Air and Root Zone Temperature for Growth of Coastal Glehnia Seedlings

Abstract

Coastal glehnia (Korean name: gaet-bang-pung) is a perennial herb belonging to the Apiaceae family and is distributed in harsh environments with high salinity and dry conditions, such as coastal dunes and sandy beaches. Both the shoots and roots of coastal glehnia contain health-promoting phytochemicals, which can be used in functional foods and in the pharmaceutical industry. In this study, the air temperature (AT) and root-zone temperature (RZT) of seedlings under different treatment combinations were evaluated to establish a cultivation protocol for high seedling quality in controlled environments such as greenhouses and plant factories with artificial lighting (PFALs). Two-week-old seedlings were transplanted to deep-flow-technique hydroponic systems and grown for four weeks. In study I, the seedlings were treated with RZTs of 15°C, 20°C, and 25°C, with or without aeration. The RZT of 25°C with aeration significantly increased the shoot fresh and dry weights compared to the other treatments. In study II, the seedlings were treated with ATs and RZTs of 20°C and 25°C along with aeration. The AT 25°C/RZT 25°C treatment improved the shoot and root growth, photosynthetic rate, and electron transport rate compared to the AT 20°C/RZT 20°C treatment. In addition, the mineral content (P, K, S, Mg, Ca, and Fe) per shoot increased significantly at an AT of 25°C with a RZT of 25°C. These results suggest that the combination of an AT of 25°C and RZT of 25°C is the appropriate temperature condition to improve productivity during the seedling stage of coastal glehnia for mass production in PFALs and greenhouses.