Free Air CO2 Enrichment (FACE) of grapevine (Vitis vinifera L.): I. Development and testing of the system for CO2 enrichment

The control of CO₂ levels is reported for a Free-Air Carbon dioxide Enrichment (FACE) facility employed in a vineyard at Rapolano, Italy in 1996 and 1997. This control is required for evaluating the validity of a biological experiment conducted on grapevine in CO₂ enriched and control experimental plots. Six rectangular emission arrays enclosing seven plants each were installed in the vineyard imposing three CO₂ exposure levels (ambient, 550 and 700 μmol mol⁻¹) and monitoring CO₂ levels at the centre of each experimental plot. In the 2 years, average seasonal (May–September) CO₂ levels during treatment hours (05:00–19:00 h) varied from 697 to 698 μmol mol⁻¹ for 700 μmol mol⁻¹ target treatment and from 549 to 550 for 550 μmol mol⁻¹ target treatment. The averaged 1 min measurements of CO₂ concentration were within 20% of the target concentrations for more the 80% of the time. The FACE facility also provided a good spatial control of CO₂ concentration for an experimental sampling volume of 15.7 m³ (8 m×1.4 m×1.4 m), including five plants per plot.     

Trade-offs between water-use related traits,yield components and mineral nutrition of wheat under Free-Air CO2 Enrichment (FACE)

This study investigated trade-offs between parameters determining water use efficiency of wheat under elevated CO₂ in contrasting growing seasons and a semi-arid environment. We also evaluated whether previously reported negative relationships between nutrient content and transpiration efficiency among wheat genotypes will be maintained under elevated CO₂ conditions. Two cultivars of wheat (Triticum aestivum L.), Scout and Yitpi, purportedly differing in water use efficiency related traits (e.g. transpiration efficiency) but with common genetic backgrounds were studied in a high yielding, high rainfall (2013), and in a low yielding, very dry growing season (2014) under Free-Air CO₂ Enrichment (FACE, CO₂ concentration of approximately 550 μmol mol⁻¹) and ambient (approximately 390 μmol mol⁻¹) CO₂. Gas exchange measurements were collected diurnally between stem elongation and anthesis. Aboveground biomass and nutrient content (sum of Ca, K, S, P, Cu, Fe, Zn, Mn and Mg) were determined at anthesis. Yield, yield components and harvest index were measured at physiological maturity. Cultivar Scout showed transiently greater transpiration efficiency (measured by gas exchange) over cultivar Yitpi under both ambient and elevated CO₂ conditions, mainly expressed in the high yielding but not in the low yielding season. Nutrient content was on average 13% greater for the lower transpiration efficiency cultivar Yitpi than the cultivar with higher transpiration efficiency (Scout) in the high yielding season across both CO₂ concentrations. Elevated CO₂ stimulated grain yield to a greater extent in the high yielding season than in the low yielding season where increased aboveground biomass earlier in the season did not translate into fertile tillers in cultivar Yitpi. Yield increased 27 and 33% in the high yielding and 0 and 19% in the low yielding season for cultivars Yitpi and Scout, respectively. Intraspecific variation in CO₂ responsiveness related mechanisms of grain yield were observed. These results suggest CO₂-driven trade-offs between traits governing water use efficiency are related to both growing season and intraspecific variations, and under very dry finishes, the trade-offs may even reverse. The negative relationship between nutrient content and transpiration efficiency among wheat genotypes will be maintained under elevated CO₂ conditions.     

Effects of Free‐Air Carbon Dioxide Enrichment on Sap Flow and Canopy Microclimate of Maize Grown under Different Water Supply

