林业科学  2016, Vol. 52 Issue (3): 112-120   PDF    
DOI: 10.11707/j.1001-7488.20160314
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文章信息

郭红艳, 王森, 晏巢, 张震, 黄雯
Guo Hongyan, Wang Sen, Yan Chao, Zhang Zhen, Huang Wen
华中五味子的雄花特征与花粉特性
Characteristics of Male Flower and Its Pollen of Schisandra sphenanthera
林业科学, 2016, 52(3): 112-120
Scientia Silvae Sinicae, 2016, 52(3): 112-120.
DOI: 10.11707/j.1001-7488.20160314

文章历史

收稿日期:2015-04-14
修回日期:2015-09-14

作者相关文章

郭红艳
王森
晏巢
张震
黄雯

华中五味子的雄花特征与花粉特性
郭红艳1, 王森1, 晏巢2, 张震1, 黄雯1    
1. 中南林业科技大学经济林培育与保护教育部重点实验室经济林育种与栽培国家林业局重点实验室 长沙 410004;
2. 中国林业科学研究院亚热带林业实验中心 分宜 336600
摘要:【目的】通过对华中五味子雄花特征及花粉特性的研究,旨在为华中五味子的传粉生物学研究、系统分类提供参考。【方法】采用体视显微镜和扫描电子显微镜(SEM)对华中五味子雄花不同发育时期(Ⅰ花蕾膨大期、Ⅱ花瓣松动期、Ⅲ花瓣开放期、Ⅳ完全开放期)的花部特征、花粉形态进行研究;利用生物光学显微镜,采用琼脂固体培养基法(培养基中琼脂浓度均为10 g ·L-1,蔗糖浓度梯度设置为50,100,150,200 g ·L-1,硼酸浓度梯度设置为0.10,0.15,0.30 g ·L-1)对花粉离体萌发特性进行研究。【结果】华中五味子蔷薇花冠,成熟时花冠朝向地面,花瓣覆瓦状排列,花瓣内外侧均具不规则纹饰,具气孔,气孔不规则分布;花柄圆柱形,外壁不光滑,具气孔,气孔椭圆形;雄蕊螺旋向上着生于柱状花托上,花丝缩短呈肉质,花药着生于花丝上;雄蕊群呈伞状,雄蕊19~22(26)。花粉扁球形,辐射对称,极观面为6裂圆形,异极,随着花朵的发育,逐渐形成6萌发沟,3长沟在一极形成合沟,3短沟不到极面,长短沟相间排列;花粉外壁具网状雕纹,网眼大小和网脊宽度不一,少数网眼中具模糊颗粒,随着花粉的发育,网眼逐渐加深,网脊变薄,颗粒物被吸收;Ⅰ(花蕾膨大期)、Ⅱ(花瓣松动期)、Ⅲ(花瓣开放期)、Ⅳ(完全开放期)时期花粉直径依次为21.96,23.73,24.00,25.65 μm。成熟华中五味子花粉在10 g ·L-1琼脂+100 g ·L-1蔗糖+0.10 g ·L-1硼酸的培养基中,萌发率最高,达到92.6%,花粉管长度最长,达454.30 μm;蔗糖浓度对花粉萌发率和花粉管伸长生长存在极显著影响,硼酸浓度对花粉的萌发率影响显著,但对花粉管长度生长影响不显著。【结论】华中五味子花冠形态、花粉形态既具有虫媒传粉特征,亦具有风媒传粉的特点;研究结果认为华中五味子为风媒、虫媒同时传粉植物,主要传粉方式、传粉途径有待进一步研究;华中五味子花粉离体培养的最佳固体培养基为10 g ·L-1琼脂+100 g ·L-1蔗糖+0.10 g ·L-1硼酸,培养基成分对花粉萌发影响显著;花粉萌发率高,在传粉受精过程中,花粉竞争优势明显。
关键词华中五味子    雄花    花粉形态    花粉萌发率    
Characteristics of Male Flower and Its Pollen of Schisandra sphenanthera
Guo Hongyan1, Wang Sen1, Yan Chao2, Zhang Zhen1, Huang Wen1     
1. Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees of Ministry of Education Key Laboratory of Non-Wood Forest Product of State Forestry Administration Central South University of Forestry and Technology Changsha 410004;
2. The Experimental Centre of Subtropical Forestry, Chinese Academy of Forestry Fenyi 336600
Abstract: [Objective] In order to provide a basis for studies of pollination biology and phylogenetic classification of Schisandra sphenanthera by investigating characteristics of the male flowers and their pollen. [Method] We studied the floral characteristics and pollen morphology of S. sphenanthera at different development stages including alabastrum intumescence stage, petals loose stage, petals opening stage and florescence stage using stereo microscope and scanning electron microscope (SEM). In vitro pollen germination of S. sphenanthera was studied using bio-optical microscope and solid agar as culture media containing 10 g·L-1 agar, and sucrose at concentrations of 50, 100, 150, 200 g·L-1 in order and boric acid at concentrations of 0.10, 0.15, 0.30 g·L-1 in order.[Result] The corolla of S. sphenanthera was rose-like and faced downwards the ground when it matured, the petals were arranged in imbrications. The inside and outside of the petals had irregular grains and irregular distribution of stomata, flower stalks were cylindrical and its outside surface was unsmooth with oblong stomata, stamens grew upwards spirally on the columnar receptacle, filaments were shortened to become fleshy and the anthers grew on it. The stamens were arranged in umbrella-form, with a number of 19-22 (26). The pollen was oblate and heteropolar, its polar view was 6-lobed circular, 6 germinal furrows was gradually formed with flower development, of which 3 long furrows joined together at one pole to form an integrated furrow and 3 short ones did not reach the poles, the long and short furrows were alternatively arranged. The extine of pollen had reticular formation with areoles and murus in different sizes, and unclear particles were contained in a few of the areoles. The areoles and the murus respectively became deepened and thinned, and the particles were absorbed with the development of pollen. The diameters at different stages of flower development were 21.96, 23.73, 24.00 and 25.65 μm, respectively. The highest germination rate of mature pollen was 92.6% when cultured in the medium of agar at a concentration of 10 g·L-1+sucrose at concentration of 100 g·L-1+boric acid at a concentration of 0.10 g·L-1, the pollen tubes could reach a length of 454.30 μm. The concentration of sucrose had extremely significant effects on pollen germination rate and elongation of pollen tubes, while the concentration of boric acid had significant effects on pollen germination rate, but not on elongation of pollen tubes.[Conclusion] The corolla form and the pollen morphology of S. sphenanthera had the typical characteristics of insect pollination and wind pollination. The results suggested that S. sphenanthera was not only animal-pollinated but also wind-pollinated, and further studies were needed to identify which was the main pollination model. The best solid media for in vitro pollen germination of S. sphenanthera was 10 g·L-1 agar+100 g·L-1 sucrose+0.10 g·L-1 boric acids, and the medium composition had a significant impact on the germination rate. The germination rate was high, indicating an obvious competitive advantage in pollination and fertilization.
Key words: Schisandra sphenanthera    male flower    pollen morphology    pollen germination rate    

