Irrigation Frequency and Shading Influences on Water Relations and Growth of Container-Grown Euonymus japonica ‘Aureo-marginata’

Abstract

Trickle irrigation frequency, shading, water relations, and plant growth of container-grown Euonymus japonica Thunb. ‘Aureomarginata’ was investigated. Plants were grown under a combination of 3 irrigation frequencies and 2 shade levels. Stomatal conductance (gs) was reduced when plants were irrigated 3 times per week compared to irrigation daily and twice daily after week 4 under full sun and after week 8 under shade. Few differences were detected in predawn shoot water potential (Ψshoot) under shade at any irrigation level. The predawn shoot water potential (Ψshoot) was reduced (rnore negative) for plants irrigated 3 times per week compared to irrigation daily and twice daily after week 8 for plants grown under full sun and week 10 for plants grown under shade. These values remained lower for the duration of the study. Plants grown under shade and irrigated once daily had greater plant dry weight and leaf area compared to plants irrigated either twice daily or 3 times per week. They were also larger than all plants grown under full sun. Plants grown under shade had greater chlorophyll levels per unit leaf area. Under shade, plant quality was not affected by irrigation rates. However, only plants grown under shade were of salable quality.