Seed Germination and Dormancy in the Woody Plant Viburnum propinquum (Caprifoliaceae) from a Temperate Mountain in Taiwan

摘要

The purpose of this study was to determine dormancy breaking and germination requirements of seeds of Viburnum propinquum, an evergreen plant with ornamental and medicinal values. The temperature for root protrusion was at alternating temperatures of15/6°C only, and 58% of seeds had rooted in week 92. In contrast, no seeds at alternating temperatures of 30/20,25/15, or 20/10°C or at a constant temperature of 25°C rooted. To simulate seasonal temperature regimes, the Viburnum seeds were incubatedat a temperature sequence (25/15°C for 12 wks —> 20/10°C for 8 wks -* 15/6°C for 4 wks 5°C for 8 wks, then moving the seeds back to 15/6, 20/10, 25/15°C) beginning at 25/15°C, no seeds rooted with 25/15,20/10, or 15/6°C incubation until they weremoved to 5°C. Seeds rooted at the end of the 5°C incubation and the percentage increased rapidly to 73% at 15/6°C and 77% at 20/10°C. Furthermore, shoot emergence occurred with the 20/10°C regime, but there was a delay of 6 weeks between the timesof root protrusion and shoot emergence. In the temperature sequence (5°C for 8 wks 15/6°C for 4 wks -> 20/10°C for 8 wks -> 25/15°C for 12 wks, then moving the seeds back to 20/10,15/6, 5°C) beginning at 5°C, no seeds rooted until they were moved back to 5°C a second time. Root protrusion began in week 7 at 5°C, increased to 38% in week 8, and then rapidly increased to 90% at 15/6°C. Similarly, shoot emergence occurred with the 20/10°C regime, but there was a delay of 7 weeks between the timesof root protrusion and shoot emergence. The small embryo had to increase in length by 696% before the root protruded. We concluded that seeds of V. propinquum have deep simple epicotyl morphophysiological dormancy (MPD); thus, root protrudes in the endof second winter or early spring and shoot emerges in spring after seeds dispersed in winter.