Ile E I, Craufurd P Q, Battey N H, Asiedu R
Plant Environment Laboratory, The University of Reading, Reading RG2 9AF, UK.
Ann Bot. 2006 Apr;97(4):497-504. doi: 10.1093/aob/mcl002. Epub 2006 Jan 30.
The control of dormancy in yam (Disocorea spp.) tubers is poorly understood and attempts to shorten the long dormant period (i.e. cause tubers to sprout or germinate much earlier) have been unsuccessful. The aim of this study was to identify and define the phases of dormancy in Dioscorea rotundata tubers, and to produce a framework within which dormancy can be more effectively studied.
Plants of 'TDr 131' derived from tissue culture were grown in a glasshouse simulating temperature and photoperiod at Ibadan (7 degrees N), Nigeria to produce tubers. Tubers were sampled on four occasions: 30 d before shoot senescence (149 days after planting, DAP), at shoot senescence (179 DAP), and twice during storage at a constant 25 degrees C (269 and 326 DAP). The development of the apical shoot bud was described from tissue sections. In addition, the responsiveness of shoot apical bud development to plant growth regulators (gibberellic acid, 2-chloroethanol and thiourea) applied to excised tuber sections was also examined 6 and 12 d after treatment.
Three phases of tuber dormancy are proposed: Phase I, from tuber initiation to the appearance of the tuber germinating meristem; Phase II, from the tuber germinating meristem to initiation of foliar primordium; and Phase III, from foliar primordium to appearance of the shoot bud on the surface of the tuber. Phase I is the longest phase (approx. 220 d in 'TDr 131'), is not affected by PGRs and is proposed to be an endo-dormant phase. Phases II and III are shorter (<70 d in total), are influenced by PGRs and environmental conditions, and are therefore endo-/eco-dormant phases. To manipulate dormancy to allow off-season planting and more than one generation per year requires that the duration of Phase I is shortened.
山药（薯蓣属）块茎休眠的调控机制尚不清楚，缩短其较长休眠期（即促使块茎更早发芽或萌发）的尝试均未成功。本研究旨在确定并界定圆果薯蓣块茎的休眠阶段，并构建一个能更有效研究休眠的框架。
将源自组织培养的“TDr 131”植株种植于温室中，模拟尼日利亚伊巴丹（北纬7度）的温度和光周期以收获块茎。在四个时间点采集块茎样本：地上部分衰老前30天（种植后149天，DAP）、地上部分衰老时（179 DAP）以及在25℃恒温储存期间两次（269和326 DAP）。通过组织切片描述顶芽的发育情况。此外，在处理后6天和12天，还检测了施加于离体块茎切片上的植物生长调节剂（赤霉素、2 - 氯乙醇和硫脲）对顶芽发育的影响。
提出块茎休眠的三个阶段：第一阶段，从块茎形成到块茎发芽分生组织出现；第二阶段，从块茎发芽分生组织到叶原基开始形成；第三阶段，从叶原基到块茎表面出现芽。第一阶段是最长的阶段（“TDr 131”中约220天），不受植物生长调节剂影响，被认为是内休眠阶段。第二阶段和第三阶段较短（总共<70天），受植物生长调节剂和环境条件影响，因此是内休眠/生态休眠阶段。要调控休眠以实现非季节种植和每年多代种植，需要缩短第一阶段的持续时间。
