January 1996, Volume 38 Issue 1

 

          Research Articles
Assimilation and Allocation of Carbon and Nitrogen in Alfalfa Under Doubled CO2 Environment
Author: Ding Li, Zhong Ze-pu, Li Shi-yi, Zhang Chong-hao, Bai Ke-zhi and Kuang Ting-yun
Journal of Integrative Plant Biology 1996 38(1)
      
    Pot-grown alfalfa (Medicago sativa L. ) were experimented in the open top chambers in which natural air (350 10-6, 1 CO2) and doubled CO2 air (700 10-6, 2 CO2) were continuous blown through bottom respectively. Results showed that the biomass in both shoot and root was increased by the 2 CO2 treatment. The root/shoot ratio was nearly unchange in the short term treatment and slightly decreased in the longer term treatment. The results differed from those reported in literatures that was attributed to the potgrown condition in this experiment. The nitrogen fixation activities (acetylene reduction) per plant were obviously promoted under the 2 CO2 condition but the difference of the specific nitrogen-fixing activities between 1 CO2 and 2 CO2 treatment was small. It implied that supplement of ATP, NADP or carbon skeleton under the 2 CO2 condition was not more than that under the 1 CO2 condition. C/N ratio in the shoot increased in the doubled CO2 treatment group, similar to the reports from other authors; but the ratio increased in the root in the 2 CO2 treatment group was ascribed to the higher nitrogen absorption from the soil and (or) N-fixing activity of the nodules as compared with that in the 1 CO2 treatment. The results demonstrated that assimilation and allocation of carbon and nitrogen in legume plant were deeply influenced by the elevated CO2.
Abstract (Browse 1745)  |  Full Text PDF       
Effect of Elevated CO2 on the Primary Conversion of Light Energy of Alfalfa Photosynthesis
Author: Zhang Qi-de, Lu Cong-ming, Feng Li-jie, Lin Shi-qing, Kuang Ting-yun and Bai Ke-zhi
Journal of Integrative Plant Biology 1996 38(1)
      
    In studying the mechanism of increase in alfalfa (Medicago sativa L. ) photosynthesis under elevated atmospheric CO2, it was found that the capacity of chloroplasts for light absorption was greater, the potential activity and efficiency of primary conversion of light enlergy of PS , quantum yield of PS electron transport, and activation capacity of PS were stimulated, photochemical quenching coefficient was increased and non-photochemical quenching coefficient was decreased under elevated atmospheric CO2.
Abstract (Browse 1762)  |  Full Text PDF       
Effect of Doubled-CO2 Concentration on the Ultrastructure of Chloroplasts from Medicago sativa and Setaria italica
Author: Zuo Bao-yu, Jiang Gui-zhen, Bai Ke-zhi and Kuang Ting-yun
Journal of Integrative Plant Biology 1996 38(1)
      
