Bienertia cycloptera Bunge ex Boiss., Chenopodiaceae, another C4 Plant without Kranz Tissues286

Abstract: Following up an earlier study on Borszczowia aralocaspica, a second C₄ leaf type without Kranz tissues is described from Bienertia cycloptera Bunge ex Boiss. The species belongs also to tribe Suaedeae and grows in similar temporarily wet saline habitats in southwestern C Asia. Like Borszczowia, the species has the ability to perform C₄ photosynthesis in single chlorenchyma cells but the cytological compartmentation differs. Evidence is cited from anatomy (cytoplasmic compartmentation, starch formation), from carbon isotope composition and from indirect sources. It is documented by micrographs and δ¹³C values (mean ‐ 14.7 %). Variations of the δ¹³C values subsequently found in newly formed leaves of the same greenhouse plants (‐ 15.5 to ‐ 21.1 %) support the hypothesis that Bienertia is a facultative C₄/C₃ species. The new described bienertioid leaf type differs from the leaves of C₃ species in Suaeda by strict separation of the mesophyll into a central aqueous tissue without chloroplasts and a peripheral 1 ‐ 3 layered chlorenchyma with elaborate cytoplasmic compartmentation. Each cell of the latter contains a peripheral cytoplasmic layer with scattered chloroplasts and a large globular cytoplasmic body located in the central vacuole which is densely packed with starch producing chloroplasts, and joined by the nucleus. Comparative studies on different leaves of the same individuals of ordinary C₄ species demonstrated a remarkable range of variation, from 1.0 % in Salsola tragus up to 2.5 % in Petrosimonia sibirica. This corresponds well with the variance in data from different individuals and populations. For explaining the larger interspecific variation from about 23 other species of Salsoloideae, the hypothesis is developed that in species or groups of taxa specific leakages of their C₄ systems do occur. By three characters unique in tribe Suaedeae and detected during the study, Bienertia is confirmed as well separated from Suaeda and as a monotypic genus.     

Foliage colour influence on seed germination of Bienertia cycloptera in Arabian deserts

Bienertia cycloptera (Chenopodiaceae) produces two types of leaf foliage colour (reddish and yellowish). In order to determine the role of leaf colour variation in regulating the germination characteristics and salinity tolerance during germination, a study was conducted on seeds collected from plants of both colours. Seeds with and without pulp were germinated under two illumination conditions (12‐h light photoperiod and continuous dark), three alternating temperature regimes (15/25°C, 20/30°C and 25/35°C), and several salinity levels at 20/30°C. Germination percentage was significantly higher for seeds without pulp as compared to the seeds with pulp. The response of B. cycloptera seeds to salinity depended on the leaf colour. Thus, the seeds collected from reddish coloured plants were able to tolerate higher salinity compared to those of yellowish coloured plant. The germination recovery results indicate that the seeds from both coloured plants could remain viable in saline condition and they will be able to germinate once the salinity level are decreased by rain. The production of different foliage colours by B. cycloptera seems to be an adaptative strategy which increases the possibility for establishment in unpredictable environments by producing seeds with different germination requirements and salinity tolerance.     

Does Bienertia cycloptera with the single-cell system of C(4) photosynthesis exhibit a seasonal pattern of delta (13)C values in nature similar to co-existing C (4) Chenopodiaceae having the dual-cell (Kranz) system?

