RELATIONSHIP BETWEEN PLOIDAL LEVEL AND CAM IN FIVE SPECIES OF TALINUM (PORTULACACEAE)

Plants (N = 102) from 23 populations of Talinum, representing five morphologically similar species, were examined in a test of the hypothesis that ploidal level may be correlated with levels of Crassulacean acid metabolism. When grouped by species and ploidal level, two groups of tetraploid plants, T. calcaricum and tetraploid individuals of T. calycinum, had significantly greater malic acid accumulations than any other group, including diploid individuals of T. calycinum. Another tetraploid, T. teretifolium, did not show greater malic acid fluctuations than the diploids, including two putative ancestors (T. mengesii and T. parviflorum). Similarly, malic acid fluctuations in tetraploid individuals of T. parviflorum were not different from diploid individuals of the same species. Nonetheless, when all plants were compared, nocturnal accumulations of malic acid in tetraploid plants were significantly greater than those of diploid plants.     

INFLUENCE OF THE PISTIL ON POLLEN TUBE KINETICS IN PEACH (PRUNUS PERSICA)

Pollen tube growth has been studied in peach and has been related to changes in the pistil structures which the pollen tube has to traverse in its way from the stigma down to the ovule. Growth of the pollen tubes along the pistil is not continuous. While pollen tubes reach the base of the style 7 days after pollination, fertilization does not take place until 12 days later. Pollen tubes stop for 5 days at the top of the obturator and they further stop for 3 days before entering the ovule. The pollen tube growth is heterotrophic; starch, present all along the pistilar tract at anthesis, vanishes as the pollen tubes pass by. Discontinuous pollen tube growth appears to be controlled by the pistil. At anthesis the pistil is not fully matured. Maturation of the pistil implies a number of secretory processes that occur in a basipetal way starting from the stigma down to the style and ending in the ovule. Some of these secretions at the stigma and the style are triggered by pollination; others appear to be a maturative stage of the pistil and are produced in a discrete way. The fact that the pollen tube depends on these secretions together with the fact that these secretions are not continuously produced confer upon the pistil a role of controlling pollen tube kinetics and point out that, for a successful fertilization, male gametophyte development and pistil maturation need to by synchronized.     

VARIABLE SELECTION ON THE TIMING OF GERMINATION IN COLLINSIA VERNA (SCROPHULARIACEAE)

Natural selection on the timing of seed germination was investigated in a natural population of the winter annual Collinsia verna (Scrophulariaceae) for two years. The goal was to quantify 1) the importance of the timing of seed germination to life history evolution in this population and 2) variation in selection in time and space. During fall germination, seedlings were assigned to cohorts on the basis of their dates of germination. Growth, survivorship, and reproduction were censused throughout both years. Selection on the timing of germination was quantified using linear and quadratic regressions during three ecologically important periods in the life cycle, using the techniques of Lande and Arnold (1983) and Arnold and Wade (1984a, 1984b). Comparisons were made between years and on two spatial scales within years. Overall, selection favored early-germinating plants in the first year. The primary determinant of the relationship of the timing of germination to fitness was fecundity selection, rather than viability selection on seedlings. Fecundity selection was respondible for from 54% to 80% of the change in the mean time of germination. Significant disruptive selection characterized the second field season, again mediated mainly through fecundity selection. There was also temporal and spatial heterogeneity in selection on this character. Transects and quadrats differed significantly in the direction and magnitude of natural selection. In addition, the direction of selection changed between episodes for the transects. The results illustrate the importance of the timing of germination to life-history evolution in this annual plant and the complex action of natural selection on this character.     

ELECTROPHORETIC STUDY OF THE ALLOPOLYPLOIDAL ORIGIN OF TALINUM TERETIFOLIUM AND THE SPECIFIC STATUS OF T. APPALACHIANUM (PORTULACACEAE)

Electrophoretic evidence supported the hypothesis that Talinum teretifolium is an allopolyploid derivative of T. mengesii and T. parviflorum. Electrophoretic variation was examined for 384 individuals from 21 populations of four Talinum species. Plants were scored for isozymes of nine enzyme systems specified by 23 gene loci of which 4 were monomorphic and 19 polymorphic. Talinum teretifolium populations were electrophoretically uniform, and all alleles of this species were accounted for by combining alleles present in its presumed parents. Genetic identity values between T. teretifolium and each of its presumed parents (I ≥ 0.817) were higher than between any other pair of the four Talinum species examined. The electrophoretic evidence did not support an alternative hypothesis that T. calycinum is a progenitor of T. teretifolium. Electrophoretic data also showed that T. appalachianum is a disjunct population of T. parviflorum. The average genetic identity between T. appalachianum and T. parviflorum (I = 0.884) was higher than the average genetic identity for conspecific populations of both T. mengesii and T. calycinum.     

