The temporal changes of pigments content and key enzyme activities during autumnal turning period of Pistacia chinensis bunge

Abstract

In this study, the temporal regularity of pigments and key enzyme intermediates of Pistacia chinensis Bunge in the color-changing period was investigated to provide a theoretical basis for exploring the mechanism of leaf discoloration. The pigment content and activities of key enzymes of P. chinensis during leaf discoloration were investigated. The correlation between leaf discoloration and environmental factors (temperature, relative humidity, light) was also analyzed. During the color change, the chlorophyll content decreased, while no significant change in the carotenoid content was observed. The anthocyanin content significantly increased in the middle of the period of color change. The ratios of carotenoids/chlorophyll and anthocyanins/chlorophyll showed an upward trend during the period of color change. The lightness parameter (L) and hue parameter (B) of P. chinensis Bunge leaves showed a fluctuating tendency, reaching the highest value at the beginning of color conversion. The hue parameter (A) showed an upward trend at the color conversion stage. The 5-aminolevulinic acid (ALA) and porphobilinogen (PBG) values showed an upward-downward-upward trend. The contents of ALA and PBG at the end of the color transformation were 2.01 times and 2.88 times higher than those at the beginning. The activity of phenylalaninammo-nialyase increased during the color change period. Chalcone isomerase and chalcone synthase first increased, then declined, reaching their highest level in the middle of color conversion, 261.0 u/g and 157.3 u/g, respectively. Although the activities of both enzymes declined at the end of the color conversion, they were higher than at the beginning of the color change. Anthocyanin content was negatively correlated with temperature, relative humidity, day length, and chalcone isomerase, whereas it was positively correlated with phenylalaninammo-nialyase. The results revealed the reasons for the discoloration of P. chinensis leaves in autumn and thus should be considered when exploring the mechanism of color-changing plants and performing color-changing plant applications.