The rise of atmospheric CO₂ concentration ([CO₂]) affects stomatal conductance and thus transpiration and leaf temperature. We evaluated the effect of elevated [CO₂] levels under different water supply on daily sap flow and canopy microclimate (air temperature (Tc) and vapour pressure deficit (VPD)) of maize. The crop was cultivated in circular field plots under ambient (AMB, 378 μmol mol^?1) and elevated [CO₂] (FACE, 550 μmol mol^?1) using free‐air CO₂ enrichment with sufficient water in 2007, while in 2008 a DRY semicircle received only half as much water as compared to the WET semicircle from mid of July. In 2007, sap flow was measured in WET simultaneously under AMB and FACE conditions and was significantly decreased by elevated [CO₂]. In 2008, sap flow was measured in all four treatments but not simultaneously. Therefore, data were correlated with potential evaporation and the slopes were used to determine treatment effects. Drought reduced whole‐plant transpiration by 50 % and 37 % as compared to WET conditions under AMB and FACE, respectively. Moreover, CO₂ enrichment did not affect sap flow under drought but decreased it under WET by 20 % averaged over both years. The saving of water in the period before the drought treatment resulted in a displacement of dry soil conditions under FACE as compared to AMB. Under WET, CO₂ enrichment always increased Tc and VPD during the day. Under DRY, FACE plots were warmer and drier most of the time in August, but cooler and damper short after the start of drought in July and from the end of August onwards. Thus, the CO₂ effect on transpiration under drought was variable and detectable rather easy by measuring canopy microclimate.     

Yield,growth and grain nitrogen response to elevated CO2 in six lentil (Lens culinaris) cultivars grown under Free Air CO2 Enrichment (FACE) in a semi-arid environment

Atmospheric CO₂ concentrations ([CO₂]) are predicted to increase from current levels of about 400 ppm to reach 550 ppm by 2050. The direct benefits of elevated [CO₂] (e[CO₂]) to plant growth appear to be greater under low rainfall conditions, but there are few field (Free Air CO₂ Enrichment or FACE) experimental set-ups that directly address semi-arid conditions. The objectives of this study were to investigate the following research questions: 1) What are the effects of e[CO₂] on the growth and grain yield of lentil (Lens culinaris) grown under semi-arid conditions under FACE? 2) Does e[CO₂] decrease grain nitrogen in lentil? and 3) Is there genotypic variability in the response to e[CO₂] in lentil cultivars? Elevated [CO₂] increased yields by approximately 0.5 t ha⁻¹ (relative increase ranging from 18 to 138%) by increasing both biomass accumulation (by 32%) and the harvest index (by up to 60%). However, the relative response of grain yield to e[CO₂] was not consistently greater under dry conditions and might depend on water availability post-flowering. Grain nitrogen concentration was significantly reduced by e[CO₂] under the conditions of this experiment. No differences were found between the cultivars selected in the response to elevated [CO₂] for grain yield or any other parameters observed despite well expressed genotypic variability in many traits of interest. Biomass accumulation from flowering to maturity was considerably increased by elevated [CO₂] (a 50% increase) which suggests that the indeterminate growth habit of lentils provides vegetative sinks in addition to reproductive sinks during the grain-filling period.     

Vulnerability of lodging risk to elevated CO2 and increased soil temperature differs between rice cultivars

Anthropogenic increases in atmospheric carbon dioxide concentration [CO₂], and subsequent increases in surface temperatures, are likely to impact the growth and yield of cereal crops. One potential means for yield reduction is for climate parameters to increase the occurrence of lodging. Using an in situ free-air CO₂ enrichment (FACE) system, two morphologically distinct rice cultivars, KH (Koshihikari) and SY (Shan you 63), were grown at two [CO₂]s (ambient and ambient + 200 μmol mol⁻¹) and two soil temperatures (ambient and ambient ± 1.8 °C) over a two year period to assess and quantify lodging risk. Elevated [CO₂] per se had no effect on lodging resistance for either cultivar. However, elevated [CO₂] and higher soil temperature increased the lodging risk for SY, due to a relatively higher increase in plant biomass and height at the elevated, relative to the ambient [CO₂] condition. Elevated soil temperature per se also increased lodging risk for both cultivars and was associated with longer internodes in the lower portion of the tillers. These findings illustrate that lodging susceptibility in rice, an important cereal crop, can be increased by rising [CO₂] and soil temperature; however, variation observed here between rice cultivars suggests there may be sufficient intraspecific variability to begin choosing rice lines that minimize the potential risk of lodging.     

