ISSN:1354-1013    

DOI:10.1111/j.1365-2486.1995.tb00036.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractShort‐ and long‐term effects of elevated CO2concentration and temperature on whole plant respiratory relationships are examined for wheat grown at four constant temperatures and at two CO2concentrations. Whole plant CO2exchange was measured on a 24 h basis and measurement conditions varied both to observe short‐term effects and to determine the growth respiration coefficient (rg), dry weight maintenance coefficient (rm), basal (i.e. dark acclimated) respiration coefficient (rg), and 24 h respiration:photosynthesis ratio (R:P). There was no response of rgto short‐term variation in CO2 concentration. For plants with adequate N supply, rgwas unaffected by the growth‐CO2despite a 10% reduction in the plant's N concentration (%N). However, rmwas decreased 13%, and rbwas decreased 20% by growth in elevated CO2concentration relative to ambient. Nevertheless, R:P was not affected by growth in elevated CO2. Whole plant respiration responded to short‐term variation of ± 5 °C around the growth temperature with low sensitivity (Q10= 1.8 at 15 °C, 1.3 at 30 °C). The shape of the response of whole plant respiration to growth temperature was different from that of the short term response, being a slanted S‐shapedecliningbetween 25 and 30 °C. While rm, increased, rgdecreased when growth temperature increased between 15 and 20 °C. Above 20 °C rmbecame temperature insensitive while rgincreased with growth temperature. Despite these complex component responses, R:P increased only from 0.40 to 0.43 between 15° and 30 °C growth temperatures. Giving the plants a step increase in temperature caused a transient increase in R:P which recovered to the pre‐transient value in 3 days. It is concluded that use of a constant R:P with respect to average temperature and CO2concentration may be a more simple and accurate way to model the responses of wheat crop respiration to ‘climate change’ than the more complex and mechanistically dubious functional analysis into growt

ISSN:1354-1013    

DOI:10.1111/j.1365-2486.1995.tb00037.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe use of fossil fuel is predicted to cause an increase of the atmospheric CO2concentration, which will affect the global pattern of temperature and precipitation. It is therefore essential to incorporate effects of temperature and water supply on carbon partitioning of plants to predict effects of elevated [CO2] on growth and yield ofTriticum aestivum.Although earlier papers have emphasized that elevated [CO2] favours investment of biomass in roots relative to that in leaves, it has now become clear that these are indirect effects, due to the more rapid depletion of nutrients in the root environment as a consequence of enhanced growth. Broadly generalized, the effect of temperature on biomass allocation in the vegetative stage is that the relative investment of biomass in roots is lowest at a certain optimum temperature and increases at both higher and lower temperatures. This is found not only when the temperature of the entire plant is varied, but also when only root temperature is changed whilst shoot temperature is kept constant. Effects of temperature on the allocation pattern can be explained largely by the effect of root temperature on the roots' capacity to transport water. Effects of a shortage in water supply on carbon partitioning are unambiguous: roots receive relatively more carbon.The pattern of biomass allocation in the vegetative stage and variation in water‐use efficiency are prime factors determining a plant's potential for early growth and yield in different environments. In a comparison of a range ofT. aestivumcultivars, a high water‐use efficiency at the plant level correlates positively with a large investment in both leaf and root biomass, a low stomatal conductance and a large investment in photosynthetic capacity. We also present evidence that a lower investment of biomass in roots is not only associated with lower respiratory costs for root growth, but also with lower specific costs for ion uptake. We suggest the combination of a number of traits in future wheat cultivars, i.e. a high investment of biomass in leaves, which have a low stomatal conductance and a high photosynthetic capacity, and a low investment of biomass in roots, which have low respiratory costs. Such cultivars are considered highly appropriate in a future world, especially in the dryer regions. Although variation for the desired traits already exists among wheat cultivars, it is much larger among wildAegilopsspecies, which can readily be crossed with T.aestivum.Such wild relatives may be exploited to develop new wheat cultivars well‐adapted to changed climatic condi

