Figure 3.

Electron micrographs of leaf mesophyll cells of 15-day hydroponically grown seedlings of Brassica napus cv. ZS 758. (a-b) TEM micrographs of mesophyll cells of ZS 758 under 400 μM lead (Pb) at low and high magnifications, respectively, show swollen and ruptured chloroplast (Chl) and absence of starch grain (S). Cell wall (CW) and cell membrane (CM) are diffused with each other and no nucleus was found. Moreover, accumulation of Pb is increased in the form of electron dense granules attached to the cell walls. (c-d) TEM micrographs of mesophyll cells of ZS 758 at 25 mg L⁻¹ 5-aminolevulinic acid (ALA) under 400 μM lead (Pb) at low and high magnifications, respectively, show an elongated nucleus (N) with well developed nucleolus (Nue) and nuclear membrane (NM). Cell wall (CW) and cell membrane (CM) are clear. Chloroplast (Chl) is well-developed in almost round shape and has thylakoids, grana, and big starch grain (S).