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1.
Increasing atmospheric carbon dioxide concentration (CO2) is an important component of global climate change that will have a significant impact on the productivity of crop plants. In recent years, growth and yield of agricultural crop plants have been shown to increase with elevated CO2 (EC) and have enticed considerable interest due to variation in the response of crop plants. In this study, comparative response of two mung bean cultivars (HUM‐2 and HUM‐6) was evaluated against EC at different growth stages under near‐natural conditions for two consecutive years. The plants were grown in ambient as well as EC (700 ppm) in specially designed open‐top chambers. Under elevated CO2, marked down‐regulation of reactive oxygen species (ROS) levels, membrane disruption and activities of superoxide dismutase and catalase were noticed in both the cultivars, but the extent of reduction was more in HUM‐6. As compared to ambient CO2, EC increased total chlorophyll, photosynthetic rate, growth and yield parameters. Cultivar‐specific response was noticed as HUM‐6 showed higher increase in yield attributes than HUM‐2. Under CO2 treatment, soluble protein and reducing sugars decreased while total soluble sugars and starch showed an opposite trend. Principal component analysis showed that both the cultivars responded more or less similarly to EC in their respective groupings of physiological and growth parameters, but the magnitude of ROS and antioxidative enzymes was variable. The experimental findings depict that both the cultivars of mung bean showed contrasting response against EC and paved the way for selecting the suitable cultivar having higher productivity in a future high‐CO2 environment.  相似文献   

2.
Atmospheric CO2 levels on Earth have risen steeply over the last 60 years and will continue to do so in future. CO2 traps heat from earth's surface, which causes an increase in temperature and leads to other climatic changes. Crop plants are currently challenged by climate change. In general, elevated CO2 increases photosynthetic rates, plant growth and the ability of plants to counteract stress. However, the effect of eCO2 on respiration is not apparent. Plants growing at eCO2 probably do not have sufficient respiratory ATP to drive cellular processes like nutrient uptake and transport, which impairs their nutritional quality. Here, we review how eCO2 modulates growth and nutritional value of crop plants, emphasizing the contribution of photosynthesis and respiration. We highlight the mechanisms that modulate acclimation and adaptive responses of plants to eCO2 and also discuss the ecological consequences. Finally, we project sorghum as a model for an eCO2 ready crop.  相似文献   

3.
Phosphorous deficiency in soil limits crop growth and productivity in the majority of arable lands worldwide and may moderate the growth enhancement effect of rising atmospheric carbon dioxide (CO2) concentration. To evaluate the interactive effect of these two factors on cotton (Gossypium hirsutum) growth and physiology, plants were grown in controlled environment growth chambers with three levels of phosphate (Pi) supply (0.20, 0.05 and 0.01 mm ) under ambient and elevated (400 and 800 μmol mol?1, respectively) CO2. Phosphate stress caused stunted growth and resulted in early leaf senescence with severely decreased leaf area and photosynthesis. Phosphate stress led to over 77 % reduction in total biomass across CO2 levels. There was a below‐ground (roots) shift in biomass partitioning under Pi deficiency. While tissue phosphorus (P) decreased, tissue nitrogen (N) content tended to increase under Pi deficiency. The CO2 × Pi interactions were significant on leaf area, photosynthesis and biomass accumulation. The stimulatory effect of elevated CO2 on growth and photosynthesis was reduced or highly depressed suggesting an increased sensitivity of cotton to Pi deficiency under elevated CO2. Although, tissue P and stomatal conductance were lower at elevated CO2, these did not appear to be the main causes of cotton unresponsiveness to elevated CO2 under severe Pi‐stress. The alteration in the uptake and utilization of N was suggested due to a consistent reduction (18–21 %) in the cotton plant tissue N content under elevated CO2.  相似文献   

