花形态和形态发生在喜树（蓝果树科）及其系统学意义。

Floral morphology and morphogenesis in Camptotheca (Nyssaceae), and its systematic significance.

机构信息

College of Life Sciences, Northwest A&F University, Yangling, China.

Herbarium of Northwest A&F University, Yangling, China.

出版信息

Ann Bot. 2018 Jun 8;121(7):1411-1425. doi: 10.1093/aob/mcy041.

DOI:10.1093/aob/mcy041

PMID:29584809

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC6007274/

Abstract

BACKGROUND AND AIMS

Camptotheca is endemic to China and there are limited data about the breeding system and morphogenesis of the flowers. Camptotheca is thought to be related to Nyssa and Davidia in Nyssaceae, which has sometimes been included in Cornaceae. However, molecular phylogenetic studies confirmed the inclusion of Camptotheca in Nyssaceae and its exclusion from Cornaceae. The aim of this study was to reveal developmental features of the inflorescence and flowers in Camptotheca to compare with related taxa in Cornales.

METHODS

Inflorescences and flowers of Camptotheca acuminata at all developmental stages were collected and studied with a scanning electron microscope and stereo microscope.

KEY RESULTS

Camptotheca has botryoids which are composed of several capitate floral units (FUs) that are initiated acropetally. On each FU, flowers are grouped in dyads that are initiated acropetally. All floral organs are initiated centripetally. Calyx lobes are restricted to five teeth. The hypanthium, with five toothed calyx lobes, is adnate to the ovary. The five petals are free and valvate. Ten stamens are inserted in two whorls around the central depression, in which the style is immersed. Three carpels are initiated independently but the ovary is syncarpous and unilocular. The ovule is unitegmic and heterotropous. Inflorescences are functionally andromonoecious varying with the position of the FUs on the inflorescence system. Flowers on the upper FU often have robust styles and fully developed ovules. Flowers on the lower FU have undeveloped styles and aborted ovules, and the flowers on the middle FU are transitional.

CONCLUSIONS

Camptotheca possesses several traits that unify it with Nyssa, Mastixia and Diplopanax. Inflorescence and floral characters support a close relationship with Nyssaceae and Mastixiaceae but a distant relationship with Cornus. Our results corroborate molecular inferences and support a separate family Nyssaceae.

摘要

背景和目的

喜树是中国特有的植物，有关其繁殖系统和花形态发生的资料有限。喜树被认为与蓝果树科的珙桐和伯乐树有关，而蓝果树科有时被归入山茱萸科。然而，分子系统发育研究证实，喜树属于蓝果树科，而不属于山茱萸科。本研究的目的是揭示喜树花序和花的发育特征，以便与Cornales 中的相关分类群进行比较。

方法

收集喜树全发育阶段的花序和花，并用扫描电子显微镜和立体显微镜进行研究。

主要结果

喜树具有头状的聚伞花序，由几个头状花单位（FU）组成，这些花单位从顶端开始发生。在每个 FU 上，花以头状的方式成对发生。所有的花器官都是从中心向四周发生的。萼片裂片限制为五个。具五齿的花萼与子房合生。五个花瓣是离生的，镊合状排列。十个雄蕊分两轮生于中央凹陷处，花柱沉浸其中。三个心皮独立发生，但子房合生且一室。胚珠为单珠被，异型。花序在功能上是雌雄同株的，随花序系统中 FU 的位置而变化。上部 FU 的花通常具有粗壮的花柱和完全发育的胚珠。下部 FU 的花具有未发育的花柱和败育的胚珠，而中部 FU 的花是过渡性的。