Family Chenopodiaceae is an intriguing lineage, having the largest number of C₄ species among dicots, including a number of anatomical variants of Kranz anatomy and three single-cell C₄ functioning species. In some previous studies, during the culture of Bienertia cycloptera Bunge ex Boiss., carbon isotope values (δ¹³C values) of leaves deviated from C₄ to C₃−C₄ intermediate type, raising questions as to its mode of photosynthesis during growth in natural environments. This species usually co-occurs with several Kranz type C₄ annuals. The development of B. cycloptera morphologically and δ¹³C values derived from plant samples (cotyledons, leaves, bracts, shoots) were analyzed over a complete growing season in a salt flat in north central Iran, along with eight Kranz type C₄ species and one C₃ species. For a number of species, plants were greenhouse-grown from seeds collected from the site, in order to examine leaf anatomy and C₄ biochemical subtype. Among the nine C₄ species, the cotyledons of B. cycloptera, and of the Suaeda spp. have the same respective forms of C₄ anatomy occurring in leaves, while cotyledons of members of tribe Caroxyloneae lack Kranz anatomy, which is reflected in the δ¹³C values found in plants grown in the natural habitat. The nine C₄ species had average seasonal δ¹³C values of −13.9‰ (with a range between species from −11.3 to −15.9‰). The measurements of δ¹³C values over a complete growing season show that B. cycloptera performs C₄ photosynthesis during its life cycle in nature, similar to Kranz type species, with a seasonal average δ¹³C value of −15.2‰. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Gametes with somatic chromosome number and their significance in interspecific hybridization in Fuchsia

Sexual polyploidization has both a theoretical as well as an applied significance. Morphological screening for large pollen grains and shape of pollen produced by the individual, cytological investigation of hybrid progeny, and unbalanced separation of chromosomes at anaphase I in pollen mother cells were used to detect the gametes with somatic chromosome number in Fuchsia. The interspecific hybrids of F. fulgens (sect. Ellobium) × F. magellanica (sect. Quelusia), F. fulgens (sect. Ellobium) × F. splendens (sect. Ellobium), and F. triphylla (sect. Fuchsia) × F. splendens (sect. Ellobium) produced at the University of Auckland, New Zealand, showed both large and normal pollen grains in the same anther indicating the presence of unreduced gametes. Cytological investigation carried out on the hybrid progeny of F. fulgens (diploid, 2n=22, sect. Ellobium) × F. magellanica (tetraploid, 2n=44, sect. Quelusia) and F. triphylla (diploid, sect. Fuchsia) × F. arborescens (diploid, sect. Schufia) revealed unexpected chromosome numbers of 2n=44 and 2n=33, respectively. In general, the hybrids showed low fertility caused by genetically unbalanced gametes resulted from random disjunction of chromosomes at anaphase I. Studies on meiosis together with the presence of different shapes and sizes of pollen grains in Fuchsia proved indirectly that unreduced gametes are the products of first division meiotic nuclear restitution. These unreduced gametes were viable irrespective of pollen shape, their predominance in the hybrids, nuclear DNA amount and species phylogenetic position.     

Differentiating pollen of Betula species from Iceland

Subfossil pollen from two co‐existing Betula species in Iceland, B. nana and B. pubescens, is frequently found in sediments and peat. Interpretation of the findings often depends on the ability to differentiate between the two species according to pollen size and structure. Fresh pollen samples were prepared from 70 individual trees/shrubs which had been identified to species by chromosome number. Grain diameters and pore depths were measured and ratios of grain diameter to pore depth (D/P ratios) were calculated. The mean grain diameters of pollen from diploid B. nana and tetraploid B. pubescens were 20.42 and 24.20?µm, whereas mean pore depths were 2.20 and 2.81?µm respectively. Mean D/P ratios were therefore 9.55 for B. nana and 8.85 for B. pubescens. The difference between species was statistically significant for all three pollen parameters. Grain diameter appeared to be the most useful parameter, as only about 20% of the samples were in the overlapping region of the species distributions. Pollen size (grain diameter) was also positively correlated to tree morphology, which was evaluated using species‐specific botanical characters. Pollen samples from different locations/populations in Iceland varied slightly in mean size and ratio. The size difference between pollen of B. nana and B. pubescens in this study is less than other papers have reported, which may be due to the effect of introgressive hybridisation between the two birch species in Iceland.     