    It has been reported in quite a number of literatures that doubled CO2 concentration increased the photosynthetic rate and dry matter production of C3 plants, but substantially affected C4 plants little. However, why may CO2 enrichment promote growth and either no change or decrease reproductive allocation of the C3 species, but havinag no effects on growth characteristics of the C4 plants? So far, there has been no satisfactory explanation on that mentioned above, except the differences in their CO2 compensatory points. In the past, although some studies on ultrastructure of the chloroplasts under doubled CO2 concentration were limitedly conducted. Almost all the relevant experimental materials were only from C3 plants not from C4 plants, and even though the results were of inconsistancy. Thereby, it needs to verify whether the differences in photosynthesis of C3 and C4 plants at doubled CO2 level is caused by the difference in their chloroplast deterioration. Experiments to this subject were conducted at the Botanical Garden of Institute of Botany, Academia Sinica in 1993 and 1994. Both experimental materials from C3 plant alfalfa (Medicago sativa) and C4 plant foxtail millet (Setaria italica) were cultivated in the cylindrical open-top chambers (2.2 m in diameter 2.4 m in height) with aluminum frames covered by polyethylene film. Natural air or air with 350 10-6 CO2 were blown from the bottom of the chamber space with constant temperature between inside and outside of the chamber 0.2桵. Electron microscopic observation revealed that the ultrastructure of the chloroplasts from C3 plant Medicago sativa and C4 plant Seteria italica growing under the same doubled CO2 concentration were quite different from each other. The differential characteristics in ultrastructure of chloro plasts displayed mainly in the configuration of thylakoid membrances and the accumulation of starch grains. They were as follows: 1. The most striking feature was the building up of starch grains in the chloroplasts of the bundle sheath cells (BSCs) and the mesophyll cells (MCs) at doubled CO2 concentra tion. The starch grains appeared centrifugally first in the BSCs and then in the chloroplast of the other MCs. It was worthy to note that the starch grains in the chloroplasts of C4 plant Setaria ira/ica were much more than those of the C3 plant Medicago sativa . The decline of photosynthesis in the doubled CO2-grown C4 plants might be caused by an over accumulation of starch grains, that deformed the chloroplast even demaged the stroma thylakoids and grana. There might exsist a correlation between the comformation of thylakoid system and starch grain accumulation, namely conversion and transfer of starch need energy from ATP, and coupling factor (CF) for ATP formation distributed mainly on protoplastic surface (PSu) of stroma thylakoid membranes, as well as end and margin membranes of grana thylakoids. Thereby, these results could provide a conclusive evidence for the reason of non effectiveness on growth characteristics of C4 plant. 2. Under normal condition , the mature chlolroplats of higher plants usually develop complete and regularly arranged photosynthetic membrane systems . Chloroplasts from the C4 plant Setaria italica, however, exerted significant changes on stacking degree, grana width and stroma thylakoid length under doubled CO2 concentration; In these changes, the grana stacks were smaller and more numerous, and the number of thylakoids per granum was greatly increased, and the stroma thylakoid was greatly lengthened as compared to those of the control chloroplasts. But the grana were mutually intertwined by stroma thylakoid. The integrity of some of the grana were damaged due to the augmentation of the intrathylakoid space . Similarly, the stroma thylakoids were also expanded. In case. the plant was seriously effected by doubled CO2 concentration as observed in C4 plant Setaria italica , its chloroplasts contained merely the stroma (matrix) with abundant starch grains, while grana and stroma thylakoid membranes were unrecognizable, or occasionally a few residuous pieces of thylakoid membranes could be visualized, leaving a situation which appeared likely to be chloroplast deterioration. However, under the same condition the C3 plant Medicago sativa possessed normally developed chloroplasts, with intact grana and stroma thylakoid membranes. Its chloroplasts contained grana intertwined with stroma thylakoid membranes, and increased in stacking degree and granum width, in spite of more accumulated starch grains within the chloroplasts. These configuration changes of the thylakoid system were in consistant with the results of the authors another study on chloroplast function, viz. the increased capacity of chloroplasts for light absorption and efficiency of PS.
Abstract (Browse 2546)  |  Full Text PDF       
Responses to Doubled CO2 in Medicago sativa: Studies on Ecophysiology and Simulation Modelling
Author: Xiang Bin, Lin Shun-hua and Gao Lei-ming
Journal of Integrative Plant Biology 1996 38(1)
      
