Changes in the activities of starch metabolism enzymes in rice grains in response to elevated CO2 concentration.

The global atmospheric CO(2) concentration is currently (2012) 393.1 µmol mol(-1), an increase of approximately 42 % over pre-industrial levels. In order to understand the responses of metabolic enzymes to elevated CO(2) concentrations, an experiment was conducted using the Free Air CO(2) Enrichment (FACE )system. Two conventional japonica rice varieties (Oryza sativa L. ssp. japonica) grown in North China, Songjing 9 and Daohuaxiang 2, were used in this study. The activities of ADPG pyrophosphorylase, soluble and granule-bound starch synthases, and soluble and granule-bound starch branching enzymes were measured in rice grains, and the effects of elevated CO(2) on the amylose and protein contents of the grains were analyzed. The results showed that elevated CO(2) levels significantly increased the activity of ADPG pyrophosphorylase at day 8, 24, and 40 after flower, with maximum increases of 56.67 % for Songjing 9 and 21.31 % for Daohuaxiang 2. Similarly, the activities of starch synthesis enzymes increased significantly from the day 24 after flower to the day 40 after flower, with maximum increases of 36.81 % for Songjing 9 and 66.67 % for Daohuaxiang 2 in soluble starch synthase (SSS), and 25.00 % for Songjing 9 and 36.44 % for Daohuaxiang 2 in granule-bound starch synthase (GBSS), respectively. The elevated CO(2) concentration significantly increased the activity of soluble starch branching enzyme (SSBE) at day 16, 32, and 40 after flower, and also significantly increased the activity of granule-bound starch branching enzyme (GBSBE) at day 8, 32, and 40 after flower. The elevated CO(2) concentration increased the peak values of enzyme activity, and the timing of the activity peaks for SSS and GBSBE were earlier in Songjing 9 than in Daohuaxiang 2. There were obvious differences in developmental stages between the two varieties of rice, which indicated that the elevated CO(2) concentration increased enzyme activity expression and starch synthesis, affecting the final contents of starch and protein in the rice grains. Our results will provide a foundation for understanding the physiological mechanisms of rice yield under elevated atmospheric CO(2) concentrations.

[Effects of elevated atmospheric CO2 concentration on mung bean leaf photosynthesis and chlorophyll fluorescence parameters].

By using free air CO2 enrichment (FACE) system, a pot experiment under field condition was conducted to study the effects of elevated CO2 concentration (550 +/- 60 micromol mol(-1)) on the leaf photosynthesis and chlorophyll fluorescence parameters of mung bean. Comparing with the control (CO2 concentration averagely 389 +/- 40 micromol mol(-1)), elevated CO2 concentration increased the leaf intercellular CO2 concentration (Ci) and net photosynthesis rate (P(n)) at flowering and pod growth stage by 9.8% and 11.7%, decreased the stomatic conductance (G(s)) and transpiration rate (T(r)) by 32.0% and 24.6%, respectively, and increased the water use efficiency (WUE) by 83.5%. Elevated CO2 concentration had lesser effects on the minimal fluorescence (F0), maximal fluorescence (F(m)), variable fluorescence (F(v)), ratio of variable fluorescence to minimal fluorescence (F(v)/F0), and ratio of variable fluorescence to maximal fluorescence (F(v)/F(m)) at bud stage, but increased the F0 at pod filling stage by 19.1% and decreased the Fm, F(v), F(v)/F0, and F(v)/F(m) by 9.0%, 14.3%, 25.8% , and 6.2%, respectively. These results suggested that elevated CO2 concentration could damage the structure of leaf photosystem II and consequently decrease the leaf photosynthetic capacity in the late growth phase of mung bean.

[Impact of climatic change on soybean production: a review].

Since the industrial revolution, the rapid increase of global atmospheric concentration of CO2 and other greenhouse gases has induced the global warming and the change of global precipitation pattern. The growth, development, yield, and quality of soybean are subject to all these changes of climatic conditions. Soybean is one of the major grain and oil crops in the world and in China, and any change in the soybean production under future climate scenario will affect the grain- and edible oil security nationally and internationally. This paper reviewed the effects of elevated atmospheric CO2, global warming, and water stress on soybean growth, and discussed the future research needs, which could provide scientific basis for realizing soybean production in the future and for implementing in advance proper policies in the context of climatic change impact on soybean production.

[Effects of CO2 enrichment on grain quality of rice and wheat: a research review].

Crop grain quality is mainly depended on variety's genetic characteristics and environmental conditions, while elevated CO2 concentration in atmosphere, one of the main factors resulting in global climate change, would have a significant effect on crop grain quality. In this paper, the research progress on the effects of CO2 enrichment on rice and wheat grain quality was summarized from the aspects of protein and nitrogen contents, trace elements, and other characters, emphasized the necessity and urgency of the study in this field, and pointed out the key directions and contents of further study, i.e., (a) direct effects of CO2 enrichment on rice and wheat grain quality and their differences for different varieties, (b) integrated effects of CO2 enrichment and other climate factors on rice and wheat grain quality and their quantitative indices, (c) action mechanisms of CO2 enrichment and other climate factors on rice and wheat grain quality formation, (d) longterm directions and strategies of rice and wheat breeding in quality improvement to adapt climate change, (e) integrated planting technology systems in quality improvement for adapting climate change, and (f) application of molecule-marker and gene-transfer in rice and wheat breeding for quality improvement.

[Grassland net primary productivity and its spatiotemporal distribution in northern Tibet: a study with CASA model].

Based on the remote sensing data, meteorological data and other related data from 1981 to 2004, the grassland net primary productivity (NPP) and its spatiotemporal distribution in Northern Tibet were analyzed by CASA (Carnegie-Ames-Stanford Approach) model. The results indicated that in the study area, the spatial distribution of grassland NPP was affected by the local water and heat conditions, and represented a horizontal zonality. From southeast to northwest, the grassland NPP reduced from 230 g C x m(-2) x a(-1) to near 0 g C x m(-2) x a(-1). The overall level of grassland NPP in Northern Tibet was rather low, with the multi-years average value of total NPP being 21.3 x 10(12) g C x a(-1) and the mean value of NPP being 48.1 g C x m(-2) x a(-1), which were obviously lower than those in Qinghai-Tibetan Plateau and other grassland areas of China. The mean values of NPP on flat land (slope gradient <1 degree) and south slope were relatively lower. On the main alpine grasslands in Northern Tibet, the NPP from July to September occupied 64.0%-70.0% of the whole year. From 1981 to 2004, the grassland NPP within the whole Northern Tibet had a greater annual fluctuation, and tended to further reduce.