INDIVIDUAL VARIATION IN THE VIGOR OF SELF POLLEN AND SELFED PROGENY IN HIBISCUS MOSCHEUTOS (MALVACEAE)

In some self-compatible species, self pollen tubes grow more slowly than outcross pollen, presumably leading to low selfing rates when mixtures of self and outcross pollen reach the stigma simultaneously. Here we show that the competitive ability of self pollen differed among individuals of Hibiscus moscheutos. Self pollen tubes grew slower than outcross pollen in three plants, faster than outcross pollen in four plants, and showed no difference in five other plants (based on rates of callose plug formation). Levels of inbreeding depression were examined by comparing progeny from self and outcross pollinations in seven maternal families. Self pollination led to reduced seed number in only one maternal family, and a slight decrease in seed size was seen in two maternal families. Considerable inbreeding depression occurred later in the life cycle, and the degree of inbreeding depression varied among maternal families of 6-week-old plants. Our results demonstrate the potential for unpredictable effects of pollen competition on individual selfing rates, which in turn may affect progeny vigor. This complex situation contrasts with previous reports of species in which outcross pollen consistently outcompetes self pollen (cryptic self-incompatibility).     

西葫芦(Cucurbita pepo L.)花粉壁和非壁蛋白中苹果酸脱氢酶的研究

西葫芦(Cucurbita pepo L.)花粉的壁蛋白和非壁蛋白中都存在苹果酸脱氢酶(EC 1.1-1.37)。壁蛋白苹果酸脱氢酶对OAA的K_m值为30.3μM,最适pH值为8.0。非壁蛋白苹果酸脱氢酶对OAA的K_m值为83.3μM,最适pH值为8.5。在0.05～0.3 M氯化钠浓度范围内,壁蛋白苹果酸脱氢酶和非壁蛋白苹果酸脱氢酶的活性都受到抑制。这种抑制作用随氯化钠浓度提高而增强。0.2 M氯化钾对酶活性的抑制作用与0.2 M氯化钠的抑制作用完全相同。0.1～0.8 M的蔗糖对壁蛋白苹果酸脱氢酶和非壁蛋白苹果酸脱氢酶活性也具有抑制作用。     

EFFECTS OF SOIL NITROGEN ON POLLEN PRODUCTION,POLLEN GRAIN SIZE,AND POLLEN PERFORMANCE IN CUCURBITA PEPO (CUCURBITACEAE)

To determine the effects of soil nitrogen on pollen production, pollen size, and pollen performance, two cultivars of zucchini (Cucurbita pepo) were grown under two nitrogen regimes in an experimental garden. The two cultivars were true breeding for alternative alleles for a one gene trait, ovary color. The soil nitrogen treatment had a significant effect on most measures of reproductive output through the female function. The nitrogen treatment did not affect the number of staminate flowers per plant but did have an effect on the number of pollen grains per staminate flower and the mean pollen grain size. A pollen mixture experiment revealed that pollen produced by plants in the high nitrogen treatment sired significantly more seeds than pollen from low nitrogen plants. Moreover, we found that the high nitrogen pollen sired even a greater percentage of seeds in the region of the fruit (ovary) previously shown to be fertilized by the fastest growing pollen tubes. Thus, the difference in the number of seeds sired by pollen from the two nitrogen treatments is due to differences in pollen performance. We conclude that spatial heterogeneity in soil nitrogen can influence the paternity of seeds in a plant population.     

嫁接早期IAA在西葫芦/南瓜嫁接面处薄壁细胞和维管分子中的免疫细胞学定位

采用免疫胶体金法对IAA在西葫芦／南瓜离体茎段嫁接早期发育时期在嫁接面处的分布进行了超微结构水平的定位。电镜观察表明在嫁接面处的薄壁细胞中IAA主要定位于细胞核、质体、内质网等细胞器上。在高尔基体、线粒体、细胞壁和液泡中,未发现胶体金颗粒的标记。在分化中的管状分子中,胶体金颗粒位于次生壁上和细胞质中。在筛分子分化过程中,IAA主要定位于筛板、筛孔和细胞质中。在伴胞中有较高的金颗粒密度。对于IAA在嫁接体维管分子分化过程中的作用进行了讨论。     

EFFECTS OF PARENTAGE AND SIZE OF THE POLLEN LOAD ON PROGENY PERFORMANCE IN CAMPANULA AMERICANA

To examine the effects of maternal and paternal parentage and the size of the pollen load on seed size and weight and on progeny performance we conducted a controlled crossing experiment using a natural population of Campanula americana. We found that seed size was positively correlated with early seedling performance for all but one of traits we measured (days to emergence), but was not significantly correlated with any of the later vegetative measures or reproductive output. We detected significant effects due to the maternal parent for the vegetative traits days to emergence, days to first leaf, and final plant height, as well as total seed weight, and mean seed weight per fruit. Significant paternal effects were found for all of the seedling traits except number of leaves after vernalization. The progeny from fruits receiving high pollen loads significantly outperformed the progeny from fruits receiving low pollen loads for the traits days to first and second leaf, numbers of leaves after vernalization, and days to first flower. These results not only demonstrate the importance of parentage and seed weight on progeny performance, but also indicate that variations in the size of the pollen load may be important in seedling establishment in natural populations.     

