اهرامات الجبزة بين التاريخ والغموض

Marine Macroalgae: A Potential Source  of Plant Growth Regulators

Emad A. Shalaby Professor of Biochemistry, Biochemistry Department, Faculty of Agriculture, Cairo University, Giza, Egypt E-mail: dremad2009@yahoo.com

1 Introduction Algae are aquatic plants that lack the leaves, stem, roots, vascular systems, and sexual organs of the higher plants. They range in size from microscopic phytoplankton to giant kelp 200 feet long (Shalaby 2011). They live in temperatures ranging from hot spring to arctic snows, and they come in various colors, mostly green, brown and red. There are about 25,000 species of algae compared to 250,000 species of land plants. Algae make up in quantity what they lack in diversity, for the biomass of algae is immensely greater than that of terrestrial plants (Lowenstein 1986). 1.1 Chemical contents of algae The current application of chemical compounds isolated from diverse classes of algae is enormous. Since 1975, three areas of research in aquatic natural products emerged: toxins, byproducts and chemical ecology. Over 15,000 novel compounds were chemically determined. Focusing on bio- products, some trends in drug research from natural sources suggested that algae are a promising group to furnish novel biochemically active substances (Singh et al. 2005, Blunt et al. 2005). To survive in a competitive environment, freshwater and marine algae developed defense strategies that resulted in a significant level of structural-chemical diversity from different metabolic pathways (Barros et al. 2005). The exploration of these organisms for pharmaceutical purposes revealed important chemical prototypes for the discovery of new agents and stimulated the use of sophisticated physical techniques and new syntheses of compounds with biomedical application. Moreover, algae were promising organisms for providing both novel biologically active substances and essential compounds for human nutrition (Mayer and Hamann, 2004). Therefore, an increasing supply of algae was needed for algal extracts, fractions or pure compounds for the economic sector (Dos Santos et al. 2005). In this regard, both primary and secondary metabolites were studied as a prelude to future rational economic exploitation as shown in Fig. 1. Algal products have been used in the food, cosmetic, agriculture and pharmaceutical industries (Fig. 2). An expanding market for these products is a reality and faces a new challenge of growing algae on a large scale without further harming the marine environment. Micro- and macroalgae are essential to the development of aquaculture since they provide the main micronutrients to many aquatic organisms, including vitamins, nitrogen-containing compounds, sterols, and specific fatty

Marine Macroalgae: A Potential Source of Plant Growth Regulators 47
acids. Total aquaculture production in 2000 was reported to be 45.71 million metric tons (mmt) by weight, valued at US$ 56.47 billion, with production up by 6.3% by weight and 4.8% by value since 1999 (Cardozo et al. 2006). 1.2 Biological activity of macroalgae (seaweeds) Algae have mainly been used in western countries as raw material to extract alginates (from brown algae) and agar and carrageenans (from red algae). However, algae have also been found to contain a multitude of bioactive compounds that might have antioxidant, antibacterial, antiviral, and anticarcinogenic properties (Plaza et al. 2008). 1.2.1 Algae as potential plant growth stimulators Crouch and Staden (1992) revealed that seaweed concentrate (SWC) prepared from Ecklonia maxima (Osbeck) Papenfuss improved the growth of tomato seedlings when applied as a soil drench but their foliar application in the form of spray had no effect on young plants. However, in a second experiment (as drench), SWC-treated plants exhibited early fruit ripening and total fruit fresh
Figure 1. Main pathways of some secondary and primary metabolite biosynthesis.
48 Seaweeds as Plant Fertilizer, Agricultural Biostimulants and Animal Fodder

