THE EFFECT OF TEMPERATURE AND PHOTOPERIOD ON THE LEAF SENESCENCE AND PARTITIONING OF ASTILBE AND PAEONIA

Abstract

The effect of temperature and photoperiod on leaf senescence and partitioning were studied in Fall 2004 using Astilbe simplicifolia `praecox alba' and Paeonia hybrid `Barrington Belle' and Fall 2005 using Paeonia Paula Fay and Astilbe chinensis ×purpurea. Bare root divisions and crowns were potted and grown outdoors during the spring and summer. Plants were treated to either Ithaca fall outdoor and controlled warm (70–60 °F) environment under normal daylength (about 12 hours) or longday (LD15 hours in 2004 and 16 hours in 2005). The chlorophyll readings and senescing leaves were significantly affected by treatments in the two plants in 2004. There was no significant difference in the change in the total dry biomass in Paeonia hybrid `Barrington Belle' grown under different treatments but the number of large buds was highest in those grown at 70–60 °F at LD. Higher total plant biomass was observed over-all in Astilbe simplicifolia `praecox alba' in warmer greenhouse environment and under LD. The effect of photoperiod and its interaction with temperature were significant in weights of Astilbe simplicifolia `praecox alba' roots. Greenhouse grown plants had higher bud numbers compared to outdoor-grown plants. In 2005, Astilbe chinensis ×purpurea in the greenhouse under LD had more shoots and large buds than the other treatments. Senescing leaf and chlorophyll reading was affected by temperature and photoperiod and its interaction. Paeonia Paula Fay under LD outdoors had more large buds than those under natural photoperiod, but is similar in effect to those in the greenhouse. Results may be used to improve propagule quality, adjust crop production cycle and cultivation in different climate.