Evapotranspiration of osteospermum 'Denebola' and New Guinea impatiens 'Timor' grown on ebb-and-flow benches as affected by climate conditions and soil water potential

Abstract

Daily evapotranspiration (EVPT) of two bedding plants osteospermum 'Denebola' and impatiens 'Timor' grown on ebb-and-flow benches was measured by weighing method, together with assessment of indoor climate parameters (solar radiation, temperature, humidity) and leaf area index (LAI) at different growth phases. The evaporation inside the greenhouse as affected by climatic factors i.e.: solar radiation, temperature, humidity and air velocity was also measured using Piche's evaporometer. Plants were irrigated according to soil water potential (irrigation at -0,5; -3; -10 and -20 kPa). Irrigation at high water potential decreased plant growth and leaf area of both plants. LAI of osteospermum decreased as water deficit increased. In the case of impatiens, the highest LAI at full flowering obtained plants irrigated at -3 kPa. The actual, daily EVPT of plants irrigated at -0,5 kPa increased with plant growth in the case ofosteospermum while that of impatiens remained at similar level. At flowering water stress decreased strongly EVPT of osteospermum and in lesser extent EVPT of impatiens. Osteospermum irrigated at -0,5 kPa had 2,5 higher EVPT than impatiens. For both plants good, positive correlation between EVPT and daily mean temperature, temperature between 7-17 h and evaporation according to Piche's evaporometer readings were obtained. As expected EVPT was negatively correlated with relative humidity, irrespective the growth phase and soil water potential. The correlation between EVPT and solar radiation, was changed during plant growth due to differences in temperature under shading screen, used during sunny days.