TRANSPIRATION RATE IN RELATION TO ROOT AND LEAF GROWTH IN CUTTINGS OFBEGONIA X HIEMALIS FOTSCH

Cuttings of Begonia x hiemalis Fotsch, cv, 'Schwabenland Red' were roo ted in an aeroponics system at 21 degrees C and 2.9 molm(-2)day(-1) ph otosynthetic photon flux density (PPFD) for 18 h day(-1). Leaf length increase rate was higher in leaves appearing at time of root formation compared with leaves starting to expand before roots were formed. Tra nspiration rate per unit leaf area increased after roots had been form ed, In cuttings potted shortly after root formation, transpiration rat e per unit leaf area decreased during the first days after potting and remained at a low level for a week. Leaf area expansion and root grow th rate were slowed down during this period. Transpiration per cutting was less correlated with leaf area two weeks after root formation in the potted cuttings compared with non-potted cuttings of the same deve lopmental stage, Cuttings with large leaf area produced greater root m ass in relation to cuttings with smaller leaf area. (C) Elsevier Scien ce B.V.