There has been a considerable amount of recent research aimed at elucidating the roles of chitinase in fungi and plants. In filamentous fungi and yeasts, chitinase is involved integrally in cell wall morphogenesis. Chitinase is also involved in the early events of host‐parasite interactions of biotrophic and necrotrophic mycoparasites, entomopathogenic fungi and vesicular arbuscular mycorrhizal fungi. In plants, induction of chitinase and other hydrolytic enzymes is one of a coordinated, often complex and multifaceted defense mechanism triggered in response to phytopathogen attack. Chitinase induction in plants is not considered solely as an antifungal resistance mechanism. Plant chitinases can be induced by various abiotic factors as well and there is some circumstantial evidence to suggest a morphogenetic role despite the apparent absence of the substrate in plant cells. Finally, some chitinases and other chitin‐binding proteins including some plant lectins share chitin‐binding domains as part of their molecular structure and provide fuel for the so‐called ‘lectin‐chitinase’ debate and speculation for the origin of chitinase in plants.

The lipid content and composition of four strains of Paracoccidioides brasiliensis were analysed to determine any possible correlation with their virulence for hamsters and mice. Two strains, Pb168 and Pb141, were equal in virulence, Pb9 was slightly virulent and Pb140 was avirulent under the experimental conditions. No correlation was observed between virulence and the total lipid or phospholipid content of the strains. The lipid yield was highest in Pb9 and lowest in Pb168. Polar lipids were highest in Pb9 and least in Pb140. Phosphatidylcholine was the dominant phospholipid in all strains but its percentage was lower in the avirulent strain Pb140. Diphosphatidylglycerol, the least saturated lipid in all strains, was less abundant in Pb140 than in the virulent strains Pb168 and Pb141. In all four strains, neutral lipids constituted the major fraction of total lipids and triglycerides were the predominant individual lipid class, being more abundant in the avirulent and slightly virulent strains that in the virulent strains. The fatty acid profiles of total lipids and individual lipid classes of neutral and polar lipids obtained from the four strains were similar; however, the individual lipid classes showed patterns of preferential distribution of these fatty acids.

Detached leaves of Little Club wheat were allowed to senesce on water or on kinetin (10 mg/l.) in petri dishes on the laboratory bench. Samples taken at intervals of 24 to 48 hours for 8 to 10 days were fixed in permanganate or osmium tetroxide, embedded, usually in araldite or epon, and examined by electron microscopy. Abnormalities were noted in the endoplasmic reticulum (ER) of the mesophyll cells 2 days after the leaves were detached; ER and cytoplasmic ribosomes were not present after 4 or 5 days. Swelling of the mitochondria and degeneration of the cristae, collapse of the chloroplast grana, and abnormalities in nuclear structure were noted after 3 days. Vacuolar contraction occurred in some cells after 4 days but the plasma membrane usually remained unbroken until the seventh or eighth day, by which time the mitochondria were no longer recognizable and most of the chloroplasts and nuclei had also disintegrated.Kinetin induced an increase in the amount of ER and ribosomes and markedly delayed the degeneration of cellular fine structure.

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