PAL Activity in Peach Fruit

In this chapter, methods of quantitative and qualitative analysis of phenolic compounds in peach fruit, and of measurement of PAL activity will be described with special reference to astringency. The relationship between the phenolic content and PAL activity in peach fruit, and some factors affecting the content and activity, will be discussed. 

Factors Affecting Phenolic Content and PAL Activity in Peach Fruit... 

Phenolic content and PAL activity in plants are affected by various internal and external factors (Camm and Towers 1973 McClure 1979). For example, PAL activity is influenced by exogenous factors such light intensity, temperature, and the application of certain growth regulators, especially ethylene. Unlike grape and apple fruits (Faragher 1983 Roubelakis-Angelakis and Kliewer 1986), there is little information about the effects of these factors on phenolic content and PAL activity in peach fruit. Based on our experimental results, the relationship between these parameters in peach fruit is discussed below. 

These findings suggested that the total phenolic content in peach fruit is closely related to the PAL activity. Further investigation is needed to identify the relationship between PAL activity and the L-phenylalanine concentration in peach fruit. 

Fig. 4. Fruit growth curves of two peach cultivars, Mishima-hakuto and Shimizu-hakuto, and changes in the total phenolic content, PAL activity, and L-phenylalanine content of their mesocarp tissues...

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