enhance the growth and yield of the crop plants, increase plant tolerance toenvironmental stresses, increase nutrient uptake from soil and enhanceantioxidant properties (Rathore 2009; Eissa et al. 2017). Ulvalactuca, also known as sea lettuce, is one of the most abundant greenmacro algae worldwide (Lahaye and Robic, 2007).
Despite its wide geographical distribution, it is poorly utilized (Ray andLahaye 2007) and only a small part of itsbiomass is used as food or animal feed because of its nutritional constituents(vitamins, oligo elements, minerals, anddietary fibers) (Pengzhan et al. 2003);organic crop fertilizer (Mulbry et al. 2005),effluent biofilter (Msuya and Neori 2002)and more recently, as plant protectant (Cluzet et al. 2004).Sridhar (2011)reported an enhanced seed germination and protein profile when the seeds offive plants were treated with 1.0% SWE of Ulva lactuca and Sargassum wightii.The earlier study revealed that SWE of Ulvareticulata could also be used as a foliar spray at low concentration (2%) tomaximize the growth and yield of Vigna mungo and also increase thenumber of stomata in the leaf (Ganapathy and Sivakumar 2013). Maize(Zea mays), a C4 plant, is one of themost important cereal crop grown worldwide, serving as an essential source offood, livestock feed, and fuel (Abdel?Latif and Osman 2017; Osman et al.
2015). In maize, the C4 photosynthetic pathway is followed, whichis characterized by several biochemical andanatomical modifications that allow plants with this photosynthetic pathway toconcentrate CO2 at the site of ribulose1,5-bisphosphate carboxylase/oxygenase (Rubisco;EC 188.8.131.52).
The enzyme of primary CO2fixation in this pathway catalyzes the photosyntheticcarbon metabolism by combining CO2 with ribulose 1,5-bisphosphate. Variousstudies have shown that the activity of Rubisco is regulated by an enzyme,Rubiscoactivase (RCA) (Portis 2003; Osman et al. 2013). RCA, a soluble chloroplast ATPase, is associatedwith a variety of cellular activities.
RCAcatalyzes the activation of Rubisco invivo by the