STUDIES IN THE FLORAL ANATOMY OF CLAYTONIA (PORTULACACEAE)

Claytonia virginica has a regular flower with two sepals, five petals with an equal number of stamens in positions opposite the petals and a many-seeded tricarpellate gynoecium with basal placentation. The flower has been interpreted as uniseriate, the putative sepals as bracts and the corolla as modified calyx lobes. Anatomical and developmental studies were undertaken to find evidence for the existence of vestigial or rudimentary parts whose existence would illuminate the true nature of the flower. Vascular and epidermal anatomy of sepals are both similar to that of leaves. Corolla and androecium develop basipetally and petals and stamens share common vascular traces in the lower part of the receptacle. Thus, in terms of both anatomy and development, evidence supports the conclusion that the perianth is essentially biseriate. Vestigial or rudimentary parts are not present which would alter the manifest design of the mature flower.     

THE ESSENTIAL ROLE OF CALCIUM ION IN POLLEN GERMINATION AND POLLEN TUBE GROWTH

Brewbaker, James L., and Beyoung H. Kwack. (U. Hawaii, Honolulu.) The essential role of calcium ion in pollen germination and pollen tube growth. Amer. Jour. Bot. 50(9): 859–865. Illus. 1963.—A pollen population effect occurs whenever pollen grains are grown in vitro. Small pollen populations germinate and grow poorly if at all, under conditions which support excellent growth of large pollen populations. The pollen population effect is overcome completely by a growth factor obtained in water extracts of many plant tissues. This factor is shown to be the calcium ion, and its action confirmed in 86 species representing 39 plant families. Other ions (K⁺, Mg⁺⁺, Na⁺) serve in supporting roles to the uptake or binding of calcium. The high requirement of calcium (300–5000 ppm, as Ca (NO₃)₂·4H₂O, for optimum growth) and low calcium content of most pollen may conspire to give calcium a governing role in the growth of pollen tubes both in vitro and in situ. It is suspected that ramifications of this role extend to the self-incompatibilities of plants and to the curious types of arrested tube growth distinguishing, for example, the orchids. A culture medium which proved its merit in a wide variety of pollen growth studies included, in distilled water, 10% sucrose, 100 ppm H₃BO₃, 300 ppm Ca (NO₃)₂·4H₂O, 200 ppm MgSO₄·7H₂O and 100 ppm KNO₃.     

南瓜雌蕊与自花及远缘花粉的相互作用

南瓜柱头表面经去垢剂、蛋白酶及Con A处理后花粉不能萌发或花粉管生长受阻,Con A能专一地与柱头表面结合。柱头块加入培养液可促进花粉萌发。不同的远缘花粉授粉后在雌蕊不同部位受阻。在成熟南瓜雌蕊提取液中检测到血凝活性,凝集素可能参与雌蕊对远缘花粉的抑制。     

SEED GERMINATION TIMING PATTERNS IN INTERMOUNTAIN PENSTEMON (SCROPHULARIACEAE)

Regulation of seed germination timing is an important component of population persistence, especially for short-lived plants in seasonal environments with unpredictable year-to-year weather variation. Seed germination patterns were examined in the laboratory for seeds from 135 populations belonging to 38 species and 13 sections of the genus Penstemon (Scrophulariaceae), from habitats ranging from warm desert to alpine tundra. Seeds of most species were dormant at dispersal and required a period of moist chilling to become germinable. Response to chilling was related to probable chilling duration at the collection site. Populations from habitats with severe winters produced seeds with long chilling requirements, while those from habitats with mild winters produced seeds with short chilling requirements. Populations from midelevation habitats produced seeds with intermediate chilling requirements but with a sizeable fraction whose dormancy was not broken by chilling of any length. Another pattern observed mostly in warm desert populations was little primary dormancy at autumn temperatures combined with induction of a fraction into secondary dormancy by short chilling. Species with a wide habitat range included populations with contrasting germination patterns. Parallel habitat-correlated patterns were observed in different sections. Most species showed germination patterns that combined predictive mechanisms with potential for carryover of a persistent seed bank. Results of common garden experiments suggested that germination differences had a strong genetic basis both among populations and among plants in a population. Adaptive radiation in the genus Penstemon has thus included the evolution of habitat-specific germination timing strategies in multiple lineages within the genus.     

