EFFECTS OF TEMPERATURE AND PHOTOPERIOD ON TROPICAL SODA APPLE (SOLANUM-VIARUM DUNAL) AND ITS POTENTIAL RANGE IN THE US

Tropical soda apple is an exotic perennial pasture weed currently repo rted in the U.S. only from Florida, Georgia, Alabama, Mississippi, and South Carolina. In experiments to determine its environmental require ments and potential range, tropical soda apple was grown in growth cha mbers in 16 day/night temperature regimes ranging from 18/8 to 36/26 C . After 100 d of growth, maximum height, leaf area, and shoot biomass occurred at day/night temperatures ranging from 24/26 to 36/26 C. The plants achieved 50% or more of maximum leaf area, biomass, and height at 18/26, 24/20, 24/26, 30/26, and 36/26 C. plants survived in 8 C nig hts with day temperatures of 18 to 36 C, but biomass and leaf area wer e only 3 to 10% of maximum. Leaf appearance rate was linearly related to mean temperature over the range of 11.3 to 29.3 C, with a slope coe fficient of 0.018 leaves/day/degree C. Flowering was delayed by photop eriods shorter than 10 h or temperatures lower than 24/20 C. In favora ble temperatures, plants flowered within 60 d after emergence in photo periods ranging from 8 to 16 h. Artificially pollinated flowers produc ed fruit with germinable seeds within 6 to 7 wk, at temperatures rangi ng from 23/17 to 32/26 C. A regression equation relating vegetative gr owth to day and night temperatures indicated that tropical soda apple could achieve 30% or more of its maximum growth rate during 7 mo of th e year in southern Alabama, Louisiana, and Texas and during 4 to 5 mo of the year at sites in Georgia, South Carolina, North Carolina, Virgi nia, Tennessee, Kentucky, Illinois, Arkansas, Missouri, Kansas, and Ok lahoma. Neither temperature nor photoperiod will limit its further spr ead in the southern U.S. and adjacent regions.