Yifan Duan’s research while affiliated with Sichuan University and other places

Plant biogenic volatile organic compounds (BVOCs) possess ecological functions in antimicrobial benefits and air purification. The objectives of the study were to determine the differences in antimicrobial capacity of bamboo forests at different sampling sites. Three common bamboo species—Phyllostachys edulis, Bambusa emeiensis, and Phyllostachys violascens—were selected to determinate the antimicrobial activity of bamboo forests as well as under ex vivo conditions. Natural sedimentation method was used to determine the microbe counts in bamboo forests, and the microbe counts in grassland in the same area was measured as control treatment. The results showed that except for the P. violascens in Ya’an, the airborne microbial content of the sampling sites in bamboo forests was significantly lower relative to that of grassland in the same area, and inhibition rate reached 74.14% in the P. violascens forest in Dujiangyan. P. edulis forest and P. violascens forest in Ya'an had significantly lower inhibition rates than the other sampling sites, and there was no significant difference in the inhibition rates among the rest of the bamboo forest. The bacterial inhibition rate of bamboo leaves under ex vivo conditions varied with bamboo species and bacterial strains, with higher antibacterial activity against Gram-negative bacteria overall. Escherichia coli was sensitive to B. emeiensis leaves, while Staphylococcus aureus and Bacillus subtilis were sensitive to P. violascens leaves. Moreover, Candida albicans, S. cremoris, and Shigella Castellani were sensitive to P. edulis leaves. An analysis of the BVOCs composition from P. edulis collected in Changning by SPME-GC/MS revealed that the relative content of ocimene was obviously higher than other components. This study showed that P. edulis BVOCs have strong inhibitory ability to the tested microorganisms, and its main constituent, ocimene, has health benefit. P. edulis has the potential to become a forest recreation bamboo species.

Under salt stress, recretohalophyte Plumbago auriculata tetraploids enhance salt tolerance by increasing selective secretion of Na⁺ compared with that in diploids, although the mechanism is unclear. Using non-invasive micro-test technology, the effect of salt gland Ca²⁺ content on Na⁺ and K⁺ secretion were investigated in diploid and tetraploid P. auriculata under salt stress. Salt gland Ca²⁺ content and secretion rates of Na⁺ and K⁺ were higher in tetraploids than in diploids under salt stress. Addition of exogenous Ca²⁺ increased the Ca²⁺ content of the salt gland in diploids and is accompanied by an increase in the rate of Na⁺ and K⁺ secretion. With addition of a Ca²⁺ channel inhibitor, diploid salt glands retained large amounts of Ca²⁺, leading to higher Ca²⁺ content and Na⁺ secretion rate than those of tetraploids. Inhibiting H2O2 generation and H⁺-ATPase activity altered Na⁺ and K⁺ secretion rates in diploids and tetraploids under salt stress, indicating involvement in regulating Na⁺ and K⁺ secretion. Our results indicate that the increased Na⁺ secretion rate of salt gland in tetraploids under salt stress was associated with elevated Ca²⁺ content in salt gland.

Main conclusion Enhanced secretion of Na⁺ and Cl⁻ in leaf glands and leaf vacuolar sequestration of Na⁺ or root retention of Cl⁻, combined with K⁺ retention, contribute to the improved salt tolerance of tetraploid recretohalophyte P. auriculata. Abstract Salt stress is one of the major abiotic factors threatening plant growth and development, and polyploids generally exhibit higher salt stress resistance than diploids. In recretohalophytes, which secrete ions from the salt gland in leaf epidermal cells, the effects of polyploidization on ion homeostasis and secretion remain unknown. In this study, we compared the morphology, physiology, and ion homeostasis regulation of diploid and autotetraploid accessions of the recretohalophyte Plumbago auriculata Lam. after treatment with 300 mM NaCl for 0, 2, 4, 6, and 8 days. The results showed that salt stress altered the morphology, photosynthetic efficiency, and chloroplast structure of diploid P. auriculata to a greater extent than those of its tetraploid counterpart. Moreover, the contents of organic osmoregulatory substances (proline and soluble sugars) were significantly higher in the tetraploid than in the diploid, while those of H2O2 and malondialdehyde (MDA) were significantly lower. Analysis of ion homeostasis revealed that the tetraploid cytotype accumulated more Na⁺ in stems and leaves and more Cl⁻ in roots but less K⁺ loss in roots compared with diploid P. auriculata. Additionally, the rate of Na⁺ and Cl⁻ secretion from the leaf surface was higher, while that of K⁺, Mg²⁺, and Ca²⁺ secretion was lower in tetraploid plants. X-ray microanalysis of mesophyll cells revealed that Na⁺ mainly accumulated in different cellular compartments in the tetraploid (vacuole) and diploid (cytoplasm) plants. Our results suggest that polyploid recretohalophytes require the ability to sequester Na⁺ and Cl⁻(via accumulation in leaf cell vacuoles or unloading by roots) and selectively secrete these ions (through salt glands) together with the ability to prevent K⁺ loss (by roots). This mechanism required to maintain K⁺/Na⁺ homeostasis in polyploid recretohalophytes under high salinity provides new insights in the improved maintenance of ion homeostasis in polyploids under salt stress.

