1.
Response of water balance and nitrogen assimilation in cucumber seedlings to CO2 enrichment and salt stress.
Li, S, Li, Y, He, X, Li, Q, Liu, B, Ai, X, Zhang, D
Plant physiology and biochemistry : PPB. 2019;:256-263
Abstract
The effects of CO2 enrichment on water balance and nitrogen (N) assimilation in cucumber (Cucumis sativus L. cv. Jinyou No.35) seedlings under salt stress were investigated. Two-way randomized block design was used: the main treatment consisted of two [CO2] levels, ambient and enriched (400 and 800 ± 40 μmol mol-1, respectively), and the minor treatment consisted on two salinity treatment levels, 0 and 80 mmol L-1 NaCl. The results showed that, under the experimental conditions, enriched [CO2] and salt stress significantly inhibited the N assimilation process in cucumber leaves; however, enriched [CO2] had no effect on the nitrate (NO3-) reduction or ammonium (NH4+) assimilation of leaves under salt stress, inhibiting only the transamination. Moreover, enriched [CO2] increased the plasma membrane H+-ATPase activity, vacuolar membrane H+-ATPase activity and root hydraulic conductivity under salt stress, thereby increasing the ion selective absorption and water absorption capacity. To a certain extent, enriched [CO2] promoted the accumulation of K+ in plants, which significantly reduced the Na+/K+ ratio; moreover, the enrichment ultimately improved the water state conditions and helped to maintain the ion balance in plants under stress, ensuring normal enzymatic activity.
2.
A meta-analysis of experimental warming effects on terrestrial nitrogen pools and dynamics.
Bai, E, Li, S, Xu, W, Li, W, Dai, W, Jiang, P
The New phytologist. 2013;(2):441-451
Abstract
Global warming may have profound effects on terrestrial ecosystems. However, a comprehensive evaluation of the effects of warming on ecosystem nitrogen (N) pools and dynamics is not available. Here, we compiled data of 528 observations from 51 papers and carried out a meta-analysis of experimental warming effects on 13 variables related to terrestrial N pools and dynamics. We found that, on average, net N mineralization and net nitrification rate were increased by 52.2 and 32.2%, respectively, under experimental warming treatment. N pools were also increased by warming, although the magnitude of this increase was less than that of N fluxes. Soil microbial N and N immobilization were not changed by warming, probably because microbes are limited by carbon sources. Grassland and shrubland/heathland were less responsive to warming than forest, probably because the reduction of soil moisture by warming offset the temperature effect in these areas. Soil heating cable and all-day treatment appeared to be the most effective method on N cycling among all treatment methods. Results of this meta-analysis are useful for better understanding the response of N cycling to global warming and the underlying mechanism of warming effects on plants and ecosystem functions.