Increased Canopy Temperature Research Articles

Study on physiological response of drought tolerant groundnut genotypes associated with different stress levels

Identification of drought tolerant genotypes with superior drought tolerant physiological traits is essential for the success of drought tolerance breeding program. This study was conducted to observe physiological response of drought tolerant groundnut genotypes associated with different stress levels. During 2021-2022 post-monsoon season, eight groundnut genotypes were evaluated under non-stress (field capacity), moderate stress (50 % available water) and severe stress (25 % available water) conditions. The experiment was undertaken using split plot design. Increasing drought stress levels decreased relative water content and increased canopy temperature and proline content. Total chlorophyll content increased under moderate stress condition and decreased under severe stress condition in some genotypes. The genotype ICGV-07235 and the drought tolerant check variety, Sinpadetha-12 showed consistent RWC values under different stress levels. The genotypes ICGV-07235, ICGV-07406 and Sinpadetha-12 possessed minimum canopy temperature values among the tested genotypes. Total chlorophyll content of the genotypes ICGV-07286 and ICGV-07235 were higher than that of the other tested genotypes. The genotypes ICGV-07390, YZG-07084 and ICGV-07286 had the highest proline content under stress conditions. Based on the results, the genotypes YZG-07084, ICGV-07286, ICGV-07235, ICGV-07390 and ICGV-07406 possessed desired physiological traits and these genotypes could be effectively utilized for developing drought tolerant groundnut genotypes.

High-throughput phenotyping for drought tolerance in rice

Most lowland rice in West Africa depends mainly on rainfall for water supply. Drought is consequently one of the major constraints on rice production, drastically affecting both plant growth and development. The objective of this work was to study the impact of water deficit both on canopy temperature and on chlorophyll fluorescence level, used as indicators of transpiration and photosynthetic activity. Measurements using infrared thermography and fluorimetry were taken on both 17 lines resulting from the cross IR64 X B6144F-MR-6-0-0 and their two parents plus one tolerant (APO) controls. These 20 lines were phenotyped after applying a drought constraint in a controlled laboratory environment in Montpellier (France) in 2013 and - 2014 and in field in the lowlands of Banfora and Farako-ba (INERA Burkina Faso) in 2014. Results showed that the drought stress sustained by the plants increased canopy temperature in all lines, entailing differential disturbance of the photosynthetic process, markedly depressed in susceptible lines. A classification of the lines with respect to their sensitivity to stress could be established by using the Drought Factor Index (DFI), and Crop Water Stress Index (CWSI) as was established a correlation between the phenotyping methods by infrared thermography and fluorimetry. This article propose an efficient application of combined imaging as a rapid and accurate phenotyping tool for crop yield improvement, in particular by monitoring the efficiency of plant responses to the fluctuating of environmental conditions. This study proved the efficiency of the method combining IR thermographie and fluorimetry as a field phenotyping tools for drought resistance.

Climate Effects on Vertical Forest Phenology of Fagus sylvatica L., Sensed by Sentinel-2, Time Lapse Camera, and Visual Ground Observations

Contemporary climate change leads to earlier spring phenological events in Europe. In forests, in which overstory strongly regulates the microclimate beneath, it is not clear if further change equally shifts the timing of leaf unfolding for the over- and understory of main deciduous forest species, such as Fagus sylvatica L. (European beech). Furthermore, it is not known yet how this vertical phenological (mis)match—the phenological difference between overstory and understory—affects the remotely sensed satellite signal. To investigate this, we disentangled the start of season (SOS) of overstory F.sylvatica foliage from understory F. sylvatica foliage in forests, within nine quadrants of 5.8 × 5.8 km, stratified over a temperature gradient of 2.5 °C in Bavaria, southeast Germany, in the spring seasons of 2019 and 2020 using time lapse cameras and visual ground observations. We explained SOS dates and vertical phenological (mis)match by canopy temperature and compared these to Sentinel-2 derived SOS in response to canopy temperature. We found that overstory SOS advanced with higher mean April canopy temperature (visual ground observations: −2.86 days per °C; cameras: −2.57 days per °C). However, understory SOS was not significantly affected by canopy temperature. This led to an increase of vertical phenological mismatch with increased canopy temperature (visual ground observations: +3.90 days per °C; cameras: +2.52 days per °C). These results matched Sentinel-2-derived SOS responses, as pixels of higher canopy height advanced more by increased canopy temperature than pixels of lower canopy height. The results may indicate that, with further climate change, spring phenology of F. sylvatica overstory will advance more than F. sylvatica understory, leading to increased vertical phenological mismatch in temperate deciduous forests. This may have major ecological effects, but also methodological consequences for the field of remote sensing, as what the signal senses highly depends on the pixel mean canopy height and the vertical (mis)match.