4.
Using phytotron growth chambers, a short‐term pot experiment under non‐limiting water condition was conducted to investigate the individual and interactive effects of elevated carbon dioxide (650 ± 10 μmol mol?1 vs. ambient), temperature (3 °C above ambient vs. ambient) and different levels of urea–N (control, 100 % N and 200 % N of recommended dose) on growth and yields of wheat crop and changes in potential nitrogen mineralization (PNM), nitrification and denitrification activities, microbial biomass carbon (MBC), nitrogen (MBN), dissolved organic carbon (DOC), and nitrifying and denitrifying organisms in a semiarid Inceptisol. The plant parameters (root, shoot and grain) responded positively (10–23 %) to elevated CO2 and negatively (?17 to ?38 %) to higher temperature. Interactive effect of elevated CO2 and temperature caused a negligible impact on root, shoot (≈?5 %) and grain yields of wheat. Soil –N content was not affected, but –N was reduced significantly. Nitrate reductase activity was decreased by 14–20 % at elevated CO2. There was positive effect of elevated temperature on PNM (+9–16 %), whereas negative effects were observed for potential nitrification activity (PNA), MBC, MBN and DOC. Elevation of atmospheric CO2 or temperature did not affect the population of ammonia (AOB) and nitrite oxidizers (NOB), but elevation of CO2 has decreased the population of denitrifiers by 4–14 %.  相似文献   

5.
Waterlogging causes long‐lasting damage to wheat (Triticum aestivum). Root growth and respiration were investigated after heading in waterlogged, pot‐grown, wheat plants and also in hydroponically grown, wheat seedlings exposed to a hypoxic treatment. In the pot experiment, plants were subjected to 8 days of waterlogging after heading. This period of waterlogging resulted in reduced shoot and root growth through to maturity. The root CO2 emission rates of previously waterlogged and well‐drained plants were about 220 and 140 nmol g?1 per s, respectively, with the rate differences persisting from 10 days after anthesis through to maturity. In the hydroponic experiments, seedlings (Feekes stage 2.0) were exposed to root‐zone, hypoxic treatment for 10–19 days. The roots showed 27 % higher CO2 emission rates and 37 % higher O2 consumption rates, compared with untreated roots. In whole root systems, the high respiration rates found during hypoxic treatment disappeared during recovery under aerated conditions as a result of the appearance of newly initiated roots. However, measurements of the respiration of the previously hypoxic roots showed abnormally high respiration rates. In roots exposed to hypoxic treatment, total sugar concentrations were 3.6‐times higher than in untreated roots indicating that this elevation of sugar may be responsible for the continued high respiration rate. This study shows that roots exposed to waterlogging or to hypoxic treatments do not increase their weights and thus recover from the metabolic disturbances resulting from these treatments.  相似文献   

6.
Elevated CO2 stimulates crop yields but leads to lower tissue and grain nitrogen concentrations [N], raising concerns about grain quality in cereals. To test whether N fertiliser application above optimum growth requirements can alleviate the decline in tissue [N], wheat was grown in a Free Air CO2 Enrichment facility in a low‐rainfall cropping system on high soil N. Crops were grown with and without addition of 50–60 kg N/ha in 12 growing environments created by supplemental irrigation and two sowing dates over 3 years. Elevated CO2 increased yield and biomass (on average by 25%) and decreased biomass [N] (3%–9%) and grain [N] (5%). Nitrogen uptake was greater (20%) in crops grown under elevated CO2. Additional N supply had no effect on yield and biomass, confirming high soil N. Small increases in [N] with N addition were insufficient to offset declines in grain [N] under elevated CO2. Instead, N application increased the [N] in straw and decreased N harvest index. The results suggest that conventional addition of N does not mitigate grain [N] depression under elevated CO2, and lend support to hypotheses that link decreases in crop [N] with biochemical limitations rather than N supply.  相似文献   

7.
Increased climatic variability and more frequent episodes of extreme conditions may result in crops being exposed to more than one extreme temperature event in a single growing season and could decrease crop yields to the same extent as changes in mean temperature. The developmental stage of the crop exposed to increased temperatures will determine the severity of possible damage experienced by the plant. It is not known whether or not the damaging effects of heat episodes occurring at different phenological stages are additive. In the present study, the interaction of high‐temperature events applied at the stages of double ridges and anthesis in Triticum aestivum (L.) cv. Chablis was investigated. Biomass accumulation of control plants and that of plants experiencing high temperatures during the double‐ridge stage were similar and were reduced by 40 % when plants were subjected to a heat event at anthesis. Grain number on the main and side tillers declined by 41 %, and individual grain weight declined by 45 % with heat stress applied at the double‐ridge stage and anthesis or at anthesis alone. The harvest index was reduced from 0.53 to 0.33. Nitrogen contents in leaves were reduced by 10 % at the double‐ridge stage and by 25 % at anthesis. The maximum rates of CO2 assimilation increased with heat stress at the double‐ridge stage and higher rates were maintained throughout the growing season. The results clearly indicate that an extreme heat event at the double‐ridge stage does not affect subsequent growth or the response of wheat to heat stress at anthesis.  相似文献   

