野牡丹异型雄蕊的功能分化

doi:10.3724/SP.J.1003.2009.08317

摘要/Abstract

摘要：

野牡丹科植物具有形态、大小和颜色显著不同的两种异型雄蕊。关于其异型雄蕊是否具有功能分化还一直存在争论。本文以野牡丹科植物野牡丹(Melastoma malabathricum)为实验材料, 比较了两种异型雄蕊在传粉过程中的功能作用。结果表明, 两种异型雄蕊在形态、花粉量和人工控制实验条件下的结籽数, 以及主要传粉昆虫木蜂(Xylocopa sp.)访花时的行为等方面都有显著差异, 说明两种雄蕊在传粉过程中存在一定的功能分化: 外轮紫色雄蕊中的花粉为后代提供雄配子, 而内轮黄色雄蕊中的花粉则为传粉昆虫提供食物。但两种雄蕊在花粉活性、花粉组织化学成分和结实率方面差异均不显著, 表明两者在生理上并没有分化。实验结果还表明, 除花前套袋不结实外, 自交、异交和自然对照都具有较高的结实率, 说明野牡丹不存在无融合生殖和主动自交及自交不亲和现象, 为兼性异交。

关键词: Melastoma malabathricum, 花部形态, 花粉, 传粉, 繁育系统

Abstract

Heteranthery in flowers has often been explained by Darwin’s ‘division-of-labor’ hypothesis. In order to test the hypothesis, we examined pollination pattern and the roles of two dimorphism stamens in pollination in Melastoma malabathricum; this species contains two sets of stamens differing markedly in shape, size and color. We found differences in morphological characters, numbers of pollen grains, seed sets following experimental treatments, with stamens removed and pollinator behaviour between the two types of stamen. The anther of purple stamens contained more pollen grains than that of yellow stamens. Carpenter bees (genus species) alighted only on the yellow stamens, and grasped their five anthers. Flowers that had their yellow stamens removed set significantly fewer seeds than intact flowers. There was no difference in the seed set of flowers with purple stamens removed and intact flowers. These results suggest that the yellow anthers function to attract pollinators and satisfy the insects’ demand for pollen, and the purple anthers satisfy plant’s need for safe gamete dispersal. However, there were no differences in pollen viability, histochemistry, or fruit set between anther type, suggesting the lack of physiological differentiation. Our experimental manipulations also demonstrate the absence of self-pollination and agamospermy in Melastoma malabathricum, and that the breeding system is facultative xenogamy.

Key words: Melastoma malabathricum, floral morphology, pollen, pollination, breeding system

路国辉, 武文华, 王瑞珍, 李新亮, 王英强 (2009) 野牡丹异型雄蕊的功能分化. 生物多样性, 17, 174-181. DOI: 10.3724/SP.J.1003.2009.08317.

Guohui Lu, Wenhua Wu, Ruizhen Wang, Xinliang Li, Yingqiang Wang (2009) Division of labor of heteromorphic stamens in Melastoma malabathricum. Biodiversity Science, 17, 174-181. DOI: 10.3724/SP.J.1003.2009.08317.

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链接本文: https://www.biodiversity-science.net/CN/10.3724/SP.J.1003.2009.08317

https://www.biodiversity-science.net/CN/Y2009/V17/I2/174

图/表 7

图1 野牡丹的花和访花昆虫。(A)野牡丹的花; (B)木蜂访花采食花粉; (C)食蚜蝇采食黄色花药的花粉; (D)食蚜蝇采食紫色花药的花粉; (E)青条花蜂采食紫色花药的花粉; (F)青条花蜂采食黄色花药的花粉; (G)甲虫访花; (H)蝇类访花; (I)草蜢访花。

Fig. 1 Flowers and the flower visitors in Melastoma malabathricum. (A) A flower of M. malabathricum; (B) A carpenter bee foraging on a flower; (C) A syrphus fly foraging on the yellow anther; (D) A syrphus fly foraging on the purple anther; (E) A blue-banded bee foraging on the purple anther; (F) A blue-banded bee foraging on the yellow anther; (G) A dung beetle and a long-horned beetle visiting a flower; (H) A fly visiting a flower; (I) A grasshopper visiting a flower.

