闭花受精

闭花受精是一种植物在关闭的花朵内完成自花授粉，并产生种子的有性繁殖方式^[1]。闭锁花（Cleistogamous Flower, CL）是闭花受精的关键，这类花朵不开放，授粉过程在花朵内部自发完成^[2]。闭花受精现象分布在50个科228个属的约693种植物中，常见于堇菜科、凤仙花科、禾本科、远志科以及豆科等植物类群^[3]。

毛葉黃堇（Viola pubescens）的（a）开放花与（b）闭锁花

分类

闭花受精植物通常分为以下三类^[2]：

• 完全闭花受精：所有花均为闭锁花，植物不产生开放花。
• 诱导闭花受精：在特定环境条件下诱发闭锁花的产生。
• 两型闭花受精（Dimorphic Cleistogamy）：同一植物在不同部位或不同时期同时产生闭锁花和开放花（Chasmogamous Flower, CH）。

闭锁花通常具有减少的花冠和雄蕊数量^[4]。相较于开放花鲜艳的花瓣和特殊气味，闭锁花花瓣发育不全或完全缺失，通常无色，且雄蕊数量减少，有时雄蕊退化为丝状或原基状^[5][6][7]。

假说

关于两型闭花受精现象，存在多种假说^[2]：

• 繁殖保障：闭锁花是一种应对开放花授粉失败的备份机制。在授粉不成功的情况下，闭锁花可以通过自交保障种子的生产，延长生长季节的有性生殖时间^{[8][9][10][11]}。

• 防止自交衰退：自交后若有害等位基因未能被清除，将增加群体遗传漂变与自交衰退的风险^[12][13]。闭锁花主要依靠自交繁殖，而开放花通过异交产生更多具遗传变异的后代，从而维持后代的遗传多样性，以适应环境变化^{[9][14][10][15]}。

• 能量分配：闭锁花的能量消耗较低，因为它们节省了产生更多花粉、蜜腺体与花瓣的成本；而开放花较大，通常具有吸引传粉昆虫的功能，因此需要更多能量^[10][16]。两型闭花受精可以通过不同花型的比例调整能量分配，以优化其生殖效益^{[9][17][18][19]}。

• 环境异质性：环境因素（如光周期、光强、温度、土壤营养和水分等）决定了闭锁花与开放花的产生，环境异质性促进了两种花型的分化与选择^{[6][20][21][15]}。

参考文献

1. Kuhn M. Bemerkungen über Vandellia und den Blüten dimorphismus. Bot. Zeitung. 1867, 25: 65–67.
2. Li, Qiaoxia; Li, Youlong; Li, Jigang; Chen, Chenlong; Sun, Kun. Effects of photoperiods on the development of chasmogamous and cleistogamous flowers in <i>Viola monbeigii</i> and <i>V. dissecta</i>. Biodiversity Science. 2024, 32 (6): 23484. doi:10.17520/biods.2023484.
3. Culley, Theresa M.; Klooster, Matthew R. The Cleistogamous Breeding System: A Review of Its Frequency, Evolution, and Ecology in Angiosperms. The Botanical Review. 2007-01, 73 (1): 1–30. doi:10.1663/0006-8101(2007)73[1:TCBSAR]2.0.CO;2.
4. Uphof, J. C. Th. Cleistogamic flowers. The Botanical Review. 1938-01, 4 (1): 21–49. doi:10.1007/BF02869833.
5. Wang, Yunjing; Ballard, Harvey E.; McNally, R. Ryan; Wyatt, Sarah E. Gibberellins are involved but not sufficient to trigger a shift between chasmogamous-cleistogamous flower types in Viola pubescens 1. The Journal of the Torrey Botanical Society. 2013-01, 140 (1): 1–8. doi:10.3159/TORREY-D-12-00044.1.
6. Li, Qiaoxia; Huo, Qingdi; Wang, Juan; Zhao, Jing; Sun, Kun; He, Chaoying. Expression of B-class MADS-box genes in response to variations in photoperiod is associated with chasmogamous and cleistogamous flower development in Viola philippica. BMC Plant Biology. 2016-12, 16 (1). doi:10.1186/s12870-016-0832-2.
7. Li, Q; Li, J; Zhang, L; Pan, C; Yang, N; Sun, K; He, C. Gibberellins are required for dimorphic flower development in Viola philippica.. Plant science : an international journal of experimental plant biology. 2021-02, 303: 110749. PMID 33487338. doi:10.1016/j.plantsci.2020.110749.
8. Le Corff, Josiane. Effects of light and nutrient availability on chasmogamy and cleistogamy in an understory tropical herb, Calathea micans (Marantaceae). American Journal of Botany. 1993-12, 80 (12): 1392–1399. doi:10.1002/j.1537-2197.1993.tb15383.x.
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12. Masuda, Michiko; Yahara, Tetsukazu; Maki, Masayuki. Evolution of floral dimorphism in a cleistogamous annual, Impatiens noli‐tangere L. occurring under different environmental conditions. Ecological Research. 2004-11, 19 (6): 571–580. doi:10.1111/j.1440-1703.2004.00673.x.
13. Ginwal, H. S. Inbreeding depression in Eucalyptus tereticornis Sm. due to cleistogamous flowering. New Forests. 2010-09, 40 (2): 205–212. doi:10.1007/s11056-010-9194-z.
14. Ansaldi, Beth H.; Weber, Jennifer J.; Goodwillie, Carol; Franks, Steven J. Low levels of inbreeding depression and enhanced fitness in cleistogamous progeny in the annual plant Triodanis perfoliata. Botany. 2019-07, 97 (7): 405–415. doi:10.1139/cjb-2019-0022.
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17. Parra-Tabla, V; Munguía-Rosas, M; Campos-Navarrete, MJ; Ramos-Zapata, JA. Effects of flower dimorphism and light environment on arbuscular mycorrhizal colonisation in a cleistogamous herb.. Plant biology (Stuttgart, Germany). 2015-01, 17 (1): 163–8. PMID 25077675. doi:10.1111/plb.12223.
18. Zhang, Li-Hui; Sun, Qi; Zhao, Ji-Min; Zhang, Yan-Wen. Plasticity in the reproductive strategy of a clonal cleistogamous species, Pseudostellaria heterophylla. Plant Ecology. 2018-12, 219 (12): 1493–1502. doi:10.1007/s11258-018-0896-1.
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21. Furukawa, T; Itagaki, T; Murakoshi, N; Sakai, S. Inherited dimorphism in cleistogamous flower production in Portulaca oleracea: a comparison of 16 populations growing under different environmental conditions.. Annals of botany. 2020-03-09, 125 (3): 423–431. PMID 31630158. doi:10.1093/aob/mcz167.