How does leaf physiological acclimation impact forage production and quality of a warmed managed pasture of Stylosanthes capitata under different conditions of soil water availability?

Tropical pastures play a significant role in the global carbon cycle and are crucial for world livestock production. Despite its importance, there is a paucity of field studies that clarify how tropical pasture species will be affected by environmental changes predicted for tropical regions. Using a temperature-free air-controlled enhancement (T-FACE) system, we increased canopy temperature (+2 °C over ambient) and evaluated the effects of warming under two soil moisture conditions in a factorial design over the physiology, forage production, and forage quality of a tropical forage legume, Stylosanthes capitata. Under well-watered conditions, warming increased the PSII efficiency, net photosynthesis, and aboveground biomass accumulation, but reduced forage quality and digestibility by decreasing crude protein content and increasing lignin content. Non-irrigated conditions under ambient temperature reduced leaf water status presumably promoting the reduction in net photosynthesis, forage production, and forage quality and digestibility. Under the combination of canopy warming and non-irrigated conditions, warming mitigated the effects of reduced soil moisture on leaf photosynthesis and biomass production, but a significant interaction reduced forage quality and digestibility more than under isolated treatments of warming or non-irrigated conditions. We found a potential physiological acclimation of the tropical forage species to moderate warming when grown under rainfed or well-watered conditions. However, this acclimation was achieved due to a trade-off that reduced forage nutritional value and digestibility that may impact future animal feeding, livestock production, and would contribute to methane emissions.

Canopy architecture and leaf type as traits of heat resistance in pea

Pea (Pisum sativum L.) is sensitive to heat stress, and thus traits of heat resistance are desirable to minimize crop damage and maintain yield stability in improved cultivars. Crop research has focused on flowering and pollination success for heat resistant traits and vegetative structure is usually overlooked. The plant canopy, through leaf shape, plant habit and resistance to lodging, may offer additional sources of heat resistance in many crops. In pea, commercial cultivars have upright or vining plant habits, and either normal leaves comprised of stipules, leaflets and tendrils or semileafless leaves lacking leaflets. To determine the best canopy architecture and leaf traits associated with heat resistance, 24 diverse pea cultivars were tested in field trials across six environments in western Canada during 2014 to 2016. Compared to control conditions, heat stress increased canopy temperature from 24.9 °C to 27.8 °C and reduced reproductive stem length by 37% (17 cm), flowering duration by 21% (4.7 days), pod number by 30% (3 pods plant−1), and seed yield by 16% (54 g m-2). Pea cultivars had differential responses for measured traits; under heat stress conditions, semileafless cultivars with the upright habit had cooler canopies and greater seed yield, pod number and pod to node ratio than normal leafed vining cultivars. Lodging was associated with increased canopy temperature, a novel finding, implying greater heat stress. In contrast, growth and yield-related traits were greater in control environments for normal leaf, indeterminate and vining cultivars. Overall, the semileafless leaf and upright plant habit were superior traits that not only reduced lodging but maintained lower canopy temperatures in heat and drought stress environments. Therefore, vegetative heat stress can be avoided by management options that resist lodging and by selecting traits in plant breeding that can keep a cultivar upright.

Application of Nano-Silicon Dioxide Improves Salt Stress Tolerance in Strawberry Plants

