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林业科学 ›› 2022, Vol. 58 ›› Issue (6): 47-55.doi: 10.11707/j.1001-7488.20220605

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濒危植物血皮槭花部特征和交配系统

孙佳伟,郑勇奇,于雪丹,夏新合,赵玉贤,武宇霞,张川红*   

  1. 林木遗传育种国家重点实验室 国家林业和草原局林木培育重点实验室 中国林业科学研究院林业研究所 北京 100091
  • 收稿日期:2021-07-19 出版日期:2022-06-25 发布日期:2022-09-24
  • 通讯作者: 张川红
  • 基金资助:
    中央级公益性科研院所基本科研业务费专项资金(CAFYBB2016MA001)

Floral Traits and Mating System of Endangered Species Acer griseum

Jiawei Sun,Yongqi Zheng,Xuedan Yu,Xinhe Xia,Yuxian Zhao,Yuxia Wu,Chuanhong Zhang*   

  1. State Key Laboratory of Tree Genetics and Breeding Key Laboratory of Tree Breeding and Cultivation, National Forestry and Grassland Administration Research Institute of Forestry, CAF Beijing 100091
  • Received:2021-07-19 Online:2022-06-25 Published:2022-09-24
  • Contact: Chuanhong Zhang

摘要:

目的: 探究我国特有濒危植物血皮槭花部特征和交配系统类型对有性生殖过程的影响, 寻找可能导致其结实率低的原因, 为缓解当前苗木供需矛盾、制定有效措施奠定理论基础。方法: 以血皮槭植人工栽培植株为材料, 通过物候观测、花形态特征测量、异交指数和花粉-胚珠比估算、花粉生活力和柱头可授性检测和人工授粉研究对象套袋试验等方法, 对血皮槭的开花动态、花部特征和交配系统进行研究。结果: 1) 血皮槭花性别表达复杂, 花基于功能可分为雄花和雌花2类; 其中雄花根据雌蕊退化程度又分为雄花Ⅰ型和雄花Ⅱ型。雄花Ⅰ型仅具有雄蕊, 雄花Ⅱ型具有雄蕊和退化雌蕊, 雄蕊长于雌蕊, 二者皆不具子房, 功能均表现为雄性。雄花Ⅰ型和Ⅱ型大小无差别, Ⅰ型较常见, Ⅱ型较少见。雌花为假两性花, 柱头高于花药, 花柱具卷曲现象, 花开放过程中花药始终不开裂散粉, 为功能雌性。2)血皮槭单花经历花蕾期、萌动期、露白期、开放期、凋零期5个阶段, 雄花从开放到脱落平均耗时7.6天, 雌花从开放到坐果(花期结束)平均耗时11.6天。常3小花组成1个聚伞花序, 由雄花和雌花组成的混合类型花序中, 通常表现为雌花先熟。3) 血皮槭每年开花1次, 花期4月, 开花历时19.5天左右。单株树表现为雌花先熟或雄花先熟, 时间有所交叉。单株树雌花数量多于雄花, 二者比例平均约为3.71∶1。4) 花粉生活力的持续时间较短, 花粉在室温干燥条件下保存, 24 h内生活力最高为63.86%±5.35%, 24 h后降至1.03%±0.13%, 近乎完全丧失生活力; 雌花柱头在露白期伸出花冠外且具有可授性, 雌花完全盛开时可授性最强, 可授性贯穿整个开放进程。柱头可授期内雄花花粉具有生活力。5) 雄花单花花粉量为45 900~58 900个, 雌花单花胚珠为4, 按照单株雌雄花比例计算花粉胚珠比为3 093~3 969, 异交指数为4, 结合人工授粉和套袋试验结果判断, 血皮槭交配系统属兼性异交, 部分自交亲和, 需要传粉者, 存在强烈单性结实现象。结论: 血皮槭花功能单性, 雌雄异花同株, 不完全雌雄异熟, 交配系统兼性异交, 传粉效率低下, 单性结实倾向强烈, 这些是导致其结实率低的重要原因。

关键词: 血皮槭, 花部特征, 交配系统, 性别表达, 单性结实

Abstract:

Objective: This study aims to explore the impact of flower traits and mating system on sexual reproduction of Acer griseum, an endangered species endemic in China, by investigating the possible causes of low seed setting rate. This study would lay a theoretical foundation for formulating effective measures to improve sexual reproduction, in order to alleviate the current contradiction between supply and demand of seedlings. Method: In this study, the cultivated A. griseum was targeted, and the flowering dynamics, floral traits and mating system were investigated through phenological observation, flower morphological characteristics determination, calculation of outcrossing index (OCI) and pollen-ovule ratio (P/O), and determination of pollen vitality and stigma receptivity. An artificial pollination and bagging experiment was carried out to explore the mating system. Result: 1) The sex expression of A. griseum florets was complicated and the florets were divided into two types based on their functions: male floret and female floret. Male florets were divided into male floret type Ⅰ and male floret type Ⅱ according to the degree of pistil degeneration. The male floret I only had stamens, while male floret Ⅱ had stamens and vestigial pistil. The length of stamens was much longer than that of the pistils. They were both male due to lack of ovary. Female florets were pseudohermaphrodite. The stigmas were longer than those of the anthers. Throughout the opening process, the stigmas were able to make curving movement, while the anthers were not dehiscent and did not release pollens. 2) The flowering process for one floret could be divided into five periods: bud stage, budding, anther or stigma appearing, blooming and withering. It took an averaged time of 7.6 days for male florets from opening to shedding, while the averaged time for female flowers from opening to fruiting was 11.6 days. The cyme usually consisted of three florets. In the inflorescences that were composed of male and female florets, the female florets usually bloomed earlier than male florets. 3) A. griseum bloomed once a year in April. Generally, the flowering lasted about 19.5 days. Protandry and protogyny coexisted for an individual tree and there was a certain overlapping time for the opening of male florets and female florets. The number of female florets was more than that of male flowers on an individual tree with the mean ratio of about 3.71∶1. 4) The duration of pollen viability was relatively short. When the pollen was stored at room temperature and dry, the maximum viability of pollens reached 63.86%±5.35% within 24 hours and then decreased to 1.03%±0.13% after 24 hours, almost losing viability. It indicated that pollens could keep their viability for a short time at room temperature. The stigma of female florets became receptive when it was out of the corolla before florets blooming. The receptivity of stigma reached its highest at full open and maintained throughout the entire opening process of female floret. Male flower pollens had viability during stigma fertile period of female florets. 5) There were 45 900-58 900 pollens for each male floret and 4 ovules of each female floret. The P/O was 3 093-3 969 based on the ratio of male and female floret per plant, and the OCI was 4. Combining the results of artificial pollination, mating system of A. griseum was facultative outcrossing and partially self-compatible, thus pollinators were necessary for the pollination process. Acer griseum showed a strong parthenocarpic tendency. Conclusion: The flower of A. griseum is functionally unisexual, monoecious and incomplete dichogamous. Its mating system is facultative outcrossing with low pollination efficiency. It shows strong parthenocarpy tendency. All the above traits are the important reasons for its low seed setting rate.

Key words: Acer griseum, floral traits, mating system, sexual expression, parthenocarpy

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