Life history and life table parameters of the predatory miceTyphlodromus talbii

The predatory miteTyphlodromus talbii Athias-Henriot occurs in European vineyards and is often associated with economically important species. Neither its role in vineyards nor the factors affecting its population dynamics and relationships with other phytoseiid species are well known. The development and the reproduction ofT. talbii were studied in the laboratory by rearing the predator on different kinds of food (Panonychus ulmi, Eotetranychus carpini, Colomerus vitis, Tydeus caudatus, Mesembryanthemum criniflorum pollen). Overwintered females reared on tydeids survived for long periods and laid eggs, but they died after a few days when spider mites or pollen were provided. Development occurred on all mite species but not on pollen. Developmental times on tydeids were shorter than on the other prey. Oviposition was recorded on tydeids and, to a lesser extent, on eriophyids but not on spider mites or pollen. Experiments on tydeids, which resulted as being the best food, were conducted at two temperatures (20° and 27°C). The highest temperature affected the duration of development and oviposition rates positively, but total fecundity was similar. Predators reared at 27°C consumed more prey than those reared at 20°C. The life table parameters of the species were evaluated onT. caudatus (at 20° and 27°C) and onC. vitis. The highest r_m ofT. talbii was found for individuals reared onT. caudatus at 27°C (0.165). Lower values were obtained on the same prey at 20°C (0.089) or onC. vitis (0.030). The feeding habits ofT. talbii may explain why the species coexists with the generalistAmblyseius aberrans orTyphlodromus pyri.     

29个蔷薇属植物的孢粉学研究

采用扫描电镜技术对蔷薇属25个种及4个月季品种的花粉形态进行观察分析,探讨单叶亚属及蔷薇亚属中的芹叶组、合柱组、桂味组、月季组及月季品种之间的亲缘关系。研究表明:(1)所有被测样品的花粉都为具三孔沟的N3P4C5型单粒花粉,形状包括近球形、长球形及超长球形,其中大部分都为极轴较长的超长球形,以小檗叶蔷薇(P/E=2.29)最长。(2)在疏花蔷薇、托木尔蔷薇以及重瓣黄刺玫中发现有花粉二型现象。(3)被测样品外壁纹饰主要包括条纹、孔穴-条纹及近孔网纹3类,条纹类型主要出现在芹叶组中,而孔穴-条纹类型则为蔷薇属植物较普遍的纹饰。(4)聚类分析表明,小檗叶蔷薇与其它种亲缘较远,被测月季品种与月季组关系较近,芹叶组与合柱组关系较近,桂味组中的弯刺蔷薇与其他蔷薇的纹饰有明显区别,被单独分开。     

Pollen morphological studies in subfamily Suaedoideae (Chenopodiaceae)

The pollen morphology of two Bienertia species and 28 Suaeda species from the Old World has been studied with light and scanning electron microscopy. Pollen morphological characters used in this study include pollen diameter, pore number, pore diameter, operculum diameter, chord distance, exine thickness, plus number and characteristics of exine spinules and operculum spinules. Using these characters, the pollen of Bienertia is clearly distinguished from that of Suaeda. In addition, pollen data support recent molecular studies which merge the genus Borszczowia into Suaeda. The pollen grains of Suaeda show notable variation; in some cases this allows morphological distinctions to be made between species. Taxonomically, pore number is observed to be a more useful character than pollen diameter. Principal components analysis (PCA) shows only a weak correlation between pollen characters and habit (life form), habitat, mode of photosynthesis or phylogenetic relationships. Interestingly, however, the annual C₃ and C₄ species of section Schoberia are usually characterised by a higher pore number than the perennial C₄ species.     

10种金花茶组植物的花粉形态及分类学意义

金花茶组(Sect.Chrysantha)植物具有很高的观赏价值,但其分类存在争议.为探讨金花茶组植物花粉的形态特征和分类学意义,该研究用扫描电镜观察了10种金花茶的花粉形状、外壁纹饰以及穿孔特征,统计了极轴长、赤道轴长和萌发沟长,并进行聚类分析.结果表明:(1)10种供试金花茶植物花粉为中粒花粉,大部分花粉形状呈近球...     

