Division of Silviculture, Taiwan Forestry Research Institute, Taipei 10066, Taiwan.
Ann Bot. 2011 Jul;108(1):13-22. doi: 10.1093/aob/mcr096. Epub 2011 May 11.
In seeds with deep simple epicotyl morphophysiological dormancy, warm and cold stratification are required to break dormancy of the radicle and shoot, respectively. Although the shoot remains inside the seed all winter, little is known about its growth and morphological development prior to emergence in spring. The aims of the present study were to determine the temperature requirements for radicle and shoot emergence in seeds of Viburnum betulifolium and V. parvifolium and to monitor growth of the epicotyl, plumule and cotyledons in root-emerged seeds.
Fresh and pre-treated seeds of V. betulifolium and V. parvifolium were incubated under various temperature regimes and monitored for radicle and shoot emergence. Growth of the epicotyl and cotyledons at different stages was observed with dissecting and scanning electron microscopes.
The optimum temperature for radicle emergence of seeds of both species, either kept continuously at a single regime or exposed to a sequence of regimes, was 20/10 °C. GA(3) had no effect on radicle emergence. Cold stratification (5 °C) was required for shoot emergence. The shoot apical meristem in fresh seeds did not form a bulge until the embryo had grown to the critical length for radicle emergence. After radicle emergence, the epicotyl--plumule and cotyledons grew slowly at 5 and 20/10 °C, and the first pair of true leaves was initiated. However, the shoot emerged only from seeds that received cold stratification.
Seeds of V. betulifolium and V. parvifolium have deep simple epicotyl morphophysiological dormancy, C(1b)B (root)-C(3) (epicotyl). Warm stratification was required to break the first part of physiological dormancy (PD), thereby allowing embryo growth and subsequently radicle emergence. Although cold stratification was not required for differentiation of the epicotyl--plumule, it was required to break the second part of PD, thereby allowing the shoot to emerge in spring.
在具有深简单下胚轴形态生理休眠的种子中，需要进行温暖和寒冷分层来分别打破胚根和芽的休眠。尽管芽整个冬天都留在种子内，但对其在春季出现之前的生长和形态发育知之甚少。本研究的目的是确定 Viburnum betulifolium 和 V. parvifolium 种子中胚根和芽出现的温度要求，并监测根出芽种子中下胚轴、胚轴和子叶的生长。
将新鲜和预处理的 Viburnum betulifolium 和 V. parvifolium 种子在不同温度条件下培养，并监测胚根和芽的出现。使用解剖和扫描电子显微镜观察下胚轴和子叶在不同阶段的生长情况。
两种物种的种子，无论是在单一温度条件下连续保持还是暴露于序列温度条件下，胚根出现的最佳温度均为 20/10°C。GA(3)对胚根出现没有影响。需要冷分层（5°C）才能出现芽。在新鲜种子中，芽顶端分生组织直到胚胎长到胚根出现的临界长度才形成凸起。胚根出现后，在 5°C 和 20/10°C 下，下胚轴-胚轴和子叶生长缓慢，第一对真叶开始出现。然而，只有接受冷分层的种子才能长出芽。
V. betulifolium 和 V. parvifolium 的种子具有深简单下胚轴形态生理休眠，C(1b)B（根）-C(3)（下胚轴）。需要温暖分层来打破第一部分生理休眠（PD），从而允许胚胎生长并随后出现胚根。虽然冷分层不是芽出现所必需的，但它是打破第二部分 PD 所必需的，从而使芽在春季出现。
