Sensitivity of rice seedlings to salinity [Philippines]
1988
Akbar, M. | Senadhira, D. (International Rice Research Inst., Los Banos, Laguna (Philippines))
The experiment aimed to determine the age at which rice seedlings are most sensitive to salinity, using salt-tolerant varieties Nona Bokra and Pokkali and salt-sensitive IR28 and IR2035-117-3. Pregerminated seeds were sown on styrofoam sheets, each with 60 holes and a nylon net bottom, at one seed/hole, 60 seeds/variety. The sheets were floated in 40-x20- x 15-cm plastic trays filled with nine liters nutrient solution N maintained at pH 5.0. Seedlings were grown at 29/21 degrees Celsius (day/night) with about 70% relative humidity in the phytotron glasshouse under natural daylight. Salinity stress of 6,800 ppm (Ec 12dS/m) was introduced by adding 1:1 mixture of NaCl and CaCl2 to the nutrient solution at 4, 5, 6, 7, 8, 9, 10, 11, and 12d after seeding. Unsalinized trays of each variety were the checks. Seedling survival was measured 14d after salinization. Survival of unsalinized checks of all varieties was 100%. Salt-tolerant Nona Bokra and Pokkali were not affected by salinity. Seedlings of sensitive variety IR28 were severely affected up to 7d, then gradually gained tolerance. IR2035-117-3 seedlings showed sensitivity up to 6d. Varietal differences in salt sensitivity were apparent. Tolerance in sensitive varieties increased with age, showing that seedling age is a critical factor in screening for salt tolerance.
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