ISSN:1354-1013    

DOI:10.1111/j.1365-2486.1995.tb00038.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAir temperature and the atmospheric concentrations of carbon dioxide are expected to rise. These two factor have a great potential to affect development, growth and yield of crops, including wheat. Rising air temperature may affect wheat development more than rising atmospheric CO2as there is not yet evidence that elevated CO2concentrations can directly induce changes in wheat development. In winter wheat, temperature has a complex effect on development due to its strong interaction with vernalization and photoperiod. In this paper, potential effects of rising temperature on the development of winter wheat from sowing to heading are considered in the light of this complex controlling mechanism. Data from a large series of field trials made in Romania is analysed at first and, subsequently, the IATA‐Wheat Phenology model is used to calculate the impact of air warming on wheat development under different climate change scenarios. Data from the field trials showed very clearly the occurrence of a complex temperature/photoperiod/vernalization interaction for field sown crops and demostrated that the photoperiodic and vernalization responses have a key role in controlling the duration of the emergence‐heading period. Temperature plays, instead, a central role in controlling seed germination and crop emergence as well as leaf inititiation and leaf appearance rate. The results of model analysis showed very well that the impact of an even or uneven distribution of warning effects may be very different. In the first case, the model predicted that the duration of the vegetative period was at least partly reduced in some years. In the second case, the model suggested that if warming will be more pronounced in winter than in spring, as predicted for some areas of the world by General Circulation Models, we may expect an increase in the duration of the vegetative phase of growth. On the contrary, in case of a spring warming but unchanged winter temperatures, we may expect a substantial decrease in the duration of the vegetative per

ISSN:1354-1013    

DOI:10.1111/j.1365-2486.1995.tb00039.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of elevated [CO2] on the productivity of spring wheat, winter wheat and faba bean was studied in experiments in climatized crop enclosures in the Wageningen Rhizolab in 1991–93. Simulation models for crop growth were used to explore possible causes for the observed differences in the CO2response. Measurements of the canopy gas exchange (CO2and water vapour) were made continuously from emergence until harvest. At an external [CO2] of 700 μmol mol−1Maximum Canopy CO2Exchange Rate (CCERmax) at canopy closure was stimulated by 51% for spring wheat and by 71% for faba bean. At the end of the growing season, above ground biomass increase at 700 μmol mol−1was 58% (faba bean), 35% (spring wheat) and 19% (winter wheat) and the harvest index did not change. For model exploration, weather data sets for the period 1975‐88 and 1991–93 were used, assuming adequate water supply and [CO2] at 350 and 700 μmol mol−1. For spring wheat the simulated responses (35–50%) were at the upper end of the experimental results. In agreement with experiments, simulations showed smaller responses for winter wheat and larger responses for faba bean. Further model explorations showed that this differential effect in the CO2response may not be primarily due to fundamental physiological differences between the crops, but may be at least partly due to differences in the daily air temperatures during comparable stages of growth of these crops. Simulations also showed that variations between years in CO2response can be largely explained by differences in weather conditions (especially temperature) between

ISSN:1354-1013    

DOI:10.1111/j.1365-2486.1995.tb00040.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA free‐air CO2enrichment (FACE) experiment was conducted at Maricopa, Arizona, on wheat from December 1992 through May 1993. The FACE apparatus maintained the CO2concentration, [CO2], at 550 μmol mol−1across four replicate 25‐m‐diameter circular plots under natural conditions in an open field. Four matching Control plots at ambient [CO2] (about 370 μmol mol−1) were also installed in the field. In addition to the two levels of [CO2], there were ample (Wet) and limiting (Dry) levels of water supplied through a subsurface drip irrigation system in a strip, split‐plot design.Measurements were made of net radiation,Rn; soil heat flux,Go; soil temperature; foliage or surface temperature; air dry and wet bulb temperatures; and wind speed. Sensible heat flux,H, was calculated from the wind and temperature measurements. Latent heat flux, λET, and evapotranspiration,ET, were determined as the residual in the energy balance. The FACE treatment reduced daily totalRnby an average 4%. Daily FACE sensible heat flux,H, was higher in the FACE plots. Daily latent heat flux, λET, and evapotranspiration,ET, were consistently lower in the FACE plots than in the Control plots for most of the growing season, about 8% on the average.Net canopy photosynthesis was stimulated by an average 19 and 44% in the Wet and Dry plots, respectively, by elevated [CO2] for most of the growing season. No significant acclimation or down regulation was observed. There was little above‐ground growth response to elevated [CO2] early in the season when temperatures were cool. Then, as temperatures warmed into spring, the FACE plants grew about 20% more than the Control plants at ambient [CO2], as shown by above‐ground biomass accumulation. Root biomass accumulation was also stimulated about 20%. In May the FACE plants matured and senesced about a week earlier than the Controls in the Wet plots. The FACE plants averaged 0.6 °C warmer than the Controls from February through April in the well‐watered plots, and we speculate that this temperature rise contributed to the earlier maturity. Because of the acceleration of senescence, there was a shortening of the duration of grain filling, and consequently, there was a narrowing of the final biomass and yield differences. The 20% mid‐season growth advantage of FACE shrunk to about an 8% yield advantage in the Wet plots, while the yield differences between FACE and Control remained at ab

