Megasporogenesis, Microsporogenesis and Development of Male and Female Gametophytes of Clematis heracleifolia

doi:10.11983/CBB18261

Abstract

Abstract: In Clematis (Ranunculaceae) species show significant differences in floral morphology and structures, consistent with their complex genetic background. Thus, it is important to study the embryological characteristics prior to any attempts of breeding by hybridization. Here, we report the characterization of microsporogenesis, microgametogenesis, megasporogenesis and macrogametogenesis of Clematis heracleifolia by floral dissection. We show that C. heracleifolia is androdioecy. Aborted microgametophyte cells are observed in the majority of bisexual flowers but occasionally found in male flowers, which results in the formation of functional female flowers. However, in a small number of normal bisexual flowers, male gametophytes mature faster than that of female gametophytes. During microsporogenesis, the tetrasporangiate anther is formed, followed by simultaneous microsporocyte cytokinesis, and the formation of glandular tapetum, occasionally with amoeboid tapetum. After meiosis, the microspores tetrads are mostly tetrahedral, and occasionally symmetrical. The wall of mature anther contains fibrous thickening epidermis and endothecium. Pollen grains are spheroidal, pantocolpate, and 2-celled. The ovary has one chamber with a normal and a few degraded ovules, which contains a anatropous, unitegmic, tenuinucellate, and Polygonum-type embryo-sac. A linear tetrad of megaspores and dikaryocyte antipodal cells can be observed. This species may belong to a transitional clade within Clematis. In breeding practice for C. heracleifolia, it is advised to use plants bearing male flowers and hermaphrodite flowers as male and female parents, respectivley, with the bisexual flowers of 0.5-0.8-cm-long to be emasculated.

Key words: Clematis heracleifolia, Clematis, gametophyte, Ranunculaceae, sporophyte

Yi Yang,Na Wang,Kuiling Wang,Qinghua Liu,Wei Li,Xiao Guo,Yingjie Ma,Qingchao Liu. Megasporogenesis, Microsporogenesis and Development of Male and Female Gametophytes of Clematis heracleifolia[J]. Chinese Bulletin of Botany, 2019, 54(5): 596-605.

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URL: https://www.chinbullbotany.com/EN/10.11983/CBB18261

https://www.chinbullbotany.com/EN/Y2019/V54/I5/596

Figures/Tables 9

Figure 1 The floral structure of Clematis heracleifolia Staminate flower; (B) Bisexual flower. Bars=5 mm

Figure 2 Microspore development in staminat e flower of Clematis heracleifolia (A) Archesporial cell (arrow, up), primary parietal cell (arrow, up) and primary sporogenous cell (arrow, down); (B) Anther wall; (C1) A row of secondary sporogenous cells; (C2) Prophase (arrow); (C3) Metaphase (arrow, right) and anaphase (arrow, left); (C4) Telophase (arrow); (D) Microspore mother cells; (E1) Microspore mother cells at prophase of prophase I of meiosis; (E2) Microspore mother cells at metaphase of meiosis I (arrow); (E3) Microspore mother cells at anaphase (arrow, right) and telophase (arrow, left) of meiosis I; (F1) Microspore mother cells at anaphase of meiosis II (arrow, left) and amoeboid tapetum (arrow, right); (F2) Microspore mother cells at telophase of meiosis II (arrow) and symmetrical microspore tetrads; (G) Degrading tetrahedral tetrad; (H) The asynchronous phases; (I1)-(I4) Aborted microspores. Bars=50 μm

Figure 3 Microgametophyte development in staminate flower of Clematis heracleifolia (A) Microspore at monokaryotic stage; (B) Microspore at monokaryotic side stage; (C1) Microspore at prophase (arrow); (C2) Microspore at metaphase (arrow, down) and anaphase (arrow, up); (C3) Microspore at anaphase (arrow); (C4) Microspore at telophase, vegetative cell and germ cell are formed (arrow); (D) The dehiscent anther, and the 2-celled mature pollen grains. (A), (B), (C1), (D) Bars=50 μm; (C2)-(C4) Bars=20 μm

Figure 4 Microspore and pollen grain development in bisexual flower of Clematis heracleifolia (A)-(D) Aborted microspore mother cells; (E), (F) Some aborted microspore mother cells; (G), (H) Normal pollen grains. an: Anther; ov: Ovary. (A), (C), (G) Bars=500 μm; (B), (F) Bars=50 μm; (D), (E), (H) Bars=200 μm

Table 1 Pollen characteristics of Clematis heracleifolia

Characters	State
Shape	Spheroidal
Type of aperture	Pantocolpate
Diameter (μm)	16.09±0.88
Spinule height (μm)	0.46±0.09
Number of spinules (3×3 μm²)	3.80±1.08

Figure 5 Scanning electron microscopy views of pollen grains of Clematis heracleifolia (A) Bar=10 μm; (B)-(D) Bars=1 μm

Figure 6 Megaspore and megagametophyte development in bisexual flower of Clematis heracleifolia (A), (B) The ovary and ovule; (C) Archesporial cells (arrow); (D) Megaspore mother cells (arrow); (E) A linear tetrad of megaspores (arrows); (F) The three endostome megaspores were degenerated and the chalazal one was a functional megaspore (arrows); (G) Binucleate embryo sac; (H) Tetranucleate embryo sac; (I) Embryo sac with 8 nuclei; (J)-(L) Mature embryo sac of seven-cell with eight nuclei. ac: Antipodal cell; cc: Central nucleus; ec: Egg cell; sy: Synergids. (A), (B) Bars=200 μm; (C)-(L) Bars=50 μm

Table 2 Relationship between gametophytes development and flower bud morphology in staminate flower of Clematis heracleifolia