8.
A FACE (Free Air CO2 Enrichment) experiment was carried out on Grapevine (Vitis vinifera L.) in 1996 and 1997 in an existing vineyard in Italy. Four FACE arrays were used to fumigate adults plants, while two arrays were used as control. Three CO2 exposure levels were used in these arrays (ambient, 550 and 700 μmol mol−1). Dynamics of vegetative and reproductive biomass and grape quality compounds (sugar and acid concentrations) were monitored during the two growing seasons. Chemical analyses of the main wine quality compounds were made after fermentations. Elevated atmospheric CO2 levels had a significant effect on biomass components (total and fruit dry weight) with increases that ranged from 40 to 45% in the 550 μmol mol−1 treatment and from 45 to 50% in 700 μmol mol−1 treatment. Acid and sugar contents were also stimulated by rising CO2 levels up to a maximum increase in the middle of the ripening season (8–14%); however, as the grapes reached the maturity stage the CO2 effect on both quality parameters almost completely disappeared. Wine quality was not significantly affected by elevated CO2. Furthermore, no significant differences were detectable among the plants grown in the two enriched treatments (550 and 700 μmol mol−1), and the effects of elevated CO2 concentration were similar in the two growing seasons. The absence of any further stimulation of the highest CO2 treatment (700 μmol mol−1) on grapevine growth and yield quality (i.e. grapes and wine) may be explained as a result of transport and/or sink limitations. We can conclude that the expected rise in CO2 concentrations may strongly stimulate grapevine production without causing negative repercussions on quality of grapes and wine.  相似文献   

9.
人参不同生育期叶片光合作用变化的研究   总被引：9，自引：0，他引：9  
田间栽培和植物生长室培养试验结果表明,净光合速率（Pn）在尚未形成生殖器官的一年生人参叶片完全展开后即达最大值,此后缓慢下降;2~6年生人参叶片完全展开后达第1个高峰,开花期略有下降,绿果期出现第2高峰,此后持续下降。去掉花蕾的人参植株叶片在对照植株的绿果期没有出现第2高峰,但在红果期和黄叶期净光合速率下降缓慢。弱光（10%透光荫棚）和适宜光（30%透光荫棚）下人参叶片绿果期后Pn下降缓慢,强光（50%透光荫棚）下下降较快,过早出现变黄早衰。强光和高温可使植株生育期缩短、叶片早衰、Pn快速下降,而弱光和低温使植株生育期延长,Pn下降时间推迟。叶片表观量子效率(AQY)、气孔导度(Gs)和蒸腾作用(Tr)自展叶期至绿果期变化不大,红果期和黄叶期持续下降。胞间CO2浓度(Ci)在展叶期至绿果期较低,红果期和黄叶期持续增加,说明生育后期Pn下降是由非气孔限制因子引起。叶片Pn与比叶重呈负相关,推测叶片光合产物的积累和消耗与Pn的生育期变化有关。绿果期Ci最低,同时水分利用效率(WUE)较高,是人参叶片光合作用对水分需求的关键时期。  相似文献   

10.
Different species have different sensitivity to heat waves; therefore, interspecific competition may affect the crop response to heat waves. We investigated the effects of heat waves on spring barley (Hordeum vulgare L.) grown with and without wild mustard (Sinapis arvensis L.) as well as the recovery of barleys from stress. The plants were exposed to a 7‐day 35/28ºC (day/night) heat wave at ambient CO2 (400 μmol/mol) and elevated CO2 (800 μmol/mol). All seedlings were rehydrated and returned to control conditions (21/14ºC, CO2 400 μmol/mol) after the cease of heat wave and grown for a 7‐day period of recovery. Heat wave had more pronounced negative effect on the barley's aboveground biomass under competition with mustard, whereas the response of root biomass was not influenced by the presence of weeds. The heat wave induced reductions in barley's photosynthetic rate, stomatal conductance and water use efficiency under interspecific competition were higher compared to monocultured conditions. Interspecific competition impaired and delayed the recovery of barley's biomass production and leaf gas exchange parameters after heat wave. Elevated CO2 slightly mitigated negative heat wave impact on the growth and leaf gas exchange parameters but had no effect during the recovery period.  相似文献   

