Growth, Photosynthesis and Distribution of Chloride, Sodium and Potassium Ions in Salt-Affected Quandong (Santalum acuminatum)

Abstract

The growth and photosynthetic responses to salinity of the partial root parasite, the quandong or native peach [Santalum acuminatum (R.Br.) A. DC.], were investigated under glasshouse conditions. Plants were established in a porous medium with strawberry clover (Trifolium fragiferum L.) as the host plant and subjected to salinities in the range 0.5-500 mol m^-3 Cl^- with accompanying cations Na⁺, Ca²⁺ and Mg²⁺ in the ratio 0.6 : 0.2 : 0.2 mequiv. L^-1.

Growth of plants ceased during treatment with 500 mol m^-3 Cl^- and was markedly reduced by 300 mol m^-3 Cl^-. Treatment with 50, 100 or 200 mol m^-3 Cl^- had little effect on growth in the short term (up to 7 weeks), but treatment with 200 mol m^-3 Cl^- in the longer term (14 weeks) did reduce growth. Removal of the clover host plant from pots at the start of treatments had a detrimental effect on growth of both control and salt-treated plants and reduced total nitrogen concentration in leaves.

Photosynthetic rates per unit leaf area were reduced at salinities above 100 mol m^-3 Cl^- . Chlorophyll concentrations were also reduced, such that photosynthetic rates on a chlorophyll basis did not decrease despite leaf Cl^- and Na⁺ concentrations (tissue water basis) of up to 490 and 404 mol mm^-3, respectively. Water content (g H₂O g^-1 dry weight) of quandong leaves was increased by salinity, while water content and area of clover leaves decreased. There was a marked increase in Na^- and reduction in K⁺ with resultant significant increases in Na : K ratio in mature leaves of salt-treated quandongs, but much smaller increases in Na : K ratio in stems and roots.

These data demonstrate the relatively high salt tolerance of the quandong, which can be classified as a salt-tolerant non-halophyte.