华中五味子(Schisandra sphenanthera)为多年生落叶木质藤本植物(Saunders,2000中国科学院中国植物志编辑委员会,1996),属于国家三级重点保护野生药材(康廷国,2004庄红卫等,2013),被《中华人民共和国药典》(中国国家药典委员会,2010)收录。

花是植物繁育系统的重要组成部分,花部的特征既受植物遗传基因控制,也与其生长条件、传粉特性相适应(Wyatt,1983)。黄双全(2014)认为传粉特性是影响花冠形态的最有效因素,两者相辅相成;肖乐希等(2009)认为华凤仙(Impatiens chinensis)的花部特征与其蜂媒传粉密切相关;国内学者对花部特征与传粉特性之间的相关性研究较少,仅见王红等(2003)对马先蒿属(Pedicularis)花冠形态的研究,其认为传粉者的选择是影响花冠类型的重要因素,花冠形态与传粉式样存在紧密的协同进化关系。植物花粉特征是植物分类的重要依据之一,也是影响植物传粉的重要因子。李佐等(2015)对莲(Nelumbo nucifera)的研究认为不同种质间花粉形态特征具有差异,花粉形态特征可为种质间亲缘关系及系统发育研究提供依据;花粉竞争是影响植物传粉的又一重要因素,花粉竞争的强度与花粉启动萌发的时间、萌发速率、花粉管数量密切相关。目前,学者对五味子属(Schisandra)植物的传粉方式持不同观点(刘忠等,2001凌凤贵等,2005艾军,2007),而花部特征、花粉特性是影响传粉方式的关键因子之一,对其花部特征及萌发特性进行研究尤为必要。

