3.6. Effects of lead on proline content
Proline is one component of the non-specific defence systems
towards lead toxicity. It alleviates metal toxicity by acting as
a metal chelator and as a protein stabilizer (Sharma and
Dubey, 2005). Proline concentrations (Fig. 4A and B) increase
in leaves of wheat and spinach exposed to increasing lead concentrations.
In wheat roots, proline concentrations (Fig. 4A)
peak significantly at 3 mM Pb and then decrease to control
levels at 15 mM Pb. In spinach, proline concentrations were
significantly higher than control values for all lead concentrations.
We reported previously (Lamhamdi et al., 2011) that
proline concentrations were also increased in young wheat
seedlings after 6 days of Pb-stress.
Total proline content (Fig. 4C) stayed constant in wheat
seedlings, and decreased only (to 63% of control value) for
15 mM Pb. By contrast, proline amounts per spinach plant
(Fig. 4D) peaked at 184% of the control value with 1.5 mM
Pb, and remained significantly higher than controls for all lead
concentrations, which might provide increased protection to
this plant