MODELING LEAF DEVELOPMENT OF THE AFRICAN VIOLET (SAINTPAULIA-IONANTHA WENDL)

Leaf unfolding rate (LUR) was determined for 'Utah' African violet plants grown in growth chambers under 20 combinations of temperature and photosynthetic photon flux (PPF). A nonlinear model was used to predict LUR as a function of shoot temperature and daily integrated which occurred at 25C and a daily integrated PPP of 10 mol/m(2) per day. The optimum temperature for leaf unfolding decreased to 23C, and the maximum rate decreased to 0.18 leaves/day as the daily integrated PPF decreased from 10 to 1 mol/m(2) per day. A greenhouse experiment using 12 combinations of air temperature and daily integrated PPF was conducted to validate the LUR model. Plant temperatures used in the model predicted leaf development more accurately than did air temperatures, but using average hourly temperature data was no more accurate than using average daily temperature data.