FACE对武香粳14根系生长动态的影响

2002－2003年利用我国惟一的农田开放式空气CO₂浓度增高(FACE)研究平台,研究大气CO₂浓度比对照高200 μmol·mol^-1的FACE处理对早熟晚粳稻品种武香粳14根系生长动态的影响。结果表明,(1)FACE处理水稻分蘖期、拔节期、抽穗期每穴的不定根数、不定根总长度、根系体积以及根干重均极显著大于对照;(2)FACE处理使水稻有效分蘖期间和无效分蘖期间发生的不定根粗度均显著大于对照,使拔节长穗期间发生的不定根粗度明显变细,因而使抽穗期每条不定根的平均粗度与对照无显著差异;（3）FACE处理水稻抽穗期每穴的不定根数、不定根总长度、根系体积和干重均极显著大于对照主要是由于FACE处理使水稻有效分蘖期间和无效分蘖期间这些根系性状的大幅度增加,而FACE处理对水稻拔节长穗期间这些根系性状的影响较小。     

Apical Development and Growth of Barley under Different CO2 and Nitrogen Regimes

Increases in atmospheric carbon dioxide (CO₂) concentration have stimulated interest in the response of agricultural crops to elevated levels of CO₂. Several studies have addressed the response of C₃ cereals to CO₂, but the interactive effect of nutrient supply and CO₂ on apical development and spikelet set and survival has not been investigated thoroughly. Hence, an experiment was conducted in the greenhouse to evaluate the effect of high (700 μmol CO₂mol^?1 air) and low (400 μmol mol^?1) levels of atmospheric CO₂ on apical development, spikelet set and abortion, and pre- and post-anthesis growth in spring barley (Hordeum vulgare L.) grown under high N (0.3 g N pot^?1 before sowing ?1–0.11 g N pot^?1 week^?1) and low N (0.3 g N pot^?1) regimes. The plants were grown in 5 L pots. Development of spike was hastened due to CO₂ enrichment, and the C+ plants pollinated few days earlier than the C— plants. Carbon dioxide enrichment had no effect on date of ripening. Development of spike slowed following application of extra N, and plants pollinated 10 days later and matured 2 weeks later when compared with plants under low N. Carbon dioxide enrichment did not affect the number of spikelets at anthesis. Excess N decreased spikelet abortion and the increased maximum number of spikelets under both [CO₂]. Barley plants did not tiller when grown in low [CO₂] and low N. Increased endogenous IAA concentration in those plants, recorded three days before tillers appeared in other treatments, may have contributed to this. Carbon dioxide enrichment increased the C concentration of plants, but decreased the N concentration under high N regime. Both the C and N concentration of plants were increased under high N regime. Carbon dioxide enrichment increased the total dry matter of mature plants by 9 % under high N regime and by 21 % under low N regime. Under high [CO₂] increased kernel number on tiller spikes, and increased kernel weight both on main stem and on tiller spikes resulted in a 23 % increase in kernel yield under low N regime and 76 % increase in kernel yield under high N regime. The rate of N application influenced growth and yield components to a greater extent than CO₂ enrichment. At maturity, plant dry matter, kernel weight, the number of kernels per spike, and the number of spikes per plant were higher under high N regime than under low N regime. Long days (16 h), low light intensity (280 μmol m^?2s^?1), and at constant temperature of 20 °C high [CO₂] increased kernel weight and the number of kernels on tiller spikes under high and low N application rate, but did not increase the number of kernels on main stem spike, or the number of tillers or tiller spikes per plant.     

Elevated CO2 increases wheat cer, leaf and tiller development, and shoot and root growth

