Avicennia alba

About: Avicennia alba is a research topic. Over the lifetime, 195 publications have been published within this topic receiving 2275 citations.

Genetic structure and evolution of species in the mangrove genus avicennia (avicenniaceae) in the indo-west pacific.

Abstract: Allozyme variation in species of the mangrove genus Avicennia was screened in 25 populations collected from 22 locations in the Indo-West Pacific and eastern North America using 11 loci. Several fixed gene differences supported the specific status of Avicennia alba, A. integra, A. marina, and A. rumphiana from the Indo-West Pacific, and A. germinans from the Atlantic-East Pacific. The three varieties of A. marina, var. marina, var. eucalyptifolia, and van australasica, had higher genetic similarities (Nei's I) and no fixed gene differences, confirming their conspecific status. Strong genetic structuring was observed in A. marina, with sharp changes in gene frequencies at the geographical margins of varietal distributions. The occurrence of alleles found otherwise in only one variety, in only immediately adjacent populations of another variety, provided evidence of introgession between varieties. The varieties appear to have diverged recently in the Pleistocene and are apparently not of ancient Cretaceous origin, as suggested earlier. Despite evidence of high degrees of outcrossing, gene flow among populations was relatively low (Ne m < 1-2), except where populations were geographically continuous, questioning assumptions that these widespread mangrove species achieve high levels of long-distance dispersal.

Assessment of mangrove vegetation based on remote sensing and ground-truth measurements at Tumpat, Kelantan Delta, East Coast of Peninsular Malaysia

Abstract: The lower reaches of River Kelantan form a vast delta (1200 ha) consisting of bay, mangrove and estuary on the northeast coast of Peninsular Malaysia. The present study was conducted to assess the mangrove vegetation at Tumpat based on ground-truth and remote sensing measurements. The mangroves are composed of several species including Nypa fruticans, Sonneratia caseolaris, Avicennia alba, Rhizophora apiculata, R. mucronata and Bruguiera gymnorrhiza, in order of dominance. The point-centred quarter method (PCQM) was used to estimate the stem density (number of stems/0.1 ha) and basal area (m2/0.1 ha) at selected sites on the ground. Recent high-resolution multispectral satellite data (QuickBird 2006, 2.4 m spatial resolution of the multispectral image) were used to produce land-use/cover classification and Normalized Differential Vegetation Index (NDVI) mapping for the delta. The area statistics reveal that mangroves occupy 339.6 ha, while coconut plantation dominates the vegetation (715.2 ha), followed by settlements (621.6 ha), sandbar (148.4 ha), agriculture (89 ha) and aquaculture (42.7 ha). Although the relationship between the spectral indices and dendrometric parameters was weak, we found a very high significance between the (mean) NDVI and stem density (p = 1.3 × 10-8). The sites with young/growing and also mature trees with lush green cover showed greater NDVI values (0.40-0.68) indicating healthy vegetation, while mature forests under environmental stress due to sand deposition and/or poor tidal inundation showed low NDVI values (0.38-0.47) and an unhealthy situation. Overall, a combination of ground survey and remote sensing provided valuable information for the assessment of mangrove vegetation types (i.e. young/growing or mature forest) and their health in Tumpat, Kelantan Delta.

Forest structure and species distribution along soil salinity and pH gradient in mangrove swamps of the Sundarbans

Abstract: An analysis has been made in the Sundarbans mangroves to relate the community structure and distribution of species with soil salinity and pH gradients. Soil salinity (13.0 to 31.2 ppt) decreased with increasing distance from the tidal coast but no such trend was noticed in soil pH (7.0 to 7.9). Frequency of tidal inundation seemed to affect soil salinity. Acanthus ilicifolius, Avicennia alba and A. marina dominate the sites having regular diurnal tidal inundation. Maximum complexity index was noted on the least saline zone. Ecological group classification indicates that Avicennia marina and A. officinalis can tolerate wide range of soil salinity while Aegiceras corniculatum, Ceriops decandra, Dalbergia spinosa, Derris trifoliata and Excoecaria agallocha are restricted to low salinity areas. Most species had an optimum pH range except Avicennia marina, which occurred in varied pH conditions. Acanthus ilicifolius was relatively insensitive to pH and salinity gradient due to its wide ecological amplitudes.

Chemical Constituents of Avicennia alba. Isolation and Structural Elucidation of New Naphthoquinones and Their Analogues

Abstract: Three new naphthoquinones and their analogues, named avicequinone-A (1), -B (2), -C (3), and avicenol-A (4), -B (5), -C (6), respectively, were isolated from the stem bark of Avicennia alba (Avicenniaceae) collected in Singapore, and their structures were elucidated by means of spectral methods. Gillan and co-workers have proposed that the structures of the new phytoalexins isolated from Avicennia marina are 1,2-naphthoquinones 8 and 9. Our synthetic and spectrometric studies showed that these structures should be revised respectively to 1,4-naphthoquinones 2 and 3, named avicequinone-B and -C by us.