Historical biogeographical patterns of the species of Bursera (Burseraceae) and their taxonomic implications

Aim The plant genus Bursera, with 104 species of trees and shrubs, has been used as a model for biogeographical analyses because of its high species richness and large number of endemic species. The biogeographical patterns of Bursera and their implications for its phylogenetic classification are reviewed in order that some hypotheses on the historical biogeography of tropical Mexico can be proposed. Location Bursera is found in the south‐western USA, most of Mexico, mainly below 1700 m elevation in tropical forests, with some species in xeric shrublands, diversifying along the Pacific slope, Central America, and north‐western South America. A few species occur on the Galapagos and Revillagigedo archipelagos, some of which are endemics, whereas in the Antilles species are distributed extensively, with several endemics in the Bahamas, Cuba, Jamaica, and Hispaniola. Methods Data from specimens in herbaria and the literature were used to construct a matrix of 104 species in 160 areas. Distributional patterns of the species of Bursera were inferred applying track analysis, parsimony analysis of endemicity (PAE), and Brooks parsimony analysis (BPA). Results Track analysis revealed four individual tracks: (1) a circum‐Caribbean track, comprising species of the Bursera simaruba species group; (2) an Antillean track, including species that have been transferred to Commiphora based on their pollen traits; (3) a Mexican Pacific track, including species of the B. fragilis, B. microphylla, and B. fagaroides species groups, called ‘cuajiotes’; and (4) a Neotropical Pacific track, including the two species groups assigned to section Bullockia, in which the individual track of the Bursera copallifera species group is nested within the track of the B. glabrifolia species group. The four tracks overlap in a node in the Mexican Pacific slope, where they are highly diversified. PAE allowed us to identify 22 areas of endemism: 12 in Mexico (11 along the Mexican Pacific slope), six in the Antilles, two in Central America, one in South America, and one in the Galapagos. The general area cladogram obtained by BPA has two main clades: one includes the greater Antilles; and the other, 12 Mexican areas of endemism. Main conclusions Bursera fragilis, B. microphylla, and B. fagaroides species groups can be treated together as a new section within Bursera, sect. Quaxiotea, because they are segregated from the other groups of sect. Bursera based on morphological, anatomical, molecular and geographical evidence.     

A new species of Sechium sect. Frantzia (Cucurbitaceae, Sicyeae, Sicyinae) from Mexico

Sechium mexicanum is described as a new species ofSechium sect.Frantzia. It differs from the remaining species of the section by several features of the inflorescences and staminate flowers, the obovoid and completely unarmed fruits, and pollen grains with 9–10 narrow, poorly defined colpi. It is endemic to Mexico and the first member of sect.Frantzia to be recorded outside of Central America. It grows at 900–2300 m in mesophilous forests and in oak and pineoak forests in the states of Hidalgo, Puebla, Querétaro, and Veracruz.     

Response of in vitro pollen germination and pollen tube growth of groundnut (Arachis hypogaea L.) genotypes to temperature

Air temperatures of greater than 35 °C are frequently encountered in groundnut‐growing regions, especially in the semi‐arid tropics. Such extreme temperatures are likely to increase in frequency under future predicted climates. High air temperatures result in failure of peg and pod set due to lower pollen viability. The response of pollen germination and pollen tube growth to temperature was quantified in order to identify differences in pollen tolerance to temperature among 21 groundnut genotypes. Plants were grown from sowing to harvest in a poly‐tunnel under an optimum temperature of 28/22 °C (day/night). Pollen was collected at anther dehiscence and was exposed to temperatures from 10° to 47·5 °C at 2·5 °C intervals. The results showed that a modified bilinear model most accurately described the response to temperature of percentage pollen germination and maximum pollen tube length. Genotypes were found to range from most tolerant to most susceptible based on both pollen characters and membrane thermostability. Mean cardinal temperatures (T_min, T_opt and T_max) averaged over 21 genotypes were 14·1, 30·1 and 43·0 °C for percentage pollen germination and 14·6, 34·4 and 43·4 °C for maximum pollen tube length. The genotypes 55‐437, ICG 1236, TMV 2 and ICGS 11 can be grouped as tolerant to high temperature and genotypes Kadiri 3, ICGV 92116 and ICGV 92118 as susceptible genotypes, based on the cardinal temperatures. The principal component analysis identified maximum percentage pollen germination and pollen tube length of the genotypes, and T_max for the two processes as the most important pollen parameters in describing a genotypic tolerance to high temperature. The T_min and T_opt for pollen germination and tube growth, rate of pollen tube growth were less predictive in discriminating genotypes for high temperature tolerance. Genotypic differences in heat tolerance‐based on pollen response were poorly related (R² = 0·334, P = 0·006) to relative injury as determined by membrane thermostability.     

