Yeast extract having effect of promoting growth of plant and elongation of root and effect of improving added values of plant

[Problem] The present invention seeks to provide a composition for plants that is highly safe and that contributes to early harvesting， increasing yield， and increasing added value of crops. Specifically， the present invention provides a yeast extract that， by addition to a foliar surface spray or to soil or water， provides an effect of promoting growth， an effect of root lengthening， an effect of improved taste， and an effect of increased amino acid content of a plant. A substance obtained from yeast that is edible and considered to be safe is preferred as the yeast extract. [Means for Solving the Problem] A yeast extract having a peptide content of 5 wt % or more and an RNA content of 5 wt % or more is sprayed onto or provided as fertilizer to a plant. The yeast extract is preferably derived from Candida utilis， which is edible and considered to be safe.