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题名: 濒危植物香木莲和红花木莲的生殖生物学研究
作者: 潘跃芝
学位类别: 硕士
答辩日期: 2000
授予单位: 中国科学院昆明植物研究所
授予地点: 中国科学院昆明植物研究所
导师: 龚洵
关键词: 香木莲 ; 红花木莲 ; 濒危植物 ; 生殖生物学
学位专业: 植物学
中文摘要: 本文利用生殖生物学的方法对濒危植物香木莲和红花木莲的生殖过程进行了研究,并在此基础上探讨了其濒危机制及保护措施。(一)香木莲的生殖生物学研究研究了西畴县法斗乡和马关县小吉厂村两个香木莲居群的生殖过程。1.大小孢子发生、雌雄配子体发育的研究香木莲花药为四囊型,腺质绒毡层有1-2层细胞,小孢子形成时胞质分裂方式为修饰性同时型,小孢子四分体排列方式为左右对称形和交叉形,成熟花粉粒为二细胞型。除减数分裂过程中出现极少数滞后染色体和后期染色体桥外,小孢子及雄配子体发育基本正常。香木莲胚珠倒生,厚珠心,双珠被,珠柄局部膨大形成珠孔塞,大孢子母细胞减数分裂形成大孢子四分体或三分体,呈直线排列;功能大孢子位于合点端。胚囊为蓼型。胚珠发育过程中有两个阶段发生败育现象:①部分胚珠的功能大孢子退化而不形成胚囊,②部分成熟胚囊的卵器退化。法斗乡居群的胚珠败育率高达89.5%,小吉厂村居群的胚珠败育率达81.3%。2.开花生物学特性的观察香木莲花被片第一次张开后约半小时,内三轮花被片又重新闭合,严密包裹着雌雄蕊群。此时柱头为乳白色,有粘液分泌,是受粉的最佳时期,但此时的花药尚未开裂。约24小时后,内三轮花被片第二次张开,花药开裂而散出花粉,但柱头已萎蔫,丧失了受粉的能力。雌雄异熟和开花生物学特性表明香木莲为异花传粉植物。传粉媒介(昆虫)只能在花被片第一次张开到闭合之间的短暂时间内携带花粉进入花内进行传粉。3.花粉离体萌发在10%蔗糖+O.01%硼酸和5%蔗糖+O.01%硼酸两种培养基上进行花粉离体培养。法斗乡居群大部分花粉不萌发,部分花粉萌发后花粉管前端破裂,内容物流出,正常萌发的花粉不足0.01%;小吉厂村居群花粉萌发率相对较高,在前种培养基上培养6小时后的萌发率可达49.2%,在后种培养基上培养6小时后的萌发率可达27.5%。4.种子萌发实验香木莲的种子有7个月左右的长休眠期,将外种皮洗去后的种子经珍珠岩室温湿藏后萌发率为65%,而经低温(4℃)珍珠岩湿藏处理后的种子萌发率为95%。这说明低温有利于休眠的解除。5.扦插繁殖香木莲扦插繁殖困难,表现在插穗生根前易褐化死亡,生根所需时间长。在本研究中,最高成活率为33.3%。从繁殖过程来看,雌配子体发育异常(功能大孢子退化、卵器退化)和花粉萌发力低是香木莲结籽率低的主要原因,而结籽率极低和无性繁殖困难是制约种群繁衍更新的主要原因。(二)红花木莲生殖生物学特性研究1.大小孢子发生、雌雄配子体发育的研究红花木莲大小孢子发生、雌雄配子体发育过程与香木莲基本相同。四囊型花药,腺质绒毡层有1-3层细胞,小孢子形成方式为修饰性同时型,小孢子四分体排列方式为左右对称形和交叉形,偶为直线式排列。成熟花粉粒为二细胞型。在与香木莲相同的培养基上,红花木莲花粉萌发率为14.7%~25.3%,通过联系红花木莲花粉粒数目和胚珠数目,认为花粉发育不是影响红花木莲结籽率的主要原因。红花木莲胚珠倒生,厚珠心,双珠被,珠柄局部膨大形成珠孔塞。大孢子母细胞减数分裂形成的大孢子呈直线排列。功能大孢子位于合点端,胚囊为蓼型。。87.0%的成熟胚囊卵器退化。胚珠败育是造成栽培红花木莲结籽率低的主要原因。2.种子储藏与萌发红花木莲种子也有约7个月的长休眠期。带外种皮的种子经室温湿藏后的萌发率只有1%,低温湿藏后的萌发率为61%;除去外种皮经室温湿藏后的萌发率为66%,低温湿藏后的萌发率为87%。联系红花木莲种子萌发特性和其生态环境情况,认为种子萌发特性是制约野生红花木莲种群更新和扩大的主要原因之一。
英文摘要: This paper deals with the reproductive biology of Manglietia aromatica and M. insignis, two endangered species in family Magnoliaceae. The endangerment mechanisms and conservation strategies of the two species are discussed based on the results of reproductive biological studies. The reproductive biology of M. aromatica. The materials were collected from two wild populations, which are distributed in Fadou of Xichou county and Xiaojichang of Maguan county in SE Yunnan respectively. (1) Microsporogenesis, Megasporogenesis, Development of male gametophyte and female gametophyte The anther is tetrasporangiate with glandular tapetum, which consists of one or two layers of cells. Cytokinesis at meiosis of microspore mother cell is modified simutaneous, and tetrads are decussate or isobilateral. Mature pollen grains are 2-celled. The microsporogenesis and development of male gametophyte are basically normal except few lagged chromosomes and chromatid bridges. The ovule is anatropous, bitegmic and crassinucellate. The development of obturator was observed. The megaspore mother cells undergo meiotic divisions and develop into linear tetrads or triads of megaspores. The chalazal functional megaspore develops into a Polygonum type of embryo sac. In the development of embryo sac, the degeneration of functional megaspore and egg apparatus were observed and resulted in the abortion of ovules. The abortion rate of ovules was 89.5% in Fadou population, and that was 81.3% in Xiaojichang population. (2) Floral biology characteristics When the outer whorl of tepals opens, the inner whorls of tepals also open, but close at about 30 minutes later and closely envelop gyneocium. While the outer whorl of tepals, stigmas are receptive, but stamens are immature and anthers don't dehisce. While the inner whorls of tepals open again after 24 hours, stamens were mature and anthers dehisced, but stigmas changed already into an