Silicon application can improve productivity outcomes for salt stressed plants. Here, we describe how strawberry plants respond to treatments including various combinations of salt stress and nano-silicon dioxide, and assess whether nano-silicon dioxide improves strawberry plant tolerance to salt stress. Strawberry plants were treated with salt (0, 25 or 50 mM NaCl), and the nano-silicon dioxide treatments were applied to the strawberry plants before (0, 50 and 100 mg L−1) or after (0 and 50 mg L−1) flowering. The salt stress treatments reduced plant biomass, chlorophyll content, and leaf relative water content (RWC) as expected. Relative to control (no NaCl) plants the salt treated plants had 10% lower membrane stability index (MSI), 81% greater proline content, and 54% greater cuticular transpiration; as well as increased canopy temperature and changes in the structure of the epicuticular wax layer. The plants treated with nano-silicon dioxide were better able to maintain epicuticular wax structure, chlorophyll content, and carotenoid content and accumulated less proline relative to plants treated only with salt and no nano-silicon dioxide. Analysis of scanning electron microscopic (SEM) images revealed that the salt treatments resulted in changes in epicuticular wax type and thickness, and that the application of nano-silicon dioxide suppressed the adverse effects of salinity on the epicuticular wax layer. Nano-silicon dioxide treated salt stressed plants had increased irregular (smoother) crystal wax deposits in their epicuticular layer. Together these observations indicate that application of nano-silicon dioxide can limit the adverse anatomical and biochemical changes related to salt stress impacts on strawberry plants and that this is, in part, associated with epicuticular wax deposition.

Phenotyping and evaluation of CIMMYT WPHYSGP nursery lines and local wheat varieties under two irrigation regimes.

Accurate evaluation of morphological and physiological traits is critical for selection of wheat (Triticum aestivum L.) cultivars exhibiting high yield, which is stable over different growing conditions. In order to use selection index based on high yield, high grain quality and drought tolerance in wheat, a set of 145 CIMMYT Wheat Physiological Germplasm Screening Nursery lines and seven local spring wheat varieties were phenotyped and evaluated for physiological and yield traits under two irrigation regimes during the 2011 and 2012 growing seasons in Xinjiang, China. The results showed that drought-stress significantly increased canopy temperature but reduced grain yield, grain weight per spike, normalized difference vegetation index at the flowering and grain filling stages, chlorophyll content at the grain filling stage, grain plumpness, grain number per spike, thousand-grain weight, and plant height. Grain weight per spike, plant height and grain plumpness explained 61.8% of the total phenotypic variation in grain yield under no-stress conditions, where they were the three principal factors most closely related to grain yield. Under drought-stress conditions, canopy temperature at the grain filling stage, plant height and grain plumpness were the three principal factors affecting grain yield, and contributed 44.8% of the total phenotypic variation in grain yield. Finally, ten genotypes, including three local varieties, ‘Xinchun 11’, ‘Xinchun 23’ and ‘Xinchun 29’, with appropriate plant height and high and stable yield under both no-stress and drought-stress conditions over the two years of trials, were identified and can be recommended as core parents for spring wheat drought tolerance breeding in Xinjiang, China.

Canopy Temperature and Water Relations of Kiwifruit Cultivar Allison in Response to Deficit Irrigation and <i>in situ</i> Moisture Conservation

The present article discusses the effect of different irrigation levels and in situ moisture conservation on canopy temperature and water relations, viz. leaf water potential, stomatal resistance, transpiration rate, leaf photosynthetic rate and chlorophyll content in kiwifruit cultivar Allison during the years 2011 and 2012 in Solan, Himachal Pradesh, India. The kiwifruit vines were subjected to seven treatments, viz. irrigation at 80% FC (field capacity); irrigation at 60% FC; irrigation at 40% FC; irrigation at 60% FC plus mulching with grass; irrigation at 60% FC plus black polythene mulching; irrigation at 40% FC plus mulching with grass and irrigation at 60% FC plus black polythene mulching applied from March to October with three replications in randomized block design. The deficit irrigation treatments resulted in increased canopy temperature and stomatal resistance and decrease the leaf water potential, transpiration rate, leaf photosynthetic rate and chlorophyll content in the leaves of kiwifruit cv. Allison, whereas the application of mulches (grass and black plastic) along with deficit irrigation levels resulted in mitigation of the effect of deficit irrigation. Application of black plastic mulch along with irrigation at 60% field capacity was observed to be the best treatment as its effect nearly similar to that of standard irrigation.

