首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The effect of low phosphate supply (low P) was determined on the diurnal changes in the rate of carbon export, and on the contents of starch, sucrose, glucose, and fructose 2,6-bisphosphate (F2,6BP) in leaves. Low-P effects on the activities of a number of enzymes involved in starch and sucrose metabolism were also measured. Sugar beets (Beta vulgaris L. cv. F58-554H1) were cultured hydroponically in growth chambers and the low-P treatment induced nutritionally. Low-P treatment decreased carbon export from the leaf much more than it decreased photosynthesis. At growth chamber photon flux density, low P decreased carbon export by 34% in light; in darkness, export rates fell but more so in the control so that the average rate in darkness was higher in low-P leaves. Low P increased starch, sucrose, and glucose contents per leaf area, and decreased F2, 6BP. The total extractable activities of enzymes involved in starch and sucrose synthesis were increased markedly by low P, e.g. adenosine 5-diphosphoglucose pyrophosphorylase, cytoplasmic fructose-1,6-bisphosphatase, uridine 5-diphosphoglucose pyrophosphorylase, and sucrose-phosphate synthase. The activities of some enzymes involved in starch and sucrose breakdown were also increased by low P. We propose that plants adapt to low-P environments by increasing the total activities of several phosphatases and by increasing the concentrations of phosphate-free carbon compounds at the expense of sugar phosphates, thereby conserving Pi. The partitioning of carbon among the various carbon pools in low-P adapted leaves appears to be determined in part by the relative capacities of the enzymes for starch and sucrose metabolism.  相似文献   

2.
Extraction of oil from rice bran with supercritical carbon dioxide (SC-C02) at pressures of 150 to 350 kg/cm2 G at 40°C was demonstrated. The constituents of the selective fractions obtained at different pressures differed. Fractions obtained at higher pressures contained less free fatty acid and waxes or unsaponifiables. The phosphorus and iron contents were very low in the SC-C02 extracted oil, while the color of the oil was significantly lighter than that of hexane-extracted oil. The yield of low acid value oil was comparable to that for hexane extraction. One problem of the SC-C02 oil is its poor oxidation stability. This method of extraction may be effective in simplifying the processing of edible rice bran oil. Grinding the raw material was found to be effective in decreasing the C02 required and shortening the extraction period.  相似文献   

3.
White clover ramets were grown at various carbon dioxide concentrations(200, 350 and 1000 µl 1–1), defoliated and regrownat the same concentrations. Morphological characteristics, dryweights and non-structural carbohydrate contents of plant organs,diurnal variation of sugar and starch content of leaves, translocationof assimilates and photosynthesis were determined. Carbon dioxide concentration influenced the dry weights, butnot the number and size of the plant organs. However, defoliationof plants at low carbon dioxide concentration resulted in decreasedleaf size and stolon length. Carbon dioxide concentration influencedthe content and diurnal variation of starch and sugar in theleaves. Starch was accumulated at medium carbon dioxide concentrationand sugar at a higher concentration when the storage capacityfor starch seemed to be exceeded. Starch was preferentiallyaccumulated in the first and sugar in the second half of thelight period. Translocation was decreased during the periodsof accumulation. Sugar accumulation in the leaves seemed tobe a consequence of the imbalance between sink and source, whereasstarch accumulation seemed to follow an in-built diurnal pattern.Accumulation of both starch and sugar during the photoperiodwas followed by degradation and export during the dark period.Decreased dark export occurred at low carbon dioxide concentrationwhen neither starch nor sugar was accumulated during the photoperiod. Carbon dioxide, white clover, Trifolium repens L., growth, carbohydrates, starch, sugar, translocation, photosynthesis  相似文献   

4.
Carbon Source Quality and Placement Effects on Soil Organic Carbon Status   总被引:1,自引:0,他引:1  
Improved management of agricultural soils has potential for sequestering carbon (C) and reducing the accumulation of atmospheric carbon dioxide. Development of management practices to increase C sequestration is dependent on improved understanding of soil processes influencing long-term storage of C. A field study was conducted to compare surface C source quality and above- vs. belowground addition of annual or perennial plant biomass effects on particulate organic matter (POM), total labile C (TLC), and total organic C (TOC). Since microaggregate stabilization within macroaggregates is the main mechanism for sequestering C, aggregate size distribution, expressed as mean weight diameter (MWD), and wet aggregate stability (WAS) was also measured. After 5 years, POM decreased in plots receiving surface application of readily available substrate (sucrose and alfalfa pellets) and the bare surface control. Plots receiving plant additions [wood chips, growing wheat (Triticum aestivum L.) crop, growing switchgrass (Panicum virgatum L.) crop, and fallow receiving either wheat or switchgrass residue] exhibited higher TLC and TOC content. Plots receiving plant residue maintained MWD, and those supporting live plants exhibited increasing WAS. Surface plant residue protected the soil against raindrop impact and reduced the intensity of wetting and drying cycles allowing the development of larger more stable aggregates resulting in C accrual.  相似文献   

