The response of snapdragons, Antirrhinum majus L., to summer greenhouse growing conditions in Tennessee

Differences in daily transpiration rates for snapdragons on days of differing humidity, temperature, and light in summer were found. Daily transpiration rates also differed significantly among cultures. Stomatal closure on bright, hot days occurred at different leaf relative hydrations among the cultivars. The lower transpiring cultivar 'Oklahoma' maintained the higher leaf relative hydration. The snapdragon cultivar 'Panama' grown in summer under two shading levels and two soil depths showed that plants grov/n under 50 percent shade or at the 15 cm soil depth produced better quality plants than those grown under 63 percent shade or at the 30 cm soil depth. Measurements of leaf relative hydrations, leaf diffusive resistances, and leaf temperatures were capable of determining differences in plant water relations on days of differing humidity, temperature, and light and at different times on a bright day. However, differences between shade and soil depth treatments were not as conclusive.