葫芦科蔬菜花粉萌发特性的研究

试验采用花粉离体萌发技术,对葫芦科７属８种蔬菜花粉生活力进行了较为深入的研究,结果表明：葫芦科蔬菜花粉属于“嗜硼、好气、喜温、较耐储藏”的类型。适量的蔗糖可以提高萌发率,并明显有利于花粉管生长。此外,试验中还发现不同种作物花粉萌发力的差异与花粉萌发孔或沟的特征有明显关系联系。     

鹅掌楸属植物花粉萌发前后壁的超微结构

观察描述了在电镜下中国鹅掌楸（Ｌｉｒｉｏｄｅｎｄｒｏｎｃｈｉｎｅｎｓｅ）和北美鹅掌楸（Ｌ．ｔｕｌｉｐｉｆｅｒａ）２种植物花粉壁的超微结构及其水合后的变化。（１）成熟花粉壁由６层组成,即外壁３层──外层,中层１和中层２,内壁３层──内壁１,内壁２和内壁３。（２）花粉水合时,在内壁３与质膜之间由Ｐ一粒子（多糖－粒子）和被膜小泡参与形成新层。（３）花粉萌发时,由内壁３的一部分和新层突出萌发孔共同形成花粉管壁。（４）新层于花粉管形成早期分成２层──外染色深的果胶层和内电子透明的胼胝质层。     

DIFFERENTIAL SEED PRODUCTION IN MIMULUS GUTTATUS IN RESPONSE TO INCREASING CONCENTRATIONS OF COPPER IN THE PISTIL BY POLLEN FROM COPPER TOLERANT AND SENSITIVE SOURCES

Selection can occur in the pistil, during a series of stages that include both pre-zygotic (pollen germination, pollen tube growth, and fertilization) and post-zygotic events. This study explores the extent to which selection, at this level, could be due to the environmental conditions under which the maternal parent is growing. Five plants of Mimulus guttatus, tolerant to copper, were vegetatively cloned and each clone was grown in control and in solutions to which copper was added. The maternal plants received pollen from plants either tolerant or sensitive to copper. Seeds and ovules were counted to estimate the number of seeds/capsule, the seed/ovule ratio, the percent fertilization, and the proportion of zygotes aborting for each clone, treatment and pollen source combination. There were large differences among the pollen recipients for each of the measurements. However, there was a consistent pattern to seed production depending on the pollen source and copper treatment. The seed/ovule ratio was unaffected if pollen came from tolerant sources but was reduced by an average of 24% for both copper supplemented treatments if pollen came from copper sensitive sources. Thus, the data indicated that selection due to environmental factors could occur within the pistil. Differences in percent fertilization were not statistically significant, but the seed/zygote ratio showed a pattern that was similar to seed production suggesting that abortion of immature seeds was responsible for most of the difference in seed production.     

花粉内的多胺和外源多胺对花粉萌发和花粉管生长的影响

测定了不同生理状态下的油松花粉内的多胺含量,并研究了腐胺和精胺对十种不同植物花粉的萌发和花粉管生长的影响。三种多胺(腐胺、亚精胺和精胺)总量贮藏花粉中高于新鲜花粉,萌发花粉内相对不变。三种生理状态不同的花粉内,亚精胺含量均高于腐胺和精胺。腐胺对花粉荫发和花粉管生长的作用不明显,精胺一般表现为抑制作用,并随浓度而加强,还与植物品种、花粉成熟度、花粉萌发速度、花粉管生长速度和培养基中硼酸的有无有关。一般,容易萌发、成熟较充分,或正在迅速生长的花粉,以及培养基中有硼时受抑制轻。     

GROWTH REGULATION BY ETHYLENE IN FERN GAMETOPHYTES. V. ETHYLENE AND THE EARLY EVENTS OF SPORE GERMINATION

Early events during the germination of spores of the fern Onoclea sensibilis were studied to determine the time during germination when ethylene had its greatest inhibiting effect. Water imbibition by dry spores was rapid and did not appear to be inhibited by ethylene. During normal germination DNA synthesis occurred about four hours before the nucleus moved from a central position to the spore periphery. Following nuclear movement, mitosis and cell division occurred, partitioning the spore into a small rhizoid cell and a large protonemal cell. Cell division was complete approximately six hours after nuclear movement. Ethylene treatment of the spores blocked DNA synthesis, nuclear movement, and cell division. The earliest DNA replication in uninhibited spores was observed after 14 hours of germination, and the maximal rate of spore labeling with ³H-thymidine was between 16 and 20 hours. Spores were most sensitive to ethylene, however, during the stages of germination prior to DNA synthesis, and it was concluded that ethylene did not directly inhibit DNA replication but blocked germination at some earlier fundamental step. The effects of ethylene were reversible. since complete recovery from inhibition of germination was possible if ethylene was released and the spores were kept in light. Recovery was much slower in darkness. It was hypothesized that light acted photosynthetically to overcome the ethylene inhibition of germination. Consistent with this, it was shown that spores exhibit net photosynthesis after only two hours of germination.     