河南伏牛山地区华中五味子花单性,雌雄异株,且目前大多处于野生状态,未实现人工栽培。本文通过体视镜、电子显微镜、扫描电镜对华中五味子雄花不同发育时期形态特征进行系统的观察,通过花粉离体萌发法对华中五味子的花粉活力进行检测,旨在为华中五味子的系统分类、传粉生物学研究提供依据。

1 材料与方法 1.1 试验地概况

华中五味子花采集于河南省栾川县伏牛山地区,地理坐标在 111°11′—112°01′E、33° 39′—34°11′N,海拔927 m,温带大陆性季风气候,年均气温12.1 ℃,年日照2 103 h,年均降水量862.8 mm;该地区有华北区系的植物、华中区系的植物和西南高寒区系的植物,土壤分为棕壤和褐土2大类。

1.2 试验材料

于2014年4—5月,采集不同发育时期的华中五味子雄株花枝,竖插于有适量水的桶中带回实验室。试验时,收集4个不同时期(Ⅰ花蕾膨大期、Ⅱ花瓣松动期、Ⅲ花瓣开放期、Ⅳ完全开放期)的花。余下的花枝置于室温下采用水培的方法等待花自然开放,取下刚开裂花药中的成熟花粉供试验用。

1.3 试验方法

1)华中五味子雄花形态观察使用QK-1536电子游标卡尺测量华中五味子不同发育时期雄花花柄的长度、花冠的纵横径、花托的长度和雄蕊长度。利用SMZ-168体视显微镜对华中五味子雄花花柄、萼片、花瓣、雄蕊群、花药进行形态观察。利用JFC-1600扫描电镜对华中五味子雄花不同发育时期的花药、花粉进行观察。观察的试验材料经2.5%的戊二醛固定24 h后,分别用PBS缓冲液、蒸馏水各清洗2次,再依次经不同浓度乙醇(体积比30%,50%,70%,100%)脱水,临界点干燥,喷金,备用。

2)花粉萌发试验试验均采用10 g ·L-1琼脂,蔗糖设置的浓度梯度为50,100,150,200 g ·L-1 ;硼酸设置的浓度梯度为0.10,0.15,0.30 g ·L-1;并设置空白对照(仅含10 g ·L-1琼脂)。配好培养基后,用移液管移取500 μL滴在载玻片上,稍冷却后将盖玻片覆于培养基表面,使培养基厚薄均匀,接近圆形。待培养基凝固后,均匀接种花粉,将接种完成的载玻片放在有湿润滤纸的培养皿中,置于培养箱25 ℃内培养8 h,在4×10倍的BA410型生物光学显微镜下观察花粉的萌发情况并进行统计。每个处理进行3次重复试验,花粉管长度超过花粉粒直径则视为萌发。计算公式:花粉萌发率(%)=(视野中萌发花粉数/视野中花粉总数)×100。

2 结果与分析 2.1 华中五味子雄花的花部特征

华中五味子雄花由花柄、花萼、花瓣、雄蕊组成。华中五味子雄花具单花萼(图 1A),花萼着生于花柄基部或中部,花柄圆柱形,表面不平整,具长圆棱状突起,存在少量气孔,气孔椭圆形(图 1B);蔷薇形花冠,花瓣覆瓦状排列(图 1C),花瓣内侧具气孔,气孔周围呈花状分布不规则脑纹状纹饰(图 1D),花瓣外侧也具有气孔,气孔无规律分布,气孔周围随机分布章鱼状光滑平台(图 1E),花瓣内外两侧气孔形状无明显差异,气孔打开时,开口边缘呈透明状,周围无规律分布颗粒状突起(图 1F);雄蕊群极观面圆形(图 1G),具肉质花顶,雄蕊反螺旋连续向上着生于肉质柱托型花托上,呈伞状(图 1H),雄蕊19~22(26)枚,肉质花丝;1枚雄蕊上对称着生2枚花药,花药全着药,药隔倒卵形,两药室向外倾斜,顶端分开,基部近邻接,药室内侧向开裂(图 1I),花粉镶嵌于花粉囊内(图 1J),成熟时散出;雄花成熟后,花粉散出,大量花粉散落于花瓣上(图 1KL)。

