Effects of Electrical Conductivity (EC) of System Water and Vapor Pressure Deficit (VPD) on the Physiological Responses and Flowering of Kalanchoe blossfeldiana in an Aquaponic System

Hyounjin Lee; Ye-Joong Yun; Ki-Young Choi

doi:10.7235/HORT.20260035

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Research Article

Effects of Electrical Conductivity (EC) of System Water and Vapor Pressure Deficit (VPD) on the Physiological Responses and Flowering of Kalanchoe blossfeldiana in an Aquaponic System 아쿠아포닉스 시스템에서 사육수의 전기 전도도 (EC) 수준과 수증기압차 (VPD) 가 칼랑코에(Kalanchoe blossfeldiana)의 생리적 반응 및 개화 특성에 미치는 영향

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Abstract

This study investigated the effects of system water electrical conductivity (EC) levels and the growing environment on the physiological responses (photosynthesis, SPAD value, and chlorophyll fluorescence), growth, and flowering characteristics of florist kalanchoe (Kalanchoe blossfeldiana) in a goldfish (Carassius auratus L.) aquaponic system over a time span of 140 days. The experiment was conducted at three EC levels (0.5, 1.0, and 1.5dS·m^-1), which were maintained by regulating fish feeding rates (50% crude protein) without the addition of chemical fertilizers. During the experimental period, mean air temperatures were similar between the growth room and the control (22.4 and 22.8°C, respectively), whereas relative humidity was markedly higher in the growth room (57.7%) than in the control (32.7%), resulting in mean vapor pressure deficit (VPD) values of 1.18 and 1.98kPa, respectively, with the control peaking at 2.22–2.30kPa during November–December. The pH of the system water remained stable within a range of 5.0–6.6, and EC was consistently maintained at designated levels without nutrient accumulation. The photosynthetic rate, stomatal conductance, and transpiration rate were more strongly influenced by the VPD than by the EC level; despite the high VPD, a continuous water supply maintained stomatal opening in the control case, resulting in photosynthetic rates 38.8–43% higher than those of the EC 1.0 growth room treatment. The maximum photochemical efficiency of photosystem II (Fv/Fm) remained stable at 0.81–0.83 across all treatments, and the performance index (PI__ABS) was highest in the control at 140 days after treatment. Plant width in the control was significantly greater than in the EC 1.0 and 1.5 treatments, and leaf hardness was significantly greater than in the EC 0.5 and 1.0 treatments, whereas stem diameter was greater in all growth room EC treatments. The cumulative flowering rate in the control (64.6%) was more than twice that of the growth room EC treatments (27.9–33.2%). Within the EC range tested, the EC level had limited effects on kalanchoe physiology and flowering, whereas differences in the growing environment, including VPD, were likely the primary factor in this aquaponic system.

Keywords

crassulacean acid metabolism (CAM)

photosystem II efficiency

reproductive transition

resource allocation

sink competition

본 연구는 금붕어(Carassius auratus L.) 아쿠아포닉스 시스템에서 140일간 사육수의 전기전도도(EC) 수준과 재배 환경이 칼랑코에(Kalanchoe blossfeldiana Poelln.)의 생리 반응(광합성, SPAD 값, 엽록소 형광), 생육 및 개화 특성에 미치는 영향을 조사하였다. 실험은 화학비료 첨가 없이 사료 급이량(조단백 50%) 조절을 통해 유지된 EC 0.5, 1.0, 1.5dS·m^-1의 3수준으로 수행하였다. 실험 기간 동안 재배실과 대조구의 평균 기온은 각각 22.4°C와 22.8°C로 유사하였으나, 상대습도는 재배실(57.7%)이 대조구(32.7%)보다 현저히 높아 수증기압차(VPD)는 재배실 평균 1.18kPa, 대조구 평균 1.98kPa로 나타났으며, 대조구에서는 11–12월에 2.22–2.30kPa에 달하였다. 사육수 pH는 5.0–6.6 범위에서 안정적으로 유지되었고, EC는 양분 축적 없이 설정 수준에서 일정하게 유지되었다. 순광합성률, 기공전도도, 증산률은 EC 수준보다 VPD 조건에 따른 차이가 뚜렷하였으며, 높은 VPD 조건에서도 지속적인 수분 공급에 의해 대조구의 기공 개방이 유지되어 재배실 EC 1.0 처리구 대비 38.8–43% 높은 광합성률을 나타냈다. 광계II의 최대 광화학 효율(Fv/Fm)은 모든 처리구에서 0.81–0.83으로 안정적으로 유지되었으며, 성능 지수(PI__ABS)는 처리 140일째 대조구에서 가장 높게 나타났다. 대조구의 초폭은 재배실 EC 1.0 및 1.5 처리구보다 유의적으로 넓었고, 엽 경도는 EC 0.5 및 1.0 처리구보다 유의적으로 높았으며, 줄기 굵기는 재배실 EC 처리구에서 더 굵었다. 대조구의 누적 개화율은 64.6%로 재배실 EC 처리구(27.9–33.2%)의 2배 이상이었다. 실험 범위의 EC 수준은 칼랑코에의 생리 및 개화 반응에 제한적 영향을 미쳤으며, VPD를 포함한 재배 환경 차이가 주요 요인으로 작용하였을 가능성이 높다.

키워드

크래슐라산대사(CAM)

광계II 효율

생식 생장 전환

자원 배분

싱크(sink) 경쟁

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Information

Publisher :KOREAN SOCIETY FOR HORTICULTURAL SCIENCE
Publisher(Ko) :한국원예학회
Journal Title :Horticultural Science and Technology
Journal Title(Ko) :원예과학기술지
Received Date : 2026-02-26
Revised Date : 2026-09-06
Accepted Date : 2026-09-07
DOI :https://doi.org/10.7235/HORT.20260035

Horticultural Science and Technology 원예과학기술지 ISSN:1226-8763(Print) 2465-8588(Online)

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