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 s ap-sucking nymphs of C. retator cause a condition in mesophyll cells t hat closely resembles the cell degeneration described for senescing le aves 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 Re d Gums, as for senescing leaves of deciduous plants, this change appea rs to be related to the mobilisation of lipids and proteins. Results w ere compared to mesophyll cells of naturally senescing leaves of E. ca maldulensis which had been abscised. These cells showed whole-scale br eakdown with the chloroplasts remaining intact and functional the long est as judged by the presence of large starch grains. There was no acc umulation of plastoglobuli. Mesophyll cells from senescing leaves appe ared to suffer from severe water stress, indicated by the deformation of the cell wall and separation of the plasmalemma from the wall. Copy right (C) 1996 Elsevier Science Ltd