GENETIC AND HORMONAL REGULATION OF GROWTH,FLOWERING, AND SEX EXPRESSION IN PLANTS

The interaction of the genetic and hormonal regulation of growth, flowering, and sex expression in plants is discussed. The genetic control of these processes is characterized, and data on their hormonal regulation are supplied. The interaction of genetic and hormonal regulation is considered with reference to tall-growing and genetic dwarf forms of the pea and wheat plants. It is shown that in the dwarf forms of the pea plant and in many other varieties, growth stimulation in response to treatment with the phytohormone gibberellic acid is clearly manifested and the expression of genetic dwarfism is eliminated, whereas in dwarf wheats it is expressed only slightly, if at all. At the same time both tall-growing and dwarf forms of both pea and wheat show a clearly defined growth retardation response to treatment with the growth inhibitor, abscisic acid, which causes the expression of physiological dwarfism. The short- and long-day characteristics of the photoperiodic response of plants are described as genetically controlled features, and data are given on the induction of flowering of a long-day variety coneflower grown under short-day conditions with the aid of gibberellins extracted from leaves of long-day vegetative plants of short-day Mammoth tobacco. Data are also supplied on the induction of flowering of a short-day variety, red-leaved goosefoot, grown under continuous light with the aid of metabolites extracted from leaves of the same Mammoth tobacco plants flowering under short-day conditions. This demonstrates the possibility of hormonal regulation of the genetically controlled long-day and short-day characteristics in photoperiodically sensitive plants. Genetic and hormonal regulation of sex expression in two dioecious plants, hemp and spinach, is discussed. It is shown that sex expression in these plants is regulated by gibberellins which are synthesized in leaves and cause male sex expression and by cytokinins which are synthesized in the roots and cause female sex expression. These data indicate that sex expression in dioecious plants is the result of interaction between the genetic apparatus and phytohormones.     

THE EFFECT OF INVESTMENT IN ATTRACTIVE STRUCTURES ON ALLOCATION TO MALE AND FEMALE FUNCTIONS IN PLANTS

Expressions for male and female fitnesses of partially self-fertilizing cosexual plants are derived, assuming that allocation to pollinator attraction at the time of flowering may decrease resources available for male and female primary structures. The total female fertility is assumed to be controlled by factors at two stages, flowering-time and fruiting-time, with resources for fruit maturation being limited so that maximum seed production may be limited by the availability of these resources. The fitness formulas are used to calculate ESS (evolutionarily stable strategy) allocations at flowering time to primary male and female sex functions and to attractive structures. These are compared with some data that are available for dry weights of different flower parts. The fitnesses of unisexual mutant forms are calculated, assuming that they are introduced into a population consisting mostly of the initial cosexual form and that they obey the same gain curves as that form. When compared with the fitness of the ESS cosexual form, this enables one to ask whether unisexual forms will be favored. We show that the spread of females is unlikely, unless there is high inbreeding depression and a rather high selfing rate, and that in some circumstances a linear relation between number of fertilized ovules and number of seeds matured can be less favorable for the invasion of females than is a highly concave relation. With a nearly linear relation between numbers of fertilized ovules and mature seeds, invasion by females is more likely when investment in attraction is low than when it is high. These effects are discussed in relation to the distribution of dioecy. The spread of male mutants is never likely in these models.     

CHROMOSOME NUMBERS OF HAWAIIAN FLOWERING PLANTS AND THE SIGNIFICANCE OF CYTOLOGY IN SELECTED TAXA

Chromosome numbers are reported for 128 species of flowering plants indigenous or endemic to Hawaii, including first reports for 13 genera and 82 species. The special significance of reports for Ilex, Tribulus, Keysseria, Pisonia, Boerhavia, Jacquemontia, Claoxylon, Lipochaeta, Railliardia, and Dubautia are discussed. The cytological and morphological variation in Railliardia and Dubautia is considered and their treatment as congeners is advocated. The cytogeogruphic pattern in Dubautia and Railliardia and other factors suggest that the ancestral chromosome number of the Hawaiian tarweeds is n = 14. Their derivation from a western North American progenitor similar to Adenothamnus is considered plausible if not indeed likely.     

