Effects of water stress on ultrastructure and membrane lipid peroxidation of leaf and root cells of Glycyrrhiza uralensis

Using transmission electron microscopy,the changes of cortical and pericycle cells in roots and mesophyll cells in leaves of one-year-old Glycyrrhiza uralensis seedlings were observed.MDA content,the effect of water stress on ultrastructure,and membrane lipid peroxidation were measured and analysed.The organelle structure changed in both root and leaf cells with time under water stress.Cell nuclei of leaf blade and root systems were obviously distorted,and chromatin agglutination and marginalization appeared.The mitochondrion outer membranes were disrupted and collapsed,and the lumen formed a cavity.Chloroplast basal granule laminae of leaf blades gradually blurred and starch degraded.Golgi bodies of roots expanded and decomposed into many small vesicles.The sensitivity to water stress varied among different organizations and organelles.The changes of organelle morphology in cortical cells occurred earlier than those in pericycle and mesophyll cells.Otherwise,nuclear chromatin condensation appeared at the initial stage of water stress and preceded membrane lipid peroxidation damage in both root and leaf cells.As the above characteristics were similar to those of programmed cell death,it was presumed that programmed cell death in leaf and root cells might be one the mechanisms to resist water stress in G.uralensis.