Available online at http://www.ifgdg.org Int. J. Biol. Chem. Sci. 10(6): 2526-2538, December 2016 ISSN 1997-342X (Online), ISSN 1991-8631 (Print) Original Paper http://ajol.info/index.php/ijbcs http://indexmedicus.afro.who.int Anatomical variability of the trunk wood and root tissues of Rhizophora racemosa (G. Mey) and Avicennia nitida (Jacq.) and bio-accumulation of heavy metals in mangrove trees Rodrigue SAFOU-TCHIAMA1,2,*, Saint Bickolard MABICKA IWANGOU1, Patrice SOULOUNGANGA3, Samuel IKOGOU1, Nelson KALENDI MATHE1,4 and Colette NDOUTOUME 1 1 Laboratoire de Recherche et de Valorisation du Matériau Bois (LaReVa Bois). Bât du Master Recherche en Sciences du Bois. Ecole Nationale des Eaux et Forêts. BP. 3950, Libreville, Gabon. 2 Laboratoire de Chimie des Substances Naturelles et de Synthèses Organométalliques. Unité de Recherche en Chimie (URChi). Université des Sciences et Techniques de Masuku. BP. 941, Franceville, Gabon. 3 Laboratoire Pluridisciplinaire des Sciences. Ecole Normale Supérieure. BP 17009, Libreville, Gabon. 4 Laboratoire de Foresterie. Département de Gestion des Ressources Naturelles. Faculté des Sciences Agronomiques de l’Université Catholique du Graben. B.P 29 Butembo, Nord-Kivu, République Démocratique du Congo. * Corresponding author; E-mail: [email protected]; Tel.:+241-02-45-77-65/+241-04-77-78-07. ABSTRACT The aim of this study was to investigate the anatomical structure of the trunk wood and the roots of A. nitida and R. racemosa, two mangrove trees from Gabon. The anatomical differences between the trunks and the roots were used to understand their bio-remediating differences through heavy metals. It was found that the roots of A. nitida were less abundant in cells number/mm2 than its trunk which exhibited the largest cells diameter. The roots and the trunk of R. racemosa didn’t exhibit significant difference between their cells number. Nevertheless, the trunk of that mangrove tree displayed the largest cells diameter and somewhat traumatic channels. Any interspecies variability was found between their trunk vessels diameter. However, a significant difference was found regarding their vessels number/mm2, the trunk of A. nitida was richer in vessels compared to R. racemosa one. The roots of the latter were more abundant in vessels and they displayed the largest cells diameter than A. nitida. Broad parenchyma bands and sclerous cells lacked within R. racemosa while they were richer in A. nitida roots and trunk. The occurrence of those anatomical structures which storage substances was thought to act in the highest heavy metals bio-remediation of Avicenniaceae than Rhizophoraceae. © 2016 International Formulae Group. All rights reserved. Keywords: Mangrove, parenchyma bands, sclerous cells, bioremediation, heavy metals. INTRODUCTION significant environment pollution (Kamal et The wastewater treatment is one of the al., 2010), insalubrity and medical risks. The major environmental issues. Its amount wastewaters from these uncontrolled activities increases with increasing population and are discharged in the sea, releasing like this industrial activities (Herteman, 2010) near toxic organic products and serious mineral rivers or waterways; which provokes pollutants including heavy metals. © 2016 International Formulae Group. All rights reserved. 2711-IJBCS DOI: http://dx.doi.org/10.4314/ijbcs.v10i6.10 R. SAFOU-TCHIAMA et al. / Int. J. Biol. Chem. Sci. 10(6): 2526-2538, 2016 National strategies for efficient an alternative for the recovery excess metallic depollution of seas or waterways are a elements from degraded soils (Almeida et al., challenge for underdeveloped countries where 2007). mangrove is growing interest because it The trend of Rhizophoraceae and should give response to sea level or climate Avicenniaceae to concentrate heavy metals changes (Blasco et al., 1996). On the other was also described (Kamaruzzaman et al., hand, mangrove is a natural stock of active 2009; Varz et al., 2012). But, the anatomical molecules; stem bark from mangrove plants variability between the trunk wood and the like Xylocarpus granatus which contain roots of R. racemosa and A. nitida regarding tannins displaying antiradical and antioxidant parenchyma as storages for substances activity (Chacha, 2010) and the roots of (Ndoutoume and Njankouo, 2012) or other marine mangrove such as Ceriops tagal characteristics like sclerous cells, vessels within chemotherapeutic drugs have been number or diameter has received little identified (Chacha, 2011) were found in that attention. ecosystem indeed. In addition, mangrove The aim of this study was to ecosystem was described as potential for investigate the anatomical variability between carbon stock (Donato et al., 2011; Jones et al., the trunk and the roots of R. racemosa and A. 2014). nitida concerning the vessels diameter and However, financial stakes and number as well as the sclerous cells width and pollutions risks connected to human and number in the cross section of the wood, in goods transport in the mangrove ecosystem