Whole-plant responses to elevated CO₂ throughout the life cycle are needed to understand future impacts of elevated atmospheric CO₂. In this study, Triticum aestivum L. leaf carbon exchange rates (CER) and carbohydrates, growth, and development were examined at the tillering, booting, and grain-filling stages in growth chambers with CO₂ concentrations of 350 (ambient) or 700 (high) μmol mol^?1. Single-leaf CER values measured on plants grown at high CO₂ were 50% greater than those measured on plants grown at ambient CO₂ for all growth stages, with no photosynthetic acclimation observed at high CO₂. Leaves grown in high CO₂ had more starch and simple sugars at tillering and booting, and more starch at grain-filling, than those grown in ambient CO₂. CER and carbohydrate levels were positively correlated with leaf appearance rates and tillering (especially third-, fourth- and fifth-order tillers). Elevated CO₂ slightly delayed tiller appearance, but accelerated tiller development after appearance. Although high CO₂ increased leaf appearance rates, final leaf number/culm was not effected because growth stages were reached slightly sooner. Greater plant biomass was related to greater tillering. Doubling CO₂ significantly increased both shoot and root dry weight, but decreased the shoot to root ratio. High CO₂ plants had more spikes plant^?1 and spikelets spike^?1, but a similar number of fertile spikelets spike^?1. Elevated CO₂ resulted in greater shoot, root and spike production and quicker canopy development by increasing leaf and tiller appearance rates and phenology.     

水稻株高性状对大气CO2浓度升高的响应

以粳稻品种Asominori与籼稻品种IR24的杂交组合所衍生的染色体片段置换系（CSSLs）为材料，田间试验分别在FACE（CO₂浓度约570 µmol mol^-1）和对照（CO₂浓度约370 µmol mol^-1）下，对水稻株高性状的数量性状位点（QTL）进行了分析。结果表明，Asominori和IR24的株高、穗长、上位第一节间长和上位第二节间长在FACE和对照下的差异达显著水平；供试株系的4个株高性状对CO₂浓度升高都呈正负两种响应，其变化最大的株系为AI7和AI44（株高分别增加14.2 cm和降低4.54 cm），AI9和AI12（穗长分别增加3.56 cm和降低2.39 cm），AI39和AI27（上位第一节间长分别增加15.74 cm和降低1.49 cm），AI32和AI53（上位第二节间长分别增加8.09 cm和降低3.00 cm）；FACE和对照下分别检测出14和15个QTL，分布在除第2、7、9和第10号染色体外的各染色体上，其中5个（qPH6^-4、qPH8^-4、qPL8^-4、qPL12^-4和qLFN6^-4）在FACE和对照条件下同时检测到，分布在第6、8和第12染色体上，而其余的只在FACE或对照下检测到。这29个QTLs中，3个（qPH6^-4QE、qPH8^-4QE和qLSN5^-4QE）具显著的基因型与环境互作。在不同的CO₂环境下，测试性状发生不同程度的表型变异。结果推论，对CO₂浓度增加敏感的QTL位点，可能受到CO₂浓度增加的诱导，可见控制水稻株高性状的QTL与CO₂增加的环境发生了互作效应。     

Atmospheric CO2 enrichment affects potatoes: 1. Aboveground biomass production and tuber yield

Despite its economic and environmental importance, information about effects of future atmospheric carbon dioxide (CO₂) enrichment on aboveground biomass production and tuber yield of potato is still rare. Responses of potato (Solanum tuberosum L. cv. Bintje) were thus investigated in two full growing seasons under 380, 550 or 680 μmol mol^?1 CO₂ in open-top chambers (OTCs). When averaged over both years, aboveground stem biomass at canopy maturity was negatively related to CO₂ enrichment. Aboveground-to-belowground biomass ratio was negatively related to CO₂ enrichment as there was a positive relationship between CO₂ and total dry yield of potato tubers. The stimulation was mainly related to an increase in the tuber size fraction for commercial yield (tubers > 35 mm). For the largest size class (tubers > 50 mm), which is important for industrial processing, large CO₂-induced impacts were observed too, although these effects were not significant. Elevated CO₂ concentrations will thus affect biomass allocation of potato plants and result in improvements concerning the market value of the commercial tuber yield.     

