Preliminary studies on the effect of different salinity levels on germination, growth and anatomy of mangrove (Avicennia marina)

Abstract

An experiment has been carried out under plastic greenhouse conditions in the soil salinity laboratory, ARC, Alexandria, to study the effect of salinity levels on germination, growth and anatomy of A. marina. Mediterranean sea water is used for irrigation. Mangrove seeds collected from Safaga coast were divided into five groups according to their sizes. Each size was exposed to five salinity levels: 100%, 75%, 50%, 25%, and tap water. The germination percentage of normal seedlings, which have both shoots and roots, was found to be affected by the size of the seeds. It was 100% in groups A, B and C, 72% in group D and 54% in the smallest group, E. It was also found that the smallest seeds need more time to germinate than the bigger ones. The results also show that there is a positive, direct relationship between seed size and both the shoot length and stem thickness of A. marina seedlings. The best concentration for seedling growth was found to be 50% salinity of the sea water, and tap water was the worst. It is also found that the growth rate was at its maximum in the period between 1.5 and 3 months from planting date. After that it declined and the main root started to develop. Three plants 5 months old grown in tap water, 50% and 100% sea water were described from the morphological and anatomical point of view. The results show that the salinity level has a considerable effect on the leaf area, the length of the first internode and the root and shoot lengths. There were not notable differences in the anatomical structures of stems, roots and leaves of A. marina individuals grown on the three levels of sea water studied. The anatomical features indicate that A. marina is a genotypic species, rather than a habitat type.

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This research is part of the ARC plan, which is supported by ARC and NARP.