5.
6.
Uprety  D.C.  Dwivedi  N.  Jain  V.  Mohan  R. 《Photosynthetica》2002,40(2):315-319
The response of stomatal parameters of four rice cultivars to atmospheric elevated CO2 concentration (EC) was studied using open top chambers. EC brought about reduction in stomatal conductance and increase in stomatal index, size of stomatal guard cells, stroma, and epidermal cells. Such acclimation helped the regulation of photosynthesis to EC. These changes in stomatal characters made rice cultivars adjustable to EC environment.  相似文献   

7.
Results have shown that, with mixed culture (sewage) inocula, the lag period in aerobic catabolism of glucose can be reduced by increased CO2 tension. Conversely, removal of CO2 from the air supply to the growth flasks and Warburg vessels may increase the lag period.  相似文献   

8.
Carbon Partitioning in Mature Leaves of Pepper: Effects of Daylength   总被引:2,自引:0,他引:2  
Grange, R. 1. 1985. Carbon partitioning in mature leaves ofpepper: effects of daylength.—J. exp. Bot. 36: 1749–1759. The partitioning of recently fixed carbon has been examinedin mature pepper leaves grown in 6, 10 or 14 h photoperiodsat different irradiances chosen to give similar radiation integralsand in a 6 h photoperiod at the lowest of these irradiances.The partitioning of carbon into export, starch, sugars and respirationwas followed over the photopenod and the subsequent night ina mature leaf. The maximum export rate during the day (approximately 18 µgC cm–2 leaf h–1) was not significantly differentamong the treatments. Net photosynthesis rate was directly relatedto irradiance; the proportion of net photosynthesis exportedduring the day was 33% in 6-h days and 57% in 14-h days. Leafstarch accumulation (as a proportion of net photosynthesis rate)increased slightly when plants were grown in 6-h days. The remobilization of starch and sugars at night allowed exportrates to remain similar over 24 h when plants were grown in10-h or 14-h photoperiods. Leaves grown in 6-h days showed nosignificant changes in export rate during the first few hoursof night but exhausted their starch reserves during the nightand export rates declined. Sucrose and hexose levels decreased at the onset of darkness,but did not fall below 40 µg cm–2 in plants grownin 10-h or 14-h photoperiods; when this level was reached after3–4 h of darkness, starch breakdown began. In leaves grownin both 6-h treatments, sucrose levels fell below 40 µgcm–2 when starch reserves were depleted during the nightand the export rate decreased concurrently. The results are discussed in relation to the control of exportand starch metabolism in the leaf. Key words: Pepper, partitioning, daylength  相似文献   

9.
Soil mineral weathering may serve as a sink for atmospheric carbon dioxide (CO2). Increased weathering of soil minerals induced by elevated CO2 concentration has been reported previously in temperate areas. However, this has not been well documented for the tropics and subtropics. We used model forest ecosystems in open-top chambers to study the effects of CO2 enrichment alone and together with nitrogen (N) addition on inorganic carbon (C) losses in the leachates. Three years of exposure to an atmospheric CO2 concentration of 700 ppm resulted in increased annual inorganic C export through leaching below the 70 cm soil profile. Compared to the control without any CO2 and N treatments, net biocarbonate C (HCO3 -C) loss increased by 42%, 74%, and 81% in the high CO2 concentration treatment in 2006, 2007, and 2008, respectively. Increased inorganic C export following the exposure to the elevated CO2 was related to both increased inorganic C concentrations in the leaching water and the greater amount of leaching water. Net annual inorganic C (HCO3 -C and carbonate C: CO3 2−-C) loss via the leaching water in the high CO2 concentration chambers reached 48.0, 49.5, and 114.0 kg ha−1 y−1 in 2006, 2007, and 2008, respectively, compared with 33.8, 28.4, and 62.8 kg ha−1 y−1 in the control chambers in the corresponding years. The N addition showed a negative effect on the mineral weathering. The decreased inorganic C concentration in the leaching water and the decreased leaching water amount induced by the high N treatment were the results of the adverse effect. Our results suggest that tropical forest soil systems may be able to compensate for a small part of the atmospheric CO2 increase through the accelerated processing of CO2 into HCO3 -C during soil mineral weathering, which might be transported in part into ground water or oceans on geological timescales.  相似文献   

