【作者】 郭春燕；

【导师】 刘果厚； 贺晓；

【作者基本信息】 内蒙古农业大学 ， 野生动植物保护与利用， 2009， 博士

【摘要】 蒙古莸(Caryopteris mongolica Bunge)为马鞭草科莸属的一种旱生灌木,主要分布在我国的河北、山西、陕西、内蒙古、甘肃这几个省区以及蒙古国的部分地区,具有药用、观赏、提取芳香油等较高的经济价值,抗性强,可用于水土保持和园林绿化。本文以内蒙古林木良种繁育中心的蒙古莸人工种群和呼和浩特大青山的自然种群作为研究对象,首次从胚胎学、开花物候、繁育系统、传粉生物学、结实结籽格局、种子萌发和染色体核型这几个方面对蒙古莸生殖生物学进行系统研究,得出以下结论:1.蒙古莸成熟花药具4个小孢子囊,花药壁由表皮、药室内壁、中层和绒毡层构成,发育类型为双子叶型;绒毡层腺质型;小孢子四分体多见四面体型,偶见左右对称型,胞质分裂为同时型;成熟花粉粒2细胞型,具3个萌发沟。蒙古莸雌蕊具2心皮,子房4室,每室具1枚倒生胚珠,单珠被,薄珠心,大孢子四分体直线排列,合点端功能大孢子发育为蓼型胚囊;珠被绒毡层在大孢子四分体时期分化完成,直到球形胚前解体。蒙古莸胚胎发生为柳叶菜型,成熟胚直立型,由子叶、胚芽、胚轴、胚根组成;胚乳发育为核型;成熟种子无胚乳。2.蒙古莸花期在7月末至9月中旬,人工种群开花物候明显早于自然种群。同一种群的开花物候不同年度间尽管在日期上有所差异,但是在各个年度间能够保持相近的开花物候进程。蒙古莸的开花模式属于“集中开花模式”,个体间具有较高的开花同步性,不同种群蒙古莸植株的开花同步性指数均大于0.80。晴好天气,绝大多数花朵都集中在上午10:00以前开放,阴雨天则延迟开放或者不开放。3.蒙古莸的花为鲜艳的蓝紫色,有香味,且可分泌蜜汁,这些花部综合特征能够招引昆虫。在开花过程中,柱头与花药有一定的空间间隔,但是二者的成熟时间没有明显的间隔,且花药散粉与柱头可授期有一定程度的重叠。花粉-胚珠比(P/O)值和杂交指数(OCI)值的测定及套袋实验结果表明:蒙古莸不存在无融合生殖,具有自交和异交兼有的混合交配系统,需要传粉媒介。4.自然条件下,蒙古莸借助风散播花粉的有效距离约为10cm,由于自然情况下植株间的距离通常大于2m,因此,风因子导致的异株异花授粉作用忽略不计。单花花期内蒙古莸的平均泌蜜量呈单峰曲线,花后10h,单花平均泌蜜量可达1.44±0.43μl,且开花当天的泌蜜量最大,以后逐渐减少。蒙古莸的传粉昆虫种类比较少,有蜂类、蝇类和蝶类的一些种,其中无垫蜂属的一种、长尾管牙蝇及熊蜂属的一种为主要传粉昆虫。由于同花期其它植物对蒙古莸传粉者的竞争和气象因子的限制,使得昆虫访花频率较低,最高为14.7蜂次/(花序·h-1),由此所导致的传粉者限制和花粉限制在一定程度上影响蒙古莸生殖成功。5.不同种群蒙古莸的结实特性表现出一定程度的差异。人工栽培种群植株的结实率和种子大小及种子千粒重均高于自然种群,单果水平种子败育率则显著低于自然种群。两个种群的结实率在空间上的垂直分布表现出相同的规律,均为枝条中部>基部>顶部,种子大小和种子千粒重则表现为枝条基部>中部>顶部。蒙古莸的同一果序中,不同位置单果结实数表现为从果序中间向两端降低,呈现出选择性败育格局。单个果实内,种子非线性排列,而是排列在同一个平面上,败育种子发生的位置和数目不固定。6.适宜温度和水分条件下,蒙古莸种子的发芽周期短,一般在置种后7～8d完成。当年成熟的种子萌发率较高,可达90%以上。蒙古莸种子以4℃恒温冷藏为宜,种子萌发的最适温度为20℃～25℃,低温和高温对种子萌发均具有明显的抑制作用;蒙古莸种子在含水量为7%～20%的土壤中具有较高的出苗率,其中以15%最为合适;在5mm左右覆土厚度下出苗率最高。蒙古莸种子具有极强的抵抗干燥、高温胁迫的能力,105℃干热处理8h后,种子发芽率仍然在46.67%左右。在高温(40℃和45℃)、高湿(100%相对湿度)的环境中经人工加速老化处理后,蒙古莸种子活力急剧下降。7 .蒙古莸染色体数目为26 ,核型为“2B”型,核型公式为:2n=2x=26=22m+4sm;染色体相对长度指数I.R.L.= 6L+6M2+8M1+6S,核型不对称系数As.K%为58.48;未观察到次缢痕和随体。更多还原

