Peltate trichomes on biogenic silvery leaves of Elaeagnus umbellata.

External and internal features of Elaeagnus umbellata leaves were investigated by optical and electron microscopy. The adaxial (upper) and abaxial (lower) leaf surfaces appeared green and silver in color, respectively. There were peltate trichomes on both the adaxial and abaxial leaf surfaces. The peltate trichomes were 200-300 µm in diameter and shield or umbrella-shaped. They had a central dome and 20-30 radiating rays that were fused to form a circular cap in the center and tapered at the end. The density of peltate trichomes was apparently higher on the abaxial leaf surface than on the adaxial leaf surface. At least two layers of peltate trichomes were commonly observed on the abaxial leaf surface. The epidermal cells on the abaxial leaf surface had convex lens-like shape in cross sections. No distinct chloroplasts were found in the cytoplasm of peltate trichomes. These results suggest that the silver coloration on the abaxial leaf surface is mostly due to structural coloration associated with the profuse overlapping peltate trichomes having a circular cap of radially fused rays. The shrub did not show any pigmentary cellular features associated with the silver coloration. With the silvery leaves as a reflective surface for shaded leaves in canopy, E. umbellata is likely to adapt to the harsh non-native light-demanding environments.

[Identification of original plants of uyghur medicinal materials fructus elaeagni using morphological characteristics and DNA barcode].

Morphology and molecular identification technology were used to identify 3 original plants of Fructus Elaeagni which was commonly used in Uygur medicine. Leaves, flowers and fruits from different areas were selected randomly for morphology research. ITS2 sequence as DNA barcode was used to identify 17 samples of Fructus Elaeagni. The genetic distances were computed by kimura 2-parameter (K2P) model, and the Neighbor-Joining (NJ) and Maximum Likelihood phylogenetic trees were constructed using MEGA5.0. The results showed that Elaeagnus angustifolia, E. oxycarpa and E. angustifolia var. orientalis cannot be distinguished by morphological characteristics of leaves, flowers and fruits. The sequence length of ITS2 ranged from 220 to 223 bp, the average GC content was 61.9%. The haplotype numbers of E. angustifolia, E. oxycarpa and E. angustifolia var. orientals were 4, 3, 3, respectively. The results from the NJ tree and ML tree showed that the 3 original species of Fructus Elaeagni cannot be distinguished obviously. Therefore, 3 species maybe have the same origin, and can be used as the original plant of Uygur medicineal material Fructus Elaeagni. However, further evidence of chemical components and pharmacological effect were needed.

Nondestructive assessment of leaf chemistry and physiology through spectral reflectance measurements may be misleading when changes in trichome density co-occur.

Reflectance indices are frequently used for the nondestructive assessment of leaf chemistry, especially pigment content, in environmental or developmental studies. Since reflectance spectra are influenced by trichome density, and trichome density displays a considerable phenotypic plasticity, we asked whether this structural parameter could be a source of variation in the values of the most commonly used indices. Trichome density was manipulated in detached leaves of three species having either peltate (Olea europaea and Elaeagnus angustifolius) or tubular (Populus alba) trichomes by successive removal of hairs. After each dehairing step, trichome density was determined by light or scanning electron microscopy and reflectance spectra were obtained with a diode-array spectrometer. Although species-specific differences were evident, most of the indices were considerably affected even at low trichome densities. In general, the less-affected indices were those using wavebands within the visible spectral region. The index that could be safely used even at very high hair densities in all species was the red edge index (lambda(RE)) for chlorophyll. The results indicate that changes in reflectance indices should be interpreted cautiously when concurrent changes in trichome density are suspected. In this case, the red edge for chlorophyll content may be the index of choice.