ENVIRONMENTAL STRESS AND THE MAINTENANCE OF SEX IN A FRESHWATER SNAIL

Synergism among mutations can lead to an advantage to sexual reproduction, provided mutation rates are high enough (the mutational deterministic hypothesis). Here we tested the idea that competition for food can increase the advantage to sexual reproduction, perhaps by increasing the synergism among mutations in asexual individuals. We compared the survivorship of sexual and asexual snails (Potamopyrgus antipodarum) under two treatments: starved and fed. We predicted higher mortality for asexual snails when starved, but found that sexual and asexual individuals survived at the same rate, independent of treatment. These results suggest that the distribution of sex in this snail may not be explained by variation in competition among populations.     

ON GENETIC SEGREGATION AND THE EVOLUTION OF SEX

It has recently been argued that because the genetic load borne by an asexual species resulting from segregation, relative to a comparable sexual population, is greater than two, sex can overcome its twofold disadvantage and succeed. We evaluate some of the assumptions underlying this argument and discuss alternative assumptions. Further, we simulate the dynamics of competition between sexual and asexual types. We find that for populations of size 100 and 500 the advantages of segregation do not outweigh the cost of producing males. We conclude that, at least for small populations, drift and the cost of sex govern the evolution of sexuality, not selection or segregation. We believe, however, that if sexual and asexual populations were isolated for a sufficiently long period, segregation might impart a fitness advantage upon sexuals that could compensate for the cost of sex and allow sexuals to outcompete asexuals upon their reunion.     

双价外壳蛋白基因植物表达载体的构建及马铃薯转基因植株的鉴定

在克隆了马铃薯Ｘ病毒（ＰＶＸ）、马铃薯Ｙ 病毒（ＰＶＹ）和马铃薯卷叶病毒（ＰＬＲＶ）的外壳蛋白基因的基础上,构建同时包含ＰＶＸ和ＰＶＹ 与ＰＶＹ 和ＰＬＲＶ 两个外壳蛋白基因植物表达框架的表达载体,通过农杆菌（Ａｇｒｏｂａｃｔｅｒｉｕｍ ｔｕｍｅｆａｃｉｅｎｓ）介导转化烟草（Ｎｉｃｏｔｉａｎａｔａｂａｃｕｍ ）和生产上常用的几个马铃薯（Ｓｏｌａｎｕｍ ｔｕｂｅｒｏｓｕｍ ）优良品种：“Ｆａｖｏｒｉｔａ”、“虎头”、“克４”。经ＰＣＲ检测证明外源基因已整合到植物的染色体上,得到批量转基因植株。在转ＰＶＸ＋ＰＶＹ 外壳蛋白基因的烟草上接种ＰＶＸ （５ μｇ／ｍ Ｌ）、ＰＶＹ（２０ μｇ／ｍ Ｌ）病毒,得到有一定抗性的植株     

三叶草素基因(tfx)在快生型大豆根瘤菌(Sinorhizobium fredii)H12-2中的表达与稳定性测定

将含有三叶草条基因的重组质粒pT2TFXK和pT2TX3K以接合转移的方式导入快生型大豆根瘤菌H12－2。转移接合子H12－2（pXK）能产三叶草素并具有抑菌活性;H12－2（P3K）表现出对三叶草素的抗性。抑菌谱试验结果表明：82％的供试快生型大豆根瘤菌菌株对三叶草素敏感;所有供试慢生型大豆根瘤菌则表现抗性。稳定性检测结果表明：在共生与人工培养条件下,导入的pXK和p3K质粒均可在宿主菌中稳定存在和表达。     

安徽天柱山夏末开花植物的花粉形态

通过光镜和扫描电镜对天柱山夏末开花的23科、39属、37种3变种的植物花粉形态进行了观察研究.从形状看,一些科内花粉形状具有一致性,如菊科[Asteraceae Dumortier (Compositae Giseke,nom.altern.)]6个种都是球形或近球形(P/E=0.95-1.03);豆科(Legumin...     