Cerastigmawillmottianum Stapf (Plumbaginaceae, Cerastigma), a native Chinese plant, has decorative and medicinal values and is used in green areas and landscapes. However, wild plants have small flowers and scattered, pendulous branches with lower compactness, making them inferior as ornamentals. Polyploidization can improve ornamental properties and carbon sequestration capacity, providing novel germplasms with higher carbon dioxide assimilation abilities based on plant-based C biosequence. This study induced polyploidy in apical buds in vitro through tissue culturing and application of colchicine, trifluralin, or pendimethalin; in the most efficient protocol, explants were cultured for 7 days in MS medium supplemented with 1200.0 μM trifluralin and 2% dimethyl sulfoxide (DMSO), with a survival rate of 74.45% and polyploidization rate of 17.78%. After 5–8 successive generations obtained by cutting aseptic apical buds for purification, ploidy level was effectively and precisely identified by morphological observation, stomatal measurement, DNA content analysis, and chromosome counting. According to our breeding goal, the morphology and photosynthetic capacity of tetraploids were screened. Compared to diploids, tetraploids have improved ornamental properties, including greater compactness, larger flowers and heart-shaped leaves, and a greater net photosynthetic rate, with higher CO2 assimilation efficiency. We developed an integrated protocol for the induction, purification, screening and identification of tetraploid C. willmottianum plants. Moreover, the newly developed tetraploid germplasm can be utilized to breed new cultivars. We hope that our research will lead to novel garden plants with improved ornamental value and high carbon sequestration ability, contributing to carbon neutrality.

The tropical plant Plumbago auriculata can tolerate subzero temperatures without induction of apoptosis after cold acclimation in autumn, making it more cold tolerant than conventional tropical plants. In this study, we found that low temperatures significantly affected the photosynthetic system of P. auriculata. Using transcriptome sequencing, PaDREB1A was identified as a key transcription factor involved in the response to cold stress in P. auriculata. This transcription factor may be regulated by upstream JA signaling and regulates downstream ERD4 and ERD7 expression to resist cold stress. Overexpression of PaDREB1A significantly enhanced freezing resistance, protected the photosynthetic system, and enhanced the ROS scavenging mechanism under cold stress in Arabidopsis thaliana. Additionally, PaDREB1A significantly enhanced the expression of CORs and CAT1 in A. thaliana, which further activated the downstream pathway to enhance plant cold tolerance. This study explored the possible different regulatory modes of CBFs in tropical plants and can serve as an important reference for the introduction of tropical plants to low-temperature regions.

Ceratostigma willmottianum (Plumbaginaceae) is a perennial herb native to China. Many species of Plumbaginaceae have been reported to exhibit heterostyly. Determining the functional breeding system of C. willmottianum can improve our understanding of the reproductive ecology of heterostylous plants. We investigated the floral traits and pollen and stigma characteristics in a natural population, and artificial pollination was carried out in an artificial population. It was found that C. willmottianum was distylous with short (S)- and long (L)-styled morphs, did not exhibit precise reciprocal herkogamy and was partially self-compatible but primarily outcrossing. In the artificial pollination experiments, the pollen tubes reached the base of the style under intermorph pollination, whereas they rarely penetrated the style under intramorph pollination and self-pollination. Both the L and S morphs exhibited a high seed set after intermorph pollination, whereas the seed set under intramorph pollination was lower. Therefore, C. willmottianum may spread the chance of receiving pollen between the two morphs by nonreciprocal heterostyly, which may be a unique mode of ecological adaptation in Plumbaginaceae. We believe that our discovery could provide new ideas regarding the origin and evolution of heterostyly.

The ornamental characteristics of Plumbago auriculata are mainly reflected in the floral organ. Exploring the genetic inheritance of flower characteristics is important for breeding new varieties. In this study, F1 segregating populations were obtained by using artificial hybridization (direct cross and reciprocal cross) between P. auriculata and its variant P. auriculata f. alba. A heterosis analysis and mixed major gene plus polygene inheritance model were used to investigate the inheritance of eight flower characteristics in the F1 generation: inflorescence length (IL), inflorescence diameter (ID), number of flowers per inflorescence (NFI), beginning of the blooming period (BBP), inflorescence number (IN), flower diameter (FD), flower length (FL) and corolla color value (CCV). In addition to the CCV, the other flower characteristics showed continuous unimodal and skewed distributions, which indicated that these characteristics were quantitative and controlled by polygenes. Although transgressive heterosis was observed only for BBP in both combinations, transgressive segregation was commonly observed, except for CCV in the F1 generation; these findings could facilitate the selection of beneficial individuals for breeding. Genetic analysis revealed that NFI could be described by a B-3 genetic model via two pairs of additive major genes; BBP could be followed by a B-2 genetic model via two pairs of additive-dominance major genes; both FL and FD could be described by a B-6 genetic model via two pairs of major genes that were equally dominant; IN was best fit by the A-1 model, which was controlled by a pair of additive-dominant-epistatic major genes; and IL and ID were best fit by the A-0 model, indicating that both characteristics were controlled by only polygenes. The heritability of the major genes controlling the NFI, BBP, FD, FL and IN traits were 92.58 %, 94.40 %, 63.42 %, 54.23 % and 65.67 %, respectively, indicating that these five characteristics were less affected by the environment. These results can provide some reference for quantitative trait locus (QTL) mapping and molecular marker-assisted breeding of the main flower characteristics in P. auriculata.