INTERSPECIFIC GENE FLOW IN CUCURBITA: C. TEXANA VS. C. PEPO

The potential for interspecific genetic exchange was examined by monitoring flowering patterns, pollinator movement, and gene flow among experimental populations of the Texas gourd (Cucurbita texana) and cultivars of Cucurbita pepo. While flowering patterns and pollinator movement tended to maximize self-pollination and local gene exchange, movement of effective pollen exceeded 1,300 m. This movement, mediated by the solitary bee Xenoglossa strenua and monitored by tracking allozyme variants, produced interspecific hybrids in 5% of the progeny from experimental plants. Interspecific gene exchange occurred in either direction with either species serving as staminate or pistillate parent. No obvious constraints to gene flow among plants representing C. texana and distinctive cultivars (vars. ovifera, medullosa, melopepo) of C. pepo were detected. Genetic exchange among different species and cultivars is enhanced by the foraging behavior of Xenoglossa. Multiple visits to either staminate (pollen carryover) or pistillate (multiple pollinations) flowers often result in the deposition of mixed pollen on receptive stigmas. The wild type (C. texana) can donate and receive effective pollen when growing under both weedy and natural conditions. The observed lack of interspecific reproductive isolation supports treatment of cultivars and wild types as a single species and, in conjunction with available data concerning temporal/geographical relationships among bees, squash, gourds, and humans in eastern North America, suggests the possibility of long-term genetic interaction between wild types and domesticates.     

FITNESS CONSEQUENCES OF MIXED-DONOR POLLEN LOADS IN THE ANNUAL LEGUME CHAMAECRISTA FASCICULATA

We experimentally examined the effects of pollen composition on progeny fitness in the self-compatible, annual plant Chamaecrista fasciculata. Plants were hand-pollinated with single- and mixed-donor pollen loads and with various combinations of self- and outcross pollen. For outcrosses, pollen was obtained from two plants at each of two different distances within the same subpopulation as the female parent. Seedlings from all crosses were planted back into the maternal site. For single-donor crosses, seed weight, progeny fruit production, and overall relative fitness were significantly higher for outcross, as compared to self-treatments, but we found no significant differences among outcross sources. For all fitness components, the value observed for crosses derived from mixed loads was intermediate between the values for the singledonor crosses that comprised the mixed load. In a parallel experiment, an analysis of seed paternity of progeny which resulted from pollen mixtures of self- and outcross pollen showed random paternity in two maternal families, and significant excess of outcross in one family. Our results demonstrate that mixed pollen loads do not confer a fitness advantage to the maternal plant in this species, and that the fitness observed for progeny derived from mixed loads is generally consistent with a hypothesis of random paternity.     

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.     

THE DISTRIBUTION AND PHYLOGENETIC SIGNIFICANCE OF BINUCLEATE AND TRINUCLEATE POLLEN GRAINS IN THE ANGIOSPERMS

Studies of the cytology of angiosperm pollen which extend our knowledge of the distribution of binucleate and trinucleate pollen to almost 2,000 species of flowering plants are summarized. Approximately 70% of the species studied release pollen in a binucleate stage, and none of them shed both types of pollen as a constant varietal trait. All phylogenetically primitive taxa are binucleate. The trinucleate trait evidently has originated independently at many times during angiosperm evolution. In no instance must one infer the origin of binucleate taxa from trinucleate ancestors. Most genera are monotypic with respect to pollen cytology, and only 10 genera are known to include both binucleate and trinucleate species. Among the 265 families studied, 179 include only binucleate genera and 54 include only trinucleate genera, while 32 include both types. Nearly all aquatic species with submersed flowers shed pollen in a trinucleate stage. A group of physiological differences which distinguish binucleate and trinucleate pollen is reviewed in relation to the survival and possible selective advantage of trinucleate mutants, and the significance of the binucleate pollen grain in the origin and evolution of flowering plants is discussed.     

沈阳地区气传致敏花粉探讨

本文报道在沈阳地区1965—1985年间于空气中间断收集大气花粉5年,共收花粉玻片1100张,花粉45780粒,属于24科37属或种。其中9种(或属)超过千粒,为优势种类花粉。每年沈阳市大气中花粉出现两个高峰,一个为春季(四、五月),另一个为夏秋季(七八月)。通过长期观察发现,花粉种类和数量每年虽有不同,伹差异不大,唯有豚草花粉消长明显。大气中花粉种类及数量的变化往往受到气温、国家有关绿化政策以及社会风气的影响。花粉与过敏症关系十分密切,我们采用17种花粉制成浸液为病人皮试和治疗。皮试结果阳性率最高的为蒿属花粉,其次为其它夏秋花粉,春季花粉阳性率不高,致敏性不强。用花粉浸液对过敏症者进行免疫治疗,收到一定的疗效。