SECRETORY ORGANELLE AND MITOCHONDRIAL ALTERATIONS INDUCED BY FUSARIC ACID IN ROOT-CELLS OF ZEA-MAYS

Respiratory inhibition, electrolyte electrolyte leakage cytological alterations and expression of plant symptoms were induced in Zea mays by treatment with fusaric acid [from Fusarium oxysporum] concentrations greater than 10-4 M. Early cytological changes included an increased release of secretory product, inhibition of secretory vesicle formation, curling or dictyosomes, elongation and stacking of endoplasmic reticulum cisternae, and swelling of mitochondrial cristae. Longer toxin treatments resulted in decreased numbers of polyribosomes, increased vacuolation and a reduction in the electron density of mitochondrial matrices. When early cytological changes had occurred, respiratory activity was partially inhibited although electrolyte loss was not yet evident. The preceding results are discussed in relation to the proposed mechanism of action and role of this toxin in plant disease.