Fungal growth response to carbon and nitrogen limitation: Application of a model to laboratory and field data

Abstract

We evaluated assumptions about fungal growth regulation by applying a model to laboratory and field experimental data. Hyphal length, dry weight, CO 2, solution N and solution C were measured during 140 h incubations in liquid batch cultures of Trichoderma harzianum on mineral media at three nitrogen concentrations. Assuming preferential allocation of N to maintain hyphal extension and including cytoplasm translocation gave the best agreement between model predictions and observed data for N-limited growth. When excluding translocation from the model, hyphal length increase could not be well predicted. Fungal growth in an arable soil was simulated for two soil moisture regimes; one receiving rainfall only and one maintained in a moist condition by daily irrigation. Simulations were compared to measured total hyphal length, FDA-active hyphae and O 2-consumption. Model results suggested that hyphal length increases were highly subsidized by translocation of cytoplasm. The response of the active biomass component to soil moisture conditions primarily influenced substrate availability.