Effect of auxins on the native proteolytic activity of forest soils

Abstract

The soil proteolytic complex plays an important role within mineral nutrient cycling in ecosystems. Both auxins and proteases are produced by soil microbiota, and reciprocally, their activities affect the metabolic role of biota in soil. The objective of this study was to find out whether auxins (indole‐3‐acetic acid, indole‐3‐butyric acid, 1‐naphthaleneacetic acid and 2‐naphthoxyacetic acid) have a stimulatory or inhibitory effect on the activity of native proteases in soil. The results presented here demonstrate the positive effect of auxins on the native proteolytic forest soil activity. For example, in organic Oe horizons synthetically produced auxins stimulated native proteolytic activity in the European beech stands, where NOA led to the highest increase in L‐tyrosine production (from 564.02 µg at 0 µg auxin to 645.19 µg at the auxin dose of 100 µg). Comparing organic and organomineral horizons, auxins promote a higher stimulation of protease activity in the organic horizons. Comparing the different forest stands, auxins promote a high stimulation of protease activity in European beech stands. In the organomineral soil horizons, auxins promote a high stimulation of protease activity in Leptosols in European beech stands and Cambisols in pedunculate oak stands. The results confirmed the interrelationships between auxins and the native proteolytic forest soil activity from the viewpoint of dead organic matter decomposition. Furthermore, the general importance of substances produced in the rhizosphere for nitrogen cycling was verified.

Proteolytic Activity in Meadow Soil after the Application of Phytohormones

“…There is little information about the effect of IBA on microorganisms in the rhizosphere. However, we found in our previous study [20] that auxins stimulated native protease activity in the organo-mineral horizon. Bacterial IAA stimulates plant root growth [21], root dilation and increases the number and length of primary and lateral roots [22].…”