高大气CO2浓度下氮素对小麦叶片光合能量分配的调节

探讨了施氮量对高大气CO₂浓度下小麦功能叶光合能量传递与分配的影响,进而明确氮素对小麦叶片光合作用适应性下调的能量分配调节作用。采用开顶式气室盆栽法,通过测定小麦拔节期和抽穗期不同大气CO₂浓度和施氮水平下的叶氮浓度、光合速率–胞间CO₂浓度(P_n–C_i)响应曲线和荧光动力学参数,测算光合电子传递速率和分配去向。与在正常CO₂浓度(400 μmol mol^-1)条件下相比,在高大气CO₂浓度(760 μmol mol^-1)下,小麦叶氮浓度显著下降,N200处理(200 mg kg^-1)叶片抽穗期叶氮浓度的下降幅度较拔节期高335.7%。N200处理较N0处理(0 mg kg^-1)提高小麦叶片光适应下PSII反应中心最大量子产额(F_v′/F_m′)、光化学效率(Φ_PSII)和开放比例(q_P),降低非光化学猝灭系数(NPQ)。高大气CO₂浓度下,小麦叶片光化学反应的非环式光合电子传递速率(J_c)和Rubisco羧化速率(V_c)显著升高,而光呼吸的非环式光合电子传递速率(J_o)和Rubisco氧化速率(V_o)明显降低;施氮使J_c、J_o、V_c和V_o值均呈上升趋势,而且J_c和V_c达到显著差异。高大气CO₂浓度下J_o/J_c和V_o/V_c显著降低,施氮后小麦拔节期叶片J_o/J_c和V_o/V_c降低,但抽穗期J_o/J_c升高而V_o/V_c无明显变化。叶氮浓度与小麦叶片J_c、J_o和V_o均呈显著线性正相关,而且高大气CO₂浓度下小麦叶片J_c、J_o和V_o对氮浓度的敏感性降低。高大气CO₂浓度下,小麦叶片PSII反应中心开放比例增加,非光化学耗能降低,更多的光合电子进入光化学过程;施氮后使小麦叶氮浓度增加,提高光合能力,改变了能量分配,这是高氮条件下光合作用适应性下调被缓解的一个关键因素。     

开放式空气CO2浓度升高对稻米品质的影响

了解大气CO₂浓度升高对粳稻和籼稻稻米品质的影响,为今后合理筛选育种材料提供依据。以粳稻Asominori与籼稻IR24为材料,田间试验,于2003年和2004年连续2年在FACE（Free Air CO₂ Enrichment,大气CO₂浓度增加200μmol/mol）和正常大气CO₂浓度（约370μmol/mol）下,分析了稻米的加工品质、外观品质和蒸煮食味品质。与对照相比,两年内IR24和Asominori的糙米率、精米率和整精米率等加工品质都显著降低了,降低幅度分别为-3.14%~-0.21%和-3.14%~-0.33%;FACE对水稻粒长、粒宽以及粒形无显著影响;但与对照相比,IR24和Asominori的垩白米率却由对照下的29.63%和30.81%显著降低至18.93%和24.78%;FACE对两品种精米中直链淀粉含量无显著影响,但对RVA(Rapid Viscosity Analyzer)谱中各指标影响显著,其中FACE处理显著提高了两品种的最高粘度,而崩解值、消减值和糊化温度由于受到其它互作效应的影响两年的变化趋势不尽相同,蒸煮食味品质变化复杂;此外,IR24和Asominori的粗蛋白含量由对照下的11.77%和10.23%显著降低至10.97%和9.91%。两年内,IR24和Asominori除加工品质和食味品质表现趋势相同外,外观品质和蒸煮品质表现出籼稻IR24对CO₂浓度升高的响应程度大于粳稻Asominori。     

Soybean (Glycine max (L.) Merr.) growth and development response to CO2 enrichment under different temperature regimes

The carbon dioxide (CO₂) concentration of the global atmosphere has increased during the last decades. This increase is expected to impact the diurnal variation in temperature as well as the occurrence of extreme temperatures. This potentially could affect crop production through changes in growth and development that will ultimately impact yield. The objective of this study was to evaluate the effect of CO₂ and its interaction with temperature on growth and development of soybean (Glycine max (L.) Merr., cv. Stonewall). The experiment was conducted in controlled environment chambers at the Georgia Envirotron under three different temperatures and two CO₂ regimes. The day/night air temperatures were maintained at 20/15, 25/20 and 30/25 °C, while the CO₂ levels were maintained at 400 and 700 ppm, resulting in six different treatments. Plants were grown under a constant irradiance of 850 μmoles m⁻² s⁻¹ and a day length of 12 h; a non-limiting supply of water and mineral nutrients were provided. Five growth analyses were conducted at the critical development stages V4, R3, R5, R6 and R8. No differences in start of flowering were observed as a function of the CO₂ level, except for the temperature regime 25/20 °C, where flowering for the elevated CO₂ level occurred 2 days earlier than for the ambient CO₂ level. For aboveground biomass, an increase in the CO₂ level caused a more vigorous growth at lower temperatures. An increase in temperature also decreased seed weight, mainly due to a reduction in seed size. For all temperature combinations, final seed weight was higher for the elevated CO₂ level. This study showed that controlled environment chambers can be excellent facilities for conducting a detailed growth analysis to study the impact on the interactive effect of changes in temperature and CO₂ on soybean growth and final yield.     

