Photosynthetic Light Utilization Efficiency, Water Relations and Leaf Growth of C3 and CAM Tropical Orchids under Natural Conditions

Native orchid species of Singapore in their natural conditions experience stress from high irradiance, high temperatures and periods of extended low rainfall, which impact orchid plant physiology and lead to reduced growth and productivity. In this study, it was found that there was a reduction in photochemical efficiency of photosystem II (PSII) in 6 native orchid species under high light (HL) and Bulbophyllum membranaceum under low light (LL). There was chronic photoinhibition in these 6 orchid species over a period of 3 months after transplanting onto the tree trunks without watering and fertilization, especially in Coelogynes mayeriana and Bulbophyllum membranaceum under both HL and LL. This chronic photoinhibition caused by sustained period of water deficit in their natural conditions was later reversed by natural re-watering conditions from higher rainfall. These results indicate that water deficit has a greater impact on photosynthetic light utilization efficiency than excess light. The present study also showed that after natural rewatering, relative water content (RWC) of leaves and pseudobulbs generally increased. During the natural re-watering, total leaf area also gradually increased and reached maximum expansion after 7 weeks under both HL and LL, with some exceptions due to leaf abscission or decline in total leaf area, possibly a strategy for water conservation.

Revision of Senegalia in China, and notes on introduced species of Acacia, Acaciella, Senegalia and Vachellia(Leguminosae: Mimosoideae)

The present work represents the first comprehensive taxonomic revision of Acacia sens.lat.(Leguminosae:Mimosoideae)in China,focusing on the indigenous species.Critical reassessments of specimens and re-defin让ion of previously recorded species have resulted in recognising 21 indigenous species under Senegalia,a segregate of the former Acacia sens.tat.Detailed botanical profiles are provided for these species,together w让h a diagnostic line drawing and distribution map;photographs of living plants are provided for more than half the species.Terser treatments are also provided for the 15 species from four genera that are regarded as major introductions of Acacia sens.lat.to the country:Acacia Mill.(12 spp.),Acaciella Britton&Rose(1 sp.),Senegalia Raf.(1 sp.)and Vachellia Wight&Arn.(1 sp.).An identification key to all Acacia sens.lat.species in China is provided.The indigenous species of Senegalia in China belong to sect.Monacanthea(Vassal)Maslin,comb,nov.,and the introduced ones to sect.Senegalia.As a consequence of this study,the number of Senegalia species now recognised for China has almost doubled.Six new species are described:Senegalia clandestina Maslin,B.C.Ho,H.Sun&LBai,sp.nov.;Senegalia guangdongensis Maslin,B.C.Ho,H.Sun&LBai,sp.nov.;Senegalia obliqua Maslin,B.C.Ho,H.Sun&LBai,sp.nov.;Senegalia orientalis Maslin,B.C.Ho,H.Sun&LBai,sp.nov.;Senegalia prominens Maslin,B.C.Ho,H.Sun&LBai,sp.nov.;Senegalia stipitata Maslin,B.C.Ho,H.Sun&LBai,sp.nov.Four new combinations are established:Senegalia garrettii(I.C.Nielsen)Maslin,B.C.Ho,H.Sun&LBai,comb.&stat,nov.;Senegalia kerrii(I.C.Nielsen)Maslin,B.C.Ho,H.Sun&LBai,comb.&stat,nov.;Senegalia kunmingensis(C.Chen&H.Sun)Maslin,B.C.Ho,H.Sun&LBai,comb.&stat,nov.;Senegalia macrocephala(Lace)Maslin,B.C.Ho,H.Sun&LBai,comb.nov.Senegalia andamanica(I.C.Nielsen)Maslin,Seigler&Ebinger and S.macrocephala are new records for China.A lectotype is designated for Acacia teniana Harms and 2nd step lectotypifications effected for Acacia delavayi Franch.,Acacia insuavis Lace,Acacia pruinescens Kurz and Acacia yunnanensis Franch.Former holotype citations are corrected to lectotype for Acacia hainanensis Hayata,Acacia macrocephala Lace,Acacia oxyphylla Graham ex Benth.and Acacia philippinarum Benth.A neotype is designated for Acacia arrophula D.Don.China is a principal area of species-richness for Senegalia in Asia.Senegalia displays a high degree of endemism within China and almost half the species are endemic or near-endemic,w让h Yunnan the most species-rich and species-diverse Province.

Genomic,transcriptomic,and metabolomic analysis of Oldenlandia corymbosa reveals the biosynthesis and mode of action of anti-cancer metabolites

Plants accumulate a vast array of secondary metabolites,which constitute a natural resource for pharmaceuticals.Oldenlandia corymbosa belongs to the Rubiaceae family,and has been used in traditional medicine to treat different diseases,including cancer.However,the active metabolites of the plant,their biosynthetic pathway and mode of action in cancer are unknown.To fill these gaps,we exposed this plant to eight different stress conditions and combined different omics data capturing gene expression,metabolic profiles,and anti-cancer activity.Our results show that O.corymbosa extracts are active against breast cancer cell lines and that ursolic acid is responsible for this activity.Moreover,we assembled a high-quality genome and uncovered two genes involved in the biosynthesis of ursolic acid.Finally,we also revealed that ursolic acid causes mitotic catastrophe in cancer cells and identified three high-confidence protein binding targets by Cellular Thermal Shift Assay(CETSA)and reverse docking.Altogether,these results constitute a valuable resource to further characterize the biosynthesis of active metabolites in the Oldenlandia group,while the mode of action of ursolic acid will allow us to further develop this valuable compound.

Phylogenetic and climatic constraints drive flowering phenological patterns in a subtropical nature reserve

Aims Exploring flowering patterns and detecting processes are essential when probing into the nature of reproductive traits during the life history and the interactions among different evolutionary clades.such patterns are believed to be influenced by many factors,but quantifying these impacts at the community-level remains poorly understood.Methods We investigated the flowering patterns based on long-term her-barium records in a given area from subtropical forest regions in southern China.We obtained 5258 herbarium voucher specimens collected from the Dinghushan National Nature reserve(DNNr)belonging to 166 families,943 genera and 2059 species and exam-ined the month when each species was flowering during the period 1920-2007.Important Findings The results showed that plants flowered sequentially almost through-out the whole year,showing the characteristics of subtropical evergreen broad-leaved forests.Flowering spectrums of the entire flora and the four life forms exhibited a clear unimodality that is probably typical of subtropical forest communities.Flowering pat-terns of the DNNr were positively correlated with mean rainfall,mean air temperature and mean sunshine duration.median flowering dates of the 38 large species-rich families ranged from early april to late august;25 families exhibited significant unimodal distribution patterns,whereas the remaining families were unclear or bimodal.median flowering dates of the 10 most species-rich genera ranged from middle may to later July.While the results are consist-ent with climatic factors playing a general role in flowering patterns,median flowering dates varied significantly among species-rich families and genera,suggesting that phylogenies could provide spe-cific constraints in subtropical forests.