MODELING LEAF DEVELOPMENT OF THE AFRICAN VIOLET (SAINTPAULIA-IONANTHAWENDL)

Leaf unfolding rate (LUR) was determined for 'Utah' African violet pla nts grown in growth chambers under 20 combinations of temperature and photosynthetic photon flux (PPF). A nonlinear model was used to predic t LUR as a function of shoot temperature and daily integrated which oc curred at 25C and a daily integrated PPP of 10 mol/m(2) per day. The o ptimum temperature for leaf unfolding decreased to 23C, and the maximu m rate decreased to 0.18 leaves/day as the daily integrated PPF decrea sed from 10 to 1 mol/m(2) per day. A greenhouse experiment using 12 co mbinations of air temperature and daily integrated PPF was conducted t o validate the LUR model. Plant temperatures used in the model predict ed leaf development more accurately than did air temperatures, but usi ng average hourly temperature data was no more accurate than using ave rage daily temperature data.