First pollen record for Ancyloscelis apiformes (Apidae: Emphorini) in Central Amazon

Abstract

The first pollen study for the solitary bee Ancyloscelis apiformes (Emphorini) in a nest aggregation in the Central Amazon was made in October 2012 at the Sucupira apiary in east Manaus, Amazonas, at 03° 00? 05″ S, 59° 51? 05″ W. A total of 15 samples/nests (N1–N15) were analysed, including intact pollen loads (stored inside the nest) and post-emergence residues, which were acetolysed and mounted in glycerine gelatin. From each sample, 500 pollen grains were counted to determine the pollen frequencies and diversity (H′) and evenness (J′) indices. The most representative pollen types were Bonamia ferruginea (N1 = 95.6% and N2 = 96.00%) and the Ipomoea (N3 = 96.40%), both of which belong to the Convolvulaceae. In addition, Byrsonima crispa (N10 = 93.40%) and Malpighia glabra (N7 = 90.20% and N9 = 97.60%), representatives of the Malpighiaceae, were classified as temporary specialisation events with frequencies above 90%. In this study, A. apiformes, which is considered an oligolectic bee species, presented a polylectic tendency since it collected large percentages of pollen types from plants in distinct families that were not phylogenetically related.     

CONTRIBUTION OF POLLEN MORPHOLOGY TO SYSTEMATICS OF COLLOMIA (POLEMONIACEAE)

Pollen morphology of 14 species of Collomia (Polemoniaceae) was examined by light microscopy, and by both scanning and transmission electron microscopy. Four distinct pollen types were observed which are based principally upon 1) shape, number and distribution of apertures, and 2) surface sculpturing: Type 1—zonocolporate with striate ridges; Type 2—zonocolporate with striato-reticulate ridges; Type 3—pantoporate with radiate ridges; Type 4—pantoporate with irregularly reticulate ridges. Evaluation of pollen morphology reveals considerable discrepancy with respect to presently accepted sectional classification. Collomia grandiflora of sect. Collomia has a pollen type similar to that of members of sect. Collomiastrum and is now interpreted as representing an independent evolutionary line derived from the latter section. Collomia diversifolia of sect. Courtoisia has a pollen morphology similar to that of sect. Collomia. whereas C. heterophylla of the same section possesses pollen unique within the genus. This last pollen type shows close similarity to the pollen of members of Polemonium, Gilia, Leptodactylon, and Ipomopsis. Pollen of C. tinctoria and C. tracyi of sect. Collomia are anomalous within Polemoniaceae. No significant difference in exine stratification was discernible among the four pollen types.     

CHLOROPLAST DNA EVIDENCE FOR GENOME DIFFERENTIATION IN WILD POTATOES (SOLANUM SECT. PETOTA: SOLANACEAE)

Chloroplast DNA restriction site analysis has been used to test Hawkes's phylogenetic interpretations of the genomic data in Solanum sect. Petota. Hawkes hypothesized a diploid (2n = 24) origin of the tuber-bearing members of this group (subsection Potatoe) in Mexico and Central America (as a B genome) with later migrations and evolution to an A genome in South America, later followed by a return migration of the A genome to Mexico and Central America with A × B hybridizations and polyploidizations to produce ser. Longipedicellata (4x) and Demissa (6x). Our results provide partial support for this hypothesis by demonstrating the paraphyletic and primitive nature of the B genome species group, and the monophyletic and derived nature of all A genome and A × B genome species, including S. verrucosum, a hypothesized A genome progenitor of ser. Demissa. Thus, the Mexican and Central American polyploid species must have obtained their cytoplasm from the A genome. However, our results question the Stellata/Rotata hypothesis of Hawkes and the taxonomic placement of S. chomatophilum in ser. Conicibaccata.     

