水烛的花部形态观察——兼论与长苞香蒲的分类学界定

通过腊叶标本研究、野外观察和文献考证,结合栽培试验,研究了香蒲科水烛（Typha angustifolia L.）花部结构特征,补充描述了该种丝状毛在子房柄上的着生方式、小穗不孕雌花数目等性状特征,观察了在成熟期不同阶段其孕性雌花柱头与小苞片的长度变异。结果显示,水烛孕性雌花小苞片呈宽披针形、匙形或条形,先端褐色,短于柱头,或与柱头近等长或稍长于柱头;子房柄上的丝状毛除少数散生外,多数基部合生呈鞘状或束状,在子房柄下部呈1～4轮排列;小穗不孕雌花常3（～4）枚。研究材料在7月中旬前后雌花小苞片明显短于柱头,随果穗成熟小苞片与柱头近等长。长苞香蒲（T.domingensis Pers.）子房柄上的丝状毛形态和着生方式与水烛中的情况基本一致,但小苞片白色透明,小穗不孕雌花常1（～2）枚。这表明水烛孕性雌花小苞片和柱头的长度比例与不同成熟阶段有关系,不宜作为与长苞香蒲的区别特征,而小穗不孕雌花数目和小苞片颜色等特征对两物种的划分有较重要的意义。     

Reproductive biology of a hummingbird‐pollinated Billbergia: light influence on pollinator behaviour and specificity in a Brazilian semi‐deciduous forest

• Ornithophily has evolved in parallel several times during evolution of angiosperms. Bird pollination is reported for 65 families, including Bromeliaceae. One of the most diverse bromeliad is Billbergia, which comprises species pollinated mainly by hummingbirds.
• Based on investigations on flowering phenology, morpho‐anatomy, volume and concentration of nectar, pollinators and breeding system, this paper explores the reproductive biology and pollinator specificity of B. distachia in a mesophytic semi‐deciduous forest of southeastern Brazil.
• The results have show that B. distachia is pollinated by a single species of hermit hummingbird, Phaethornis eurynome, which search for nectar produced by a septal nectary, where the secretory tissue is located above the placenta. The species is self‐incompatible. The combination of pollinator specificity, due to long corolla tubes that exclude visitation of short‐billed hummingbirds, complete self‐incompatibility and non‐territorial behaviour of pollinators, it is very important to reduce pollen loss and increase gene flow within population.
• Our results indicate that studies on pollination biology and reproduction are essential to understand the evolutionary history of pollination systems of plants since, at least in Billbergia, variation in the pollinator spectrum has been recorded for different habitats among Brazilian forests. Furthermore, according to our data, foraging of Phaethornis on flowers is independent of air temperature and humidity, while the main factor influencing hummingbird visitation is daylight. Considering current knowledge on climatic parameters influencing hummingbird foraging, pollination and reproductive biology of Neotropical flora and environment of the hermit hummingbird in tropical forests, new insights on plant–pollinator interaction are provided.

     

火龙果转录组测序、基因表达与功能分析

利用高通量测序技术对火龙果(Hylocereus undulatus Britt)红肉品种‘大红二号’的花芽、果实和枝条不同发育阶段的基因表达进行研究。结果显示,转录组测序共获得468.68 Gb原始数据(Raw data),从头组装获得239 152条转录本和162 519条unigene,约53.74%的unigene得到注释。分别在43 506条和16 251条unigene中检测到600 283个SNP位点和56 147个SSR位点。基因表达分析结果表明,在火龙果不同组织Fl510、Fl513、Fl514、Fl518、F711、F715、S513、S419中分别有31、7、5、152、17、63、17、8个特异表达的unigene。通过GO和KEGG富集分析,发现了一些组织特异的GO条目和代谢通路,如在Fl510中富集的类萜骨架生物合成代谢通路等。本研究还对参与花发育的候选基因进行了鉴定和表达分析,他们包括COL基因、FT-like基因、分生组织决定基因和器官决定基因等。     

乙烯诱导水仙成花相关代谢物和基因的筛选与分析

为了解乙烯诱导水仙(Narcissus tazetta var. chinensis)成花的生理和分子机制,利用代谢组和转录组测序技术,筛选乙烯诱导水仙成花的差异表达代谢物和基因。结果表明,乙烯处理的侧芽检测到12个差异表达代谢物(DEM),包括7个上调,5个下调,其中,(±)7-表茉莉酸、多巴胺、亚精胺可能与乙烯诱导水仙成花正相关,而吲哚及其衍生物呈负相关。转录组共获得1 021个差异表达基因(DEG),包括615个上调,406个下调,在DEG中鉴定筛选了45个与乙烯信号传导和开花相关的差异表达基因。乙烯诱导水仙成花启动可能先激活水仙鳞茎内源植物激素(尤其乙烯)信号通路的变化,与开花促进基因FPF1和MADS15的上调表达密切相关。9个基因的qRT-PCR结果验证了RNA-Seq的正确性。这些差异表达的代谢物和基因在水仙成花启动过程中可能具有重要作用。     

Can a stench be beautiful? – Osmophores in stem-succulent stapeliads (Apocynaceae-Asclepiadoideae-Ceropegieae-Stapeliinae)

Carrion flower stapeliads are examples of olfactory mimicry, forming sapromyiophilous flowers, which mimic food sources or oviposition sites to attract fly pollinators. The aim of this work was to investigate the ultrastructure of osmophores involved in the release of the carrion odor of Orbea variegata and Boucerosia indica flowers. In spite of their similar architecture (epidermal epithelium+subepidermal secretory layers), the osmophores of stapeliads feature some differences in morphology and ultrastructure. The epidermal epithelial cells of O. variegata and B. indica differ in shape, but both are extremely rich in endoplasmic reticulum and flocculent material in the vacuole. Unlike the Orbea, Boucerosia has starchless leucoplasts in the epidermal epithelium. Orbea features a cuticle with microchannels, while Boucerosia has a different mechanism for the pathway of scent substances to the cell exterior. They are released by rupturing of the outer layer of cuticle at the apex of the papillae. The epidermal cells of the adaxial corolla differ even between parts of the corolla, the corolla lobes and the annulus in the flower. This diversity may be connected with an odor gradient. The morphological and anatomical features of stapeliad (subtribe Stapeliinae) osmophores are generally similar to osmophores of members of subtribe Ceropegiinae (Ceropegia), thus, we suggest that this model of osmophores evolved before early diversification of Ceropegieae. The ultrastructural features of stapeliad osmophores are generally similar to those of Araceae, Orchidaceae and Passifloraceae.     

Floral scent evolution in the section Pseudophrys: pollinator‐mediated selection or phylogenetic constraints?

• Sexually deceptive orchid species from the Mediterranean genus Ophrys usually interact with one or a few pollinator species by means of specific floral scents. In this study, we investigated the respective role of pollinator‐mediated selection and phylogenetic constraints in the evolution of floral scents in the section Pseudophrys.
• We built a phylogenetic tree of 19 Pseudophrys species based on three nuclear loci; we gathered a dataset on their pollination interactions from the literature and from our own field data; and we extracted and analysed their floral scents using solid phase microextraction and gas chromatography‐mass spectrometry. We then quantified the phylogenetic signal carried by floral scents and investigated the link between plant–pollinator interactions and floral scent composition using phylogenetic comparative methods.
• We confirmed the monophyly of the section Pseudophrys and demonstrated the existence of three main clades within this section. We found that floral scent composition is affected by both phylogenetic relationships among Ophrys species and pollination interactions, with some compounds (especially fatty acid esters) carrying a significant phylogenetic signal and some (especially alkenes and alkadienes) generating dissimilarities between closely related Pseudophrys pollinated by different insects.
• Our results show that in the section Pseudophrys, floral scents are shaped both by pollinator‐mediated selection and by phylogenetic constraints, but that the relative importance of these two evolutionary forces differ among compound classes, probably reflecting distinct selective pressures imposed upon behaviourally active and non‐active compounds.

     

Breeding system in the dichogamous hermaphrodite Silene acutifolia (Caryophyllaceae)

The breeding system of the dichogamous hermaphrodite species Silene acutifolia, endemic to north-west Spain and north and central Portugal, is examined. Pollen germinability and style-stigma receptivity were analysed to determine whether protandry is a barrier to self-fertilization. By 48 h after anthesis, pollen germinability had declined to approx. 10 %. The short straight styles are not receptive when flowers first open. They gradually elongate and curve outwards, develop stigma papillae and become receptive. There is no clear separation between stigma and style: the stigma papillae appear in a line along the length of the style. Fruit set is high regardless of pollen source; however, seed set is significantly reduced after both spontaneous and facilitated autogamy. Seed set following spontaneous autogamy was 30 % (86 % in controls) in 1998 and 33 % (87 % in controls) in 1999. Seed set following facilitated autogamy was 62 % (86 % in controls) in 1998 and 67 % (89 % in controls) in 1999. Thus, separation of the male and female phases does not prevent production of seeds by self-pollination, although it does reduce the likelihood of this. Furthermore, results of the present experiments indicate that this species has no self-incompatibility mechanisms (self-compatibility index = 0.98). The selfing rate in the study population was 0.41, which is supported by the lack of self-incompatibility systems and by the incomplete protandry.     

The flowering-time geneFT and regulation of flowering inArabidopsis

Transition from vegetative to reproductive development (flowering) is one of the most important decisions during the post-embryonic development of flowering plants. More than twenty loci are known to regulate this process inArabidopsis. Some of these flowering-time genes may act at the shoot apical meristem to regulate its competence to respond to floral inductive signals and floral evocation. Genetic and phenotypic analyses of mutants suggest that the late-flowering geneFT may be a good candidate for such genes. To test this, we have cloned theFT gene using aFT-deficiency line associated with a T-DNA insertion. Cloned genes and loss-of-function mutants in hand, it is now possible to analyse the role ofFT and other genes in flowering at the biochemical and cellular levels as well as at the genetic level. The deduced FT protein has homology with TFL1 and CEN proteins believed to be involved in regulation of inflorescence meristem identity. Phylogenetic analysis suggests that theFT group and theTFL1/CEN group of genes diverged before the diversification of major angiosperm clades. This raises the interesting question of the evolutionary relationship between the regulation of vegetative/reproductive switching in the shoot apical meristem and the regulation of inflorescence architecture in angiosperms. The extended abstract of a paper presented at the 13th International Symposium in Conjugation with Award of the International Prize for Biology “Fronitier of Plant Biology”