    A world-wide spread forage grass, Medicago sativa, was grown in two open-top chambers maintained at either normal (350 mol mol-1) or doubled (700 mol mol-1) CO2 concentration, from seedling to maturity. During the whole growth season, ecophysiological measurements and observations were conducted over different phenological stages and the main results were as follows: (1) With similar environmental factors, in terms of RH (relative humidity), irradiance, and watering, a slight shift in temperature (about 0.77, averaged over the whole growth season) within the chamber maintained at doubled CO2 did not affect instantaneous physiological processes at leaf level, but had some impacts on the effect of doubled CO2 over a long period. (2) Over the whole growth season, physiological variables showed differences between two chambers. The net photosynthesis of plant grown under higher CO2 increased by 18.7 %, while stomatal conductance fell slightly as compared with that of the control. So was the water use efficiency which was also 30.1% higher than the control. Based on the above results from field studies, we concluded that photosynthetically active radiation (PAR) and RH were the main factors affecting photosynthesis and stomatal behavior. Then we combined a widely accepted model of C3 leaf photosynthesis with an empirical model of stomatal conductance and made some modifications according to our experiments. This model was parameterized using field data sets of net CO2 assimilation, stomatal conductance, intercellular CO2 concentration of plants grown at both doubled and control CO2 levels. Variances of main parameters between two treatments reflected some biochemical changes in leaf cell. The maximum efficiency of light energy conversion () increased by 22 % and light-saturated rate of electron transport (Jmax) rose by 15 %. The maximum stomatal conductance was slightly reduced by 8 %. The increases in parameters ( and Jmax) indicate accelerated biochemical processes in leaf cell, which means that the photosynthetic capacity of M. sativa may increase at elevated CO2. These results agree well with biochemical measurements at cell level.
Abstract (Browse 1807)  |  Full Text PDF       
Approach for a Vegetation Index Resistant to Atmospheric Effect
Author: Zhang Ren-hua, Rao N X and Liao K N
Journal of Integrative Plant Biology 1996 38(1)
      
    Estimation of vegetation information at the regional scales using remote sensing data has been a subject of considerable research and development in view of the importance of land-atmosphere interactions in global climate change. The normalized difference vegetation index (NDVI) approach has been a popular method. Many experiments on the' ground had indicated that NDVI was closely correlated to the leaf area index (LAI) and photosynthetically active radiation (PAR). In order to determine LAI and PAR accurately in a region by means of NDVI from available satellite inages, atmospheric effects must be largely elucidated. Although substantial progress has been made to improve the NDVI method, removal of the atmospheric effects has not been completely satisfactory. The atmospheric effect on NDVI has been contemplated in the experiments conducted at Yucheng Experimental Comprehensive Station, China. Kaufman and his colleagues also had verified the atmospheric effect on NDVI even the effect still existed after using 5s algorithm to remove rayleigh scattering and ozone absorption. For this reason they presented an atmosphere resistant vegetation index (ARVI) which was based on correlation between blue and red wave bands of the atmo. The authors also proposed the values for calculating IAVI in absence of the gound-based spectrum-radiometer measurements to approximately correct the atmosphere effect. For summer condition: á=0. 656C0.006 sin+0.124 Sin2 for rural area, visibility22 km á=0. 656C0. 018 sin+0. 106 Sin2 for urban area, Visibility22 km á =0. 722C0. 011 sin+0.165 sin2 for rural area, 7 kmvisibility20 km á=0. 646C0.002 sin+0, 140 sin2 for urban area, 7 kmvisibility20 km á =0. 788+0. 015 sin+0. 206 sin2 for rural area, visibility<5 km á =0. 643+0. 007 sin+0. 174 sin2 for urban area, visibility5 km For winter condition á =0. 677+0. 019 sin+0. 200 sin2 for rural area, visibility>22 km á =0. 642-0. 009 sin+0. 196 sin2 for urban area, visibility>22 km á =0. 785+0, 040 sin+0. 237 sin2 for rural area, 7 kmvisibility20 km á =0. 664+0. 021 sin+0.223 sin2 for urban area, 7 kmvisibility20 km á =0. 893+0.060 sin+0. 273 sin2 for rural area, visibility5 km á =0. 686+0. 051 sin+0. 249 sin2 for urban area, visibility5 km The correction factor á was a crucial parameter for upward path radiance. It varied with atmosphere aerosol co ndition and viewing angles and was deviated from 1. Based on the above analysis: the range of á was from 0.65 to 1.21. For hazy atmosphere conditions it varied more significantly with aerosol type and viewing angles than clear condition. The percentage of error of vegetation index for the two cases studied were less than 4 % as compared with 16% and 31% using NDVI, and 19% using ARVI.
Abstract (Browse 1932)  |  Full Text PDF       
Dynamics of Primary Productivity and Soil Organic Matter of Typical Steppe in the Xilin River Basin of Inner Mongolia and Their Response to Climate Change
Author: Xiao Xiang-ming, Wang Yi-feng and Chen Zuo-zhong
Journal of Integrative Plant Biology 1996 38(1)
      
