have been raised over the harmful effects of chemical fertilizers on humans and
environment directly or indirectly (Dubey 2010).
Consequently, farmers began to shift from conventional chemical-based farming
systems to organic, alternative, or low-input sustainable agriculture. Seaweed
extracts (SWE) as foliar sprays for several crops have gained significant importance
as they contain growth promoting hormones (IAA and IBA), cytokinins, minerals (Fe, Cu, Zn, Co, Mo, Mn, Ni), vitamins, and
amino acids (Sivasankari 2006). Seaweed
extracts have been suggested to enhance the growth and yield of the crop
plants, increase plant tolerance to environmental stresses, increase nutrient
uptake from soil and enhance antioxidant properties (Rathore 2009; Eissa
et al. 2017).
Ulva lactuca, also known as sea lettuce, is one of the most abundant green
macro algae worldwide (Lahaye and Robic, 2007).
Despite its wide geographical distribution, it is poorly utilized (Ray and
Lahaye 2007) and only a small part of its
biomass is used as food or animal feed because of its nutritional constituents
(vitamins, oligo elements, minerals, and
dietary 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).
reported an enhanced seed germination and protein profile when the seeds of
five plants were treated with 1.0% SWE of Ulva lactuca and Sargassum wightii.
The earlier study revealed that SWE of Ulva
reticulata could also be used as a foliar spray at low concentration (2%) to
maximize the growth and yield of Vigna mungo and also increase the
number of stomata in the leaf (Ganapathy and Sivakumar 2013). Maize
(Zea mays), a C4 plant, is one of the
most important cereal crop grown worldwide, serving as an essential source of
food, livestock feed, and fuel (Abdel?Latif and Osman 2017; Osman et al. 2015). In maize, the C4 photosynthetic pathway is followed, which
is characterized by several biochemical and
anatomical modifications that allow plants with this photosynthetic pathway to
concentrate CO2 at the site of ribulose
1,5-bisphosphate carboxylase/oxygenase (Rubisco;
EC 184.108.40.206). The enzyme of primary CO2
fixation in this pathway catalyzes the photosynthetic
carbon metabolism by combining CO2 with ribulose 1,5-bisphosphate. Various
studies have shown that the activity of Rubisco is regulated by an enzyme,
activase (RCA) (Portis 2003; Osman et al. 2013). RCA, a soluble chloroplast ATPase, is associated
with a variety of cellular activities. RCA
catalyzes the activation of Rubisco in