Bud length (cm)	Stamen length (cm)	Male gametophyte
0.22-0.40	0.15-0.31	Microsporocyte, meiosis
0.40-0.85	0.31-0.51	Meiosis, microspore
0.85-1.09	0.51-0.86	Microspore, monokaryotic side stage, mitosis
1.09-1.39	0.86-1.12	Mitosis, 2-celled pollen
1.39-2.14	1.12-1.32	2-celled pollen

Table 3 Relationship between gametophytes development and flower bud morphology in bisexual flower of Clematis heracleifolia

Bud length (cm)	Stamen length (cm)	Pistil length (cm)	Male gametophyte	Female gametophyte
0.16-0.36	0.10-0.14	0.05-0.11	Microsporocyte, meiosis, microspore	-
0.36-0.50	0.14-0.34	0.10-0.18	Microspore monokaryotic side stage, mitosis	Archesporium, megasporocyte
0.50-0.88	0.34-0.48	0.18-0.21	Mitosis, 2-celled pollen	Megasporocyte, uninucleate embryo sac
0.88-0.95	0.48-0.52	0.21-0.30	2-celled pollen	Uninucleate embryo sac, 2-nucleate or 4-nucleate embryo sac
0.95-1.42	0.52-0.60	0.30-0.42	2-celled pollen	4-nucleate or 8-nucleate embryo sac, mature embryo sac

References 24

1	管开云, 李志坚, 李景秀, 匡建 (2002). 铁线莲属植物的引种栽培研究初报. 植物分类与资源学报 24, 392-396.
2	李杨, 张伟, 赫雪锋, 汤海峰 (2018). 铁线莲属植物的化学成分及药理作用研究进展. 中南药学 16, 355-362.
3	刘萍 (2006). 铁筷子(毛茛科) 的形态、结构、发育及系统位置的研究. 硕士论文. 西安: 陕西师范大学. pp. 15-35.
4	刘庆超, 王奎玲, 卢婉佩, 刘庆华 (2014). 我国铁线莲属植物资源研究进展. 植物遗传资源学报 15, 483-490, 497.
5	全雪丽, 刘继生, 吴松权 (2012). 棉团铁线莲小孢子发生和雄配子体的形成. 辽宁林业科技(1), 9-10, 32.
6	宋春慧 (2006). 黄三七属(毛茛科) 植物的形态、结构、发育及系统位置研究. 硕士论文. 西安: 陕西师范大学. pp. 25.
7	宋萍 (2007). 金莲花属和驴蹄草属(毛茛科)的比较形态学研究——基于形态、结构、花发育及胚胎学的证据. 硕士论文. 西安: 陕西师范大学. pp. 11-18.
8	孙诚, 谢磊, 李良千 (2007). 铁线莲属尾叶铁线莲组(毛茛科)基于形态学证据的分支系统学. 植物学通报 24, 87-98.
9	王玖瑞, 刘玲, 刘孟军, 周俊义 (2006). 枣树雄性不育新种质的获得. 园艺学报 33, 374-377.
10	王娜, 王奎玲, 刘庆华, 刘庆超 (2017). 七种野生铁线莲属植物核型分析. 草业学报 26(11), 123-130.
11	王述彬, 罗向东, 戴亮芳, 钱春桃, 陈劲枫 (2004). 辣(甜)椒细胞质雄性不育系减数分裂和雄配子发生过程. 园艺学报 31, 807-810.
12	王文采, 李良千 (2005). 铁线莲属一新分类系统. 植物分类学报 43, 431-488.
13	王永周, 古松, 江莎, 任艳萍, 许珂, 李清河 (2008). 臭椿雄蕊的发育和雄配子体的形成. 园艺学报 35, 577-586.
14	王自芬 (2008). 毛茛科植物胚珠形态、结构、发育及其系统学意义. 博士论文. 西安: 陕西师范大学. pp. 25.
15	杨艺, 王娜, 马颖杰, 王奎玲, 刘庆华, 刘庆超 (2018). 4种铁线莲属植物种子萌发特性. 草业科学 35, 2395-2402.
16	杨艺, 王娜, 王奎玲, 刘庆华, 刘庆超 (2019). 铁线莲属4种植物的花芽分化研究. 园艺学报 46, 87-95.
17	张阿娟 (2006). 类叶升麻(毛茛科) 形态结构、发育及系统位置的研究. 硕士论文. 西安: 陕西师范大学. pp. 14-27.
18	张克中, 赵祥云, 梁励, 黄善武, 张启翔 (2003). 王百合雄性不育突变体小孢子败育的细胞学研究. 北京林业大学学报 25(3), 124-126.
19	张敏涛, 张荻, 申晓辉 (2016). ‘东方晨曲’铁线莲小孢子发生和雄配子体发育进程的解剖学研究. 西北植物学报 36, 2213-2219.
20	张燕, 黎斌, 李思锋 (2010). 铁线莲属植物分类学及园艺学研究进展. 中国野生植物资源 29(5), 6-10.
21	赵桦, 孟华菊, 徐娟 (2011). 七叶树小孢子发生及雄配子体发育研究. 西北植物学报 31, 217-222.
22	Bhandari NN (1968). Studies in the family Ranunculaceae. X. Embryology of Anemone L. Phytomorphology 18, 487-497.
23	Xie L, Li LQ (2012). Variation of pollen morphology, and its implications in the phylogeny of Clematis(Ranunculaceae). Plant Syst Evol 298, 1437-1453.
24	Zhang Q, Hao Q, Guo X, Liu QC, Sun YK, Liu QH, Wang KL (2017). Anther and ovule development in Camellia japonica(Naidong) in relation to winter dormancy: climatic evolution considerations. Flora 233, 127-139.