Algal biomass as plant fertilizers and Growth Stimulants.
Literature review
Overview
In this literature review, we discuss algae characteristics, and cultivation. Moreover, we provide information about the use of algae as fertilizers and growth stimulants, the definition of biofertilizers and biostimulants, and how they help the plant to grow and to produce higher yield. Also, we provide several case studies of researches aimed to elucidate the role of algae as biofertilizers and biostimulants.
General characteristics of algae
Algae are one of the largest groups in the eukaryote domain; it consists of a vast group of organisms that differ in shape and size. They may be single-cellular such as Chlorella or multicellular that may reach to more
Open systems are cheap, easy to construct and have high production capacity. However, open systems have several disadvantages including, the uncontrolled environment in and around it, and this result in lower biomass productivity (Singh, 2012). Moreover, open ponds have high rates of contamination by other microorganisms such as bacteria, fungi and other algae species. PBRs are stable environment for the growth of many organisms including algae. Moreover, photobioreactors offer the ability to produce specific biomolecules such as vitamins, lipids, and biopharmaceuticals. However, photobioreactors are expensive, requires special sophisticated equipment’s and not easy to construct. There are different types of PBRs such as vertical tubular, bubble column, flat panel, airlift, stirred tank, and hybrid type PBR (Ugwu, 2008, Singh and Sharma,
It has been reported that algae produce these phytohormones in order to adapt to it environment. Cytokinins like isopentenyladenine (IPA) and zeatin has been observed in Anthronema africanum, Chlorella vulgaris and Chlamydomonas reinhardtii, it increase growth rate, oil content and stress tolerant (Tarakhovskaya et al., 2007, Lu and Xu, 2015). Abscisic acid (ABA) is produce in several cyanobacteria and algae species such as the green microalgae Dunaliella salina and Chlorella, it function as a stress molecule especially for salt, osmotic pressure and drought (Lu and Xu, 2015, Jiraskova et al., 2009). Moreover, auxins like indole acetic acid (IAA) have been identified in macroalgae Nerocystis and in cyanobacteria Nostoc and Anabaena, and it play essential role in cell-cell positioning (Rastogi and Sinha, 2009, Crouch and van Staden, 1993). Gibberellins like substances is well documented in many algae species as in brown algae Ecklonia radiate and green algae species Enteromorpha prolifera (Ulva prolifera), Chlamydomonas and Chlorella, its action includes regulation of cell growth and senescence (Crouch and van Staden, 1993, Lu and Xu,