Quantitatively monitoring the plant evapotranspiration (ET) and water consumption is significant important in selecting appropriate plants, planning urban ecology and garden, and precision management of water resources. This study carried out daily monitoring of ET and water consumption for subtropical urban potted plants, Hydrocotyle vulgaris (HV), Narcissus jonquilla (NJ), Peperomia tetraphylla (PT) and Phalaenopsis hybrid (PH) in Guangzhou by weighing from November 1, 2019 to October 31, 2020. The results showed the daily mean ET against the pot area was 3.5, 2.5, 2.5 and 1.8 mm, and the annual ET against the total leaf areas were 162, 29, 74 and 123 mm for the HV, NJ, PT and PH, respectively. The variation of ET for the 4 plants were positively related with air temperature and negatively associated with relative humidity (RH) during day and night time. The Pearson correlation coefficient (CC) of HV’s ET with air temperature and RH were significant. Surprisingly, NJ’s ET showed weak CC with air temperature. Both PT and PH’s ET displayed significant CC with air temperature and RH during day time but weak CC with RH during night time. The 4 plants had evidently higher ET during days with larger wind speed, but similarly low ET in conditions of continuously dry soil or damp air (RH >80%). Based on the daily mean temperature and RH, the improved approach of air saturation deficiency could well estimate the 4 plants’ ET (R2 =0.52-57, RD = -0.9%-4.4%), and has significant implication for estimating their potential ET and designing automated watering system.
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