Department of Plant Sciences, University of California, Davis, CA 95616, USA.
Ann Bot. 2014 Feb;113(3):545-54. doi: 10.1093/aob/mct282. Epub 2013 Dec 15.
Shoot characteristics differ depending on the meristem tissue that they originate from and environmental conditions during their development. This study focused on the effects of plant water status on axillary meristem fate and flowering patterns along proleptic and epicormic shoots, as well as on shoot growth rates on 'Nonpareil' almond trees (Prunus dulcis). The aims were (1) to characterize the structural differences between proleptic and epicormic shoots, (2) to determine whether water deficits modify shoot structures differently depending on shoot type, and (3) to determine whether shoot structures are related to shoot growth rates.
A hidden semi-Markov model of the axillary meristem fate and number of flower buds per node was built for two shoot types growing on trees exposed to three plant water status treatments. The models segmented observed shoots into successive homogeneous zones, which were compared between treatments. Shoot growth rates were calculated from shoot extension measurements made during the growing season.
Proleptic shoots had seven successive homogeneous zones while epicormic shoots had five zones. Shoot structures were associated with changes in growth rate over the season. Water deficit (1) affected the occurrence and lengths of the first zones of proleptic shoots, but only the occurrence of the third zone was reduced in epicormic shoots; (2) had a minor effect on zone flowering patterns and did not modify shoot or zone composition of axillary meristem fates; and (3) reduced growth rates, although patterns over the season were similar among treatments.
Two meristem types, with different latency durations, produced shoots with different growth rates and distinct structures. Differences between shoot type structure responses to water deficit appeared to reflect their ontogenetic characteristics and/or resource availability for their development. Tree water deficit appeared to stimulate a more rapid progression through ontogenetic states.
芽的特征取决于其起源的分生组织和发育过程中的环境条件。本研究重点关注植物水分状况对腋芽命运和沿预枝和副梢的开花模式以及“Nonpareil”巴旦木（Prunus dulcis）树的侧枝生长速率的影响。目的是：（1）描述预枝和副梢之间的结构差异，（2）确定水分亏缺是否根据枝型不同而对枝结构产生不同的影响，以及（3）确定枝结构与枝生长速率之间的关系。
为在暴露于三种植物水分状况处理的树上生长的两种枝型构建了腋芽命运和每个节位花数的隐式半马尔可夫模型。该模型将观察到的枝分段成连续的同质区，然后在处理之间进行比较。从生长季节的枝延伸测量中计算出枝生长速率。
预枝有七个连续的同质区，而副梢有五个区。枝结构与整个季节的生长速率变化有关。水分亏缺（1）影响预枝第一区的发生和长度，但仅减少了副梢第三区的发生；（2）对区开花模式的影响较小，不改变侧芽分生组织命运的枝或区组成；（3）降低了生长速率，尽管各处理之间的季节模式相似。
两种具有不同潜伏期的分生组织类型产生的枝具有不同的生长速率和不同的结构。枝型结构对水分亏缺的反应差异似乎反映了它们的个体发生特征和/或发育所需的资源可用性。树木水分亏缺似乎刺激了更快速地通过个体发生状态的进展。