Effects of four constant temperatures on the development of two Bradysia (Diptera: Sciaridae) species

In this study, the effects of temperature on the growth, development, survival, fecundity and other population parameters of two local Bradysia species B. odoriphaga and B. impatiens were studied at four constant temperatures (25, 28, 31 and 34°C). The results show that 25°C is the optimum temperature for the growth and development of B. odoriphaga, while 28°C is more favourable for B. impatiens. The temperature of 31°C restricted the growth and development, while the temperature of 34°C inhibited the eggs hatching in both species, resulting in no egg survival and no subsequent development. High temperatures (>28°C) prolonged the 4th larval stage duration, mean generation time (T) and population doubling time (Dt) of both species. The high temperature of 31°C greatly shortened the female longevity, weakened the oviposition and reduced the survival of both species. Moreover, the life table parameters R₀, r_m and λ were also suppressed by this high temperature. However, the high temperature of 31°C had little impact on the egg survival, pupal weight and male longevity. In addition, at 31°C, the values of R₀, r_m and λ of B. odoriphaga were higher than those of B. impatiens, suggesting that B. odoriphaga is more tolerant to high temperature than B. impatiens. The differences between two Bradydsia species seem determined genetically. Our findings are important for better understanding their biological characteristics at a certain constant temperature and demonstrate the possibility to control and manage those two Bradysia species by increasing ambient temperature.     

A modern pollen–climate calibration set based on lake sediments from the Tibetan Plateau and its application to a Late Quaternary pollen record from the Qilian Mountains

Aim Fossil pollen spectra from lake sediments on the Tibetan Plateau have been used for qualitative climate reconstruction, but no modern pollen–climate calibration set based on lake sediments is available to infer past climate quantitatively. This study aims to develop such a dataset and apply it to fossil data. Location The Tibetan Plateau, between 30 and 40° N and 87 and 103° E. Methods We collected surface sediments from 112 lakes and analysed them palynologically. The lakes span a wide range of mean annual precipitation (P_ann; 31–1022 mm), mean annual temperature (T_ann; −6.5 to 1 °C), and mean July temperature (T_July; 2.6–19.7 °C). Redundancy analysis showed that the modern pollen spectra are characteristic of their respective vegetation types and local climate. Transfer functions for P_ann, T_ann and T_July were developed with weighted averaging partial least squares. Model performance was assessed by leave-one-out cross-validation. Results The root mean square errors of prediction (RMSEP) were 104 mm (P_ann), 1.18 °C (T_ann) and 1.17 °C (T_July). The RMSEPs, when expressed as percentages of the gradient sampled, were 10.6% (P_ann), 15.7% (T_ann) and 11.9% (T_July). These low values indicate the good performance of our models. An application of the models to fossil pollen spectra covering the last c. 50 kyr yielded realistic results for Luanhaizi Lake in the Qilian Mountains on the north-eastern Tibetan Plateau (modern P_ann 480 mm; T_ann−1 °C). T_ann and P_ann values similar to present ones were reconstructed for late Marine Isotope Stage 3, with minimum values for the Last Glacial Maximum (c. 300 mm and 2 °C below present), and maximum values for the early Holocene (c. 70 mm and 0.5 °C greater than present). Main conclusions The modern pollen–climate calibration set will potentially be useful for quantitative climate reconstructions from lake-sediment pollen spectra from the Tibetan Plateau, an area of considerable climatic and biogeographical importance.     