10.
Understanding the climatic and biotic controls of interannual variability (IAV) in net ecosystem exchange (NEE) is important for projecting future uptake of CO2 in terrestrial ecosystems. In this study, a statistical modeling approach was used to partition climatic and biotic effects on the IAV in NEE, gross primary productivity (GPP) and ecosystem respiration (RE) at a subtropical evergreen plantation in China (QYZ), a deciduous forest (MOZ), and a grassland (DK1) in the USA. The climatic effects in the study are defined as the interannual anomalies in carbon (C) fluxes directly caused by climatic variations, whereas the biotic effects are those caused by the IAV in photosynthetic and respiratory traits. The results showed that the contribution of biotic effects to the IAV in NEE increased significantly as the temporal scale got longer from daily to annual scales. At the annual scale, the contribution of biotic effects to the IAV in NEE was 47, 69, and 77% at QYZ, MOZ, and DK1, respectively. However, the IAV in NEE was mainly controlled by GPP at QYZ, and by RE at DK1, whereas the contributions of GPP and RE to the IAV in NEE were similar at MOZ, indicating different mechanisms regulating the IAV in NEE among ecosystems. Interestingly, there was a strong negative correlation between the climatic and biotic effects at the annual scale from 2003 to 2009 at QYZ (r 2 = 0.80, P < 0.01), suggesting these two effects counteracted each other and resulted in a relatively stable C sink, whereas no correlations were found at the other two sites. Overall, our study revealed the relative importance of climatic and biotic effects on the IAV in NEE and contributed to our understanding of their underlying mechanisms.  相似文献   

11.
Flooded rice fields are an important source of the greenhouse gas CH4. Possible carbon sources for CH4 and CO2 production in rice fields are soil organic matter (SOM), root organic carbon (ROC) and rice straw (RS), but partitioning of the flux between the different carbon sources is difficult. We conducted greenhouse experiments using soil microcosms planted with rice. The soil was amended with and without 13C-labeled RS, using two 13C-labeled RS treatments with equal RS (5 g kg−1 soil) but different δ13C of RS. This procedure allowed to determine the carbon flux from each of the three sources (SOM, ROC, RS) by determining the δ13C of CH4 and CO2 in the different incubations and from the δ13C of RS. Partitioning of carbon flux indicated that the contribution of ROC to CH4 production was 41% at tillering stage, increased with rice growth and was about 60% from the booting stage onwards. The contribution of ROC to CO2 was 43% at tillering stage, increased to around 70% at booting stage and stayed relatively constant afterwards. The contribution of RS was determined to be in a range of 12–24% for CH4 production and 11–31% for CO2 production; while the contribution of SOM was calculated to be 23–35% for CH4 production and 13–26% for CO2 production. The results indicate that ROC was the major source of CH4 though RS application greatly enhanced production and emission of CH4 in rice field soil. Our results also suggest that data of CH4 dissolved in rice field could be used as a proxy for the produced CH4 after tillering stage.  相似文献   

12.
《CMAJ》1926,16(3):307-309
  相似文献   

13.
14.
15.
锗对水稻萌芽期的生理效应   总被引:6,自引:0,他引:6  
将水稻(OryzasativaL.)种子浸于从0到3mg·L-1不同浓度梯度的GeO2溶液中,测量其生理指标:呼吸强度,可溶性糖含量,淀粉酶活性等。发现在浸种的前期,GeO2对以上各项生理指标均有促进作用,而随着浸种时间的延长,促进逐渐减弱并转为抑制,淀粉酶同功酶电泳则表明,植物体内复杂多样的同功酶系统在一定范围内对GeO2的毒害作用有某种程度的适应与调节能力  相似文献   

16.
The effects of various mineral salts have been studied, bothsingly and in combination, on the uptake and distribution ofphotosynthetically incorporated carbon-14 in Chlorella. Whenmagnesium sulphate, potassium nitrate, and potassium phosphatewere combined in the same concentrations as are found in thenormal nutrient solution, the uptake of carbon-14 was increasedand more radioactivity was incorporated into the amino-acids,with a decrease in the percentage of radioactivity in the sugarphosphates when compared to the controls in distilled water.The most striking effect of the addition of just one salt wasobtained with salts containing nitrogen, particularly ammoniumchloride, which in one experiment increased the radioactivityfound in the amino-acids from 9.9 per cent. (expressed as percentageof the total soluble radioactivity found in this group of compounds)in the controls to 57 per cent., while the radioactivity inthe sugar phosphates fell from 64 to 7 per cent., correspondingly.The total uptake of carbon dioxide by the cells supplied withammonium chloride was three times as great as that in the controlsin distilled water. The relevance of these findings to the methodology involvedin experiments dealing with the path of carbon in photosynthesisis discussed, with particular emphasis upon the concept of a‘steady state’ and how it is thought this may bestbe achieved.  相似文献   

