a b s t r a c tThe scarcity of research on the interactive effects of multi-limiting resources has hampered the success in ecological restoration. The effects of water (W), nitrogen (N) and phosphorous (P) on the performance of a perennial shrub, Bauhinia faberi seedlings were studied through a full factorial experimental design. Eighteen treatments was involved including three water (W1: 10, W2: 20 and W3: 40% field capacity), two N (N1: 100 and N2: 280 mg N kg À1 soil) and three P (P1: 12, P2: 24 and P3: 48 mg P kg À1 soil) for 19 weeks in a greenhouse experiment. P strongly regulated the biomass allocation under severe drought stress. Elevated W and P with N1 or N2 level increased root surface area and length, root and shoot mass, water-use efficiency and tissue P concentration, but did not significantly decrease tissue N concentration. The interaction of N and P was significant. Compared to N1, N2 significantly decreased growth parameters at P1 and P2, slightly reduced them at P3, suggesting that P3 alleviated the negative effects of N2.Therefore, the interactive effects of soil N and P should be examined thoroughly in seedlings plantation sites in arid regions to avoid excess level of nitrogen. Crown

Opisthopappus taihangensis (Ling) Shih, as a relative of chrysanthemum, mainly survives on the cracks of steep slopes and cliffs. Due to the harsh environment in which O. taihangensis lives, it has evolved strong adaptive traits to drought stress. The root system first perceives soil water deficiency, triggering a multi-pronged response mechanism to maintain water potential; however, the drought tolerance mechanism of O. taihangensis roots remains unclear. Therefore, roots were selected as materials to explore the physiological and molecular responsive mechanisms. We found that the roots had a stronger water retention capacity than the leaves. This result was attributed to ABA accumulation, which promoted an increased accumulation of proline and trehalose to maintain cell osmotic pressure, activated SOD and POD to scavenge ROS to protect root cell membrane structure and induced suberin depositions to minimize water backflow to dry soil. Transcriptome sequencing analyses further confirmed that O. taihangensis strongly activated genes involved in the ABA signalling pathway, osmolyte metabolism, antioxidant enzyme activity and biosynthesis of suberin monomer. overall, these results not only will provide new insights into the drought response mechanisms of O. taihangensis but also will be helpful for future drought breeding programmes of chrysanthemum. Drought stress is one of the most common abiotic stresses that threatens the healthy growth and development of plants. With the further aggravation of global warming and shortages of fresh water associated with population growth, it is estimated that drought stress will severely reduce the yield and quality of crops and ornamental plants 1. Therefore, further exploration of the physiological and molecular mechanisms is necessary for breeding drought-tolerant plants. Plants have evolved physiological, biochemical and molecular strategies to adapt to arid environments and to prevent cells from water deficiency. Physiological adaptability, including abscisic acid (ABA) content changes, proline accumulation, and superoxide dismutase (SOD) and peroxidase (POD) enzyme activities, are fundamental for plants to withstand drought stress 2-5. Drought-responsive molecular mechanisms have been divided into two terms: those that directly protect plants against drought stress and those that regulate targeted gene expression and signal transduction in plants in response to drought 6. The first term includes genes encoding proteins that function by protecting cell turgor, such as enzymes participating in the biosynthesis of various osmoprotectants 4,7,8. Moreover, late-embryogenesis-abundant proteins, chaperones and antioxidant enzymes directly prevent plants from drought damage. The second term of genes mainly comprises transcription factors, which are activated by signal transduction pathways and regulate functional genes 2,9. Furthermore, protein kinases, protein phosphatases, enzymes related to phospholipid metabolism and ubiquitin ligase play significant roles in the signal trans...

Opisthopappus taihangensis (Ling) Shih, a wild relative germplasm of chrysanthemum, releases a completely different fragrance from chrysanthemum species. We aimed to identify the volatile compounds of the leaves of O. taihangensis and four other Chrysanthemum species using headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC/MS). In total, 70 compounds were detected, and terpenoids accounted for the largest percentage in these five species. Many specific compounds were only emitted from O. taihangensis and not from the other four species. In particular, 1,8-cineole could be responsible for the special leaf fragrance of O. taihangensis as it accounted for the largest proportion of the compounds in O. taihangensis but a small or no proportion at all in other species. The glandular trichomes (GTs) in the leaves are the main organs responsible for the emission of volatiles. To explore the relationship between the emissions and the density of the GTs on the leaf epidermis, the shape and density of the GTs were observed and calculated, respectively. The results showed that the trichomes have two shapes in these leaves: T-shaped non-glandular trichomes and capitate trichomes. Histochemical staining analyses indicated that terpenoids are mainly emitted from capitate glandular trichomes. Correlation analysis showed that the volatile amount of terpenoids is highly related to the density of capitate trichomes. In O. taihangensis, the terpenoids content and density of capitate trichomes are the highest. We identified the diversity of leaf volatiles from O. taihangensis and four other Chrysanthemum species and found a possible relationship between the content of volatile compounds and the density of capitate trichomes, which explained the cause of the fragrance of O. taihangensis leaves.

As one of the most destructive oligophagous pests, the chrysanthemum aphid (Macrosiphoniella sanborni) has seriously restricted the sustainable development of the chrysanthemum industry. Olfaction plays a critical role in the environmental perception of aphids, but very little is currently known about the chemosensory mechanism of M. sanborni. In this study, four MsanOBPs, four MsanCSPs, eight MsanORs, two MsanIRs and one MsanSNMP were identified among the 28,323 unigenes derived from the antennal transcriptome bioinformatic analysis of M. sanborni adults. Then, comprehensive phylogenetic analyses of these olfactory-related proteins in different aphid species were performed using multiple sequence alignment. Subsequently, the odor-specific and wing-specific expression profiles of these candidate chemosensory genes were investigated using quantitative real-time PCR. The data showed that most of these chemosensory genes exhibited higher expression levels in alate aphids. Among them, MsanOBP9, MsanOR2, MsanOR4, MsanOR43b-1, MsanCSP1, MsanCSP2, MsanCSP4, MsanIR25a and MsanIR40a in alate aphids showed remarkably higher expression levels than in apterous aphids under the effect of the host plant volatiles, indicating that these genes may take part in the specific behaviors of alate adults, such as host recognition, oviposition site selection and so on. This study lays the groundwork for future research into the molecular mechanism of olfactory recognition in M. sanborni.

Potato, a cool-weather crop, emits volatile organic compounds (VOCs) which attract the specialist herbivore, Phthorimaea operculella, but also this herbivore's parasitic wasp, Trichogramma chilonis, an important biocontrol agent. What happens to this trophic system when heat stress challenges this agro-ecosystem? We studied how high temperature (HT) pre-treatments influence potato's VOC emissions and their subsequent effects on the preferences of insects, as evaluated in oviposition assays and Y-tube olfactometers. HT pre-stressed plants were less attractive to P. operculella adult moths, which were repelled by HT VOCs, but increased the recruitment of the parasitoid, T. chilonis, which were attracted. VOC emissions, including the most abundant constituent, ß-caryophyllene, were enhanced by HT treatments; some constituents elicited stronger behavioural responses than others.Transcripts of many genes in the biosynthetic pathways of these VOCs were significantly enhanced by HT treatment, suggesting increases in de novo biosynthesis. HT increased the plant's stomatal apertures, and exogenous applications of the hormone, ABA, known to suppress stomatal apertures, reduced leaf volatile emissions and affected the HT-altered plant attractions to both insects.From these results, we infer that HT stress affects this plant-insect interaction through its influence on VOC emissions, potentially decreasing herbivore ovipositions while increasing ovipositions of the parasitoid.