图 1 华中五味子雄花形态特征 Fig. 1 Features of male flower of S. sphenanthera A:华中五味子雄花花柄及萼片;B:花柄电镜扫描500倍;C:盛开期花冠;D:花瓣内侧电镜扫描500倍;E:花瓣外侧电镜扫描500倍;F:花瓣上的气孔,电镜扫描3 000倍;G:雄花雄蕊群;H:雄花雄蕊群电镜扫描500倍;I:雄花雄蕊;J:开裂的花药,电镜扫描500倍;K:成熟时花粉散落在花瓣上;L:散落在花瓣上的花粉,电镜扫描1 000倍。
A:The flower stalk and sepal of S. sphenanthera male flower; B: The flower stalk magnified 500 times by SEM; C: The corolla at florescence stage; D: The inside of the petals magnified 500 times; E: The outside of the petals magnified 500 times; F: The stomata of the petals magnified 3 000 times; G: The androecia of male flower; H: The androecia of male flower magnified 500 times; I: The androecium of male flower; J: The dehiscent anther magnified 500 times; K: The pollens fall on the petals; L: The pollens falling on the petals magnified 1 000 times.
2.2 华中五味子雄蕊及花粉形态

为了详细比较各个时期的雄花具体变化情况,对4个时期(Ⅰ花蕾膨大期、Ⅱ花瓣松动期、Ⅲ花瓣开放期、Ⅳ完全开放期)的华中五味子雄花的花瓣数量、花冠大小、雄蕊长宽厚、雄蕊群个数以及花柄长度进行观察与测量。研究结果表明,华中五味子雄花花瓣6~11个;花冠直径随着花蕾发育增长明显;雄花进入花瓣开放期,雄蕊发育成熟,开始散粉,散粉后,雄蕊失水,雄蕊长度变短,宽度变窄,厚度变薄;花柄随着雄花生长时间的增长而变长。雄花4个时期的形态特征见表 1

表 1 不同发育时期华中五味子雄花的形态特征 Tab.1 Characteristics of male flower of S.sphenanthera in four periods

通过扫描电镜的观察可以看出,4个不同时期的花粉粒的外形均为扁球形,辐射对称(表 2图 2)。从外壁纹饰来看,外壁具有网状雕纹,网眼形状不规则,大小不一,网脊宽度不一致。Ⅰ时期花瓣绿色,紧紧闭合(图 2Ⅰ),花粉镶嵌在花粉囊内(图 2Ⅰ-1),胼胝质累积形成,中层已被吸收,绒毡层明显,花粉初具形状(图 2Ⅰ-2),极面观为椭圆形,极轴为6.97 μm,赤道面扁长圆形,赤道轴为21.96 μm;花粉粒外壁上开始形成萌发沟(图 2Ⅰ-3),长达两极的3萌发沟可见雏形,并在远极面形成初始合沟,突起在远极面外壁上,萌发沟较宽,不能分辨出花粉粒内壁,未达两极点3短萌发沟的萌发沟不可见;网眼、网脊模糊,网眼直径0.6~1.8 μm,网脊宽0.63 μm。Ⅱ时期外侧花瓣淡黄色,由闭合状逐渐开裂,内部花瓣紧紧合抱,红色(图 2Ⅱ),花粉形状清晰,镶嵌在花粉囊内,部分花粉从花粉囊内散出(图 2Ⅱ-1),中层和绒毡层逐渐被吸收,变薄;花粉可单粒存在,极观面为三角圆形或圆形(图 2Ⅱ-2),极轴为8.68 μm,赤道面观为宽椭圆形,赤道轴为23.73 μm;已形成6条萌发沟(图 2Ⅱ-3),3长萌发沟在极面相连接,其中达两极点的2条清晰可见,另一条可见雏形,较宽且突出于花粉外壁、已开始分化吸收,未达两极点的3短萌发沟清晰可见;网眼、网脊清晰(图 2Ⅱ-4),网脊变薄,网眼加深,网眼内可见白色颗粒,网眼0.45~2.95 μm,网脊宽度为0.43 μm。Ⅲ时期外侧花瓣由黄绿色逐渐变成红色,开裂角度增大,内侧花瓣开始开裂,花瓣由黄绿色逐渐变成红色(图 2Ⅲ),花粉接近成熟(图 2Ⅲ-1),逐渐从花粉囊内散出,中层和绒毡层已被完全吸收;花粉独粒存在,极观面圆形(图 2Ⅲ-2),极轴长8.44 μm,赤道轴为24 μm;花粉的6萌发沟(图 2Ⅲ-3)分化完成,3长萌发沟在极点形成合沟,合沟内陷,3短萌发沟相间排列于3长萌发沟,未达到极点,不闭合,花粉内壁外壁明显;网眼、网脊清晰(图 2Ⅲ-4),网脊更薄,网眼加深,网眼内颗粒消失,网眼大小在0.68~3.18 μm,网脊宽度0.38 μm。Ⅳ时期花瓣全部红色,外侧开裂角度增大,内侧花瓣离生开裂(图 2Ⅳ),花粉成熟,大部分从花粉囊内散出(图 2Ⅳ-1);各花粉间自然分离,独立存在(图 2Ⅳ-2),极观面圆形,极轴长10.02 μm,赤道面椭圆形,赤道轴为25.65 μm;6萌发沟发育完成(图 2Ⅳ-3),网脊、网眼清晰(图 2Ⅳ-4),网眼0.45~3.27 μm,网脊宽度0.34 μm。

