THERMOMORPHOGENIC AND PHOTOPERIODIC RESPONSES OF NEPHROLEPIS-EXALTATADALLAS JEWEL

Nephrolepis exaltata (L.) Schott 'Dallas Jewel' plants were grown for 92 days under 16 day/night temperature (DT/NT) regimes and two photope riods for a total of 32 environments. Temperatures ranged from 15 to 3 0 +/- 1.5C. Photoperiod was either 9 hours (short days) or 9 hours plu s a 4-hour night interruption (long days) using incandescent lamps. Ph otoperiod had no significant effect on either morphology or developmen t rate. Frond length and leaflet count per frond were highly correlate d with the average daily temperature (ADT). Frond length increased fro m 9.3 to 21.9 cm and leaflet count increased from 21 to 42 leaflets pe r frond as ADT increased from 15 to 30C. Stolon count and frond orient ation were highly correlated with the weighted difference (WDIF) betwe en DT and NT. The weighted difference between DT and NT was equal to: (DT x photoperiod) - (NT x scotoperiod). The scotoperiod was inclusive of the night interruption. Stolon count increased as the weighted NT increased relative to the weighted DT, i.e., as WDIF decreased. In con trast, frond angle relative to the soil surface, i.e., frond orientati on, increased as WDIF increased. Frond unfolding rate and total plant dry weight increased as temperature increased to almost-equal-to 25C, then decreased.