以阶段观剖视荔枝的花芽分化

以阶段观剖视荔枝的花芽分化,重新审视了相关研究资料,对影响成花的关键因子作了阐释,廓清了一些概念性问题。引进了俗称的“白点”(拟改称“白小米粒”)作为“成花诱导期”和“花穗发端发育期”的分界标识。指出水分胁迫对于秋梢的停止生长和成熟是必需的,但对于花诱导本身则非所必需,因为尚无证据可证明干旱能够代替荔枝的低温成花诱导。荔枝成花诱导期需要低温,而花穗发端发育期则需要适度升温和水分。低温的成花诱导的效果不会被随后的水分增多所逆转。茎端感受诱导性低温时处于非细胞分裂的“静止”状态,而“白小米粒”的出现标志着茎端进入了细胞分裂的活跃状态。充分成熟的秋梢接受成花诱导的效果最佳,但未充分成熟的秋梢上处于“静止”状态的芽也可以感受诱导性低温,只是抽发的带叶花穗率往往较高。花穗发端发育期气温过高会导致花穗上叶原基的进一步发育成叶片和花序原基的萎缩,即俗称的“冲梢”。若诱导期经受的低温不足,则此情况会更甚。

A Phasic Approach Towards the Floral Formation in Litchi chinensis Sonn

This paper discusses the current knowledge on floral formation in litchi ,clarifying some crucial issues and con-ceptual controversies.The sequence of floral formation in litchi exhibits obvious phase changes and different requirements.Cease-growth brought on by moisture stress is the prerequisite for shoot maturation and the ensuing floral induction under chilling temperatures.The amount of chilling required for floral induction varies among cultivars.Chilling,which appears as a continuous spell,is more effective than that appears in a scattered manner.No evidence so far that soil moisture stress can replace chilling over the induction process.The chill-induction effect cannot be reversed by soil moisture increase after the beginning of floral initiation in the late winter.Floral induction occurs when the apex meristem is in a quiescent stage whereas floral initiation starts from the“millet stage”when cell division in the apex meristem becomes active.The newly introduced notion of“whitish millet”symbolizes the“demarcation”separating floral induction and floral initiation.The slow growing buds in the leaf axils appearing as“whitish millets”have acquired the potential for further differentiating and developing into flowering panicles under gradually ascending air temperatures and moderate moisture.Exposing litchi plants to excessively high temperatures during panicle differentiation will cause the leaves on the panicles to develop and flowers to atrophy,es-pecially when induction phase has been suspended with insufficient exposure to chilling temperatures.