    At the site level, the authors used the Century plant-soil ecosystem model and Landsat remote sensing to estimate the aboveground biomass of Aneurolepidium chinense steppe and Stipa grandis steppe in the Xilin river basin, Inner Mongolia China. The results of century simulation matched well in terms of the seasonal and yearly change of biomass, with those of field moniforing. The results of field monitoring replicated well were about 142.45144.37 g/m2 and 210. 38~227.44 g/m2 on S. grandis and A. chinense steppe, respectvely, whereas the simulation results were 127. 04156. 23 g/m2 and 189.25~193.98 g/m2, respectively. Simulated soil organic matter was around C25% of the observed data. Normalized differnce vegetation index derived aboveground biomass was around 25 % of the observed field biomass on the A. chinence and S. grandis steppe, using Landsat TM imagecries on July 31, 1987 and August 11, 1991. The effect of global climate change and elevated CO2 on these steppe was examined, using the climate fields from Global Change Models of Canadian Climate Center and Geophysics Flow Dynamics Laboratory under 1 CO2 (350 X 10-6) and 2 CO2 (700 X 10-6) sceneries. Climate change resulted in considerable decrease of primary productivity and soil organic matter of A. chinense and S. grandis steppe, the former being more sensitive to climate change.
Abstract (Browse 1814)  |  Full Text PDF       
Methods for Collecting Vegetation Information in Loess Plateau
Author: Chi Hong-kang
Journal of Integrative Plant Biology 1996 38(1)
      
    The optimum vegetation indexand methods for collecting vegetation information in loess plateau area were studied and appraised. In this area, there were deciduous broadleaved forest, steppe and desert. Vegetation types were rich and diverse. However, collection of vegetation information was strongly influenced by the soil background. The modified soil-adjusted vegetation index (MSAVI) after being compared and analysed not only could enhance vegetation signal, but also could minimize greatly the soil background effects. It could also reflect the distribution of the vegetation types macroscopically in this area. At present, it has been a more or lessideal vegetation index for collection vegetation information in loess plateau area. The collection and monitering of vegetation information for the normalized difference vegetation index (NDVI), soil-adjusted vegetation index (SAVI) and perpendicular vegetation index (PVI) were used in high, medium density and rare vegetation area respectively. For a variety of vegetation indices, the images which were produced by cumulative multitemporal vegetation indices could extract vegetation information well reflecting the vegetation distribution of that particular area.
Abstract (Browse 1727)  |  Full Text PDF       
Estimating the Net Primary Productivity in China Using Meteorological Satellite Data
Author: Xiao Qian-guang, Chen Wei-ying, Sheng Yong-wei and Guo Liang
Journal of Integrative Plant Biology 1996 38(1)
      
    Net primary productivity (NPP) is one of the cruces for global changes studies, utilizing remote sensing data from meteorological satellite is an objective way to estimate NPP. Usually, the normalized difference vegetation index (NDVI) is derived from channel 1 and channel 2 of NOAA/AVHRR to monitor vegetation. Using the processed annual NDVIs, the authors could estimate the NPP values from an experimental model. The result showed that NPP derived from NDVIs was highly compatible to that estimated in the conventional way.
Abstract (Browse 1793)  |  Full Text PDF       
Structural Response of Soybean Leaf to Elevated CO Concentration
Author: Lin Jin-xing and Hu Yu-xi
Journal of Integrative Plant Biology 1996 38(1)
      
