INFLUENCE OF DAY AND NIGHT TEMPERATURES ON SWEET-PEPPER SEEDLING DEVELOPMENT

Sweet pepper (Capsicum annuum 'Resistant Giant no. 4') seedlings were grown for 6 weeks in 128-cell plug trays under 16 day/night temperatur e (DT/NT) regimes from 14 to 26 degrees C. Seedling stem length, inter node length, stem diameter, leaf area, internode and leaf count, plant volume, shoot dry weight (DW), seedling index, and leaf unfolding rat e (LUR) were primarily functions of average daily temperature (ADT); i .e., DT and NT had similar effects on each growth or development param eter. Compared to ADT, the difference (DIF, where DIF = DT - NT) betwe en DT and NT had a smaller but still statistically significant effect on stem and internode length, leaf area, plant volume, stem diameter, and seedling index. DIF had no effect on internode and leaf count, sho ot DW, and LUR. The root : shoot ratio and leaf reflectance were affec ted by DT and DIF. Positive DIF (DT higher than NT) caused darker-gree n leaf color than negative DIF. The node at which the first Bower init iated was related to NT. The number of nodes to the first flower on pe pper plugs grown at 26 degrees C NT was 1.2 fewer than those of plants grown at 14 degrees C.