Effect of elevated carbon dioxide and temperature on phosphorus uptake in tropical flooded rice (Oryza sativa L.)

A field experiment was carried out to assess the impact of elevated carbon dioxide (CO₂) and temperature on phosphorous (P) nutrition in relation to organic acids exudation, soil microbial biomass P (MBP) and phosphatase activities in tropical flooded rice. Rice (cv. Naveen) was grown under chambered control (CC), elevated CO₂ (EC, 550 μmol mol⁻¹) and elevated CO₂ + elevated temperature (ECT, 550 μmol mol⁻¹ and 2 °C more than CC) in a tropical flooded soil under open top chambers (OTCs) along with unchambered control (UC) for three years. Root exudates were analyzed at different growth stages of rice followed by organic acids determination. Rhizospheric soil was used for analysis of soil phosphatase, MBP and available P. The total organic carbon (TOC) in root exudates was increased by 27.5% and 30.2% under EC and ECT, respectively over CC. Four different types of organic acids viz. acetic acid (AA), tartaric acid (TA), malic acid (MA) and citric acid (CA) were identified and quantified as dominant in root exudates, concentration of these was in the order of TA > MA > AA > CA. The TA, MA, AA and CA content were increased by 34.4, 31.1, 38.7 and 58.3% under ECT compared to that of UC over the period of 3 years. The P uptake in shoot, root and grain under elevated CO₂ increased significantly by 29, 28 and 22%, respectively than CC. Soil MBP, acid and alkaline phosphatase activity was significantly higher under elevated CO₂ by 35.1%, 27 and 36%, respectively, compared to the CC. Significant positive relationship exists among the organic acid exudation, MBP, phosphatase activities and P uptake by rice. The enhanced organic acid in root exudates coupled with higher soil phosphatase activities under elevated CO₂ resulted in increased rate of soil P solubilization leading to higher plant P uptake.     

Elevated CO2 affects plant nitrogen and water‐soluble carbohydrates but not in vitro metabolisable energy

The effects of elevated concentrations of atmospheric CO₂ (e[CO₂]) on the nutritive value of wheat vegetative matter and grain as a feedstock for ruminants were investigated in a study undertaken at the Australian grains free‐air CO₂ enrichment (AGFACE) facility. The study included two commercial wheat cultivars (Janz and Yitpi) and two genetic selections from a Seri/Babex population (SB003 and SB062) which had previously been characterised for low and high water‐soluble carbohydrate accumulation efficiency. The trial was grown under ambient (~390 µmol/mol) and elevated (~550 µmol/mol) CO₂ conditions, and plants harvested at tillering, anthesis and physiological maturity. Composition analyses to determine the nutritive value for ruminant feed were undertaken on stems, leaves and grain. Plant and grain nitrogen were reduced in the e[CO₂] treatments, and as expected, the water‐soluble carbohydrates increased. All genotypes responded to e[CO₂] with the effects of altered composition evident within 60 days of sowing. Determinants of ruminant feed quality such as neutral and acid detergent fibre and estimated in vitro metabolisable energy were not significantly affected. The reduced plant and grain N will impact on the nutritive value and supplementation may be required. The impact of e[CO₂] on chemical composition of wheat plants may be greater if the predicted climate change is associated with concomitant abiotic stress such as high ambient temperature or low soil moisture.     

