Ultrastructural aspects of damage to leaves of Eucalyptus camaldulensis by the psyllid Cardiaspina retator

The ultrastructural changes to leaf mesophyll cells in River Red Gum, Eucalyptus camaldulensis Dehnh., which occur during feeding by nymphs of Cardiaspina relator Froggatt were characterised using Transmission Electron Microscopy. Image analysis of micrographs revealed that the sap-sucking nymphs of C. retator cause a condition in mesophyll cells that closely resembles the cell degeneration described for senescing leaves of deciduous trees. The most conspicuous change was the breakdown of the thylakoid membranes in chloroplasts coupled with a massing of electron-dense globules (plastoglobuli). For psyllid-affected River Red Gums, as for senescing leaves of deciduous plants, this change appears to be related to the mobilisation of lipids and proteins. Results were compared to mesophyll cells of naturally senescing leaves of E. camaldulensis which had been abscised. These cells showed whole-scale breakdown with the chloroplasts remaining intact and functional the longest as judged by the presence of large starch grains. There was no accumulation of plastoglobuli. Mesophyll cells from senescing leaves appeared to suffer from severe water stress, indicated by the deformation of the cell wall and separation of the plasmalemma from the wall. Copyright (C) 1996 Elsevier Science Ltd