Twenty-eight ornamental species commonly used for interior plantscapes were screened for their ability to remove five volatile indoor pollutants: aromatic hydrocarbons (benzene and toluene), aliphatic hydrocarbon (octane), halogenated hydrocarbon [trichloroethylene (TCE)], and terpene (α-pinene). Individual plants were placed in 10.5-L gas-tight glass jars and exposed to ≈10 ppm (31.9, 53.7, 37.7, 46.7, and 55.7 mg·m−3) of benzene, TCE, toluene, octane, and α-pinene, respectively. Air samples (1.0 mL) within the glass containers were analyzed by gas chromatography–mass spectroscopy 3 and 6 h after exposure to the test pollutants to determine removal efficiency by monitoring the decline in concentration over 6 h within sealed glass containers. To determine removal by the plant, removal by other means (glass, plant pot, media) was subtracted. The removal efficiency, expressed on a leaf area basis for each volatile organic compound (VOC), varied with plant species. Of the 28 species tested, Hemigraphis alternata, Hedera helix, Hoya carnosa, and Asparagus densiflorus had the highest removal efficiencies for all pollutants; Tradescantia pallida displayed superior removal efficiency for four of the five VOCs (i.e., benzene, toluene, TCE, and α-pinene). The five species ranged in their removal efficiency from 26.08 to 44.04 μg·m−3·m−2·h−1 of the total VOCs. Fittonia argyroneura effectively removed benzene, toluene, and TCE. Ficus benjamina effectively removed octane and α-pinene, whereas Polyscias fruticosa effectively removed octane. The variation in removal efficiency among species indicates that for maximum improvement of indoor air quality, multiple species are needed. The number and type of plants should be tailored to the type of VOCs present and their rates of emanation at each specific indoor location.

No abstract

Summary• The chemistry, crystallography and ultrastructure of intracellular calcium oxalate deposits in the angiosperm, Dracaena sanderiana are reported here.• Crystalline deposits extracted from mature leaves and leaf primordia of D. sanderiana were studied by scanning electron microscopy and X-ray powder diffractometry techniques, and compared with X-ray standards for calcium monohydrate and calcium oxalate dihydrate.• Intracellular calcium oxalate deposits were of two types; calcium oxalate monohydrate raphides or solitary calcium oxalate dihydrate crystals. Raphide-containing cells exhibited lamellate sheaths around the chamber walls, mucilage-like materials surrounding the developing crystal chambers, and paracrystalline bodies with closely spaced subunits within the chambers. The intracellular calcium oxalate dihydrate crystals usually displayed typical tetragonal-dipyramidal morphology, but development of some unusual crystal faces occasionally occurred.• Two intracellular hydrate forms of calcium oxalate (monohydrate and dihydrate) exist in D. sanderiana . The elaboration of crystal vacuoles derived from rough endoplasmic reticulum and modified crystals with energetically unfavourable faces suggest that precipitation of calcium oxalate dihydrate in D. sanderiana cells might be biologically controlled.

Summary• The chemical nature and biological basis for crystal deposition in epidermal subcuticular areas are reported here for the angiosperm Dracaena sanderiana .• Position, development and identification of crystals in adult leaves of D. sanderiana was carried out using X-ray diffraction, crystal morphology and scanning and transmission electron microscopy techniques.• Numerous small (< 1-6 µ m) calcium oxalate monohydrate crystals were found between the primary epidermal cell wall and the cuticle. Their formation was highly specific and predictable with respect to location and relative timing of development during leaf ontogeny. The crystals were perisplasmic as, at formation, the nascent epidermal cell wall was external to the crystals. Cuticular crystallization of calcium oxalate monohydrate in D. sanderiana occurred in crystal chambers situated between the plasma membrane and the primary cell wall. Crystal deposition did not occur in developing guard cells.• The spatial pattern of calcium oxalate monohydrate within the epidermal cells, orientation of the crystallographic axes and the existence of crystal chambers outside the plasma membrane suggest biologically controlled crystal deposition in D. sanderiana .