Using palynomorphological characteristics for the identification of species of Alsinoideae (Caryophyllaceae): a systematic approach

Palynological characters of 18 species belonging to seven genera of the traditional subfamily Alsinoideae including Arenaria, Cerastium, Eremogone, Lepyrodiclis, Minuartia, Sabulina and Stellaria were studied in detail using light and scanning electron microscopy. Pollen grains of subfamily Alsinoideae are subspheroidal or prolate, pantoporate and 20.04 to 51.4 µm in size, prominent and sunken apertures uniformly distributed on the pollen surface. Two types of pollen grain ornamentation were observed, i.e. microechinate-punctate or microechinate-perforate. Echini are present on the surface of the pollen of all investigated species with medium, dense, or sparse echinodensity. These species exhibit variation in polar view, equatorial diameter, number of apertures, exine thickness, diameter of pore, appendages per pore, pore ornamentation, echini arrangement, echinidensity and shape of pollen. Based on qualitative characters, a dichotomous key has been developed for quick and easy identification. The present investigation contributes to the systematic approach using palynological characteristics and correct identification of species for members of subfamily Alsinoideae (Caryophyllaceae).     

Pollination and seed set in tropical wetland grasses

This study concerns 39 different grass species occurring in the wetland regions of Godavari delta in the west Godavari district (16°15′–17°30′N and 80°50′–81°55′E) of Andhra Pradesh, southern India. In each species, the sexual status of lemmas, the period of stigma receptivity, pollen/ovule ratio, pollen longevity and daily pollen release were examined. The functional sexual systems were determined after performing controlled pollinations and testing seed quality by weight and germination potential. The florets of 35 species are morphologically hermaphroditic. Among the other four species, Chionachne koenigii and Iseilema laxum are monoecious; Chrysopogon aciculatus and Pennisetum pedicellatum are andromonoecious. Examination of the sequential opening of florets and controlled pollinations revealed that C. koenigii and I. laxum are obligate outcrossers with incompatibility to geitonogamous pollen; C. aciculatus and P.pedicellatum have a high level of compatibility to xenopollen. These and another nine species were treated as predominantly outcrossing species. Yet another five species were predominantly self‐fertilized, while the remaining 21 species displayed a mixed breeding system. In a majority of the species the P/O ratios are not high and thus do not conform to the expected large P/O ratios in wind‐pollinated plants and postulated breeding systems except in a few species. The majority of these grasses shed pollen over a short period spreading from 2 am to 8 am, when usually low turbulent conditions exist, thus allowing short distance transport and restricted pollen shadows with higher concentration of pollen near the source. This appears to be the appropriate strategy for maximization of pollination in view of the short lifespan of pollen that extends mostly over 1–3 h period, and the patchy distribution of the grasses under study. The restricted pollen shadows facilitate the low levels of pollen production in the grass species under study to fertilize most or all the available ovules.     

Pollen morphology of Quercus sect. Ilex and its relevance for fossil pollen identification in southwest China

Pollen grains of 16 modern species of Quercus were examined by scanning electron microscopy (SEM) and light microscopy (LM). The focus of this investigation was on a small group (c. eight species) of alpine, sclerophyllous oaks that may form a monophyletic group within sect. Ilex. The data were combined with published data for Polar axis (P) and Equatorial diameter (E) for more than 80 species. Based on pollen morphology Quercus pollen grains were divided into three types: (1) The Cyclobalanopsis type is smallest (generally < 23 μm) in size, with P/E ratios of approximately 1.08 and a psilate or fine-grained surface; (2) Quercus sect. Ilex type is 23–29 μm, the P/E ratio is approximately 1.24 (prolate) and it has a rugulate pollen surface; (3) the Quercus sect. Quercus type is generally > 29 μm in size, has a P/E ratio of approximately 1.04, and a clearly verrucate pollen surface. Based on a comparison with modern pollen size and ornamentation, fossil pollen grains of the Quaternary Qinghai Lake core can be assigned to the Chinese southwest mountain oak group of Quercus sect. Ilex (in particular Quercus semecarpifolia). In addition, we show that the pollen percentages of Quercus rapidly increased to the highest level during the glacial period. Using SEM for the identification of fossil Quercus pollen grains is essential to ensure the accuracy of differentiating evergreen Quercus types (sect. Ilex versus sect. Cyclobalanopsis) during the last glacial period in southwest China.