Salinity is one of the major threats facing the cultivation of field crops. The response of six rice (Oryza sativus L.) cultivars to different sodium chloride levels; 0, 30, 60, 90, 120, and 150 mM were investigated during germination and early seedling stages. Germination percent, mean germination time (MGT), shoot and root length and dry weight were all decreased as the levels of NaCl used increased. Percent reduction in dry weight over control was increased as the NaCl levels increased. Forat and Amber 33 were more salt tolerant cultivars with regard to germination percent, while Hwazawi cultivar was more sensitive. Hwazawi cultivar recorded the lower MGT while Amber 33 cultivar showed the higher MGT. Length of radicle and plumule of all cultivars were differently affected by salt, as Hwazawi and Mushkab cultivars showed more reduction in length while Amber 33 was less affected. Forat cultivar dry weight was more affected by salt compare to other cultivars. The effect of NaCl on salt tolerance index of cultivars was significant. The ranges of salt tolerance indices among salt levels were very wide, ranging from 95.42 at 30 mM of NaCl to 71.38 at 150 mM of NaCl. Interaction between salt levels and cultivars showed varying degree of differences. It is concluded that the different cultivars differ in their salt tolerance with respect to seed germination and seedling growth.

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Quantitative and qualitative diatom analyses from the Edku Lake core sediments were used to assess the environmental history of the lake during the Late Holocene. A total of 128 diatom species and varieties were identified from 118 samples representing of four short cores obtained from the lake. The topmost samples represent the recent time are dominant by diatom taxa than that recorded in the lowered cores samples. Detailed diatom investigation indicated a considerable variation in the composition and distribution of the diatom taxa among the studied cores. The non-planktonic epiphytic taxa Cocconeis placentula, Epithemia sorex, Epithemia adnata and the benthic forms Navicula aegyptiaca, Campylodiscus biocostatus and Campylodiscus clypeus were the most dominant species in the core sediments, which mainly reflect slightly brackish, alkaline, eutrophic shallow lake condition during the time of deposition. Multivariate statistical analysis included hierarchical ascending clustering and Detrended correspondence analyses were used to identify ecological groups of diatoms. The results distinguished six ecological groups that reflect changes in the water quality, water salinity, lake-level, pH and eutrophication of the lake, which in turn may related to climatic changes and anthropogenic impacts.

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