Nanometric and monodisperse starch acetate nanospheres can be prepared through a simple procedure of nanoprecipitation, by the dropwise addition of water to an acetone solution of starch acetate, without any stabilizing agent. This is the first report of the preparation of starch-based nanospheres by this method. The size of the nanospheres obtained can be easily controlled by a number of simple and efficient modifications, i.e., through regulation of the polymer concentration in acetone, the proportions of the water and organic phases, and the molecular weight and degree of substitution of the starch esters. A number of reasons are suggested to explain the observed transitions in the particle size. Fluorescence spectroscopic studies proved that these types of nanospheres could be potentially used for the encapsulation of hydrophobic drugs.

A robust method to prepare hydrogels with high mechanical strength is presented. Core/shell nanospheres with derivatizable allyl groups in the shell were first prepared. Starch‐based nanospheres were used as crosslinker to prepare polyacrylamide hydrogels. The starch‐based nanospheres were bridged by acrylamide to form crosslink points in the hydrogel network. They possess an extremely high mechanical strength. The results show that starch‐based nanosphere hydrogels can sustain strengths of 10.34 MPa, which is 60 times greater than for a normal hydrogel. The mechanical properties of SNH can be tailored by varying the content of SN. This approach offered a new way of making functional hydrogel with biodegradable component as a substitute for tissue.magnified image

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Ptilagrostis Grisebach (1852: 447) is a small genus of the grass family, including approximately 11 species (Wu & Phillips 2006, Barkworth 2007). It occurs in both Asia and North America with about eight species distributed in Qinghai-Tibet Plateau, its diversity center. Ptilagrostis yadongensis Keng & Tang (1985: 44) is one of the species that occurs in this region, which was described based on materials from Yadong, China, the southern slope of Himalayas. The paper was published in a Chinese journal, viz. Journal of Southwest Agriculural University, and had not been noticed until 2005 (Peterson et al. 2005, Wu & Phillips 2006). The author pointed out that P. yadongensis is distinguished from its morphological close, Ptilagrostis concinna (Hooker 1897: 230) Roshevitz (1934: 75) by linear panicles with fewer spikelets, longer and unequal glumes, and shorter and glabrous anthers.

Recent molecular phylogenetic studies indicate that Phaenospermateae and Duthieeae are among the early diverging lineages of Pooideae and that they are closely related to each other. Here, we test this with cytotaxonomical data. The monotypic tribe Phaenospermateae, represented by Phaenosperma globosum, has a chromosome number of 2n = 2x = 24 and a fairly symmetric karyotype consisting of 22 median (m) and 2 submedian (sm) chromosomes varying in length between 1.8–3 μm. Duthieeae, represented by Duthiea brachypodium, Sinochasea trigyna, Stephanachne monandra and Stephanachne pappophorea, also share the chromosome number 2n = 2x = 24 and similar symmetric karyotypes with the chromosomes varying in length between 1.4–5 μm. Thus, the close relationship of Phaenospermateae and Duthieeae is corroborated.

A new species, Ptilagrostis arcuata, from Qinghai-Tibet Plateau is described and illustrated. It is easily distinguished from the similar P. concinna by its arcuate or heliciform awns with golden yellow or pale yellow hairs, narrower basal leaves, and absence of bracts below the panicles. The chromosome number of the new species is 2n=22, karyotype 2n=22=14m+6sm+2st.

A new species, Ptilagrostis contracta, endemic to Qinghai-Tibet Plateau is described and illustrated. It is distinguished from other species in Ptilagrostis by having contracted panicles, 1-geniculate awns with hairy columns and scabrous bristles and evenly pubescent lemmas. Evidence from lemma epidermal pattern, cytology and molecular phylogenetic analyses based on the nuclear ITS sequence data confirm its systematic position in Ptilagrostis.

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