Trait value and phenotypic integration contribute to the response of exotic Rhus typhina to heterogeneous nitrogen deposition: A comparison with native Rhus chinensis.

The temporal heterogeneity of nitrogen availability in soils is increasing due to agricultural deposition. We here compared the effects of gradually increasing nitrogen deposition rate and its increasing temporal heterogeneity patterns on the functional traits of seedlings of exotic species Rhus typhina and the native species Rhus chinensis. Nitrogen deposition rates of 0, 8, 20 g N m-2 year-1 and constant, single-peak, and double-peak nitrogen were added to simulate deposition rate and temporal heterogeneity. After 60 days of treatment, R. typhina seedlings had several advantageous growth trait values, such as higher total biomass production, but lower phenotypic plasticity than R. chinensis seedlings. R. typhina seedlings also had higher phenotypic integration, measured as the correlation among functional traits. The increased nitrogen deposition rate affected several traits of the two species differently. Thus, while R. chinensis seedlings allocated more biomass to leaves and less to roots with increasing N deposition, R. typhina seedlings had stable biomass allocation among all N treatments. Chlorophyll content, leaf phosphorus concentration, and water use efficiency increased, but the maximum net photosynthetic rate decreased, with N availability in R. chinensis, but not in R. typhina. Temporal heterogeneity had no significant effect on the total biomass of R. typhina and R. chinensis seedlings. Overall, the performance of R. typhina is better than that of R. chinensis seedlings under different nitrogen deposition treatments, which is due to the significantly advantageous trait values and greater phenotypic integration of R. typhina seedlings, whereas R. chinensis seedlings have higher phenotypic plasticity.

Macro- and Microscopic Analyses of Anatomical Structures of Chinese Gallnuts and Their Functional Adaptation.

The galls induced by Schlechtendaia chinensis, Schlechtendaia peitan and Nurudea shiraii on Rhus chinensis and gall induced by Kaburagia rhusicola rhusicola on Rhus potaninii Maxim. are the largest plant galls and have great economic and medical values. We examined the structures of galls and their functional adaptation using various macro- and microscopic techniques. The highly adapted structures include a stalk at the base that is specialized for mechanical support and transport of nutrients for aphids, and a network of vascular bundles which accompanying schizogenous ducts arranged in a way to best support aphid feeding and population growth. There are many circular and semicircular xylems traces in an ensiform gall in cross sectional views, which would provide more nutrition and occupy less space. We infer the evolution trail was flower-like gall, horned gall, circular gall and ensiform gall. And the possible evolutionary trend of the gall was bigger chamber, more stable mechanical supporting, easier for exchanging substance and transporting nutrients.

Woody species Rhus chinensis Mill. seedlings tolerance to Pb: Physiological and biochemical response.

Screening potential plant species is a crucial consideration in phytoremediation technology. Our previous study demonstrated that Rhus chinensis Mill. seedlings had potentials for phytoremediation of Pb contaminated soil. However, its bioaccumulation and tolerance characteristics remain unclear. Seedling growth, LMWOAs secreted by roots, Pb subcellular distribution and chemical forms, and mineral elements in R. chinensis tissues were evaluated under different Pb concentrations (0, 25, 50, 100, 200 and 400 mg/L) in culture solution at 14 days after planting. R. chinensis did not show visual symptoms of Pb toxicity under lower Pb treatments; however, Pb significantly declined the growth of seedlings under higher Pb treatments. Higher Pb stress also decreased the concentrations of nitrogen in leaves, but increased the concentrations of P and K in roots. Pb stress also decreased Mn concentrations in leaves. A great quantity of Pb was uptake and mostly retained in R. chinensis roots. Nonetheless, R. chinensis can still concentrate 459.3 and 1102.7 mg/kg Pb in leaves and stems, respectively. Most of Pb in R. chinensis tissues was stored in the cell wall with HAc-, HCl-, and NaCl-extractable form. LMWOAs secreted by R. chinensis roots showed a strong positive correlation with Pb concentrations in all plant tissues and with P in roots. Our results suggested that Pb deposited in the cell wall and integration with phosphate or oxalate might be responsible for the tolerance of R. chinensis under Pb stress in short period.

Rhus coriaria induces senescence and autophagic cell death in breast cancer cells through a mechanism involving p38 and ERK1/2 activation.