11.
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.  相似文献   

12.
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.  相似文献   

13.
Photosynthetic Response of Wheat to Soil Water Deficits in the Tropics   总被引：1，自引：0，他引：1  
The changes in photosynthetic rate and translocation of photosynthates in winter wheat (Triticum Aestivum L.) grown in lysimeters were studied, in response to periodic soil water deficit during late tillering and flowering stages. Soil water deficits were imposed to previously nonstressed plants during late tillering and flowering states. Timing of irrigation was scheduled according to the ratio between irrigation water applied and cumulative pan evaporation (IW/CPE) of 0.75 (low deficit), and 0.5 (moderate deficit), as well as by suspending irrigations after crown root initiation stage (severe deficit). To determine the rate of photosynthesis, a short radioactive pulse of 14CO2 with 300 ppm concentration was given to second leaf from the top at tillering, and to the flag leaf at flowering stages for 20 second exposure time. The translocation of photosynthates was estimated by scanning 14C activity in different plant parts. In late tillering the midday Photosynthetic rate (PR) was significantly 3 mg CO2 dm?2 h?1 lower under low water deficit (WD1) than under zero water deficit (WD0). Under higher stress conditions, soil water acted as a limiting factor to keep the rate from rising above 13.2 during stress at late tillering (WD2), 14.5 flowering (WD4), and 10.0 mg CO2 dm?2 h?1 for stress at both the growth stages (WD5), respectively. The difference in daily accumulated photosynthesis (8 h), between stressed and nonstressed were 15, 40, 42, and 77 mg CO2 dm?2 h?1 respectively at WD1 WD2, WD4, and WD5. The retention of 14C in flag leaf decreased considerably after 24 hours of exposure time when the labelled assimilates were translocated in bulk to the ear head. Under stressed condition a general trend was observed for upward translocation of assimilates towards the ear, even from the stem and root. The percent 14C activity observed in ear after 24 hours was greatest in severely stressed plants. The photosynthetic rate is reasonable predicted by midday LDR and surface moisture.  相似文献   

14.
Susceptibility of crops to drought may change under atmospheric CO2 enrichment. We tested the effects of CO2 enrichment and drought on the older malting barley cultivar Golden Promise (GP) and the recent variety Bambina (BA). Hypothesizing that CO2 enrichment mitigates the adverse effects of drought and that GP shows a stronger response to CO2 enrichment than BA, plants of both cultivars were grown in climate chambers. Optimal and reduced watering levels and two CO2 concentrations (380 and 550 ppm) were used to investigate photosynthetic parameters, growth and yield. In contrast to expectations, CO2 increased total plant biomass by 34 % in the modern cultivar while the growth stimulation was not significant in GP. As a reaction to drought, BA showed reduced biomass under elevated CO2, which was not seen in GP. Grain yield and harvest index (HI) were negatively influenced by drought and increased by CO2 enrichment. BA formed higher grain yield and had higher water‐use efficiency of grain yield and HI compared to GP. CO2 fertilization compensated for the negative effect of drought on grain yield and HI, especially in GP. Stomatal conductance proved to be the gas exchange parameter most sensitive to drought. Photosynthetic rate of BA showed more pronounced reaction to drought compared to GP. Overall, BA turned out to respond more intense to changes in water supply and CO2 enrichment than the older GP.  相似文献   