安徽菜子湖早春开花植物花粉形态及生态意义

采用光学显微镜和扫描电镜对安徽安庆菜子湖早春开花植物15科22种2亚种的花粉形态进行了观察和研究。对这些植物的生态因子,包括地理位置、海拔高度、年降水量、年积温及生境进行了调查和归纳。在此基础上,根据该区域内相同或相似的生态环境条件下分布的现代植物各种花粉类型,间接得出一定花粉类型综合特征所指示的现代气候和环境,为利用菜子湖湖泊孢粉资料来研究区域气候和环境变化提供现代孢粉学资料和依据。     

玉米Ubi-1启动子在可育转基因玉米植株中的表达活性

本工作将玉米泛素基因-1启动子(Ubi-1)与大肠杆菌β-葡糖苷酸酶基因(gus,uidA)的编码区融合,通过基因枪粒子轰击方法转化来自玉米未成熟胚盾片组织的I-型愈伤组织,经PPT选择获得可育的玉米转基因植株,并采用组织化学方法分析了Ubi-1启动子驱动的gus基因在不同组织、细胞中的表达活性,发现gus基因在除花药壁以外的其它所试组织中均可以有效表达.UbiGUS在花粉、卵细胞和T1代转基因植株未成熟胚中的表达显示该启动子在植株发育的早期阶段即具有活性.对T0代转基因植株的花粉进行GUS组织化学染色,gus基因呈11分离,显示外源基因在转基因植株中以孟德尔方式遗传.同时发现,使用玉米本身的启动子Ubi-1可以降低外源基因在转基因玉米中的拷贝数,进而避免基因沉默现象的发生.目前已得到第二代转基因种子.     

准噶尔盆地荒漠灌丛对融雪水空间分布的反馈初探

温带荒漠的积雪沿灌丛始融,并以灌丛为中心形成融雪漏斗,导致融雪水向灌丛基部汇集。观测资料表明:通过灌丛对融雪水分布的反馈,使灌丛周围的沙层含水量明显增加,为裸沙区的152.1-228.9％,从而提高融雪水的利用率并改善灌丛自身的供水条件,对荒漠植被的分布格局亦起一定影响。     

OLFACTORY RESPONSES OF LYSIPHLEBIA JAPONICA TO VOLATILE CHEMICALS AND FRESH LEAVES OF THE HOST PLANTS OF COTTON APHIDS IN OLFACTOMETER

Abstract The behavioral responses of the female adult parasitoids Lysiphlebia japonica to plant volatile chemicals, host plants and cotton aphids were tested in a four arm air flow olfactometer. The results indicated that the female parasitoids were strongly attracted by the odors from cotton aphids and their host plants. Damaged cotton leaves were more attractive than intact ones. Among the four olfactory stimuli from the plant volatile chemicals dissolved in liquid paraffin oil at the concentration of 0.01 (volume fraction), the female parasitoids only positively responded to benzaldehyde, but did not show any preference to β-caryophyllene and β-pinene. Although heptanol elicited the highest EAC response of the parasitoids, the behavioral test showed that it repelled the parasitoids, and β-pinene shared the same feature with heptanol at the concentration of 1 (volume fraction). Our results also showed that the female parasitoids only preferred the cotton leaf from which the mummified aphids were collected, and did not express any interest to the three plants of melon family in the olfactometer, The possible mechanisms are discussed.     

