Effect of Salinity and Irrigation Frequency on Seed Germination, Seedling Growth and Mineral Content of Five Forest Tree Species

No Thumbnail Available
Alshara, Tayseer Yassin
Journal Title
Journal ISSN
Volume Title
Three studies were carried out to evaluate the effect of salinity and irrigation Frequency on seed germination and seedling growth of Acacia nilotica, Acacia senegal, Albizzia lebbeck, Caseuiarina equisetifolia and Eucalyptus camaldulensis. The first experiment evaluated the effect of salinity on seed germination parameters under laboratory and nursery conditions. Five concentrations of saline solution with electric conductivity (EC) of 0.4, 2, 5, 10 and 15 dSm-1 were prepared and used. Seeds were germinated using petri dishes in the laboratory and pots in the nursery. Seeds were irrigated with the assigned salinity solution throughout the course of the germination test and germination counts were performed daily for 25 days. The results showed that significant effect on seed germination where total germination percentage decreased gradually with increase of salinity levels. On the other hand germination rate increased with increasing salinity level except for A. senegal. Under the laboratory conditions the highest salinity level tested (15 dSm-1) A. lebbeck showed the highest germination percent (58%) followed by A. nilotica (38%) and A. senegal (36%) and lower tolerance by C. equisetifolia (17%) and E. camaldulensis (10%). Similar trends were observed under the nursery conditions, except that A. lebbeck dropped to 20% at EC of 15 dSm-1. Using the criteria of 50% reduction in germination percentage as compared to 0.4 dSm-1, A. lebbeck, A. nilotica and A. senegal were classified as salt tolerant and C. equistifolia and E. camalduleensis were as moderately salt tolerant at seed germination stage. The second experiment investigated the above salinity levels (EC 0.4, 2, 5, 10 and 15 dSm-1) of irrigation water on seedling growth, survival and mineral content. Application of treatments started after 45 days from seed sowing, using for irrigation the prepared saline solutions every three days until the end of the experiment and four serial harvests were carried out from seedlings. The results showed a significant effect of salinity on growth parameters with variation in tolerance among the five species. Generally, the increase of salinity was associated with a decrease in shoot, root and total dry weights and increased Na+, Cl- and Ca2+ contents of shoot and root tissues. Using the criteria of 50% reduction in seedling weight compared 0.4 dSm-1, A. nilotica was tolerant to salinity followed by E. camaldulensis, A. lebbeck, A. senegal and C. equisetifolia. On other hand, C. equisetifolia showed the highest survival percentage (95%) in high salinity level (15 dSm-1) followed by A. lebbeck 80%, E. camaldulensis 60 %, A. nilotica 50% and A. senegal (25%). The third experiment investigated the effect of water stress on seedling growth and survival. Five irrigation frequencies (every 3, 6, 9, 12 and 15 days) were applied after 45 days from seed sowing and four serial harvests were carried. The results showed that irrigation frequency had significant effect on most of the measured growth parameters and the species varied in their tolerance to water stress. Using the 50% reduction in weight as compared to 3 days A. senegal was rated as the most tolerant to water stress, followed by C. equisetifolia, A. nilotica, E. camaldulensis and A. lebbeck. High survival percentages were observed even at every 15 day irrigation frequency, where A. nilotica, C. equisetifolia and A. lebbeck had 100% followed by senegal (85%) and E. camaldulensis (75 %). The results of the three experiments revealed that the species are generally drought and salt tolerant with variation among them. Species tolerance to salt and was not entirely consistent with that to drought.
Effect,Salinity,Irrigation,Frequency ,Germination, Seedling,Growth,Mineral,Forest Tree