Exploring options for managing strategies for pea–barley intercropping using a modeling approach

Although quality of potato tubers is an important topic with regard to food and industrial processing, the consequences of future atmospheric carbon dioxide (CO₂) enrichment on related attributes are still unclear. Effects of elevated CO₂ concentrations on yield quality of potato (Solanum tuberosum L. cv. Bintje) were thus investigated in two full growing seasons under 380, 550 or 680 μmol mol^?1 CO₂ in open-top chambers (OTCs). When averaged over both years, tuber malformation was increased by 62.8% as CO₂ levels raised from 380 to 550 μmol mol^?1, resulting in a negative impact on tuber quality. In contrast, elevated CO₂ caused lower tuber greening and therefore enhanced tuber market value. Physical potato quality remained largely unchanged, except for the positive relationships between CO₂ and dry matter content, resulting in higher tuber quality for industrial processing. Significant relationships were also observed between CO₂ concentrations and several chemical quality parameters. The concentrations of glucose, fructose and total reducing carbohydrates were positively related to CO₂ levels, which decrease tuber quality due to the higher risk for browning and generation of acrylamide of fried products. The concentrations of protein, potassium, and as a trend of calcium, were negatively related to CO₂ enrichment, suggesting adverse impacts on tuber quality for human nutrition and aesthetic and sensory quality during processing. Significant negative relationships between CO₂ treatments and concentrations of leucine, phenylalanine and methionine, and as a trend for di-tyrosine, histidine and aspartic acid, were also indicated, which may decrease nutrition quality of potatoes because of the reduction in physiologically valuable amino acids. With regard to organic acids, CO₂-related alterations were restricted to lower concentrations of citric acid. This may reduce the processing quality of potato tuber, as there is a higher risk of discoloration, and at the same time improve quality aspects related to taste. In addition, the experiments indicated negative relationships between CO₂ concentrations and total glycoalkaloids and α-chaconine, which may have negative effects on the taste of potato at low concentration of glycoalkaloids of the present study. Concomitantly, the CO₂-induced decrease in glykoalkaloids may be regarded as an improvement of quality in terms of lower toxicological potential. CO₂ enrichment may thus cause substantial impacts, both positive and negative, on tuber quality of potato with regard to commercial value, industrial processing and consumer nutrition and health in the future. Currently, no clear evidence exists whether CO₂-induced beneficial changes will outweigh adverse effects on tuber quality.     

FACE对武香粳14根系活性影响的研究

利用我国惟一的农田开放式空气CO₂浓度增高(Free-air CO₂ enrichment-FACE)研究平台,研究大气CO₂浓度比对照（现大气CO₂浓度）高200 μmol·mol^-1的FACE处理对水稻品种武香粳14根系活性的影响。结果表明：(1)FACE处理使水稻单位干重根系的总吸收面积、活跃吸收面积的最大值比对照提早10 d左右,移栽后18 d及其以后不同生育时期的单位干重根系的总吸收面积、活跃吸收面积、α-萘胺氧化量等根系活性指标均显著或极显著低于对照,但FACE处理对每穴根系活性的影响相对较小;(2)移栽后28 d及其以后不同生育时期每穴的不定根数、不定根总长度、根系体积、根干重与单位干重根系的活性关系密切,根量越大单位干重根系的活性越低;(3)不同生育时期的植株含氮率与单位干重根系的活性多呈正相关,植株碳氮比与单位干重根系的活性多呈负相关。笔者认为,FACE处理水稻生育前期根系生长量大、植株含氮率低、碳氮比高等可能是造成其单位干重根系活性显著低于对照的重要原因。     

Controlled atmosphere treatment for control of grape mealybug,Pseudococcus maritimus (Ehrhorn) (Hemiptera: Pseudococcidae), on harvested table grapes