棉蚜茧蜂对某些挥发性次生化合物及棉蚜寄生植物的嗅觉反应(英)

本文利用四臂嗅觉计测定了雌性棉蚜茧蜂Lysiphlebia japonica对棉蚜四种寄主植物新鲜叶片、棉蚜和几种挥发性次生化合物的嗅觉反应,结果表明新鲜棉叶片和棉蚜的气味对棉蚜茧蜂有强烈的吸引作用,两者相混合使吸引作用明显增强;切碎的叶片比未切碎的叶片更具吸引作用。所测试的四种挥发性物质β-caryophyllene、heptanol、benzaldehyde和β-pinene,在浓度为0.01(体积分数)时,只有benzaldebyde对棉蚜茧蜂具有吸引作用,β-caryopbyllene和β-pinene对棉蚜茧蜂的吸引作用不明显,而heptanol对该蜂具有排斥作用。β-pinene在浓度为1(体积分数)时,也对该蜂具有排斥作用。对于棉蚜的四种寄主植物棉花、黄瓜、南瓜和丝瓜的完整叶片,棉蚜茧蜂只对棉花叶片产生定向反应,而对其它三种瓜类叶片没有反应。根据上述结果可以推知嗅觉在寄生蜂的寄主寻找过程中起着重要作用,绿叶气味物质和寄主气味可能是寄生蜂寻找寄主的远距离化学线索。棉蚜茧蜂对寄主定向是识别了特定化学指纹图谱,单一的某种化合物在寄主定向过程中所起的作用并不象预测的那样重要,而且组成图谱的物质并不是简单地混合在一起,而是相互作用,或加强或抑制。羽化前经历能够对寄生蜂的行为产生较大影响。     

LIGHT AND SCANNING ELECTRON MICROSCOPIC INVESTIGATIONS OF SEXUAL REPRODUCTION IN HYDRA CARNEA

In the freshwater hydrozoan Hydra carnea, the egg, matured and grown between the mesoglea and the epitheliomuscular cells of the ectoderm, is extruded after the emission of the second polar body. Surrounded by a clear jelly layer the egg remains attached to the polyp. Sperm which are released from the testicular sacs of male polyps are attracted by the egg. The jelly layer is penetrated only at the site of emission of the polar bodies by sperm which lack a structurally distinct acrosome. One sperm fuses with the egg at that site where the female pronucleus is found to lie close to the egg membrane. After fertilization and cleavage an acellular embryotheca is secreted by the blastomeres. These events were investigated by light and scanning electron microscopy.     

SEX RATIO SELECTION AND THE EVOLUTION OF ENVIRONMENTAL SEX DETERMINATION IN LABORATORY POPULATIONS OF MENIDIA MENIDIA

What happens when a population with environmental sex determination (ESD) experiences a change to an extreme environment that causes a highly unbalanced sex ratio? Theory predicts that frequency-dependent selection would increase the proportion of the minority sex and decrease the level of ESD in subsequent generations. We empirically modeled this process by maintaining five laboratory populations of a fish with temperature-dependent sex determination (the Atlantic silverside, Menidia menidia) in extreme constant temperature environments that caused highly skewed sex ratios to occur initially. Increases in the minority sex consistently occurred from one generation to the next across all five populations, first establishing and then maintaining a balanced sex ratio until termination of the experiment at 8 to 10 generations. The extent to which the level of ESD changed as balanced sex ratios evolved, however, was not consistent. Two populations that experienced high temperatures each generation displayed a loss of ESD, and in one of these ESD was virtually eliminated. This suggests that temperature-insensitive, sex-determining genes were being selected. In populations maintained in low temperature environments, however, the level of ESD did not decline. Instead, the response of sex ratio to temperature was adjusted upward or downward, perhaps by selection of sex-determining genes sensitive to higher (or lower) temperatures. The two different outcomes at low versus high temperatures occurred independent of the geographic origin of the founding population. Our results demonstrate that ESD is capable of evolving in response to selection.     

乌鲁木齐附近早春植物生物学和生态学特性的初探

本文根据作者对乌鲁木齐附近的早春植物在春季生长,发育节律与水热等主要生态因子的关系的观测,论述了它们的生物学和生态学特点,为充分利用早春植物萌发返青早,生长发育快的优势,为合理开发利用,改良建设这类草场提供科学依据。