order to understand the differences observed (Ajonina et al., 2013, 2015) as well as the in the storage of heavy metals within those decrease of socio-economic profits for rural mangrove wood tissues. communities as consequence of mangrove degradation by drought and hydraulic dam has MATERIALS AND METHODS been pointed out (Tendeng et al., 2016). Chemicals Nevertheless, the ability of mangrove for Blue of methylene, ethanol (90%), metals accumulation was previously discussed and concentrated xylene (98.5%) were (MacFarlane et al., 2003; Ramos e Silva et al., purchased from Aldrich and used without any 2006; Almahasheer et al., 2014), and about purification. Javel La Croix (8° chl eq.2.4% 400 species including mangrove trees were c.a.) and distilled water were obtained from identified as potential factories for toxic heavy MEDILAB. metals storage from wastewaters (Jemal and Ghorbal, 2002). R. racemosa and A. nitida Area of study belonging to the family of Rhizophoraceae The samples were collected in the and Avicenniaceae respectively, have roots mangrove of Ayeme Maritime, located system with high capability for filtering approximately at 40 km from Libreville in the wastewater nutriments and decrease province of Estuaire. This zone is hazardous metals in the costal seas or characterized by a low tide in the morning; mangrove soils (Wong et al., 1995). Previous high tide in afternoon and the mangrove is studies have found that Avicennia wood consequently invaded by water. concentrated more metals than Rhizophora (Marchand, 2003) one. Furthermore, Wood sampling Avicennia marina roots concentrated more Collection of the wood samples heavy metals compared to its air parts Four trees of each mangrove wood (MacFarlane and Burchett, 2002). On the were randomly harvest on the morning in other hand, the high capacity of trunk woody Ayeme Maritime in the month of March 2015 tissues to allocate metals was described to be at high tide. The trees were randomly chosen 2527 R. SAFOU-TCHIAMA et al. / Int. J. Biol. Chem. Sci. 10(6): 2526-2538, 2016 following their vigorous aspect, good The thin wood test-tubes were soaked conformity of stem and superior or equal to in water and scalded in a Javel: water (10:90) the minimum 16-18 cm of diameter. R. mixture until fading the samples. The faded racemosa was in the mud, at the edge of the wood stickers were soaked once in distilled river; that mangrove tree was sampled water to eliminate any traces of Javel. The between 940' 31.22 '' for longitude and 017' rinsed wood stickers were then coloured in 17.41 '' for Northern latitude. Avicennia blue of methylene and successively nitida was on the same area but in the opposed dehydrated by soaking in ethanol solution and side, in a totally dry medium located between concentrated xylene. The colorful cuts were 940' 26.57 '' for longitude and 017' 07.15 '' for then deposited on a blade carrying an object, Northern latitude. For each tree tank, the and a cover-object was carefully set down geographic data were taken with a Garmin above the cuts to avoid bubbles of air between map 60 csx GPS mark. Then, small wood the blade and the gill. The blades were dried discs of 10 cm of thickness were collected at to eliminate any traces of chemicals used for 1.30 m of height from each tree with a dehydration. chainsaw STILL 066 trade mark. The anatomical analysis was Samples were placed on shelves and performed with an optic microscope “Motic air dried to avoid any deterioration by the 2.0” to a magnification of forty x. The light or biological agents. Then, wood discs observation was facilitated by a Ken-A-Vision were polished and three types of sticks were camera connected to a computer. The software sawn in the radial direction and in North Vision 4 allowed to take pictures and to exposition: the first according to the East- measure the constituent of the woody plan. West direction, the second following the The following anatomical characters were Nord-South direction and the third in the measured: the number of vessels or sclerous 2 oblique direction at more or less +45 °C of the cells by mm and the lumen vessels diameter first setting stick. in transverse section. Samples cutting for analysis The polished wood discs were cut into Data analysis 128 test-tubes of 10 cm x 10 cm x10 cm in the All the data were analysis using the radial, tangential and longitudinal (R x T x L) one-way analysis test of variance (ANOVA) direction according to Normand (1982) followed by the Fischer’s LSD (last procedure. significant difference) test at α=0.05 level of significance with Rr643.0.2 software. Anatomical structure analysis by microscopy RESULTS The anatomical structure of R. Variability within R. racemosa in racemosa and A. nitida was performed by an transverse section adaptation of a published procedure (Berrichi, The anatomical structure of R. 2009) as follows: the test-tubes were softened racemosa trunk is depicted in Figures 1 and 2, in hot distilled water for 24 and 18 hours, and the roots can be observed in Figure 3.