表 2 华中五味子不同发育时期花粉形态特征比较 Tab.2 Pollen morphology of S. sphenanthera at different development stages
图 2 华中五味子雄花不同发育时期花粉形态 Fig. 2 Pollen morphology of S. sphenanthera at different development stages Ⅰ:膨大期的花蕾;Ⅰ -1:扫描电镜1 000倍,花粉初具形状,镶嵌在花粉囊内;Ⅰ -2:扫描电镜2 000倍,各花粉间紧密相连,花粉间及绒毡层间有胞间连丝存在,胼胝质累积形成胼胝质壁并逐渐加厚;Ⅰ -3:扫描电镜3 000倍,花粉极点、网眼、网脊模糊,3长萌发沟可见雏形,3短萌发沟未形成;Ⅰ -4:扫描电镜6 000倍,网脊清晰,网眼部分可见。Ⅱ:花瓣松动期花蕾;Ⅱ -1:扫描电镜500倍,花粉形状趋于清晰,部分花粉镶嵌在花粉囊内,部分花粉从花粉囊内散出,中层和绒毡层逐渐被吸收,变薄;Ⅱ -2:电镜扫描1 200倍,花粉间胞间连丝消失,各花粉间可分开,胼胝质壁开始溶解;Ⅱ 3:扫描电镜3 500倍,花粉极点明显,达两极点的2长萌发沟清晰可见,另1条可见雏形并开始分化吸收,未达两极点的短萌发沟2条可见,网眼、网脊清晰;Ⅱ -4:扫描电镜6 000倍,网眼加深,网眼内可见白色小点,网脊变薄,清晰。Ⅲ:花瓣开放期的花;Ⅲ -1:扫描电镜1 000倍,花粉已成熟,逐渐从花粉囊内散出,中层和绒毡层已被完全吸收;Ⅲ -2:扫描电镜1 500倍,花粉间胞间连丝消失,各花粉间自然分离,胼胝质壁完全溶解;Ⅲ -3:扫描电镜3 500倍,花粉极点明显,内凹,6条萌发沟全部形成,网眼、网脊清晰;Ⅲ -4:扫描电镜6 000倍,网脊更薄,清晰,网眼加深,网眼内白色小点消失。Ⅳ:完全开放期的花;Ⅳ -1:扫描电镜500倍,成熟的花药及花粉;Ⅳ -2:扫描电镜1 500倍,自然分离的成熟花粉;Ⅳ -3:扫描电镜3 500倍,花粉饱满,极点明显,6条萌发沟、网眼、网脊均完成分化;Ⅳ -4:扫描电镜5 000倍,成熟的花粉。
Ⅰ: The bud of alabastrum intumescence stage; Ⅰ -1: Magnified 1 000 times by SEM, pollens begun to take shape and inlaid into the anther; Ⅰ -2:Magnified 2 000 times by SEM, each pollens are closely linked, there were plasmodesmata between pollens and tapetum, callose accumulated to form callose wall which thicken gradually; Ⅰ -3: Magnified 3 000 times by SEM, the areoles, murus and pole of pollen were fuzzy,the 3 long germinal furrows made shape, the 3 short germinal furrows could not be seen;Ⅰ -4: Magnified 6 000 times by SEM, some areoles and murus could be seen. Ⅱ: The bud of petals loose stage; Ⅱ -1: Magnified 500 times by SEM, the shape of pollens came clearer, some pollens inlaid anther, some pollens dropt from it, the middle layer and the tapetum were absorbed; Ⅱ -2: Magnified 1 200 times by SEM, the plasmodesmata were disappeared, the pollens could separated with each other, the callose wall began to dissolve;Ⅱ -3: Magnified 3 500 times by SEM, the pole of pollen was clear, the 2 long germinal furrows which form in the pole could be seen, the other one was made shape and began to differentiate, the 2 short germinal furrows which could not form in the pole could not be seen, the areoles and murus were clear; Ⅱ -4: Magnified 6 000 times by SEM, the areoles were deepened and there were some white spots in it, the murus came to thinner and clearer. Ⅲ: The flower of petal opening stage; Ⅲ -1: Magnified 1 000 times by SEM, the pollens dropt from anther at maturity stage, all middle layer and the tapetum were disappeared; Ⅲ -2: Magnified 1 500 times by SEM, the plasmodesmata were disappeared, the pollens separated with each other natively, the callose wall dissolved entirely; Ⅲ -3: Magnified 3 500 times by SEM, the pole of pollen was clearer and concave, the 6 long germinal furrows had developed completely, the areoles and murus were clear; Ⅲ -4: Magnified 6 000 times by SEM, the areoles and murus were clearer and thinner, the areoles were more deepened and the white spots were disappeared. Ⅳ: The flower of florescence stage; Ⅳ -1: Magnified 1 000 times by SEM, mature pollens and anther; Ⅳ -2: Magnified 1 500 times by SEM, the mature pollens separated with each other natively; Ⅳ -3: Magnified 3 500 times by SEM, the pollens were full, the pole of pollen was clearer, the 6 long germinal furrows, areoles and murus all had developed completely; Ⅳ -4: Magnified 5 000 times by SEM, the mature pollen.
2.3 华中五味子花粉离体萌发

