Seedling emergence, growth and mineral concentration of three citrus rootstocks under salt stress.
Zekri M.
Author Affiliation: École Superieure d'Horticulture de Chott-Mariem, Sousse, Tunisia.
Journal of Plant Nutrition 16 : 1555-1568
Abstract : Seeds of Carrizo citrange, sour orange and Cleopatra mandarin rootstocks were germinated in a greenhouse and the sowing medium was watered immediately and every other day thereafter with a modified Hoagland solution at one-tenth normal concentration. Five salinity treatments (5, 10, 20, 40 and 80 mmol [/litre?]) were obtained by adding NaCl and CaSO4 at a ratio of 4:1 (mol:mol) to the Hoagland solution. Ten weeks after sowing, the seedlings were harvested, weighed and analysed. Increasing the salt concentration in the solution delayed and depressed seedling emergence, increased the time to 50% emergence and reduced seedling growth in comparison with the non-saline control, but it did not affect the number of days between the emergence of the first and last seedlings. At 5 mmol, emergence of the first seedling was delayed by 2-3 days in citrange and one day in sour orange but was unaffected in mandarin. At the 2 lowest salinity levels, the final % emergence was not affected in citrange but was reduced in the other rootstocks; the shoot biomass was reduced in citrange only. Although emergence responses showed a non-consistent trend among the rootstocks, the seedling growth was generally more affected by salinity than was emergence, especially at high levels of salinity. Shoot and root N and Cl concentrations generally increased with salinity. Shoot Cl was shown to be more useful than root Cl for evaluating the extent of the injurious effect of salt stress and was a better parameter in ranking salt tolerance of the rootstocks. The findings also showed that salt tolerance was not a constant character in rootstocks but varied with the stage of seedling development.