Geastrumsuae sp. nov. (Geastraceae, Basidiomycota) a new species from Yunnan Province, China.

Background: Geastrum is the largest genus of Geastraceae and is widely distributed all over the world. Four specimens which belong to Geastrum were collected during our scientific expedition to Cangshan Mountain, Yunnan, China. Based on morphological characteristics and phylogenetic analysis, a new species was introduced. New information: Geastrumsuae is characterised by its large basidiomata (height 35-70 mm, diameter 18-37 mm) with long stipe (height 10-45 mm), smooth pink exoperidium and sessile globose endoperidial body. Phylogenetic analysis has been carried out, based on the internal transcribed spacer (ITS) and large subunit ribosomal ribonucleic acid (nrLSU) sequence data. The illustration and description for the new taxa are provided.

[Effects of tillage and straw returning on microorganism quantity, enzyme activities in soils and grain yield].

A two-year field study with split plot design was conducted to investigate the effects of different soil tillage (conventional tillage, CT; deep tillage, DT; subsoil tillage, ST) and straw returning (all straw retention, AS; no straw returning, NS) on microorganism quantity, enzyme activities in soil and grain yield. The results showed that, deep or subsoil tillage and straw returning not only reduced the soil bulk density and promoted the content of organic carbon in soil, but increased the soil microbial quantity, soil enzyme activities and grain yield. Furthermore, such influences in maize season were greater than that in wheat season. Compared with CT+NS, DT+AS and ST+AS decreased the soil bulk density at 20-30 cm depth by 8.5% and 6.6%, increased the content of soil organic carbon by 14.8% and 12.4%, increased the microorganism quantity by 45.9% and 33.9%, increased the soil enzyme activities by 34.1% and 25.5%, increased the grain yield by 18.0% and 19.3%, respectively. No significant difference was observed between DT+AS and ST+AS. We concluded that retaining crop residue and deep or subsoil tillage improved soil microorganism quantity, enzyme activities and crop yield.

[Effects of nitrogen fertilization rate and harvest time on summer maize grain yield and its quality].

In order to approach the optimal nitrogen fertilization rate and suitable harvest time for the high grain yield and quality of summer maize in Huanghe-Haihe Area, a field experiment with five nitrogen fertilization rates (0, 113, 181, 249, and 375 kg N x hm(-2)) and two harvest time (S1: September 23, conventional harvest time for local farmers, and S2: September 29, 6 days delayed) was conducted. The results showed that the kernel number, grain yield, and 1000-grain mass increased with nitrogen fertilization rate, but the differences were not significant. With increasing nitrogen fertilization rate, the protein and lysine contents of the grains increased, while the starch content decreased. After 6 days delayed for harvest, the grain yield, 1000-grain mass, and the starch and lysine contents of the grains increased, but the protein and crude fat contents decreased. Based on the yield level, the optimal nitrogen fertilization rate for the summer maize in Huanghe-Haihe Area was 113-180 kg N x hm(-2), and the suitable harvest time was from September 29 to October 5.

[Shade-tolerance indices of maize: selection and evaluation].

A field experiment was conducted to study the morphological, physiological, and yield traits of 24 maize cultivars under 50% shading. Comparing with the control, 50% shading decreased the plant height, stem diameter, leaf net photosynthetic rate (Pn), specific leaf weight (SLW), aboveground dry matter accumulation, ear length and diameter, axis diameter, and kernels per row. The interval from anthesis to silking (ASI) was prolonged, and the grain yield was decreased significantly. The percent changes of ASI, Pn, SLW, and kernels per row were significantly correlated with aboveground dry matter accumulation and grain yield, being able to be used as the indices to evaluate the maize shade-tolerance in field. Cluster analysis using comprehensive shade-tolerance traits as evaluation parameters indicated that 14 maize cultivars including Zhengdan 958, Xundan 20, and Denghai 602, etc. were of shade-tolerance type, and 10 cultivars (Anyu 12 and Yuyu 22, etc. ) were of shade-sensitive type. It was suggested that adopting the morphological, physiological and yield traits as the indices to evaluate the shade-tolerance of maize would be more objective, simple and practical.

