A thermal time model for predicting time to aerial shoot elongation in Variegated Solomon's Seal

Aerial shoot development in Variegated Solomon's Seal (Polygonatum odoratum 'Variegatum') was studied under warm (mean 18 degrees C) conditions after dormant rhizomes had been stored at a range of temperatures. After chilling at 0.8-5.5 degrees C for 21-77 days, all rhizomes produced elongated aeria l shoots, with mean lengths from 33 cm to 44 cm. Exposure of rhizomes to 15 degrees C or 20 degrees C for 21-77 days resulted in 17% to 50% of buds em erging as shoots, but these either aborted or failed to extend beyond a ros ette. The earliest aerial shoot elongation was observed after 7-13 days at 18 degrees C in rhizomes that had been chilled at 0.8-2 degrees C treatment s for 59-72 days. The base, optimum and maximum temperatures during pre-pla nting storage for subsequent aerial shoot elongation were derived respectiv ely as -1.5 degrees C, 1.9 degrees C and 15.8 degrees C. A thermal time of storage was calculated from these cardinal temperatures and the rate of pro gress to normal aerial shoot elongation was shown to increase linearly with increasing thermal time to c. 150 degrees Cd. The thermal time procedure f or predicting time to aerial shoot elongation constructed hom growth room/c hamber data was validated using rhizomes that had been exposed to varying t emperatures in shadehouse conditions during the winter in Taiwan.