Effect of different salts and of ABA on growth and mineral uptake in jojoba shoots grown in vitro

ABA and different kinds of salinity were compared for their effect on shoot development in salt-sensitive and salt-tolerant jojoba clones. Shoot segments were proliferated in vitro in the presence of different salts or different concentrations of ABA. Growth parameters (shoot elongation, new node production, dry weight, leaf length) and accumulation of Na⁺, K⁺, Ca²⁺,Cl^-, and SO₄^2- were examined. Wax deposition on leaves was detected by electron scan microscopy. Chloride salinity reduced shoot elongation, node production, and biomass production in salt-sensitive clones, while in salt-tolerant clones its adverse effects were generally less pronounced (although significant inhibition was observed in the presence of Na₂SO₄) or it even enhanced growth. The effect of ABA on shoot growth was similar to that of the chloride salinities, with salt-sensitive clones responding to much lower ABA concentrations than the salt-tolerant ones. Unlike ABA, salinity (mainly salts containing Cl^- anions) significantly promoted leaf expansion in both sensitive and tolerant clones. ABA and salinity induced some epicuticular wax deposition on leaves of salt-sensitive clones. The conclusion is that the salt sensitivity of jojoba clones is partly related to sensitivity to ABA.