研究结果(表 34)显示,CK空白对照组的花粉萌发率为20.54%,花粉管的平均长度为62.80 μm,空白对照中的花粉萌发率及花粉管长度与添加了蔗糖、硼酸的培养基中的花粉萌发率及花粉管长度存在明显差异,表明蔗糖、硼酸对华中五味子的花粉萌发具有明显的促进或抑制作用,且不同蔗糖、硼酸浓度对华中五味子的花粉萌发率以及花粉管的生长影响程度不同。在硼酸浓度一定的情况下,花粉在蔗糖浓度为100 g ·L-1 时萌发率最高,在蔗糖浓度高于100 g ·L-1时,萌发率及花粉管长度下降;在蔗糖浓度一定的情况下,硼酸浓度为0.10 g ·L-1时,花粉萌发率最高,在硼酸浓度高于0.10 g ·L-1时,萌发率及花粉管长度下降。华中五味子花粉萌发最优的培养组合为10 g ·L-1琼脂+100 g ·L-1蔗糖+0.10 g ·L-1硼酸,萌发率高达92.60%,花粉管长度达454.30 μm。

表 3 不同蔗糖、硼酸浓度对华中五味子花粉萌发率的影响 Tab.3 The effect of different concentrations of sucrose and boric acid on pollen germination rate of S. sphenanthera
表 4 不同蔗糖、硼酸浓度对华中五味子花粉长度的影响 Tab.4 The effect of different concentrations of sucrose and boric acid on pollen tube length of S. sphenanthera

对不同的蔗糖、硼酸浓度对华中五味子的花粉萌发率及花粉管长度的影响方差分析(表 5)显示,蔗糖浓度对华中五味子的花粉萌发率的影响达显著性(P < 0.05)水平,对花粉管长度的影响达极显著性(P < 0.01)水平;硼酸浓度对华中五味子的花粉萌发率存在显著性的影响,对花粉管长度影响未达显著水平。

