The present invention is directed to methods and compositions for increasing a growth characteristic of a plant, increasing nutrient use efficiency of a plant, or improving a plant's ability to overcome biotic or abiotic stress comprising applying a composition comprising a fungal mycelia extract comprising piperidine and/or an analogue thereof (e.g., 6-oxopiperidine-2-carboxylic acid) and/or a salt thereof (e.g., 6-oxopiperidine-2-carboxylate), or any combination thereof to a plant, plant part, or to a propagation material of the plant.