Effect of Salinity on Seedling Emergence of Seven Banksia Species Cultivated for Cut Flower and Foliage

ABSTRACT

Seven Banksia species were tested in order to determine their salinity tolerance at seedling emergence. Five water salinity levels (0.5, 1.7, 2.7, 4.8, and 8.2 dS m⁻¹ for B. burdettii, B. hookeriana, B. menziesii, and B. victoriae; and 0.2, 1.3, 2.4, 4.7, and 8.5 dS m⁻¹ for B. coccinea, B. occidentalis, and B. speciosa) were imposed by irrigating with water that contained sodium chloride (NaCl) and calcium chloride (CaCl₂) (normal ratio 2:1). With regards to seedling emergence rates, the species that showed greater salinity tolerance were B. menziesii and B. occidentalis. With regards to the seedling emergence percentages, B. speciosa was the most salinity-tolerant. The calculation of the thresholds expressed as electrical conductivity of saturated soil extract gave that, at seedling emergence, B. speciosa and B. occidentalis are moderately tolerant to salinity, B. menziesii, B. coccinea, and B. hookeriana are moderately sensitive to salinity, and B. burdettii and B. victoriae are sensitive to salinity.

Keywords:

• Australian proteas
• Banksia
• calcium chloride
• salt tolerance
• seedling emergence
• sodium chloride
• threshold salinity

ACKNOWLEDGMENTS

The author thanks M. T. Van Genuchten (U.S. Salinity Laboratory, Riverside, CA, USA), for providing the “Salt” computer program.

Notes

∗Within the same column, treatments that show the same letter are not significantly different at the 5% level.

∗Within the same column, treatments that show the same letter are not significantly different at the 5% level.

^a EC′_t = salinity thresholds for seedling emergence rate.

^b s′ = slopes.