    The effects of CO2 concentration on the morphological and anatomical characters of soybean (Glycine max) leaf were investigated by means of light microscopy and SEM. It was noticed that exomorphology did not show dramatic change, while stomatal density decreased with increasing CO2 concentration. Under SEM, no epicuticular wax was observed on both abaxial and adaxial sides of the control group as well as on adaxial side of the treatment group. However, leaf surface of abaxial side was noticed to be densely covered with microasterisk epicuticular wax when they were exposed to CO2-enriched environment. The epicuticular wax deposition was present in equal abundance on both stomatal and nonstomatal areas. Furthermore, leaf thickness increased significantly due largely to the origin of an extra layer of palisade in the treatment group. The results confirmed that CO2 enrichment might enhance cell division and induce greater quantity of epicuticular wax.
Abstract (Browse 1772)  |  Full Text PDF       
A Modeling Study on Responses of Alkaline Grassland Ecosystems to Climate Change in Light of Diversity and Spatial Patterns
Author: Gao Qiong, Li Jian-dong and Zheng Hui-ying
Journal of Integrative Plant Biology 1996 38(1)
      
    Temporal variations of spatial coverage patterns of major plant species in the alkaline grasslands in northeast China subject to climate change were studied using a spatial simulation model. The model stressed the coupling between soil alkali and vegetation coverage. The modeled species coverage patterns were shown in close agreement with observations on a fenced one-hectare alkaline grassland from 1989 to 1993. The impacts of climate change on the species coverage were studied by subtracting the output patterns of the model under contemporary climate from those under altered climate. To relate the difference patterns to various landscape indices, the one-hectare region was divided into 25 subregions. The differencein species coverage between the present and altered climate and spatial pattern and diversity indices were computed for each subregion. A statistical analysis showed that for plants with wide ranges of tolerance to soil alkali and strong spatial migration capability, the impact of climate change was significantly related to spatial patterns, but not to diversity. However, for plants with narrow ranges of tolerance to soil alkali and less capability to migrate spatially, the impact of climate change was related to both diversity and spatial patterns.
Abstract (Browse 1922)  |  Full Text PDF       
Study on ClimateVegetation Classification for Global Change in China
Author: Zhou Guang-sheng and Zhang Xin-shi
Journal of Integrative Plant Biology 1996 38(1)
      
