By measurement of gas exchange and chlorophyll fluorescence, the effects of salt shock on photosynthesis and the mechanisms to protect photosynthetic machinery against photodamage during salt shock were investigated in leaves of Rumex seedlings. Salt shock induced significant decrease in photosynthesis both in 21 and 2 % O 2 . In 21 % O 2 , quantum yield of photosystem 2 (PS2) electron transport (Ф PS2 ) decreased slightly and q P remained constant, suggesting that the excitation pressure on PS2 did not increase during salt shock. In 2 % O 2 , however, both Ф PS2 and q P decreased significantly, suggesting that the excitation pressure on PS2 increased during salt shock. NPQ increased slightly in 21 % O 2 whereas it increased significantly in 2 % O 2 . The data demonstrated that during salt shock a considerable electron flow was allocated to oxygen reduction in the Mehler-peroxidase reaction (MPR). Under high irradiance and in the presence of saturating CO 2 , the susceptibility of PS2 to photoinhibition in salt-shocked leaves was increased when the electron flow to oxygen in MPR was inhibited in 2 % O 2 . Hence, MPR is important in photoprotection of Rumex seedlings during salt shock.
Cool-season grasses (Poaceae subfamily Poöideae) are an important forage component for livestock in western China, and many have seed-transmitted symbionts of the genus Epichloë, fungal endophytes that are broadly distributed geographically and in many tribes of the Poöideae. Epichloë strains can produce any of several classes of alkaloids, of which ergot alkaloids and indole-diterpenes can be toxic to mammalian and invertebrate herbivores, whereas lolines and peramine are more selective against invertebrates. The authors characterized genotypes and alkaloid profiles of Epichloë bromicola isolates symbiotic with Elymus dahuricus, an important forage grass in rangelands of China. The endophyte was seed-transmitted and occasionally produced fruiting bodies (stromata), but its sexual state was not observed on this host. The genome sequence of E. bromicola isolate E7626 from El. dahuricus in Xinjiang Province revealed gene sets for peramine, ergot alkaloids, and indole-diterpenes. In multiplex polymerase chain reaction (PCR) screens of El. dahuricus-endophyte isolates from Beijing and two locations in Shanxi Province, most were also positive for these genes. Ergovaline and other ergot alkaloids, terpendoles and other indole-diterpenes, and peramine were confirmed in El. dahuricus plants with E. bromicola. The presence of ergot alkaloids and indole-diterpenes in this grass is a potential concern for managers of grazing livestock.
Long‐term series of vegetation change is one of the key study contents for evaluating terrestrial ecosystems and plays an important role in global change study. The CSCS (Comprehensive and Sequential Classification System) model was used in the paper to analyze the change of Potential Natural Vegetation (PNV) types during the period 1951–2000 and for the three future years 2020, 2050 and 2080. The growth conditions for each PNV type were analyzed based on MODIS Normalized Difference Vegetation Index (NDVI) datasets on the Tibetan Plateau (TP) from 2001 to 2010. The results showed that: (i) The mean annual precipitation (MAP) and mean annual temperature (MAT) had increasing trends (1.72 mm year−1 and 0.025°C year−1, respectively) over the past 50 years from 1951 to 2000. (ii) Based on the three general circulation models (CCCMA, CSRIO and HadCM3), the MAT and MAP on TP would increase in the future, with magnitudes 3.54 to 6.08°C and 28.71 mm to 126.84 mm from 2000 to 2080, respectively; it is also predicted that two new vegetation categories: warm desert and savanna would appear in the future and that the area of forest would increase significantly, while the area of grassland would have an obvious decreasing trend. And (iii) Overall, the ecological environment of vegetation in the recent 10 years has been improved in most of the areas in central and southern regions of Qinghai Province, but degraded in some areas of Sichuan Province, and the southwest and south of Tibet.
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