15.
In this study, we developed and analyzed a new model for the simulation of photosynthetic active nitrogen (NP) turnover dynamics in crops and assessed its impact on the acclimation of canopy photosynthesis to atmospheric CO2 enrichment. Typical canopy models assume a vertical exponential decline of light interception following the Beer–Lambert law and vertical distributions of leaf NP contents directly proportional to the light distribution. This assumption is often inconsistent with experimental observations. We therefore modified and extended the photosynthesis model of the GECROS crop model to consider the trade-off that occurs between the use of degraded NP for plant growth and the synthesis of new NP. This model extension thus enabled the examination of the CO2-induced down-regulation of photosynthesis hypothesis using a crop model. The simulation results of the original and modified GECROS model were compared and evaluated based upon measurements of field-grown spring wheat. The modified GECROS model better simulated the dynamics of crop growth under varying atmospheric CO2 concentrations. Furthermore, the application of different temperature functions to NP degradation strongly influenced the simulation results, revealing the necessity for improving the understanding of the temperature dependence of NP turnover for different crop species and varieties. In conclusion, the redistribution of nitrogen within the plant and its alternative use either for growth or the optimization of the photosynthetic apparatus is an important mechanism for crop growth acclimation to regionally changing climatic conditions and in particular, atmospheric CO2 enrichment.  相似文献   

16.
Based on the carboxylation kinetics of the C3 and C4 photosynthetic pathway, it is anticipated that C3 crops may be favored over C4 weeds as atmospheric CO2 increases. In the current study, tomato (Lycopersicon esculentum), a C3 crop species, was grown at ambient (~400 μmol mol−1) and enhanced carbon dioxide (~800 μmol mol−1) with and without two common weeds, lambsquarters (Chenopodium album), a C3 weed, and redroot pigweed (Amaranthus retroflexus), a C4 weed, from seedling emergence until mutual shading of crop-weed leaves. Because growth temperature is also likely to change in concert with rising CO2, the experiment was repeated at day/night temperatures of 21/12 and 26/18 °C. For both day/night temperatures, elevated CO2 exacerbated weed competition from both the C3 and C4 weed species. A model based on relative leaf area following emergence was used to calculate potential crop losses from weeds. This analysis indicated that potential crop losses increased from 33 to 55% and from 32 to 61% at the 21/12 and 26/18 °C day/night temperatures, for ambient and elevated CO2, respectively. For the current study, reductions in biomass and projected yield of tomato appeared independent of the photosynthetic pathway of the competing weed species. This may be due to inherent variation and overlap in the growth response of C3 and C4 species, whether weeds or crops, to increasing CO2 concentration. Overall, these results suggest that as atmospheric CO2 and/or temperature increases, other biological interactions, in addition to photosynthetic pathway, deserve additional consideration in predicting competitive outcomes between weeds and crops.  相似文献   

17.
Previous experiments have shown that, at harvest of winter wheat, recovery of fertilizer N applied in early spring [tillering, Zadok’s growth stage (GS) 25] is lower than that of N applied later in the growth period. This can be explained by losses and immobilization of N, which might be higher between GS 25 and stem elongation (GS 31). It was hypothesized that a higher crop density (i.e. more plants per unit area) results in an increased uptake of fertilizer N applied at GS 25, so that less fertilizer N is subject to losses and immobilization. Different crop densities of winter wheat at GS 25 were established by sowing densities of 100 seeds m–2 (Slow), 375 seeds m–2 (Scfp= common farming practice) and 650 seeds m–2 (Shigh) in autumn. The effect of sowing density on crop N uptake and apparent fertilizer N recovery (aFNrec = N in fertilized treatments ? N in unfertilized treatments) in crops and soil mineral N (Nmin), as well as on lost and immobilized N (i.e. non‐recovered N = N rate ? aFNrec), was investigated for two periods after N application at GS 25 [i.e. from GS 25 to 15 days later (GS 25 + 15d), and from GS 25 + 15d to GS 31] and in a third period between GS 31 and harvest (i.e. after second and third N applications). Fertilizer N rates varied at GS 25 (0, 43 and 103 kg N ha–1), GS 31 (0 and 30 kg N ha–1) and ear emergence (0, 30 and 60 kg ha–1). At GS 25 + 15d, non‐recovered N was highest (up to 33 kg N ha–1 and up to 74 kg N ha–1 at N rates of 43 and 103 kg N ha–1, respectively) due to low crop N uptake after the first N dressing. Non‐recovered N was not affected by sowing density. Re‐mineralization during later growth stages indicated that non‐recovered N had been immobilized. N uptake rates from the second and third N applications were lowest for Slow, so non‐recovered N at harvest was highest for Slow. Although non‐recovered N was similar for Scfp and Shigh, the highest grain yields were found at Scfp and N dressings of 43 + 30 + 60 kg N ha–1. This combination of sowing density and N rates was the closest to common farming practice. Grain yields were lower for Shigh than for Scfp, presumably due to high competition between plants for nutrients and water. In conclusion, reducing or increasing sowing density compared to Scfp did not reduce immobilization (and losses) of fertilizer N and did not result in increased fertilizer N use efficiency or grain yields.  相似文献   

