Effect of a Brassinosteroid Analogue and High Temperature Stress on Leaf Ultrastructure of Lycopersicon Esculentum

The ultrastructure of tomato leaf disks treated with a biostimulator (0.01 mg dm-3 BB6, brassinosteroid analogue from Cuba), and subjected to high temperature (40 °C for 1.5 h) was studied. High temperature stress caused the appearance of granules in the nucleus, nucleolus and cytoplasm. In chloroplasts and in mitochondria the internal membrane system was disorganised and in chloroplasts some starch granules were detected. These symptoms were more marked in the cells treated with BB6. The influence of BB6 on the ultrastructure of leaf cells was apparent also before being subjected to heat stress.