表 5 不同浓度的蔗糖和硼酸对华中五味子花粉萌发率和花粉管长度影响的方差分析 Tab.5 Analysis of variance of effect of different concentrations of sucrose and boric acid on pollen tube length of S. sphenanthera
3 讨论 3.1 花部特征

被子植物花进化的主要推动力是植物与其传粉者的相互作用,花部特征与传粉者行为、传粉机制和植物适合度联系密切(黄双全等,2000)。郁文彬等(2008)对马先蒿属植物花冠形态的研究认为,花冠的多样性与传粉行为关系密切。凌凤贵等(2005)对五味子(S. chinensis)的研究认为五味子雌雄异株,属风媒植物;刘忠等(2001)认为五味子属植物的花为非专性虫媒花,雄花花托、花丝、药隔的增生变厚是昆虫咬食进化的结果;艾军(2007)也认为五味子是雌雄同株异花,虫媒传粉为主的植物。本研究发现华中五味子雄花成熟后,大量花粉散落到外侧花瓣及附近叶片上,花瓣上具脑纹状纹饰,有利于花粉的附着,便于风媒传粉,这与凌凤贵等(2005)关于五味子传粉方式的观点相似。以昆虫为主的虫媒传粉植物,在昆虫的传粉过程中,被传粉植物既要昆虫帮助其完成传粉来保证其本身的物种延续,又要尽可能地减少传粉过程中的伤害(Macior,1974);昆虫在传粉的过程中,通常咬食花部器官或者吸食花蜜(Leppik,1971);华中五味子雄花花托、花丝、药隔肉质增厚,是长期受昆虫咬食带来的繁育压力而进化的结果,同时在调查时也发现花瓣、雄蕊有被咬食的情况,也有大量小型鞘翅目(Coleoptera)昆虫以采食花粉为目的进行访花,这说明华中五味子亦有虫媒传粉的现象。

3.2 花粉形态

花粉特征是植物分类的重要依据之一。王振江等(2015)对广东桑(Morus atropurpurea)的研究认为亚显微结构特征可作为广东桑倍性鉴定及品种间鉴别的重要标准之一;张煜等(2015)对西南银莲花(Anemone davidii)花粉形态的研究结果推翻了以前学者关于西南银莲花产西藏东南部的结论。五味子科(Schisandraceae)花粉形态是被子植物类群中独一无二的一类(Praglowski,1976),属演化程度很高的进化类型(Jalan et al.,1964)。不同学者对五味子属植物有不同的分类系统。Smith(1947)将五味子属分为多蕊五味子组(Section Pleiostema)、少蕊五味子组(Section Maximowiczia)、五味子组(Section Schisandra)、团蕊五味子组(Section Sphaerostema),将华中五味子与大花五味子(Schisandra grandiflora)都归为多蕊五味子组;而刘玉壶等(2002a2002b)将五味子科分为南五味子属(Kadusura)与五味子属,将华中五味子归入五味子属,并将其编写于《中国树木志》(中国科学院中国树木志编辑委员会,2004);《中国植物志》(中国科学院中国植物志编辑委员会,1996)将华中五味子归入木兰科(Magnoliaceae)五味子属。对华中五味子花粉形态特征的深入研究可为华中五味子的分类提供理论依据。同时花粉的形态特征也与其传粉方式相适应。周凌瑜等(2008)对不同传粉方式的花粉形态比较研究发现,虫媒花的花粉形状长球形,单花粉体积较大,外壁较粗糙,一级雕纹深刻,大多具次级雕纹;风媒花花粉个体较小,形状倾向于球形,其外壁比较光滑,一级雕纹大多较浅,为微弱或模糊的细网状或细颗粒状雕纹,基本上无明显的次级雕纹。对不同时期华中五味子花粉结构特征的观察测量发现,不同时期的华中五味子花粉结构特征存在一定差异,造成这种差异的原因是由于发育的进度的不同,其次在试验过程中,真空脱水时水分散失引起一定程度的形态差异。与孙成仁(2000)对五味子科植物花粉形态的研究相比较可以发现,华中五味子具有明显的6条萌发沟,相对于五味子属其他种而言具有较细的外壁网纹(多数为6 μm以下),按照孢粉学资料(6沟花粉比3沟花粉进化,且外壁网纹的演化趋势是由粗到细),认为华中五味子属于较为进化的类群。根据周凌瑜等(2008)的研究,华中五味子花粉体积与风媒传粉花粉体积大小相似,花粉形态及外壁纹饰与虫媒传粉花粉特征相似。

