Use of lighting and temperature strategies to control flowering and architecture of select herbaceous plants

Successful production of many floricultural crops requires precise timing of flowering and a final plant height that meets preset specifications. Stem extension is suppressed in many herbaceous plants when the day temperature is cooler than that during the night, and when the incident radiation provides a high red (R, 600 to 700 nm) to far-red (FR, 700 to 800 nm) ratio. However, a high R:FR can delay flowering in some long-day plants, which is often undesirable. Experiments were performed to determine: (1) if phytochrome A mediated the reduction in stem extension from cool day-temperature treatments, (2) how flowering and stem extension of Echinacea purpurea L. were mediated by lighting duration and quality, and (3) extension growth and flowering responses of a variety of herbaceous species, particularly long-day plants (LDP), in environments deficient in blue (B, 400 to 500 nm), R, or FR light.; Transgenic potato over- or under-expressing phytochrome A (phyA) and tomato phyA mutants were grown at one of three temperature regimens with a daily mean of 20°C. Compared with that under a constant 20°C, an 8°C temperature depression at the onset of the photoperiod or a 16/24°C day/night temperature suppressed extension growth of tomato, potato, or both, regardless of phyA level. Therefore, it appears that phyA does not control extension growth in relation to cool temperature treatments.; Experiments were performed to determine how light regulates growth and development of Echinacea purpurea. Plants were exposed to a variety of photoperiods (9 to 24 h), night-interruption (NI) lighting durations (7.5 to 240 min), and photoperiods deficient in B, R, or FR light. Flowering was most complete and rapid under photoperiods of 13 to 15 h, which indicates that Echinacea purpurea is an intermediate-day plant. Plants flowered when 15-h dark periods were interrupted with low-intensity lighting for 7.5 min, but flowering was most rapid when lighted for 30 to 60 min. A model composed of two distinct mechanisms is proposed to explain the flowering behavior of intermediate day plants such as E. purpurea.; Finally, experiments with photoselective plastic filters were performed to determine how photoperiods deficient in B, R, and especially FR light influenced stem extension and flowering in a variety of herbaceous annual and perennial plants. Photoperiods deficient in B or R generally promoted extension growth but had little or no effect on time to flower. However, an FR-deficient photoperiod inhibited extension growth and flowering in some LDP, such as pansy ( Viola x wittrockiana). Further experiments were performed to determine if lighting strategies could be used to produce short, compact plants without a concomitant delay in flowering. Results with pansy indicate that extension growth and flowering can not readily be separated with lighting strategies.