EFFECT OF SALINITY ON SEEDLING EMERGENCE OF PROTEA COMPACTA, P. CYNAROIDES, AND P. MAGNIFICA (PROTEACEAE)

Abstract

Protea compacta, P. cynaroides, and P. magnifica, South African protea species cultivated for cut flowers, were tested in order to determine their salinity tolerance at seedling emergence. The seeds were sown in a mixture of peat-moss and volcanic ash (1:1 v/v). Five water salinity levels (0.5, 1.7, 2.7, 4.8 and 8.2 dS m−1 for P. cynaroides, and 0.2, 1.3, 2.4, 4.7 and 8.5 dS m−1 for P. compacta and P. magnifica) were imposed by irrigating with water that contained sodium chloride (NaCl) and calcium chloride (CaCl2) (normal ratio 2:1). In the Tenerife coastal area, water from wells has a similar or higher sodium (Na)/ calcium (Ca) ratio. Seedling emergence percentages and rates (speed of emergence) were measured. In general, the increased salinity caused a decrease in the percentage of seedling emergence and retarded the emergence process. With regard to seedling emergence rates, the species that showed a greater salinity tolerance was P. cynaroides which had a salinity tolerance index (ST-Index) of 7.93, followed by P. compacta and P. magnifica with ST-Indices of 5.93 and 5.08, respectively. With regard to the seedling emergence percentages, the species that showed a greater salinity tolerance was P. cynaroides which had a ST-Index of 8.01, followed by P. compacta and P. magnifica, with ST-Indices of 7.91 and 6.39, respectively. The calculation of the ST-Indices using the electrical conductivity of the saturated soil extract (ECe) allowed us to observe that, at seedling emergence, P. compacta, P. cynaroides, and P. magnifica are moderately sensitive to salinity.