[Effects of subsoil bulk density on late growth stage photosynthetic characteristics and grain yield of maize].

A pool-culture experiment was conducted to study the effects of different subsoil bulk density at the depths of 20-40 and 40-60 cm on the late growth stage photosynthetic characteristics and grain yield of maize. The results showed that there existed significant differences in the net photosynthetic rate (Pn) and grain yield when the subsoil bulk density was differed. The Pn and grain yield decreased with increasing subsoil bulk density, and the higher the bulk density, the more significant the decrement in Pn and grain yield. The diurnal changes of Pn and intercellular CO2 concentration (Ci) were not in the same trend. Pn was high at noon and low at twilight and dusk, and decreased with increasing subsoil bulk density; while Ci was in adverse. The stomatal limitation (Ls) and stomatal conductance (Gs) also decreased with increasing subsoil bulk density. With the development of maize, the Pn, Ls and Gs, decreased gradually, while Ci increased continuously.

[Effects of shading on photosynthetic characteristics of different genotype maize].

A pot experiment with 4 genotype maize varieties showed that light intensity had strong effects on their leaf light saturation point, diurnal variation of net photosynthetic rate (Pn), estimated electron transport rate (ETR), maximal photochemical efficiency of PS II (Fv/Fm), and actual photochemical efficiency of PSII (Phi(PS II)). Under shading, the light saturation point of test varieties decreased. For example, shading at seedling stage made the varieties Yuyu 2 and Danyu 13 get to light-saturated when the photon flux density (PFD) was 1400 micromol.m(-2).s(-1) and 1100 micromol.m(-2).s(-1), respectively. Shading also decreased the Pn, ETR, Fv/Fm and Phi(PS II), but the responses differed with the varieties. The decrement of these parameters was remarkably lesser for Yuyu 2 and Yedan 22 than for Danyu 13 and Yedan 6.

Effects of osmotic stress on the kinds, forms and levels of polyamines in wheat coleoptiles.

The changes in levels and forms of polyamine (Pa) in the coleoptiles of two wheat (triticum aestivum L.) cultivars differing in drought tolerance were investigated under osmotic stress. The drought-tolerant 'Yumai 18' showed marked increases in free spermidine (Spd) and spermine (Spm) levels in coleoptiles after being treated with polyethylene glycol (PEG)-6000 for 2 d in the dark, while drought-sensitive 'Yangmai 9' showed a significant increase in free putrescine (Put) content. Treatment of coleoptiles with methylglyoxal-bis (guanylhydrazone) (MGBG), an S-adenosylmethionine decarboxylase (S-AMDC) inhibitor, resulted in reduction of free Spd and free Spm levels in coleoptiles and aggravation of PEG-induced injury to 'Yumai 18' coleoptile, while exogenous Spd treatment resulted in an increase in free Spd + free Spm content of coleoptiles, and an alleviation of PEG-induced injury to 'Yangmai 9' coleoptile. Osmotic stress induced significant increases in perchloric acid-soluble conjugated PA (PS conjugated PA) and perchloric acid-insoluble conjugated PA (PIS conjugated PA) levels in coleoptiles of 'Yumai 18' whereas osmotic stress affected only slightly the PS-conjugated PA and PIS-conjugated PA levels in 'Yangmai 9' coleoptiles. Treatment of coleoptiles with phenanthroline (o-Phen), an inhibitor of transglutaminase (TGase), also aggravated the PEG-induced injury to 'Yumai 18' coleoptiles, accompanied by the decreases in the level of PIS-conjugated PA. These results suggest that free Spd, free Spm and conjugated PA enhance the osmotic stress tolerance of wheat coleoptiles.