ISSN:1354-1013    

DOI:10.1111/j.1365-2486.1995.tb00041.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSoil water deficits are likely to influence the response of crop growth and yield to changes in atmospheric CO2concentrations (Ca), but the extent of this influence is uncertain. To study the interaction of water deficits and Caon crop growth, the ecosystem simulation modelecosyswas tested with data for diurnal gas exchange and seasonal wheat growth measured during 1993 under high and low irrigation at Ca= 370 and 550 μmol mol−1in the Free Air CO2Enrichment (FACE) experiment near Phoenix, AZ. The model, supported by the data from canopy gas exchange enclosures, indicated that under high irrigation canopy conductance (gc) at Ca= 550 μmol mol−1was reduced to about 0.75 that at Ca= 370 μmol mol−1, but that under low irrigation, gcwas reduced less. Consequently when Cawas increased from 370 to 550 μmol mol−1, canopy transpiration was reduced less, and net CO2fixation was increased more, under low irrigation than under high irrigation. The simulated effects of Caand irrigation on diurnal gas exchange were also apparent on seasonal water use and grain yield. Simulated vs. measured seasonal water use by wheat under high irrigation was reduced by 6% vs. 4% at Ca= 550 vs. 370 μmol mol−1but that under low irrigation was increased by 3% vs. 5%. Simulated vs. measured grain yield of wheat under high irrigation was increased by 16% vs. 8%, but that under low irrigation was increased by 38% vs. 21%. Inecosys, the interaction between Caand irrigation on diurnal gas exchange, and hence on seasonal crop growth and water use, was attributed to a convergence of simulated gctowards common values under both Caas canopy turgor declined. This convergence caused transpiration to decrease comparatively less, but CO2fixation to increase comparatively more, under high vs. low Ca. Convergence of gcwas in turn attributed to improved turgor maintenance under elevated Cacaused by greater storage C concentrations in the leaves, and by greater rooting densi

ISSN:1354-1013    

DOI:10.1111/j.1365-2486.1995.tb00042.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractMany facilities for growing plants at elevated atmospheric concentrations of CO2([CO2]) neglect the control of temperature, especially of the soil. Soil and root temperatures in conventional, free‐standing pots often exceed those which would occur in the field at a given air temperature. A plant growth facility is described in which atmospheric CO2can be maintained at different concentrations while soil and air temperatures mimic spatial and temporal patterns seen in the field. It consists of glasshouse‐located chambers in which [CO2] is monitored by an infra‐red gas analyser and maintained by injection of CO2from a cylinder. Air is cooled by a heat exchange unit. Plants grow in soil in 1.2 m long containers that are surrounded by cooling coils and thermal insulation. Both [CO2] and temperature are controlled by customized software. Air temperature is programmed to follow a sine function of diurnal time. Soil temperature at a depth of 0.55 m is programmed to be constant. Temperature at 0.1 m depth varies as a damped, lagged function of air temperature; that at 1.0 m as a similar function of the 0.55 m temperature. [CO2] is maintained within 20 μmol mol−1of target concentrations during daylight. A feature of the system is that plant material is labelled with a13C enrichment different from that of carbon in soil organic matter. The operation of the system is illustrated with data collected in an experiment with spring wheat (Triticum aestivumL., cv Tonic) grown at ambient [CO2] and at [CO2] 350 μmol mol−1greater t

ISSN:1354-1013    

DOI:10.1111/j.1365-2486.1995.tb00043.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY