Phylogeny and Evolution of Bracts and Bracteoles in Tacca (Dioscoreaceae)

Most species in the genus Tacca （Dioscoreaceae） feature green to black purple, conspicuous inflorescence involucral bracts with variable shapes, motile filiform appendages （bracteoles）, and diverse types of inflorescence morphology. To infer the evolution of these inflorescence traits, we reconstructed the molecular phylogeny of the genus, using DNA sequences from one nuclear, one mitochondrial, and three plastid loci （Internal Transcribed Spacer （ITS）, atpA, rbcL, trnL-F, and trnH-psbA）. Involucres and bracteoles characters were mapped onto the phylogeny to analyze the sequence of inflorescence trait evolution. In all analyses, species with showy involucres and bracteoles formed the most derived clade, while ancestral Tacca had small and plain involucres and short bracteoles, namely less conspicuous inflorescence structures. Two of the species with the most elaborate inflorescence morphologies （T. chantrieri in southeast China and T. integrifolia in Tibet）, are predominantly self-pollinated, indicating that these conspicuous floral displays have other functions rather than pollinator attraction. We hypothesize that the motile bracteoles and involucres may facilitate selfing; display photosynthesis in the dim understory, and protect flowers from herbivory.

Cone and Ovule Development in Platycladus orientalis (Cupressaceae)

Seed cone in Platycladus orientalis (L.) France consists of four or five pairs of decussate bracts. Usually, two pairs of the fertile bracts in the middle of the cone subtend six ovules, which initiate in an acropetal manner. Only one ovule presents on each of the upper fertile bract, while two ovules initiate from a common primordium in the axil of lower bracts. In Beijing, most female cones initiated in July. All parts of the cone formed before dormancy, which occurred during November to the next January. After pollination in March, bract morphology changed dramatically; intercalary growth of the bract base formed a conspicuous protuberance, in which inverted vascular system developed. Furthermore, ovules on different pairs of bracts initiated in an acropetal manner and two ovules in each lower fertile bract initiated from a common primordium, which was different from the basipetal initiation of ovules and independently formed single ovule as reported by Takaso in Calltris

Ontogeny and Metamorphic Patterns of Female Reproductive Organs of Ephedra sinica Stapf (Ephedraceae)

Ontogeny and metamorphic. development of female reproductive organs in Ephedra sinica Stapf were surveyed. At the end of April, female cones began to initialize from the vegetative buds. Pollination occurred in mid-May and seeds matured at the beginning of July. The ontogenetic pattern of female reproductive organs of E. sin ca is basically similar to that of E. distachya L. The foliar nature of the outer envelope of the ovule in Ephedra is corroborated. Reduction of ovule number as a tendency of speciation in the genus is substantiated by the occurrence of tri-ovulate cones coupled with comprehensive characters of the genus. The metamorphic patterns as well as the leaf nature of the outer envelope indicate that female cones of Ephedra are compound while the female reproductive units of the ovulate cone have been reduced from secondary reproductive shoots similar to those of cordaites by phylogenetic transformation, fusion and reduction. Each fertile bract together with its axillary female reproductive unit composed the Bract Scale and Seed Scale Complex of Ephedra.

A new flavonoid from the bract of Zea mays L.

A new flavonoid was isolated from the bract of Zea mays L.The structure of the compound was identified as 4＇,5,7-trihydroxy-3＇,5＇-dimethoxyflavone 7-O-[β-D-apiofuranosyl（1→2）]-β-D-glucopyranoside on the ground of chemical and spectroscopic methods.

The Origin and Identity of the Calyculus in Loranthaceae:Inferred From the Floral Organogenesis of Loranthus tanakae Franch.&Sav.

The flowers of the hemiparasitic family Loranthaceae are always subtended by a rimmed structure known as the calyculus.The origin and identity of the calyculus have been disputed for more than a century.Various hypotheses have been proposed,for example,an outgrowth of the axis,a reduced calyx,and a bracteolar(prophyllar)origin,but controversies remain.To obtain a plausible explanation of the origin of the calyculus,we investigated the flowers of Loranthus tanakae using scanning electron microscopy and light microscopy to observe the entire developmental process of the floral parts.Our results show that bracts are not present in L.tanakae.The calyculus,which lacks serving vascular bundles,initiates as a semicircular primordium and then develops into a circular structure by an adnation at both sides.The flower primordium usually cleaves into six petals from its centre along a whorled pattern in two series with three petals each,before or after the calyculus closed.Isomerous stamen primordia probably follow the same initiation pattern as petals do.Several carpels of different sizes initiate simultaneously as a united primordium.We support the hypotheses that the calyculus is of bract or bracteole origin due to its independent initiation from the inflorescence rachis,its similar morphology and positioning as the bract or bracteole,and that having no developmental relationship with the petals.We suggest keeping the usage of the term“calyculus”.Loranthus flowers should be considered monochlamydeous with three whorls of floral parts,namely petal,androecium,and gynoecium.

Study on Chloroplast Ultrastructure in Different Color Period of Euphorbia pulcherrima

By the observation of chloroplast ultrastructure in different period of bract colors of Euphorbia pulcherrima, the paper studied the change of chloroplast ultrastructural in the transition process of bract colors, identified the relationship between E.pulcherrima color change and the chloroplast ultrastructure to provide theorical bases for the cultivation management and further study of E. pulcherrima. Ultrastructural study showed that in the process of change from green to red, the chloroplast of bracts disintegrated gradually, lamellar structure was destroyed gradually, and the content of chloroplasts in mesophyll cells was also reduced gradually. When bracts color resumed to turn green gradually, the content of chloroplasts in mesophyll cells was also increased gradually.

The Evolution of Stinging Hairs and Other Characters in Nettle Family

Urticaceae Juss.is a large cosmopolitan family and taxonomically difficult group,partly because it encompasses a broad range of morphological diversity and many of the diagnostic characters（e.g.flower,achene.stipule,bract）require a microscope for accurate determination.Meanwhile,most Uriiceae species have stinging hairs which make them more difficult to collect and identify.As a result,the infra-familial classification of Urticaceae has been controversial for more than a century.A research group led by Prof.

Bract suppression regulated by the miR156/529-SPLs-NL1-PLA1 module is required for the transition from vegetative to reproductive branching in rice

Reproductive transition of grasses is characterized by switching the pattern of lateral branches,featuring the suppression of outgrowth of the subtending leaves(bracts)and rapid formation of higher-order branches in the inflorescence(panicle).However,the molecular mechanisms underlying such changes remain largely unknown.Here,we show that bract suppression is required for the reproductive branching in rice.We identified a pathway involving the intrinsic time ruler microRNAI56/529,their targets SQUAMOSA PROMOTER BINDING PROTEIN LIKE(SPL)genes,NECK LEAF1(NL1),and PLASTOCHRON1(PLA1),which regulates the bract outgrowth and thus affects the pattern switch between vegetative and reproductive branching.Suppression of the bract results in global reprogramming of transcriptome and chromatin accessibility following the reproductive transition,while these processes are largely dysregu-lated in the mutants of these genes.These discoveries contribute to our understanding of the dynamic plant architecture and provide novel insights for improving crop yields.

Pollinator attraction in Cornus capitata (Cornaceae): the relative role of visual and olfactory cues

Aims it is generally accepted that visual displays and floral scent play important roles in communication between flowering plants and their pollinators.However,the relative role of visual and olfactory cues in pollinator attraction is largely unknown.in this study,we determined the roles of both types of cue in attracting pollinators to Cornus capitata,a medium sized tree with each capitulum sur-rounded by four large,white,petaloid bracts.Methods Pollinator observations and pollination experiments were con-ducted in a natural population;the inflorescences’visual and olfactory signals were characterized by spectral and chemical analyses;the responses of pollinators to visual and olfactory cues were tested using dual-choice behavioural bioassays;the relative roles of visual and olfactory cues in pollinator attrac-tion were tested by comparing the responses of pollinators to inflorescences subjected to three experimental treatments(intact,all bracts removed,and capitulum removed)within the natural population.Important Findings For fruit set,C.capitata is entirely dependent on pollinators,with a bee,Anthophora sp.,being the main pollinator.bracts present high colour distance and green contrast against the leaves.Twelve volatile compounds in the floral scent were detected,most of which have previously been reported to be attractive to a broad spectrum of bee species.behavioural bioassays showed that both,visual cues alone and olfactory cues alone,are attractive to pollinating bees.However,vis-ual cues alone attracted significantly more approaches than olfactory cues alone,while olfactory cues alone elicited a significantly higher landing percentage than visual cues alone.The finding suggests that,in the C.capitata-Anthophora sp.interaction,visual cues are mainly used for location from long distances,while olfactory cues mainly aid landing from short distances.our results indicate that different modalities of floral cues should be considered together to understand fully the communication between flowering plant and pollinators.