    The study on climate-vegetation relationship is the basis for determining the re sponse of terrestrial ecosystem to global change. By means of quantitative analysis on climate-vegetation interaction, vegetation types and their distribution pattern could be corresponded with certain climatic types in a series of mathematical forms. Thus, the climate could be used to predict vegetation types and their distribution, the same is in reverse. Potential evapotranspiration rate is a comprehensive climatological index which combines temperature with precipitation, and could be used to evaluate the effect of climate on vegetation. In this respect, Holdridge life zone system has been drawing much attention and widely applied internationally owing to its simplicity. It is especially used in the assessment of sensibility of terrestrial ecosystems and their distribution in accordance with climate change and in prediction of the changing pattern of vegetation under doubled CO2 condition. However, Prentice (1990) pointed out that the accurancy of Holdridge life zone system is less than 40 % when it is used at global scale. The reason may be that the potential evapotranspiration calculated by Thornthwaite method, which is used in Holdridge life zone system, reflects the potential evapotranspiration from small evaporated area, while climate-vegetation classification is based on the regional scale. The authors try to establish a new climate-vegetation classification system based on the regional potential evapotranspiration. According to the following formula: where E designates regional actual evapotranspiration: Ep local potential evapotran-spiration: Epo, regional potential evapotranspiration. Ed can be calculated from Penman model or other models. E can be calculated from the following model: E=r Rn (r2+Rn2+r Rn) / (2) (r+Rn) (r2+Rn2)where r designates precipitation (mm); Rn, net radiation (mm). Thus, Ep0 can be easily obtained. It is used as the regional thermal index (RTI) of climate-vegetation classification,and can be expressed as: RTl = Epo (3) Moisture index is another index of climate-veggetation classification. Usually, it can be expressed as the ratio between potential evapotranspiration and precipitation. However, this ratio can not reflect soil moisture, which is important for plant. The ratio between regional actual evapotranspiration and regional potential evapotranspiration is associated not only with climatic condition but also with soil moisture. So it can be used as the moisture index of climate-vegetation classification, and is defined as regional moisture index (RMI): RMI = E/Epo (5) Based on the average climatological data of 30 years from 647 meteorological observation stations in China. It was found that RTl could well reflect a regional thermal level. The values of RTI were less than 360 mm in cold temperate zone, 360650 mm in temperate zone, 650380 mm in warm temperate zone, 7801100 mm in subtropical zone. And more than 1100 mm in tropical zone. RMI also reflects a regional moisture level very well. The values of RMI was less than 0.4 in desert area, 0.40.7 in grassland area and more than 0.7 in forest area. Thus, the climate-vegetation classification in China is established on the basis of the two indices: RTI and RMI. According to this model, the changing patterns of vegetation zones in China are given under the conditions of mean annual temperature in creasing by 2 and 4 and mean annual precipitation increasing by 20%. The results showed that the areas of forest and grassland would decrease, the vegetation zones would move northward and upward, and the area of desert would increase. The results also indicate that the Tibetan Plateau is an area highly sensitive to global change. It could be considered as an indicative or forewarning area for global change , and therefore, an area of great siginificance for monitoring and research. The possible beneficial effect of global change on China terrestrial ecosystems is that the plantation boundary will move northwards and upwards; and the disadvantageous effect is the expansion of desertification and the increase of instability in climatic conditions.
Abstract (Browse 2232)  |  Full Text PDF       
Feedback of Vegetation on Climate
Author: Zhou Guang-sheng and Zhang Xin-shi
Journal of Integrative Plant Biology 1996 38(1)
      
    Global change has been received more and more attention for the decades, Coz concentration in the atmosphere has been increasing at a much faster rate than that has been observed in the historical record. Scientific evidence from long-term monitoring had revealed the creeping destruction of ecosystems upon which human existence depended. Recognition of this destruction has impelled to changing international policies used to manage our planet. A lot of research on terrestrial ecosystems and global change have been done. However, they were mainly concentrated on the responses of terrestrial ecosystems to global change, the studies on the feedback of vegetation on climate have been seldom done. The study on the effect of vegetation on climate would enhance the understanding of global change, and promote the accuracy of evaluating and predicting the responses of terrestrial ecosystems to global change. The authors would discuss the feedback of plant on climate based on the two well-known balance equations. There are two well-known balance equations on the earths surface. For long period, such as year, heat balance equation expressed as Rn = P+LE and water balance equation expressed as r=f+E, where Rn designates net radiation; P. sensible heat; LE, latent heat: r, precipitation; f, runoff; E, evapotranspiration. Therefore, the difference Af between fa and fo (after and before the surface change respectively) could be expressed as f = faCfo = (LrCRn + p)/L f= C2. 7 10C5 g/(cm2 min), w = C0. 05 . then the effect becomes negative. These results indicate that the effect of plant on temperature depends on specific area. If w=0, that is to say, the effect of plant on temperature for the loess plateau is zero, f = 5a 10C4 g/(cm2 min) This result also indicates the reason why the relationship between the surface temperature on forest surface and on cut forest surface is uncertain. In a word, the effect of vegetation on climate deponds on specific regions. Vegetation has the function of reducing run off. The effect of vegetation on precipitation may not be considered. This paper provides a long-term and region-scale based method for evaluating the effect of vegetation on climate.
Abstract (Browse 1714)  |  Full Text PDF       
 

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