ABSTRACT

Endogenous phytohormones profile of auxins, Abscisic acid, Gibberellins were identified qualitatively and quantitatively in two different habitats as marine red alga sarconema filiformae, green alga Ulva rigida and brackish green alga Ulva lactuca. The analysis was carried out by using GC/MS technique. The algal samples were harvested in May 2015 from Suez Canal and Timsah Lake. Identification of isolated hormones based on data obtained of their mass spectrum and fragmentation pattern. Ulva rigida registered the highest concentration of total phytohormones, than Sarconema filiforme and Ulva lactuca. Ulva rigida recorded high concentrations of auxins followed by Sarconema filiforme and then Ulva lactuca. Sarconema filiforme and Ulva rigida were characterized by the same auxin constituents of (Indole-3-acetyl-L-isoleucine, Indole-3-acetyl-L-leucine methyl ester and Indole-3-butyryl-L-valine). 4-chloro indol-3-acetic acid and 3-indoxyl-β-D-Galacto pyronoside methyl ester were recorded in Ulva lactuca. Ulva lactuca contained the highest concentration of ABA than Ulva rigida and Sarconema filiforme. In ABA profile, 3 compounds were detected of the selected species (cis,trans-Abscisic acid-L-Alanine methyl ester, cis, trans-Abscisic acid-L-Valine and Cis, trans-Abscisic acid-L-Alanine). GAs constituent of Sarconema filiforme revealed high concentration than Ulva lactuca and finally Ulva rigida. At least 14 well known gibberellins (GA1, GA1 methyl ester, GA4, GA7 methyl ester, GA8, GA13, GA19, GA23, GA29, GA44, GA75, Kaurene, Kaurenoic acid and Kaurenal methyl ester). GA13 and GA23 only shared at the three studied algal species. GA8 shared at two seaweed species (Ulva lactuca and Ulva rigida) and Kaurene (Sarconema filiforme and Ulva lactuca). Generally, the bioactivity of phytohormones attributed to the methods of seaweed extraction and according to the types of seaweed, particularly due to differences in their chemical components, and environmental conditions stress.

INTRODUCTION

Plant hormones play an important role in mediating plant growth as well as signaling environmental changes, initiating stress responses and indicator molecules in the regulation of almost all phases of plant development from embryogenesis to senescence1,2. Auxins in seaweed extracts were shown to initiate root formation, inhibit its elongation, differentiation of phloem elements, apical dominance and tropisms. Plants are able to synthesize these compounds from tryptophan or indole3. The concentrations of auxins in seaweed extracts are different and strongly depend on the species. Auxins and their inactive analogs were present in brown (Macrocystis and Laminaria), red (Botryocladia), and green (Enteromorpha, Chlorella, and Cladophora) algae and also in Cyanobacteria (Oscillatoria)4. Recently, using modern methodologies, it was demonstrated the presence of auxins (IAA in particular) in green and characean algae and in the extracts from brown algae (Fucus and Ascophyllum)5-7, Caulerpa paspaloides8, Ecklonia maxima9 and Undaria pinnatifida10. Other indole derivatives, such as indole-3-carboxylic acid (ICA), have been identified in Botryocladia leptopoda11, Prionitis lanceolata12. In various groups of algae, some compounds were repeatedly detected, which suppressed plant growth in bioassays as abscisic acids13. Abscisic acid (ABA) synthesized from carotenoids by more than 60 species of algae (e.g. Chlorella spp., Haemato-coccus pluvialis). ABA is mostly responsible for synthesis of proteins required for the response to drought14. It is supposed that algae produce a complex responsible for growth inhibition consisting of several components which act as ABA in algae3, in addition, ABA plays an important role in controlling of the stomatal apparatus function and seed dormancy15. This hormone was found in green microalgae (Chlorella sp., Dunaliella salina, and Haematococcus pluvialis) and also in the thalli of brown macrophytes from the genus Ascophyllum nodosum16 and some species of Laminaria17-19, Chlorophyta species such as Chara foetida, Draparnaldia mutabilis, Ulva lactuca20. Among plant hormones, gibberellins were also isolated from seaweed extracts. Gibberellins (GAs) were identified in extracts from Fucus vesiculosus , Fucus spiralis3 and Ascophyllum nodosum14. The main role of gibberellins is to initiate seeds germination, stem elongation, leaf expansion, flower development and fruit maturity21.

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