weight increase by 17%. The number of harvested fruits was also increased by about 10%. These activities may be due to the algae content from the essential and bioactive forms of the five classical phytohormones—auxin, ABA, CKs, GAs, and ET—as reported in Table 1 (Lu and Xu 2015). Johansen (1993) reported that the activities of soil algae were thought to enhance soil formation and water retention, stabilize soil, increase the availabilit0y of nutrients of plants growing nearby, and reduce soil erosion. Because of their benefit to agriculture, they were suggested for use as biofertilizers. Bograh et al. (1997) found an increase in pigments (chlorophylls and total carotenoids)
Figure 2. Some macroalgae products (agriculture, foods, pharmaceuticals). Color version at the end of the book
Marine Macroalgae: A Potential Source of Plant Growth Regulators 49
Table 1. Existence of phytohormones in cyanobacteria and algae (Lu and Xu 2015)
PhytohormoneCyanobacteriaDiatomsEustigmatophytesBrown algae (multicellular)
Red algae (multicellular)
Green algae
AuxinSynechocystis sp.. Chroococcidiopsis sp., Anabaena sp., Phormidium sp., Oscillatoria sp., Nostoc sp.
N/AN/AEctocarpus siliculosus
Prionits lanceolata,  Porphyra sp., Gelidium sp., Gracilaria sp., Gracilariopsis sp., Chondracanthus sp., Hypnea sp.
Scenedesmus armatus, Chlorella pyrenoidosa. Chlorella minutissima
ETSynechococcus sp., Anabaena sp., Nostoc sp., Calothrix sp., Scytonema sp., Cylindrospermum sp.
N/AN/APadina arborescens, Ecklonia maxima
Porphyra teneraChlorella pyrenoidosa
ABASynechococcus leopoliensis, Nostoc muscomm,  Trichormus variabilis, Anabaena variabilis
Coscinodiscus granii
Nannochloropsis oceanica
Ascophyllum nodosum
Porphyra sp., Gelidium sp.. Gracilaria sp., Gracilariopsis sp., Chondracanthus sp., Hypnea sp.
Chlamydomonas reinhardti. Dunaliella sp. Draparnaldia mutabilis, Chlorella minutissima
CKSynechocystis sp.. Chroococcidiopsis sp., Anabaena sp.. Phormidium sp., Oscillatoria sp., Calothrix sp., Chlorogloeopsis sp., Rhodospirillum sp.
Ecklonia sp.Nannochloropsis oceanica
Ecklonia maxima, Laminaria pallida
Porphyra sp., Gelidium sp., Gracilaria sp., Gracilariopsis sp., Chondracanthus sp., Hypnea sp., Gigartina dathrata. Hypnea sp.
Chlorella minutissima
GAAnabaenopsis sp., Cylindrospermum sp., Phormidium foveolarum
N/ANannochloropsis oceanica (Y. Lu et a!., unpublished)
Ecklonia radiata
Hypnea musciformisChlorella sp.,  Chlamydomonas reinhardtii
Abbreviation: N/A, no reports available.
50 Seaweeds as Plant Fertilizer, Agricultural Biostimulants and Animal Fodder and carbohydrate production in Lupinus leaves pretreated with algal filtrate of Cylindrospermum (Cyanobacteria). Adam (1999) found that algal filtrate of the cyanobacterium Desmonostoc muscorum (formerly Nostoc muscorum) increased germination of wheat seeds as well as their growth parameters and nitrogen compounds, compared to controls. Also, Lozano et al. (1999) stated that the application of an extract from algae to soil or foliage increased ash, protein and carbohydrate contents of potato tubers (Solanum tuberosum). In field experiments, Ghallab and Salem (2001) studied the effect of some biofertilizer treatments—“Cerealin” (Azospirillum spp.) and Nemales (Serratia spp.)—on wheat plant. They found that the two biofertilizers increased growth characters (plant height and weight) and nutrients, sugar, amino acids and growth regulators (IAA, GA3 and cytokinin) (the chemical structures are shown in Fig. 3), and crude protein content in the plants. On the other hand, Abdel-Monem et al. (2001) reported that fertilization with Azospirillum brasilense or commercial biofertilizer “Cerealin” improved the growth and yield of maize in rotation with wheat as affected by irrigation regime. Ascophyllum nodosum (Ochrophyta, Phaeophyceae) extracts (at 0, 1%, 5% and 10%) were reported to improve germination, root growth, flower production, fruit set, and crop quality and increase yield as well as enhancing stress and disease resistance of cabbage and tomato plant dry weight with the 5% treatment, followed by decreases at 10% (Carolyn et al. 2001). Also, Zaccaro et al. (2001) documented that the algal biofertilizers were likely to assume greater importance as complement and/or supplement to chemical fertilizers in improving the nutrient supplies to cereal crops because of high nutrient turnover in the cereal production system, exorbitant cost of fertilizers and greater consciousness of environmental protection. The current work will focus on macroalgae (seaweed) contents from plant growth regulator compounds and methods of determination and pilot experiment for applications of seaweed extracts on plant and crops.
Figure 3. Structure of phytohormones. (A) Abscisic acid, (B) salicylic acid, (C) indole-3-acetic acid, (D) ortho

2. Application of Algae as Source for Phytohormones 2.1 Extraction and quantitative determination of endogenous phytohormones
2.1.1 Extraction Ten grams of the dried algal materials (Asparagopsis taxiformis, Sargassum vulgare, Gelidium corneum, Corallina officinalis, Ulva intestinalis) collected from Marsa Matrouh (Egypt) for the first species and from Alexandria beach (Egypt) for the remaining species were homogenized, extracted twice with 200 ml methanol (96%), then twice with 200 ml methanol (40%), each for 24 h. The combined methanolic extract was evaporated in a rotary evaporator (100 rpm at 40ºC) to an aqueous solution. The aqueous solution was adjusted to pH 2.6-2.8 and extracted four times with ethyl acetate (50 ml each). The ethyl acetate extract was dried on anhydrous sodium sulfate (10 g/100 ml), then filtered and evaporated in a rotary evaporator to dryness; the residue was dissolved in 4 ml absolute methanol. This methanolic solution was used for the determination of gibberellic acid, abscisic acid and indole-3-acetic acid by gas-liquid chromatography (GLC) (Vogel 1975). -