Factors driving the biomass and species richness of desert plants in northern Xinjiang China.

The desert ecosystem is an important part of the terrestrial ecosystem. Accurate estimations of the biomass and species richness of desert plants are of great value for maintaining ecosystem stability; however, current assessments remain a challenge due to the large spatial heterogeneity in biomass and species richness and difficulties posed by time-consuming field surveys, particularly in remote areas. In the present study, There were 527 sampling sites, and each sampling site contained approximately 9 quadrats. Approximately 4500 quadrats in total were taken from the Junggar Desert of northern Xinjiang, and the spatial distribution and factors driving the biomass and species richness of the desert ecosystem were quantitatively analyzed. The results showed that the average aboveground biomass, belowground biomass, litter, and the Patrick index of the Junggar Desert in northern Xinjiang were 115.42 gm-2, 924.77 gm-2, 13.06 gm-2, and 63, with values ranging from 2-708.12 gm-2, 120.25-3537.3 gm-2, 2-56.46 gm-2, and 0-377, respectively, The mean of the variation coefficient was 56.19%, 41.16%, 62.16% and 73.83%, suggesting moderate variation. The result is affected by the differences between the desert environment and climate. Climate factors had a relatively large impact on species richness, and the variation coefficient of species richness was large, indicating a large degree of dispersion of species richness. The direct influence of environmental and climatic factors on underground biomass (BGB) is relatively small, and its coefficient of variation is small. The spatial distribution of biomass and species richness in northern Xinjiang gradually decreased from west to east. Redundancy analysis showed that climate was the main factor driving desert biomass and species richness in northern Xinjiang, with an average independent explanatory power of 20.38% and 18.57%, respectively. Structural equation modeling indicated that climate factors, elevation, and community coverage had a direct positive effect on the aboveground biomass of the desert plants in northern Xinjiang and a direct negative effect on the belowground biomass. Moreover, climate factors and biological factors showed a direct positive effect on the species richness in northern Xinjiang.

Characterization of PSII photochemistry and thermostability in salt-treated Rumex leaves.

A study was conducted, using chlorophyll fluorescence, rapid fluorescence induction kinetics, and polyphasic fluorescence transients, to determine the effect of salt treatment and heat stress on PSII photochemistry in Rumex leaves. Salt treatment was accomplished by adding NaCl solutions of different concentrations ranging from 50 to 200 mmol/L. Heat stress was induced by exposing the plant leaves to temperatures ranging from 29 to 47 degrees C. The control plants were grown without NaCl treatment. The data acquired in this study showed that NaCl treatment alone had no effect on the maximal photochemistry of PSH or the polyphasic rise of chlorophyll fluorescence. However, the NaCl treatment modified heat stress on PSII photochemistry in Rumex leaves, which was manifested by a lesser heat-induced decrease in photochemical quenching (qP), efficiency of excitation energy capture by open PSII reaction centers (Fv'/Fm'), and quantum yield of PSII electron transport (phiPSII). The data also showed that NaCl treatment compromised the impact of heat stress on the capacity of transferring electrons from Q(A)- to Q(B). Furthermore, the NaCl treatment promoted heat resistance of O2-evolving complex (OEC). In summary, NaCl treatment enhanced the thermostability of PSII.

[NaCl stress increases the heat tolerance of PSII in leaves of rumex K-1 seedlings].

By measuring chlorophyll fluorescence, the effects of NaCl treatment on the maximal efficiency and heat tolerance of PSII were examined in leaves of Rumex seedlings. NaCl 200 mmol/L treatment had no effect on the maximal efficiency of PSII, but increased the heat tolerance of PSII in Rumex leaves. Compared with control leaves, the heat stress-induced decrease in F(v)/F(m) and the increase in F(k)/F(j) ratio were less in NaCl-treated leaves. In addition, the heat stress-induced decrease in photochemical quenching (q(P)), the efficiency of excitation energy capture by open PSII reaction center (F(v)' /F(m)') and the quantum yield of electron transport (PhiPSII) were less in NaCl-treated leaves. Moreover, the increase in the Q(B)-non-reducing PSII reaction center content was less in NaCl-treated leaves than in control leaves. Discussion was made on the possible mechanisms of the increase in the heat tolerance of PSII in NaCl-treated leaves.