17.
Klein U 《Plant physiology》1987,85(4):892-897
Using enzymic and isotope techniques the intracellular partitioning of newly fixed carbon was studied in synchronized cells of Chlamydomonas reinhardtii. Starch and growth metabolism, i.e. the use of carbon in biosynthesis, were found to be the major sinks for photosynthetically fixed carbon in the alga. Sucrose does not accumulate in significant quantities. The amount of carbon partitioned either into starch or growth varies during the 12 hour light/12 hour dark cell cycle. Starch is accumulated at the beginning and at the end of the light period while a net breakdown is observed in the middle of the light period and in the dark. In contrast, nonsynchronized cells accumulate starch all the time in the light which suggests that carbon partitioning is controlled by the cell cycle. Labeled bicarbonate is incorporated into starch even at times when the total intracellular level of starch is decreasing. This indicates a turnover of the starch pool in the light with synthesis and degradation occurring simultaneously and at different rates.  相似文献   

18.
INGOLD  C. T.; NAWAZ  M. 《Annals of botany》1967,31(2):351-357
In cultures bathed in air deprived of its CO2 fruiting in Sphaerobolusis greatly reduced or fails completely. However, increasingthe concentration of CO2 in the air to 1or 5 per cent tendsto reduce fruiting as compared with normal air. The stimulatoryeffect of CO2 in normal air appears to be exerted at the stageof development when sporophore primordia are being produced.The CO2 does not seem to require the immediate presence of lightto exert its effect. It has not been found possible to replacethe effect of CO2 by substituting Krebs-cycle organic acids.Using 14CO2 it is shown that 14C is incorporated in the myceliumboth in light and in darkness.  相似文献   

19.
BUNCE  JAMES A. 《Annals of botany》1990,65(6):637-642
Dark carbon dioxide efflux rates of recently fully expandedleaves and whole plants of Amaranthus hypochondriacus L., Glycinemax (L.) Merr., and Lycopersicon esculentum Mill. grown in controlledenvironments at 35 and 70 Pa carbon dioxide pressure were measuredat 35 and 70 Pa carbon dioxide pressure. Harvest data and whole-plant24-h carbon dioxide exchange were used to determine relativegrowth rates, net assimilation rates, leaf area ratios, andthe ratio of respiration to photosynthesis under the growthconditions. Biomass at a given time after planting was greaterat the higher carbon dioxide pressure in G. max and L. esculentum,but not the C4 species, A. hypochondriacus. Relative growthrates for the same range of masses were not different betweencarbon dioxide treatments in the two C3 species, because highernet assimilation rates at the higher carbon dioxide pressurewere offset by lower leaf area ratios. Whole plant carbon dioxideefflux rates per unit of mass were lower in plants grown andmeasured at the higher carbon dioxide pressure in both G. maxand L. esculentum, and were also smaller in relation to daytimenet carbon dioxide influx. Short-term responses of respirationrate to carbon dioxide pressure were found in all species, withcarbon dioxide efflux rates of leaves and whole plants lowerwhen measured at higher carbon dioxide pressure in almost allcases. Amaranthus hypochondriacus L., Glycine max L. Merr., Lycopersicon esculentum Mill., soybean, tomato, carbon dioxide, respiration, growth  相似文献   

20.
Barley roots contain a CO2 sensitive respiratory fraction which is inhibited in 50 per cent CO2 and is partially restored upon subsequent exposure to air. The residual O2 consumption occurring at CO2 concentrations between 50 per cent and 95 per cent amounts to about 40 per cent of the O2 uptake in air and can support K+ uptake for a limited time at a rate equal to or higher than occurs in air. Above 95 per cent CO2 both O2 and K+ uptakes decrease rapidly. 2,4-dinitrophenol (DNP), in the range of 10?6 to 10?5M, stimulates O2 uptake by the roots in air. The stimulation is absent when roots are treated with DNP in 80 per cent CO2, presumably because of the reduced demand for inorganic phosphate and phosphate acceptor at the lower respiratory level in high CO2. In either air or CO2, K+ uptake is strongly inhibited by DNP. A comparison of the respiratory and K+ uptake data indicates that O2 consumption is a necessary requirement for the uptake process in high CO2. Protoplasmic streaming in the root cells is rapidly stopped by high CO2 although K+ uptake and O2 consumption continue. The cation uptake mechanism in high CO2 appears to be limited to the stationary cytoplasm. It is also possible that a similar mechanism may be involved in cation uptake in air.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号