表1 野牡丹两种雄蕊的特征及花粉组织化学成分比较(平均值 ± 标准差)

Table 1 Stamen characters and pollen histochemistry of Melastoma malabathricum (mean ± SD)

雄蕊 Stamens	花药颜色 Anther color	药隔附属物 Elongated connective	花丝长度 Filament length (cm)	花粉囊长度 Anther length (cm)	花粉组织化学 Pollen histochemistry
雄蕊 Stamens	花药颜色 Anther color	药隔附属物 Elongated connective	花丝长度 Filament length (cm)	花粉囊长度 Anther length (cm)	淀粉 Starch	脂质 Lipid
外轮雄蕊 Outer stamens	紫色 Purple	紫色, 弓形弯曲 Purple, curved	1.21 ± 0.08^a	0.90 ± 0.12^a	+	+
内轮雄蕊 Inner stamens	黄色 Yellow	无 Absent	0.92 ± 0.09^b	0.82 ± 0.08^b	+	+

图2 野牡丹的花粉活性和柱头可受性

Fig. 2 Pollen viability and stigma acceptability in Melastoma malabathricum

表2 野牡丹两种雄蕊的单花花粉量、胚珠数量及花粉/胚珠比率(平均值 ± 标准差)

Table 2 Pollen grain numbers, ovule numbers and P/ O ratios of Melastoma malabathricum (mean ± SD)

雄蕊 Stamens	单个雄蕊的花粉数 Pollen grain number per stamen	单花花粉数 Pollen grain number per flower	胚珠数 Ovule number per flower	花粉/胚珠比 P/O ratios per flower
外轮紫色雄蕊 Outer purple stamens	191,590 ± 43,371^a	1,619,300 ± 348,578	1,904 ± 239	863.40 ± 217.57
内轮黄色雄蕊 Inner yellow stamens	132,270 ± 29,864^b	1,619,300 ± 348,578	1,904 ± 239	863.40 ± 217.57

图3 木蜂的访花频率 (平均值 ± 标准差)

Fig. 3 Visiting frequency of Xylocopa sp. to Melastoma malabathricum flowers (mean ± SD)

表3 不同授粉处理的结实率比较(平均值 ± 标准差)

Table 3 Fruit sets following different experimental pollination treatments in Melastoma malabathricum (mean ± SD)

处理 Treatments	处理花数(株数) No. of flowers (No. of stems)	结实率 Fruit sets (%)
自然对照 Open pollination	93 (8)	64.02 ± 23.96^a
黄色花药花粉自交 Experimentally selfed by pollen of yellow anthers	16 (9)	66.67 ± 43.30^a
黄色花药花粉异交 Experimentally out-crossed by pollen of yellow anthers	30 (15)	75.56 ± 33.25^a
紫色花药花粉自交 Experimentally selfed by pollen of purple anthers	46 (15)	78.23 ± 29.83^a
紫色花药花粉异交 Experimentally out-crossed by pollen of purple anthers	49(19)	73.68 ± 38.11^a
花前套袋 Bagged flowers	52 (4)	0^b

表4 野牡丹不同处理的结实率和结籽率比较(平均值 ± 标准差)

Table 4 Fruit sets and seed sets following different experimental treatments in Melastoma malabathricum (mean ± SD)

处理 Treatments	结实率 Fruit sets (N)	结籽数 No. of seeds per fruit (n)
自然对照 Open pollination	64.02 ± 23.96^a (93)	548.11 ± 174.90^a(27)
去黄色雄蕊 Yellow stamens removed	78.57 ± 36.60^a (19)	336.92 ± 234.42^c(13)
去紫色雄蕊 Purple stamens removed	86.11 ± 33.21^a (23)	660.64 ± 247.21^a(14)
去全部雄蕊 All stamens removed	60.61 ± 41.68^a(29)	384.76 ± 305.63^bc(17)
去花瓣 Petals removed	78.89 ± 34.34^a (37)	512.89 ± 258.06^ab(28)

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