Cucumber cuticles

Cuticular erosion results in the formation of imprints on the leaf surface that can easily be detected by scanning electron microscopy (A2.) Comparison of Erysiohe graminis with . cichoracearum demonstrated that . graminis erodes both barley and cucumber cuticles, but that 21. cichoracearum only eroded or left imprints on cucumber cuticles (A3.). These results suggest a level of host specificity, possibly for the enzymatic erosion of the cuticle, that may also be involved in the successful penetration of the leaf. 

Smit and Rechnitz [299] introduced plant leaves as biocatalysts in combination with potentiometric gas-sensing electrodes. They detached the cuticle from either the upper or low er epidermal layer and fixed the remaining leaf structure at the surface of a gas-sensing potentiometric electrode where the epidermal layer contacted the sample and the gas-permeable waxy cuticle was attached to the sensor. In the case described, the substrate L-cysteine is degraded by L-cysteine desulphhy-drase, present in cucumber leaf discs, to pyruvate and ammonia which is monitored by an ammonia electrode [302]. 

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