Controlled atmosphere (CA) treatments with ultralow oxygen (ULO) alone and in combinations with 50% carbon dioxide were studied to control grape mealybug, Pseudococcus maritimus (Ehrhorn) on harvested table grapes. Two ultralow oxygen levels, 30 and <0.01 μL L⁻¹, were tested in both ULO and ULO + 50% CO₂ treatments. The ULO treatments with the lower oxygen level were more effective than the ULO treatments at the higher oxygen level. The ULO + 50% CO₂ treatments were more effective than the ULO treatments. Grape mealybug eggs were significantly more tolerant of ULO and ULO + CO₂ treatments than nymphs and adults. A 14 day ULO treatment with 30 μL L⁻¹ O₂ at 2 °C did not achieve 100% mortalities of any life stage. In the presence of 50% CO₂, the 14 d treatment achieved complete mortality of all life stages of the grape mealybug. A 3 d ULO treatment with <0.01 μL L⁻¹ O₂ at 2 °C resulted in 93.3% mortality of nymphs and adults. The 3 d ULO treatment in combination with 50% CO₂ treatments, however, achieved complete control of grape mealybug nymphs and adults and caused 70.5% relative egg mortality. Complete egg mortality was achieved in a 10 d ULO + 50% CO₂ treatment with <0.01 μL L⁻¹ O₂ at 2 °C. Both the 14 d CA treatment with 30 μL L⁻¹ O₂ and 50% CO₂ and the 10 d CA treatment with <0.01 μL L⁻¹ O₂ and 50% CO₂ were tested on table grapes and grape quality was evaluated after two weeks of post-treatment storage. The CA treatments did not have a significant negative impact on grape quality and were safe for table grapes. The study indicated that CA treatments have potential to be developed for postharvest control of grape mealybug on harvested table grapes.     

玉米和高粱用于碳同化和光呼吸的电子效率估算

为了探讨C₄植物碳同化和光呼吸的电子效率,运用Li-6400光合仪同时测定玉米和高粱在30℃和380 μmol CO₂ mol^-1下叶片的气体交换和叶绿素荧光,结果表明,直角双曲线修正模型可较好地拟合所测的光响应曲线和快速光曲线,其拟合值与实测值较为一致。在此基础上算得玉米和高粱在光呼吸条件下参与碳同化的电子流分别为198.60 μmol m^-2 s^-1和178.00 μmol m^-2 s^-1,所占比率分别为75.34%和74.81%;参与光呼吸的电子流分别为7.04 μmol m^-2 s^-1和7.84 μmol m^-2 s^-1,所占比率分别为2.67%和3.29%。而根据Valentini和Epron的方法算得玉米和高粱碳同化的电子流分别为210.45 μmol m^-2 s^-1和188.54 μmol m^-2 s^-1,所占比例分别为82.68%和79.24%;参与光呼吸的电子流则分别为45.67 μmol m^-2 s^-1和49.40 μmol m^-2 s^-1,所占比率分别为17.32%和20.76%。以前法研究表明,玉米和高粱在光呼吸条件下,来自PSII的电子除流向光呼吸和碳还原外,还存在其他消耗电子的途径,证明其他消耗电子的途径并不能被忽略或其他途径所消耗电子的量并不是常数。后法过高地估算了玉米和高粱叶片中来自PSII的电子用于光呼吸的消耗量。两法的结果相差6倍左右。这对重新评估光呼吸在植物的光保护中所起的作用提供了理论依据。     

Deastringency treatment with CO2 induces oxidative stress in persimmon fruit

Because of astringency at harvest, ‘Rojo Brillante’ persimmons are regularly submitted to deastringency treatment based on exposing fruit to a high CO₂ concentration. The treatment conditions that ensure total astringency removal throughout the various maturity stages have been determined to be 95% CO₂, 20 °C, 24 h. The aim of this study was to investigate changes in the redox state of persimmon fruit associated with this deastringency treatment. The levels of reactive oxygen species (ROS) (O₂⁻ and H₂O₂), and the activities of the main ROS scavenging enzymes (CAT, POD, APX, and SOD), were determined at harvest and after deastringency in fruit at three different maturity stages.Our results showed that during ‘Rojo Brillante’ persimmon maturation, the level of O₂⁻ gradually increased, while APX activity was lowered. The deastringency treatment with CO₂ induced oxidative stress in the fruit, observed as an over-accumulation of O₂⁻ and H₂O₂. As a response to ROS accumulation, the activities of the CAT, APX and SOD scavenging enzymes were up-regulated after deastringency treatment. The response of POD enzyme was dependent on maturity stage, showing enhanced activity after CO₂ treatment only for the fruit at the most mature stage.