Here, we investigated the anticancer effect of Rhus coriaria on three breast cancer cell lines. We demonstrated that Rhus coriaria ethanolic extract (RCE) inhibits the proliferation of these cell lines in a time- and concentration-dependent manner. RCE induced senescence and cell cycle arrest at G1 phase. These changes were concomitant with upregulation of p21, downregulation of cyclin D1, p27, PCNA, c-myc, phospho-RB and expression of senescence-associated ß-galactosidase activity. No proliferative recovery was detected after RCE removal. Annexin V staining and PARP cleavage analysis revealed a minimal induction of apoptosis in MDA-MB-231 cells. Electron microscopy revealed the presence of autophagic vacuoles in RCE-treated cells. Interestingly, blocking autophagy by 3-methyladenine (3-MA) or chloroquine (CQ) reduced RCE-induced cell death and senescence. RCE was also found to activate p38 and ERK1/2 signaling pathways which coincided with induction of autophagy. Furthermore, we found that while both autophagy inhibitors abolished p38 phosphorylation, only CQ led to significant decrease in pERK1/2. Finally, RCE induced DNA damage and reduced mutant p53, two events that preceded autophagy. Our findings provide strong evidence that R. coriaria possesses strong anti-breast cancer activity through induction of senescence and autophagic cell death, making it a promising alternative or adjunct therapeutic candidate against breast cancer.

Gall development and clone dynamics of the galling aphid Schlechtendalia chinensis (Hemiptera: Pemphigidae).

The aphid Schlechtendalia chinensis (Bell) induces galls on its primary host, Rhus chinensis Mill. We studied temporal changes in gall and aphid clonal population size throughout the period of gall development. Gall-size changes occurred in four stages: a first slow growth period, a fast growth period, a second slow growth period, and a growth reduction period. Gall volume and surface area increased abruptly toward the end of July, peaking during October, in parallel with an increase in aphid clonal population size, from one individual to > 10,000 aphids per gall. Clear changes were seen in the clone dynamics of S. chinensis. Fundatrix began to produce first-generation apterous fundatrigenia during late May to early June. Second-generation apterous fundatrigenia appeared at the start of July. Alate fundatrigeniae with wing pads first appeared at the end of August, but accounted for < 1% of the individuals in the galls. Adult alate fundatrigeniae first appeared at the start of October. Abrupt changes in aphid density and crowding might trigger the induction of alate morphs in the galls. Of the eight gall properties that we recorded, gall volume was the most accurate measure of gall fitness.

Ecophysiological evaluation of the potential invasiveness of Rhus typhina in its non-native habitats.

Rhus typhina L. (staghorn sumac) is a clonal woody species that is considered potentially invasive in its non-native habitats. It is slow growing as seedlings, but grows fast once established. Its growth in the early stages is limited by many abiotic factors, including light intensity. To evaluate its potential of becoming invasive in areas it has been introduced into, we conducted a field experiment to investigate the effects of light intensity on the physiology and growth of R. typhina. Two-month-old R. typhina seedlings were examined under five light levels, that is, 100% full sunlight (unlimited light), moderate stress (50% or 25% of full sunlight) and severe stress (10% or 5% of full sunlight), for 60 days in Hunshandak Sandland, China. Net photosynthetic rate (PN) was reduced significantly under severe light stress, but PN of the moderately stressed seedlings was unaffected. Light stress also led to a reduction in saturated light intensity of the moderately stressed seedlings by 20% and of the severely stressed seedlings by 40%, although the light saturation points were as high as 800 and 600 micromol m(-2) s(-1) for the moderately and severely stressed seedlings, respectively. Under severe light stress, the maximum quantum yield of Photosystem II (Fv/Fm) decreased significantly, but the minimal fluorescence yield (F0) increased compared to that of the control plants. The number of newly produced leaves and the stem height, however, decreased as the light intensity became lower. Root length and leaf area decreased, whereas specific leaf area significantly increased as light became increasingly lower. Biomass production was significantly reduced by light stress, but the allocation pattern was unaffected. Our results demonstrated that R. typhina seedlings can survive low light and grow well in other light conditions. The physiology and growth of R. typhina will likely enable it to acclimate to varying light conditions in Hunshandak Sandland, where R. typhina has been widely cultivated for sand stabilization and other purposes. Because of its ability to tolerate low light and to compete aggressively for light resource once established, that is, becoming invasive, we urge caution when it comes to introducing R. typhina into its non-native habitats, despite its many ecological benefits.

Allocation to reproduction and relative reproductive costs in two species of dioecious Anacardiaceae with contrasting phenology.

