Effects of amino acids on the growth and flowering of Eustoma grandiflorum under autotoxicity in closed hydroponic culture

• Amino acids were applied in recovering autotoxicity in Eustoma grandiflorum.
• Growth was reduced greatly if nutrient solutions were non-renewed.
• His application only in seedling stage and Leu and Bet application either in seedling or seedling to reproductive stage increased the shoot dry weight at final harvest.
• His treated plants showed early flowering.

Foliar application of amino acids was investigated for the recovery of the growth of Eustoma grandiflorum (Raf.) Shinn cv. Ichiban-boshi under autotoxicity developed in the closed hydroponic system. Twenty three water soluble amino acids were applied on Eustoma seedlings grown in either renewed or non-renewed nutrient solution under controlled environment facility of Shimane University. The concentrations of all amino acids were adjusted to nitrogen content of Proline at 200 mg L−1. Compared to the control, His and GABA application increased the dry matter contents in renewed nutrient solution. In non-renewed nutrient solution, higher dry matter was produced by the Pro and Gln treated seedlings whereas, Ala treated seedlings produced the lowest dry matter. Based on the seedling growth in non-renewed nutrient solution six amino acids namely Gln, Gly, Pro, Met, Leu and His were selected for further investigation along with Bet as a new amino acids following Eustoma seedling grown in horticultural soil substrate and the same seedlings were transferred to the container based closed hydroponic system in the greenhouse. All amino acids application increased the seedling height in horticultural soil substrate condition. Higher shoot fresh weight and root length were measured in Pro treated seedlings. Amino acids treated seedlings were continued under solution culture with either foliar application of amino acids or water in the greenhouse. All amino acids treated plants height was increased either continued with amino acids application or water. Unlike urea, Leu and Bet, continuous application of His did not improved shoot dry weight but earlier flowering of Eustoma was evidenced. Therefore, foliar spray of His can recover the growth with early flowering of Eustoma during autotoxicity in closed hydroponic system.