Abstract
The alternating component of leaf electric potential is used to study and determine the plant nutrient status. Some research has been done in external environments on the relationship between the alternating component and light, but little research has been done on humidity. We therefore examined the influence of different humidity conditions alternating component of leaf electric potential of cultivated Qing-geng-cai in a greenhouse. Under high humidity, both plant fresh weight and water absorption from culture solution increased. Over the leaf electric potential spectrum 1.0∼45.0 Hz, the minimum peak was at about 16 Hz, and the maximum peak at about 18Hz. Under high humidity the 16 Hz peak became smaller, and the 18Hz peak became larger. Under high humidity the amplitude of leaf electric potential was large. This result is similar to that found for the direct current component of leaf electric potential. In the research reported here, changing conditions of humidity and nitrogen nutrition, did not influence the point at which frequency peaked, but they did influence in the magnitude of amplitude. The, peak position of a specific frequency of the alternating component depends on plant nutrient status, but environmental conditions affect only the amplitude. The diagnosis of plant nutrient status is possible using the specific frequency of the alternating component of leaf electric potential.
