Effect of microenvironments and exogenous substance application on 5’-nucleotidase activities in apple peel

Abstract

The present experiment was conducted to examine the effect of microenvironments and exogenous substance application on 5’-nucleotidase activity in apple peel tissue. By enclosing apple fruits in bags, treating them with exogenous active oxygen species and regulative agents or placing them under controlled conditions at different fruit temperatures or relative humidity, the 5’-nucleotidase activities were compared with the corresponding controls. The results indicated that, a considerable effect of the microenvironments was found on 5’-nucleotidase activities in fruit peel tissue. The highest enzymatic activity appeared in fruits on the southwest exposure of canopy, regardless of bagged or non-bagged fruits, significantly higher than those from any other exposures. Fruits with bags had a significantly higher 5’-nucleotid-ase activity than the exposed ones. A variation in enzymatic activities was observed in fruits enclosed with different types of bags, which were supposed to alter the microenvironments around them. Within a certain range, gradual or fluctuating rise of fruit temperatures could favor the increase of 5’nucleotidase activities as a result of heat adaptation, whereas the activity would be inhibited if the temperature-rising period was too short or temperature differential was too large. No matter what temperatures fruits were subjected to, high relative humidity was favorable for stimulating the 5’nucleotidase activities, which might partly explain why fruit sunburn would not happen in humid climates. Treatments with four kinds of exogenous active oxygen species could reduce the 5’-nucleotidase activities significantly but spraying with CaCl2 was able to enhance 5’-nucleotidase activities by 55.39%, reaching a 5% significant level.

Key words： microenvironment; exogenous substance; apple; 5’-nucleotidase; enzymatic activity

Acknowledgements This study was financially supported by the Natural Science Foundation of Hebei Province, China (No. 303203).

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