S13 - Session P2 - The effect of high concentration of liquid fertilizer and high temperature to water uptake of paprika seedlings

Authors: Jinen Hojo *, Takashi Ikeda

Conventional growth conditions in commercial for paprika plants are generally using high concentration of fertilizers and at low temperature condition. However, there are few research which have investigated the physical effects of such conditions to paprika growth, especially root growth. In this research, we investigate the effects of 2 different stresses to paprika root growth under hydroponic culture conditions. Paprika （ Capsicum annum L.）seedlings were grown hydroponically at a greenhouse. Three weeks after transplanted to hydroponic culture seedlings were used for following studies. The seedlings were grown at 6 different concentrations of liquid fertilizer (EC 0.5, 1.0, 1.5, 2.5, 3.5 and 4.5 dS m -1 ) (Experiment 1). When seedlings were grown for root zone temperature regime (Experiment 2), the season was summer. We used radiators for cooling liquid fertilizer at 20 and 25 ℃. Thus, the control which has no radiator regime was exposed to hot summer condition (almost 28- 33 ℃ at day time). The physical uptakes of liquid fertilizer by each seedling were measured by a pressure chamber, and the solute osmotic pressure for extract sap from stem cut surface by using isopiestic psychrometer. As results, at Experiment 1, the water uptake was decreased when the seedlings were subject to high concentration of liquid fertilizer condition. Also, the osmotic pressure of extracted sap was high at similar condition. At Experiment 2, when seedlings were exposed to high root zone temperature, the uptake was significantly decreased. However, the osmotic pressure for extract saps were similar among these regimes. In this study, we demonstrated that physical water uptakes were different when plants were subjected to different environmental stresses. We have to have further demonstration for tolerance of paprika plants toward to various environmental stresses.