EFFECT OF SALINITY ON SEEDLING EMERGENCE OF LEUCOSPERMUM CUNEIFORME (PROTEACEAE)

Abstract

Leucospermum cuneiforme, a South African protea species cultivated for cut flowers, was tested in order to determine its 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) were imposed by irrigating with water that contained NaCl and CaCl 2 (normal ratio 2:1). In Tenerife, water from wells in coastal areas has a similar or higher Na/Ca ratio. Seedling emergence percentages and rates were measured. The increased salinity caused a decrease in the percentage of seedling emergence and a slowing of the process. In regard to seedling emergence rates, L. cuneiforme had a salinity threshold of 2.8 dSm -1 , with a decrease of 28.4% per dS m -1 in the ratio of seedling emergence. In regard to seedling emergence percentages, L. cuneiforme showed a salinity threshold of 3.0 dS/m, with a decrease in the percentage of seedling emergence of 30.8% per dS/m. Threshold expressed as electrical conductivity of saturated soil extract was calculated, showing that, at seedling emergence, L. cuneiforme is moderately tolerant to salinity.