【Abstract】 Caryopteris mongolica Bunge is a type of subshrubs belonging to Verbenaceae, Caryopteris. It is mainly found in provinces of Hebei, Shanxi, Shanxi, Inner Mongolia, Gansu in China and some areas in Mongolia. C. mongolica is able to survive under severe environmental conditions; therefore, it has been widely planted for soil and water conservation in arid and semi-arid regions. C. mongolica is also used for purposes of gardening and Chinese medicine. In this thesis, reproductive biology of C. mongolica was studied, as the first time, in details by using artificial populations and natural populations. The research focuses on embryology, flowering phenology, breeding system, pollination biology, patterns of fruit and seed set, seeds germination, and karyotype analysis. Main conclusions are presented as follows.1. It was observed that the anther of C. mongolica has 4 microsporangiums. The wall of a mature anther is composed of epidermis, endothecium (1 layer), middle layer (1 layer) and glandular tapetum (1 layer). Its development follows the dicotyledonous type. Cytokinesis are carried on simultaneously by microspore mother cells meiosis. Tetrads are mostly tetrahedral, but occasionally isobilateral. The mature pollen grain is a two-celled type with three colpates. After the microspore tetrad is formed, some forms of the microspore are under developed, and lose protoplasm. Therefore, sterile pollens are about 4.74% of the mature pollen grains.C. mongolica has 2 carpels in pistil, and 4 locules in ovary. Each locule has 1 ovule, and axile placenta. The ovule is anatropous, unintegmic, and tenuinucellatae. The megaspore tetrads are linear and the chalazal megaspore is functional. The embryo sacs consists of 7 cells with 8 nucleus, and belongs to Polygonum type. The differentiation and development of integumentary tapetum are accomplished during the megaspore tetrads stage. The disintegration comes before the formation of globular embryo.The embryo development is of the onagrad type. The erect mature embryo consists of cotyledon, germ, hypocotyl and radicle. The development of endosperm is a nuclear type and the primary endosperm nucleus divides earlier than the zygote. Mature seeds are exendospermous.2. There are significant differences in flowering phenology of C. mongolica between aretificial and natural populations. The dates of flowering phenology are also different in the same population in different years, but the flowering processes are in similar model of“Mass-flowering pattern”. The synchronous index of both populations are more than 0.80. Most flowers opened before 10:00AM in sunny days and delayed or non-flowering in cloudy or rainy days.3. Flowers of C. mongolica are fragrant and nectariferous. Petals are in blue purple color. Such floral characteristics could attract insects. The stigma and anthers are not at the same height and separate in space during the flowering process, while both of them matured simultanousely. The pollen vigor and the stigma viability are temporally overlapped to a great degree. The values of P/O, OCI and bagging tests indicated that there is no apomixes in C. mongolica; the breeding system of the species is mixed with self-compatible and outcrossing; and the pollinators are required during the pollination process.4. The results of gravity slide experiment showed that the wind pollination is in a short distance and the outcrossing of wind pollination can be ignored. During flowering process, average amounts of nectar secretion follow the normal distribution. The average nectar secretion reached 1.44±0.43μl after flowered for 10h. Maximium nectar secretion was observed in the first day of blooming, and gradually decreased afterwards.Pollinators of C. mongolica include bees, flies and butterflies. One species of Amegilla, one of Bombus and Eristalis tenax Linnaeus were observed as main pollinators. Because of influences of pollination competitors and climatic and environmental factors, the pollinator visiting frequencies were always lower than 15 insect times/ inflorescence/h, which result in limited pollinators and pollen deficiency. These limiting factors have great influence on the reproductive success and probably make the flowers produce“few fruits”.5. There are certain degrees of differences in seed setting of C. mongolica in different populations. All of the seed setting percentage, seed size and thousand-seed weight of the artificial populations are higher than the natural one. However, the seed set rates of different populations exhibited the same regulation on branches, manifested as the middle part>basal part>top part, while the seed size and thousand-seed weight in different populations manifested as the basal part>middle part>top part. The number of abortive seeds in single fruit of the artificial populations is significantly less than that of the natural populations.The percentage of abortive nutlets increases from the intermediate part to the edges in a single infructescence. The arrangement of seeds in single fruit is nonlinear and the numbers and positions of abortive seeds are uncertain.6. The seeds of C. mongolica germinate in a short period under optimum temperature and humidity, usually within 7-8 days. The seed germination rates of C. mongolica were found more than 90% in both artificial and natural populations in the current year.When kept at 4℃, the seeds vigor are higher than those kept in indoors and outdoors. The optimum temperature for seed germination is 20-25℃and the optimum soil water content is 7-20%. A layer of 2-5mm covering soil leads to the best of seed germination.The seeds of C. mongolica have resistant ability to heat and drought stress, but their vigor are greatly reduced under high temperature (40-45℃) and high humidity (100% relative humidity).7. The study results indicated that C. mongolica has chromosome number of 2n=26 and base number of x=13. The index relative length (I.R.L.) is 6L+6M2+8M1+6S. The karyogram fits well to the formula of 2n=2x=26=22m+4sm, and the karyotype belongs to the type of“2B”. Its karyotype asymmetry index As.K% is equal to 58.48. Secondary constriction and satellite were not found.更多还原