Effects of Salt Solution Concentration on the Germination Success of Podocarpus latifolius Seeds
Abiti, May Francis
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The study was carried out to investigate the effects of sodium chloride solution on the germination success of Podocarpus latifolius seeds under nursery conditions. The aim was to find out the most appropriate salt solution concentration for enhancing germination of. Podocarpus latifolius seeds. The seeds were subjected to seven different salt solution concentrations of 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6M. Seeds were soaked for 6 hours, 12 hours and 24 hours after which seeds samples from each hour set were divided into two; one lot sown directly/ immediately after rinsing and the other first rinsed in distilled water for 6 hours and then sown. The experiments were monitored for three months during which data were collected on: Days of seed germination (Unrinsed seeds: 55.76±11.74 days; rinsed seeds: 59.72±10.31 days), height of leaf formation (Rinsed seeds: 6.6 cm; unrinsed seeds: 5.9±0.801cm), and number of leaves formed (rinsed seeds: 12±2.524 leaves; unrinsed seeds: 11±1.988 leaves). Sodium chloride salinity (p<0.05) significantly reduced the number of days and also increased the number of leaves, height of leaves formation and the number of seeds germinated for Podocarpus latifolius. There was no significant difference in the number of days taken for the seeds to germinate for the seeds soaked in 0.0 and 0.3M NaCl solution. However, significant differences were witnessed between seeds soaked in 0.0 to 0.3M category and seeds soaked in solution of concentration 0.6M. This is an indication that Podocarpus latifolius has a long salinity tolerance range with 0.3M solution being the most appropriate solution concentration for pre-treating Podocarpus latifolius seeds. The germination responses of Podocarpus latifolius seedlings in terms of (height of leaves formation, number of leaves and days to formation of leaves) were all best for seeds soaked in 0.3M of NaCl for 12 hours. The results further showed that time of soaking seeds during pre-treatment, height of seedlings and number of leaves were suitable parameters for evaluating the effects of sodium chloride solution on Podocarpus latifolius seeds. Soaking Podocarpus latifolius seeds in solution concentrations more than the range within which it can germinate especially for more hours (0.6M for 24hours), will impede its germination. In general, unrinsed Podocarpus latifolius seeds had better germination rate (67.01 ±11.43 days) for their leaves to unfold compared to soaked and rinsed seeds which took 70.10±9.66 days for their leaves to unfold. These results indicate that sodium chloride can influence the growth responses of Podocarpus latifolius seedlings. The reduction in the number of leaves unfolded and lesser height at which leaves were formed for seedlings whose seeds were soaked in solutions of concentration 0.4M and above is an indication of the effect of sodium chloride solution on the growth responses of Podocarpus latifolius seedlings. Germination rate in Podocarpus latifolius, amount of biomass formed and the rate of biomass formation are higher and relatively the same within the non-lethal ranges of sodium chloride solution (0.0 to 0.3M) though any increase in NaCl solution concentration beyond optimum, leads to a reduction in amount of biomass and the rate of biomass production, implying that sodium chloride concentrations above the optimum concentrations are lethal to germination success of Podocarpus latifolius. For Podocarpus latifolius, the optimum NaCl solution concentrations that are non-lethal are 0.0 to 0.3M; moderately high concentrations are 0.4 to 0.5M and extremely lethal concentrations range from 0.6M and above. For the shortest germination days, greater amounts of biomass addition and greater rates of biomass addition, salt solution concentrations within the optimum levels of up to 0.3M solution should be considered. For the best germination results of Podocarpus latifolius, seeds should be soaked in NaCl solution of 0.3M solution for 12 hours. For the best germination responses in Podocarpus latifolius seedlings, their seeds have to soaked solution of concentration of 0.3M solution for 12 hours. Dry matter, root length, sodium chloride solution effect on the cellular component should be investigated to find out whether sodium chloride solution has significant effects on these. Further germination experiments can also be done to investigate the effects of watering with sodium chloride solution on the Podocarpus latifolius seeds.