Emission of sunscreen salicylic esters from desert vegetation and their contribution to aerosol formation

Biogenic volatile organic compounds (BVOC) produced by plants are known to have an important role in atmospheric chemistry. However, our knowledge of the range of BVOCs produced by different plant processes is still expanding, and there remain poorly understood categories of BVOCs. In this study, emissions of a novel class of BVOC emissions were investigated in a desert region. Our study considered 8 species of common desert plants: blackbrush (Coleogyne ramosissima), desert willow (Chilopsis linearis), mesquite (Prosopis glandulosa), mondel pine (Pinus eldarica), pinyon pine (Pinus monophylla), cottonwood (Populus deltoides), saguaro cactus (Carnegiea gigantea) and yucca (Yucca baccata). The measurements focused on BVOCs with relatively high molecular weight (>C15) and/or an oxygenated functional group. Significantly high emission rates of two salicylic esters were found for blackbrush, desert willow and mesquite with emission rates of 3.1, 1.0 and 4.8μgC dwg−1 h−1, respectively (dwg; dry weight of the leaves in gram). The salicylic esters were identified as 2-ethylhexenyl salicylate (2-EHS) and 3,3,5-trimethylcyclohexenyl salicylate (homosalate) and are known as effective ultraviolet (UV) absorbers. We propose that the plants derive a protective benefit against UV radiation from the salicylic esters and that the emission process is driven by the physical evaporation of the salicylic esters due to the high ambient temperatures. In addition, the salicylic esters are predicted to be an effective precursor of secondary organic aerosol (SOA) because they probably produce oxidation products that can condense onto the aerosol phase. We estimated the contribution of the sunscreen esters themselves and their oxidation products on the SOA formation for the Las Vegas area using a BVOC emission model. The contribution was estimated to reach 50% of the biogenic terpenoid emission in the landscapes dominated by desert willow and mesquite and 13% in the Las Vegas area. The contributions to biogenic SOA are likely to be higher due to the potentially high SOA yields of these compounds.

Emission of sunscreen salicylic esters from desert vegetation and their contribution to aerosol formation

Biogenic volatile organic compounds (BVOC) produced by plants are known to have an important role in atmospheric chemistry. However, our knowledge of the range of BVOCs produced by different plant processes is still expanding, and there remain poorly understood categories of BVOCs. In this study, emissions of a novel class of BVOC emissions were investigated in a desert region. Our study considered 8 species of common desert plants: blackbrush (Coleogyne ramosissima), desert willow (Chilopsis linearis), mesquite (Prosopis glandulosa), mondel pine (Pinus eldarica), pinyon pine (Pinus monophylla), cottonwood (Populus deltoides), saguaro cactus (Carnegiea gigantea) and yucca (Yucca baccata). The measurements focused on BVOCs with relatively high molecular weight (>C15) and/or an oxygenated functional group. Significantly high emission rates of two salicylic esters were found for blackbrush, desert willow and mesquite with emission rates of 1.4, 2.1 and 0.46 μgC dwg−1 h−1, respectively. The salicylic esters were identified as 2-ethylhexenyl salicylate (2-EHS) and 3,3,5-trimethylcyclohexenyl salicylate (homosalate) and are known as effective ultraviolet (UV) absorbers. We propose that the plants derive a protective benefit against UV radiation from the salicylic esters and that the emission process is driven by the physical evaporation of the salicylic esters due to the high ambient temperatures. In addition, the salicylic esters are predicted to be an effective precursor of secondary organic aerosol (SOA) because of their low vapor pressure due to a high number of carbon atoms (15 or 16) and the presence of three oxygen atoms. We estimated the contribution of the sunscreen esters themselves and their oxidation products on the SOA formation for the Las Vegas region using a BVOC emission model. The contribution was estimated to reach 90% of the biogenic SOA in the landscapes dominated by desert willow and mesquite and 25% in Las Vegas area.

Improving gold phytoextraction in desert willow (Chilopsis linearis) using thiourea: a spectroscopic investigation

Environmental context. The conventional methods used for the extraction of gold from mine tailings and runoff are costly and often require harsh chemical treatment. Using plants to extract gold is more environmentally friendly and economically feasible. Plants are especially appealing because they can uptake low levels of gold and accumulate them in their tissues, whereas conventional methods are less effective at extracting gold at low levels. Thiourea has been proposed as an alternative gold chelator that could help in gold phytomining. It is less toxic than cyanide, which is the chemical commonly used to dissolve gold from mine ores. Abstract. Phytomining, the use of plants to recover noble metals, is developing as a feasible option to extract gold from mine tailings. In this study, thiourea (TU) was used to increase gold availability and to enhance gold accumulation by the desert plant Chilopsis linearis. Seedlings of C. linearis were grown in a hydroponic solution containing 25 μM Au and TU at 25, 50, 100, 200, and 400 μM. After two weeks of growth, the concentration of Au, micro- and macronutrients was determined using inductively coupled plasma–optical emission spectroscopy. In addition, X-ray absorption spectroscopy was used to determine the oxidation state and the coordination of the Au atom within the plant tissues. The effect of TU on plant growth was determined as well. The results of the present study demonstrated that TU at 25 μM was able to increase the Au uptake by C. linearis plants grown in hydroponics without any toxic effect. However, the translocation to stem and leaves was better at 100 and 200 μM of TU, respectively. The addition of TU to hydroponic solutions did not affect the uptake of Ca, Mg, P, and K. However, TU induced an increase in uptake of S, Fe, Cu, and Zn and a decrease in Mn uptake. When Au was chelated with TU, the plant transformed 64% of the Au–TU complex to Au(0) and the other 36% remained in the ionic form.