3.3 花粉萌发特性

花粉间干扰竞争对植物的繁殖和进化具有重要的影响,在自然界的传粉中,花粉常常是混合的,异种花粉的干扰、种间花粉的竞争是影响传粉及结实率的关键因素。花粉竞争的强度与花粉萌发率、花粉管生长密切相关。蔗糖和硼酸是影响花粉萌发率、花粉管生长的2个重要因素,蔗糖为花粉的萌发提供碳素营养,又起到维持外界环境一定的渗透压的作用,花粉管的脉冲式生长是由膨压决定的(Pierson et al.,1995),培养基中蔗糖浓度可能与花粉管中的膨压大小有关,从而影响花粉管的伸长,而硼元素是花粉萌发的必需元素,具有增加花粉对糖的吸收、运转和代谢,促进果胶物合成的作用(Fernando et al.,2005Barnabas et al.,1984)。艾军(2007)采用固体培养基对五味子的花粉萌发研究表明,五味子在蔗糖浓度50~100 g ·L-1、硼酸浓度0.2 g ·L-1时花粉萌发率最高,花粉管生长最好;王善光等(2008)采用液体培养对五味子花粉萌发的研究结果与艾军(2007)一致;夏广清等(2009)的研究结果表明五味子花粉离体萌发最适宜的培养基为150 g ·L-1蔗糖+0.03 mg ·L-1硼酸。本研究对华中五味子花粉离体萌发采用固体培养基培养法,研究结果表明:100 g ·L-1的蔗糖和0.10 g ·L-1的硼酸,最适宜其花粉萌发,萌发率为92.6%,花粉管长度454.30 μm。在试验中,蔗糖的浓度过低,花粉的萌发率也比较低,浓度过高会导致外部环境的渗透压过高,从而使花粉失去活力,降低萌发率;硼酸对华中五味子花粉的萌发率影响显著,而对花粉管的长度影响不显著;蔗糖对花粉的生长及其重要,作用大于硼酸。本研究结果蔗糖浓度与艾军(2007)王善光等(2008)对五味子的研究结果一致,硼酸浓度存在一定的差异,导致这种差异的原因可能是由于试验材料的差异性;就萌发率及花粉管生长情况而言,河南伏牛山地区华中五味子花粉竞争优势明显。

4 结论

河南伏牛山地区华中五味子均为雌雄异株,雄花具单花萼,萼片着生于花柄底部或中部,花柄圆柱形,外表不光滑,具长圆形气孔,蔷薇花冠,花瓣红色或黄色,成熟时花冠朝向地面,花瓣覆瓦状排列,内外侧均具气孔,雄蕊群伞状,雄蕊紧密相连,每花19~22枚雄蕊,少量具26枚雄蕊,在花蕾形成初期雄蕊形成,在生长发育过程中雄蕊数量不变,每枚雄蕊含2个花药。花粉为单花粉,异极,辐射对称,大多呈扁球形,花粉直径为16.50~26.32 μm,按G Erdtman的分级标准,属于中型或小型花粉(小型花粉0~20 μm,中型花粉20~50 μm),萌发沟为6沟型,3长萌发沟在一极形成合沟,3短萌发沟未达极点,长短萌发沟相间排列,外壁具网状雕纹。花粉的最适培养基为10 g ·L-1琼脂+100 g ·L-1蔗糖+0.10 g ·L-1硼酸,萌发率为92.6%,花粉管长度454.30 μm。花冠、花粉形态均既具有典型的虫媒传粉特征,亦具有风媒传粉的特征;花冠展开时,大量成熟花粉散落于花冠外侧的花瓣及附近叶片上,便于花粉的风媒传播。本研究结果认为华中五味子为风媒、虫媒同时传粉植物,主要传粉方式、传粉途径有待进一步研究;花粉萌发率高,在传粉过程中,花粉竞争优势明显。

本研究对华中五味子雄花不同开花时期的花部特征、花粉特性进行了系统的研究。对了解河南地区华中五味子的野生资源状态,进行系统分类和传粉生物学研究等具有重要意义。

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