unreceptive state. So, M. aromatica is a cross-pollinated plant, and the maturity of gynoecium is earlier than that of androecium. It is successfully pollination that the pollinators with pollen grains get inside for pollinating in only the short duration of the first opening of the inner whorls. (3) Pollen germination The pollen grains of M. aromatica were artificial cultured on two culture media (5% sucrose + 0.01% boric acid, 10% sucrose + 0.01% boric acid) for germination rate. The results shown that the pollen grains of Fadou population had a low germination rate of only 0.01% but the pollen grains of Xiaojichang population had a relatively high germination rate of 49.2%. (4) Seed germination The seeds of M. aromatica have a long dormancy stage (about 7 months). The dormancy of seeds can be broken by low temperature under humid conditions. But in its natural habitation, the seeds could not acquire enough environmental low temperature and high humidity to break their dormancy in the dry winter. (5) Cutting propagation The cutting propagation of M. aromatica was difficult. The cuttings changed into brown state soon due to oxidation of tannin. It took about six months for the cuttings to root. The highest rooting rate was 33.3% in the cutting experiments here. (6) Summary The factors mentioned above have resulted in low seed production of M. aromatica, such as, the low germination rate of pollen grains and the high abortion of ovules. The main factors which endangered exist and multiplication of M. aromatica are as follows: 1) low seed set rate, 2) a long dormancy stage of seeds, 3) difficult vegetative propagation. 2. The reproductive biology of M. insignis The materials studied here were collected from Kunming Botanical Garden. (1) The development of pistil and stamen The development of pistil and stamen of M. insignis -ase similar to that of M. aromatica. The anther of M, insignis is tetrasporangiate and the wall of anther is composed of epidermis, fibrous endothelium, middle layer (1-2 layers) and glandular tapetum (1-3 layers). Cytokinesis at meiosis of microspore mother cells is modified simutaneous, and tetrads are decussate or isobilateral, occasionally linear. Mature pollen grains are 2-celled. The results of artificial germination of pollen grains showed that the germination rates were 14.7-25.3%, The process of male gametophyte formation was not considered as an important factor responsible for the low seed set rate. The ovule of M. insignis is anatropous, bitegmic and crassinucellate. The obturator was observed. The chalazal functional megaspore develops into a Pofygonum type of embryo sac. The degeneration of egg apparatus was observed, and the abortion rate of ovules was 87.0%. This was considered as an main factor responsible for the low rate of bearing seeds. (2) Seed storage and seed germination The seeds of M. insignis have also a long dormancy stage. When seeds with the outer seed coat were kept in room and refrigerator, the germination rates were 1 % and 61% respectively. But when seeds that the outer seed coat was removed were kept in room and refrigerator, the germination rates increased to 66% and 87% respectively. So, the outer seed coat and temperature were main two factors that affected the germination rate of the seeds. And the low germination rate of seeds in wild restricted that the population of M. aromatica increased gradually in number.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.kib.ac.cn/handle/151853/602
Appears in Collections:昆明植物所硕博研究生毕业学位论文_学位论文

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