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Atmospheric and soil nitrogen levels are increasing across the world. Nitrogen addition can alter vegetative and flower traits, including flowering phenology, floral production, and flower morphology, and the quantity and quality of floral rewards such as nectar. However, it is not well understood if and how these changes in floral traits will affect foraging preferences and pollination by different pollinator species. We hypothesized that honey bees (Apis mellifera) would exhibit a preference for plants with increased numbers of flowers, while bumble bees (Bombus spp.) would exhibit a preference for plants with increased nectar production as a result of soil nitrogen addition. A 2-yr field experiment was conducted to investigate the effects of varying nitrogen supply levels (e.g., 0, 4, 8 kg N ha–1 yr–1 of N0, N4, and N8) on the vegetative and floral traits of a perennial plant (Saussurea nigrescens), as well as the visitation rates of introduced managed honey bees (A. mellifera) and the native wild bumble bees. The results showed that adding nitrogen increased the number of flowers and nectar production. However, honey bees and bumble bees were responding to different floral resources that induced by nitrogen addition, with honey bees prioritizing the number of flowers and bumble bees prioritizing nectar quantity. The findings shed new light on how plants and pollinators interact when nitrogen is added, as well as how pollinator communities will be affected in the future. [ABSTRACT FROM AUTHOR]

Agriophyllum squarrosum (L.) Moq. is a highly prevalent xerophytic species found throughout northern China. It is suitable for cultivation in semi-arid sandy environments and may establish roots in arid desert locations. This species plays a pioneering and exploratory role in the colonization of desert plants. In this study, we selected A. squarrosum from the Urat desert steppe (UD) and Horqin sandy land (HS) to explore their adaptation mechanisms to drought and rehydration environments by using the pot weighing control method to simulate an arid environment. The findings showed that the control (watering to 60–65% of field capacity) exceeded its required amount and the leaves turned yellow. The chlorophyll content was lower than those under moderate and severe drought, and rehydration caused a decrease. However, the contents of malondialdehyde, soluble sugar, and proline in the drought treatment were higher than those in the control. Under moderate and severe drought, the chlorophyll content and the quantum efficiency of photosystem II (Fv/Fm) of A. squarrosum from UD were higher than those from HS. During drought and rehydration processes, the proline content was relatively lower, while the activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) and the content of soluble sugar and soluble protein were higher. However, antioxidant enzymes and osmoregulators from UD were higher than those from HS. The results suggest that the stronger ability of A. squarrosum to endure drought environments in UD is due to the high level of antioxidant enzymes and osmoregulators, which are conducive to relieving cell membrane damage when subjected to drought and rehydration. [ABSTRACT FROM AUTHOR]

Bassia dasyphylla is a prevalent herbaceous plant that exhibits enhanced resilience to dryness and elevated temperatures. It is frequently found in dispersed or grouped formation on sandy soil within steppe, semi-desert, and desert regions. Herein, we conducted experiments to examine the growth and physiological traits of B. dasyphylla seeds originated from various regions in response to water scarcity. The study seeks to investigate the ability of these seeds to germinate under drought conditions and offer valuable insights for the development and breeding of high-quality germplasm resources in Inner Mongolia. The results demonstrated that B. dasyphylla originating from desert steppe (DS) exhibited a greater capacity to endure drought conditions in comparison to its counterparts from sandy land (SL). At a water potential of -0.30 MPa, the Seed germination rate from DS was 33.3%, while from SL it was 22.7%. With the increase in drought duration and intensity, germination rate, plumule length, both single-seed weight (SSW) and seed water content (SWC) of B. dasyphylla declined. The protective enzyme activity exhibited an initial increase, followed by a subsequent decline as the duration of the drought increased. Notably, we found that the protective enzyme activity from DS was higher than that from SL. During the initial and intermediate stages of dryness, the soluble sugar and protein of the plant from DS effectively inhibited the peroxidation of membrane lipids, whereas the osmoregulatory properties from SL did not have a significant impact. The findings suggest that the ability of B. dasyphylla to withstand drought conditions in DS can be attributed to its elevated amounts of protective enzymes and osmoregulatory factors, which serve to safeguard the cell membrane during periods of drought. [ABSTRACT FROM AUTHOR]

Age-related macular degeneration (AMD) is a complex multifactorial disease associated with the dysfunction of retinal pigment epithelium (RPE). Aloperine is a quinolizidine alkaloid that has been proven to possess broad pharmacological activities. However, the effects of aloperine on AMD remain unclear. In the present study, we used hydrogen peroxide (H2O2) to induce oxidative injury in human RPE cells (ARPE-19 cells). ARPE-19 cells were pretreated with different concentrations of aloperine for 2 h, followed by H2O2 exposure. Cell cytotoxicity was determined using lactate dehydrogenase (LDH) release assay. Cell viability was measured using Cell Counting Kit-8 (CCK-8) assay. The reactive oxygen species (ROS) generation, malondialdehyde (MDA) level, superoxide dismutase (SOD) activity and glutathione peroxidase (GSH-PX) activity were detected to reflect oxidative status. Western blot was performed to detect the expressions of bcl-2, bax, nuclear factor-erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1). The activity of caspase-3 was also assessed to indicate cell apoptosis. In addition, ARPE-19 cells were transfected with siNrf2 to knock down Nrf2. Our results showed that pretreatment with aloperine elevated the reduced cell viability of H2O2-induced ARPE-19 cells in a dose-dependent manner. Aloperine greatly decreased the production of ROS and MDA, and increased the activities of SOD and GSH-PX in H2O2-stimulated ARPE-19 cells. H2O2-caused a decrease in bcl-2 expression and increases in bax expression and caspase-3 activity were mitigated by aloperine. Moreover, aloperine treatment enhanced the expression levels of Nrf2 in nuclear fraction and the HO-1 expression in lysates. Knockdown of Nrf2 reversed the protective effects of aloperine on H2O2-induced ARPE-19 cells. In conclusion, these findings demonstrated that aloperine protected ARPE-19 cells from H2O2-induced oxidative stress and apoptosis in part via activating the Nrf2/HO-1 signaling pathway. The findings suggested a therapeutic potential of aloperine for the treatment of ADM. [ABSTRACT FROM AUTHOR]