Reproductive Behavior of Induced Allotetraploid ×Chitalpa and In Vitro Embryo Culture of Polyploid Progeny

×Chitalpa tashkentensis Elias & Wisura is a sterile intergeneric hybrid [Catalpa bignonioides Walt. × Chilopsis linearis (Cav.) Sweet]. To restore fertility in ×Chitalpa the following were evaluated: 1) oryzalin as a polyploidization agent, 2) fertility of induced polyploids, and 3) in vitro culture methods for embryo rescue of interploid crosses. Meristems of ×Chitalpa `Pink Dawn' were submerged in an aqueous solution of 150 μm oryzalin for 0, 6, 12, or 24 hours and ploidy analyzed via flow cytometry. As treatment duration increased, recovery of diploids decreased as mixoploids and shoot mortality increased. Two tetraploid shoots occurred in the 24-hour treatment. Four tetraploids and two cytochimeras were stabilized in total. Tetraploids flowered sparsely; however, cytochimeras flowered profusely and these were used to study fertility at the tetraploid level. Diploid ×Chitalpa `Pink Dawn' pollen was essentially nonviable, but cytochimera pollen stained and germinated equal to or greater than pollen of C. bignonioides and C. linearis `Bubba'. Cytochimera ×Chitalpa were selfed yielding tetraploid seedlings, crossed with C. bignonioides to yield triploids, but failed in reciprocal crosses with C. linearis `Bubba' and `Burgundy Lace'. To increase recovery of triploids, germination of triploid and tetraploid embryos was investigated, as either intact ovules or excised embryos, on Schenk and Hildebrandt (SH) basal salts supplemented with sucrose at 20, 40, and 80 g·L-1, presence or absence of 2% coconut-water, and gibberellic acid (GA3) at 0, 1, 2, or 4 μm, and harvested weekly beginning 2 weeks after pollination (WAP). Germination of triploids (cytochimera ×Chitalpa × diploid C. bignonioides) and tetraploids (selfed cytochimera ×Chitalpa) were greatest with excised embryos at 7 WAP on SH supplemented with sucrose at 20 g·L-1 and ≥1 μm GA3. Germination of triploids (diploid C. linearis × cytochimera ×Chitalpa) was <5% at 4, 5, or 6 WAP on the same medium as above. Oryzalin effectively induced polyploidy and restored fertility in ×Chitalpa `Pink Dawn'. Successful crosses between hybrid and parental taxa of different ploidy levels, coupled with embryo culture will facilitate a ×Chitalpa breeding program. Chemical names used: 4(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin).

Molecular Confirmation of Intergeneric Hybrid ×Chitalpa tashkentensis (Bignoniaceae)

Intergeneric hybrids are generally rare; nevertheless, such putative hybrids need confirmation from other lines of evidence besides morphological intermediacy. In this study the authors used DNA sequences of nuclear and chloroplast genes to determine the hybrid identity of ×Chitalpa. Their results confirm that both ×Chitalpa tashkentensis `Pink Dawn' and ×C. tashkentensis `Morning Cloud' are the result of an Chilopsis linearis ×Catalpa sp. cross. However, Catalpa bignonioides does not seem to have participated in the cross, as speculated before. Different species of Catalpa may have been used as the paternal parent. ×C. tashkentensis `Morning Cloud' is the result of the C. linearis × C. speciosa cross, whereas the paternal parent of ×C. tashkentensis `Pink Dawn' may be a hybrid plant of C. ovata and C. speciosa.

Effect of Reclaimed Water and Drought on Salt-sensitive Perennials

Four species of salt-sensitive perennials (Chilopsis linearis, Tecoma stans, Salviagreggii, and Verbena pulchella gracilior) were grown in containers and were irrigated with potable or reclaimed water. Electrical conductivity (EC) was 0.3 dS·m-1 for potable irrigation water and 1.0 dS·m-1 for reclaimed irrigation water. After 12 weeks of growing plants with reclaimed vs. potable water, C. linearis leaf dry weight was reduced by 15%, T. stans root dry weight was reduced by 41%, V. puchella gracilior stem dry weight was reduced by 35%, and S. greggii total dry weight was reduced by 56%. The increase in canopy size was calculated 4, 8, and 12 weeks after treatments began and was not affected by water source for C. linearis and T. stans, but was reduced for S. greggii and V. pulchella gracilior treated with reclaimed water. Up to 12% dieback and reduced flowering were observed on S. greggii irrigated with reclaimed water. Within 4 weeks of treatments, EC in the root zone was 0.5 dS·m-1 for plants irrigated with potable water and 1.9 dS·m-1 for those irrigated with reclaimed water. When exposed to drought, C. linearis and T. stans grown with reclaimed water maintained a more negative water potential as soil moisture was depleted. Osmotic potential started to increase significantly for both irrigation treatments when more than 25% moisture from fully saturated containers were lost. In general, plants irrigated with potable water sustained more damage than those irrigated with reclaimed water after recovering from a drought cycle.