THE EVOLUTION OF INSECT-MEDIATED SELF-POLLINATION FROM AN OUTCROSSING SYSTEM IN CALYPTRIDIUM (PORTULACACEAE)

Calyptridium monospermum (Portulacaceae) comprises two biological races visited by different groups of insects. One race, pollinated by a bumblebee, Bombus vosnesenskii (Apidae), is outcrossing, while the other race is pollinated casually by a variety of other insects whose visits result in insect-mediated self-pollination and geitonogamy within the inflorescence. Insect-mediated selfing is also the mode of pollination in the closely related species, C. umbellatum. While all plants of both species are self-compatible, insect visitation is necessary for good seed set. Selfing populations of C. monospermum exhibit many floral adaptations for insect-mediated self-pollination which parallel those of the selfing C. umbellatum, while retaining vegetative characteristics typical of C. monospermum. These floral traits involve flower color and odor, style and stamen orientation, size of stigmatic surfaces, number of pollen grains produced, density of open flowers on inflorescences, and presence or absence of protogyny. Artifical pollination experiments show that these floral adaptations are effective in increasing the probability of insect-mediated self-pollination. Insect-mediated selfing in C. umbellatum and in some populations of C. monospermum is encouraged and probably made necessary by the inconstant pollinating behavior of the insects which visit these plants, as shown by the large percentage of non-Calyptridium pollen recovered from the bodies of insects captured while visiting these plants.     

赤霉素与脱落酸对番茄种子萌发中细胞周期的调控

利用细胞流检仪检测番茄（Ｌｙｃｏｐｅｒｓｉｃｏｎ ｅｓｃｕｌｅｎｔｕｍ Ｍｉｌｌ．） ＧＡ－缺陷型、ＡＢＡ－缺陷型和相应的正常品种（野生型）成熟种子胚根尖细胞倍性水平时发现：ＧＡ－缺陷型和野生型种子绝大多数细胞ＤＮＡ 水平为２Ｃ,而ＡＢＡ－缺陷型种子则含有较多的４Ｃ细胞。在标准发芽条件下,ＡＢＡ－缺陷型和野生型种子浸种１ ｄ 后胚根尖细胞ＤＮＡ 开始复制,随后胚根突破种皮而发芽。然而ＧＡ－缺陷型种子除非加入外源ＧＡ,否则既不发生细胞ＤＮＡ 复制,也不发芽。这说明内源ＧＡ 是启动番茄种子胚根尖细胞ＤＮＡ 复制的关键因素,同时也说明番茄根尖细胞ＤＮＡ 复制是种子发芽的必要条件。实验证明：ＡＢＡ 不抑制细胞ＤＮＡ 合成,但阻止Ｇ２ 细胞进入到Ｍ 期。外源ＡＢＡ处理野生型种子与渗控处理结果相似,可以大幅度提高胚根尖４Ｃ／２Ｃ细胞的比例,但抑制种子的最终发芽     

Ca^2＋载体A23187对烟草生殖核分裂的调节

用Ｃａ＾２＋载体Ａ２３１８７研究了高钙水平对烟草离体花粉管内生殖核分裂的影响。结果表明,Ａ２３１８７抑制花粉管生长,影响其正常形态,调节生殖核分裂,较高浓度Ａ２３１８７可阻断生殖核分裂,而较代浓度的效应因处理时间而异;萌发６ｈ处理显著抑制生殖核分裂。     

芸苔属脱外壁花粉的分离与人工萌发

芸苔属青菜（Ｂｒａｓｓｉｃａ ｃｈｉｎｅｎｓｉｓ）与紫菜苔（Ｂ． ｃａｍ ｐｅｓｔｒｉｓｖａｒ． ｐｕｒｐｕｒｅａ）的花粉经低温水合、热激、渗激三步程序,分离出大量具萌发能力的脱外壁花粉,脱外壁率可高达６０％ 以上。在含有碳源与氮源及Ｒｏｂｅｒｔｓ培养基盐成分的碱性ＰＥＧ 培养基中,首次使芸苔属脱外壁花粉萌发,萌发率可达３３％ ～４１％ 。在扫描电镜下观察了花粉脱外壁与萌发的过程。讨论了不同植物花粉脱外壁的方法与花粉壁生物学特点的对应关系,以及外壁对花粉萌发的可能作用