Question 18M.3.SL.TZ2.9c.ii

A build-up of salt (NaCl) in soil is known as salinization. This can make the soil unsuitable for agriculture. One strategy that has been used to address this problem is to add compost mixed with salt-metabolizing bacteria to this soil. The bacteria loosen the association of the Na⁺ with the soil and allow it to be washed out by rain more effectively. The graph shows the effect of bacteria over time on the amount of salt in the soil.

Another strategy for addressing soil salinization is to use genetically modified plants. A gene from Arabidopsis thaliana that codes for a vacuole membrane protein (AtNHX1) known as the Na⁺/H⁺ antiport was inserted into tomato plants. The transgenic plants increased storage of salt in their leaves yet the tomato fruit grew normally compared to unmodified plants.