BACKGROUND AND AIMS: The cost of reproduction in dioecious plants is often female-biased. However, several studies have reported no difference in costs of reproduction between the sexes. In this study, the relative reproductive allocation and costs at the shoot and whole-plant levels were examined in woody dioecious Rhus javanica and R. trichocarpa, in order to examine differences between types of phenophase (i.e. physiological stage of development). METHODS: Male and female Rhus javanica and R. trichocarpa were sampled and the reproductive and vegetative allocation of the shoot were estimated by harvesting reproductive current-year shoots during flowering and fruiting. Measurements were made of the number of reproductive and total current-year shoots per whole plant, and of the basal area increment (BAI). The numbers of reproductive and total current-year shoots per 1-year-old shoot were counted in order to examine the costs in the following year at the shoot level. KEY RESULTS: A female-biased annual reproductive allocation was found; however, the ratio of reproductive current-year shoots per tree and the BAI did not differ between sexes in Rhus javanica and R. trichocarpa. The percentage of 1-year-old shoots with at least one reproductive current-year shoot was significantly male-biased in R. trichocarpa, but not in R. javanica, indicating that there was a relative cost at the shoot level only in R. trichocarpa. The female-biased leaf mass per shoot, an indicator of compensation for costs, was only found in R. javanica. CONCLUSIONS: Relative reproductive costs at the shoot level were detected in Rhus trichocarpa, which has simultaneous leafing and flowering, but not in R. javanica, which has leafing followed by flowering. However, the costs for the whole-plant level were diminished in both species. The results suggest that the phenophase type may produce the different costs for R. javanica and R. trichocarpa through the development of a compensation mechanism.

Below-ground interactions with arbuscular mycorrhizal shrubs decrease the performance of pinyon pine and the abundance of its ectomycorrhizas.

Few studies have examined how below-ground interactions among plants affect the abundance and community composition of symbiotic mycorrhizal fungi. Here, we combined observations during drought with a removal experiment to examine the effects of below-ground interactions with arbuscular mycorrhizal (AM) shrubs on the growth of pinyon pines (Pinus edulis), and the abundance and community composition of their ectomycorrhizal (EM) fungi. Shrub density was negatively correlated with pinyon above- and below-ground growth and explained 75% of the variation in EM colonization. Consistent with competitive release, pinyon fine-root biomass, shoot length and needle length increased with shrub removal. EM colonization also doubled following shrub removal. EM communities did not respond to shrub removal, perhaps because of their strikingly low diversity. These results suggest that below-ground competition with AM shrubs negatively impacted both pinyons and EM fungi. Similar competitive effects may be observed in other ecosystems given that drought frequency and severity are predicted to increase for many land interiors.

Do xylem fibers affect vessel cavitation resistance?

Possible mechanical and hydraulic costs to increased cavitation resistance were examined among six co-occurring species of chaparral shrubs in southern California. We measured cavitation resistance (xylem pressure at 50% loss of hydraulic conductivity), seasonal low pressure potential (P(min)), xylem conductive efficiency (specific conductivity), mechanical strength of stems (modulus of elasticity and modulus of rupture), and xylem density. At the cellular level, we measured vessel and fiber wall thickness and lumen diameter, transverse fiber wall and total lumen area, and estimated vessel implosion resistance using (t/b)(h)(2), where t is the thickness of adjoining vessel walls and b is the vessel lumen diameter. Increased cavitation resistance was correlated with increased mechanical strength (r(2) = 0.74 and 0.76 for modulus of elasticity and modulus of rupture, respectively), xylem density (r(2) = 0.88), and P(min) (r(2) = 0.96). In contrast, cavitation resistance and P(min) were not correlated with decreased specific conductivity, suggesting no tradeoff between these traits. At the cellular level, increased cavitation resistance was correlated with increased (t/b)(h)(2) (r(2) = 0.95), increased transverse fiber wall area (r(2) = 0.89), and decreased fiber lumen area (r(2) = 0.76). To our knowledge, the correlation between cavitation resistance and fiber wall area has not been shown previously and suggests a mechanical role for fibers in cavitation resistance. Fiber efficacy in prevention of vessel implosion, defined as inward bending or collapse of vessels, is discussed.

Effects of herbivory on the reproductive effort of 4 prairie perennials.

BACKGROUND: Herbivory can affect every aspect of a plant's life. Damaged individuals may show decreased survivorship and reproductive output. Additionally, specific plant species (legumes) and tissues (flowers) are often selectively targeted by herbivores, like deer. These types of herbivory influence a plant's growth and abundance. The objective of this study was to identify the effects of leaf and meristem removal (simulated herbivory within an exclosure) on fruit and flower production in four species (Rhus glabra, Rosa arkansana, Lathyrus venosus, and Phlox pilosa) which are known targets of deer herbivory. RESULTS: Lathyrus never flowered or went to seed, so we were unable to detect any treatment effects. Leaf removal did not affect flower number in the other three species. However, Phlox, Rosa, and Rhus all showed significant negative correlations between seed mass and leaf removal. Meristem removal had a more negative effect than leaf removal on flower number in Phlox and on both flower number and seed mass in Rosa. CONCLUSIONS: Meristem removal caused a greater response than defoliation alone in both Phlox and Rosa, which suggests that meristem loss has a greater effect on reproduction. The combination of leaf and meristem removal as well as recruitment limitation by deer, which selectively browse for these species, is likely to be one factor contributing to their low abundance in prairies.