18.
This study was conducted to elucidate the crop physiological basis for yield differences frequently observed in experiments comparing top‐dressing of N fertilizers with injection of ammonium or ammonium/urea solutions into the soil. The effects of diammonium phosphate (NH4‐N) injected at the two‐leaf stage, calcium nitrate (NO3‐N) broadcasted and incorporated before sowing, and a control without N fertilization (‐N) were assessed from measurements of growth, N‐uptake and N‐partitioning, light interception, gas exchange, leaf anatomy and the activity of key enzymes of N‐metabolism. The experiment was performed with spring barley (Hordeum vulgare L.) grown in 80‐l containers in a vegetation hall in Braunschweig, Germany. The plants in the NH4‐N treatment produced a 20 % higher grain yield than those in the NO3‐N treatment. The grain yield superiority of the NH4‐N plants was attributable to a higher number of ears per plant (+13 %) and more grains per ear (+6 %). The NH4‐N plants exhibited lower concentrations of inorganic cations than plants supplied with NO3‐N. In the NH4‐N treatment, the light penetrated more deeply into the crop canopy and the NH4‐N plants exhibited a higher leaf carbon exchange rate at the different leaf layers than the NO3‐N plants. It is concluded that as opposed to predominantly nitrate nutrition, provision of a persistent source of ammonium enables plants to take advantage of the positive yield effect of mixed N nutrition.  相似文献   

19.
This study analysed the alleviating effect of elevated CO2 on stress‐induced decreases in photosynthesis and changes in carbohydrate metabolism in two wheat cultivars (Triticum aestivum L.) of different origin. The plants were grown in ambient (400 μl l?1) and elevated (800 μl l?1) CO2 with a day/night temperature of 15/10 °C. At the growth stages of tillering, booting and anthesis, the plants were subjected to heat stress of 40 °C for three continuous days. Photosynthetic parameters, maximum quantum efficiency of photosystem II (PSII) photochemistry (Fv/Fm) and contents of pigments and carbohydrates in leaves were analysed before and during the stress treatments as well as after 1 day of recovery. Heat stress reduced PN and Fv/Fm in both wheat cultivars, but plants grown in elevated CO2 maintained higher PN and Fv/Fm in comparison with plants grown in ambient CO2. Heat stress reduced leaf chlorophyll contents and increased leaf sucrose contents in both cultivars grown at ambient and elevated CO2. The content of hexoses in the leaves increased mainly in the tolerant cultivar in response to the combination of elevated CO2 and heat stress. The results show that heat stress tolerance in wheat is related to cultivar origin, the phenological stage of the plants and can be alleviated by elevated CO2. This confirms the complex interrelation between environmental factors and genotypic traits that influence crop performance under various climatic stresses.  相似文献   

20.
A substantial proportion of ammonical fertilizers applied to lowland rice is lost as gaseous N from the soil–plant system. Besides various environmental factors, the low N use efficiency of flooded rice is also attributed to this factor. As atmospheric ammonia found in the leaf environment of the plants could also be responsible for differences in N use efficiency and fertilizer N losses from lowland rice, a greenhouse study was conducted on three rice cultivars varying in physio-morphological characteristics for their dry matter and nitrogen distribution to grains at maturity in response to ammonia (NH3) exposure at tillering and anthesis growth stages. The results revealed that ammonia exposure of plants at two growth stages did not affect the total dry matter and total N yield of the rice cultivars at maturity; however, the grain yield and grain N yield were negatively effected by NH3 exposure of the plants at anthesis. The variation observed in dry matter and N partitioning at maturity to grains/roots of the plants exposed to NH3 at anthesis indicated that the growth stage of the plants at which they are exposed to NH3 has an influence on N use efficiency of crop plants and subsequent vegetative as well as total N losses from the soil–plant system.  相似文献   

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