Growth and ajoene concentrations in garlic plants cultured hydroponically with different aeration regimes

Abstract

SummaryA hydroponic culture system was developed for producing garlic bulbs and roots containing a precursor of ajoene. Garlic plants were cultured in a growth chamber under artificial lighting for 2 months at air temperatures of 25º/21ºC (light/dark), relative humidities of 75%/90% (light/dark), a photosynthetic photon flux density of 450 µmol m–2 s–1, and a photoperiod of 12 h d–1. The growth and ajoene concentrations of garlic plants cultured hydroponically with different aeration regimes were compared in order to examine the effects of dissolved O2 levels on these parameters. The four aeration treatments included 12 h dark-time aeration (12 h-D), 12 h illuminated-time aeration (12 h-L), 24 h continuous aeration (24 h) using a pump, or no aeration (control). Dissolved O2 concentrations increased in the order: 24 h >12 h-L >12 h-D > control. Fresh weights (FW), dry weights (DW), and ajoene concentrations were increased in each part of the garlic plants by increasing the levels of dissolved O2. The FWs of bulbs, leaves, and roots in the 24 h aeration treatment were 27.7, 41.4, and 80.3 g per plant, respectively. These values were 4.3-, 2.0-, and 5.6-times higher, respectively, than those in the controls. The ajoene contents of bulbs, leaves, and roots were 18.7, 6.7, and 14.6 mg per plant, respectively, in the 24 h treatment, which were 6.4-, 5.2-, and 11.2-times higher, respectively, than those in the controls. In conclusion, garlic plants grown at higher levels of dissolved O2 showed higher growth rates and greater ajoene contents. The roots of garlic plants cultured hydroponically contained ajoene, and were expected to be a healthy food, as are the bulbs.