4.4. Sclerenchyma and lignin
In experiments in summer, the stem parts lower than about 20 cm beneath the floral head contained a rather thick The results agree with those of Gerasopoulos and Chebli (1998) who injected cut Gerbera stems with 1-aminocyclopropane-1- carboxylic acid (ACC), the precursor of ethylene, prior to vase life. Ethylene production by the flowers increased and an increase was found in the activity of phenylammonia lyase (PAL). PAL has several functions, one of which is to regulate the synthesis of lignin monomers. The treatment enhanced firmness of the stems and delayed stem bending. Similarly, Ferrante et al. (2007) found a decrease in stem lignification after treating cut Gerbera flowers with inhibitors of PAL. These treatments drastically increased stem bending. These results fit the idea that insufficient stem lignification considerably contributes to Gerbera stem bending.