Evaluation of Water Stress on Yield, Its Components and Some Physiological Traits at Different Growth Stages in Grain Sorghum Genotypes

Investigation on yield improvement and development under drought condition using breeding techniques is difficult, due to the association with low heritability of specific traits. Even more, investigation of physiological indicators (stomatal conductance, chlorophyll index, relative water content, chlorophyll fluorescence, canopy temperature, radiation use efficiency, stay-green etc.) is of interest as they are more accessible, with a low cost, therefore these indicators of physiological traits can be used as good criteria in selecting valuable species. In order to evaluate the effects of water stress on grain yield, its components and some physiological traits of grain sorghum genotypes (Sorghum bicolor L.), a field experiment using split plot design with three replications was carried. The main plots included three water stress treatments: normal irrigation as control, halting irrigation at the stage of terminal leaf emergence and halting irrigation at the stage of 50% flowering. The sub-plots included 10 genotypes of sorghum (‘KGS29’, ‘MGS2’, ‘Sepideh’, ‘KGFS27’, ‘MGS5’, ‘KGFS5’, ‘KGFS17’, ‘KGFS13’ and ‘KGFS30’). Results showed that water stress significantly decreased grain yield and its components (1,000 seed weight, number of seed per panicle) and had various effects on physiological traits. The water stress increased canopy temperature and radiation use efficiency, while stomatal conductance, chlorophyll index (SPAD) and stay-green of genotypes were decreased; the maximum efficiency of photosystem II of photosynthesis remained unchanged between the treatments. Genotypes turned out to have significantly different responses to the drought treatments for all the studied traits, indicating the existence of a high variability among them. In general, physiological traits could be used as good indicators in water stress investigations and might provide comprehensive information as compared with morphological traits.

Evaluation of Water Stress on Yield, Its Components and Some Physiological Traits at Different Growth Stages in Grain Sorghum Genotypes

Investigation on yield improvement and development under drought condition using breeding techniques is difficult, due to the association with low heritability of specific traits. Even more, investigation of physiological indicators (stomatal conductance, chlorophyll index, relative water content, chlorophyll fluorescence, canopy temperature, radiation use efficiency, stay-green etc.) is of interest as they are more accessible, with a low cost, therefore these indicators of physiological traits can be used as good criteria in selecting valuable species. In order to evaluate the effects of water stress on grain yield, its components and some physiological traits of grain sorghum genotypes (Sorghum bicolor L.), a field experiment using split plot design with three replications was carried. The main plots included three water stress treatments: normal irrigation as control, halting irrigation at the stage of terminal leaf emergence and halting irrigation at the stage of 50% flowering. The sub-plots included 10 genotypes of sorghum (‘KGS29’, ‘MGS2’, ‘Sepideh’, ‘KGFS27’, ‘MGS5’, ‘KGFS5’, ‘KGFS17’, ‘KGFS13’ and ‘KGFS30’). Results showed that water stress significantly decreased grain yield and its components (1,000 seed weight, number of seed per panicle) and had various effects on physiological traits. The water stress increased canopy temperature and radiation use efficiency, while stomatal conductance, chlorophyll index (SPAD) and stay-green of genotypes were decreased; the maximum efficiency of photosystem II of photosynthesis remained unchanged between the treatments. Genotypes turned out to have significantly different responses to the drought treatments for all the studied traits, indicating the existence of a high variability among them. In general, physiological traits could be used as good indicators in water stress investigations and might provide comprehensive information as compared with morphological traits.

Thermal infrared imaging of the temporal variability in stomatal conductance for fruit trees

Repeated measurements using thermal infrared remote sensing were used to characterize the change in canopy temperature over time and factors that influenced this change on ‘Conference’ pear trees (Pyrus communis L.). Three different types of sensors were used, a leaf porometer to measure leaf stomatal conductance, a thermal infrared camera to measure the canopy temperature and a meteorological sensor to measure weather variables. Stomatal conductance of water stressed pear was significantly lower than in the control group 9 days after stress began. This decrease in stomatal conductance reduced transpiration, reducing evaporative cooling that increased canopy temperature. Using thermal infrared imaging with wavelengths between 7.5 and13μm, the first significant difference was measured 18 days after stress began. A second order derivative described the average rate of change of the difference between the stress treatment and control group. The average rate of change for stomatal conductance was 0.06 (mmolm−2s−1) and for canopy temperature was −0.04 (°C) with respect to days. Thermal infrared remote sensing and data analysis presented in this study demonstrated that the differences in canopy temperatures between the water stress and control treatment due to stomata regulation can be validated.

Evaluation of Colorants on ‘Sharpshooter’ and ‘Cody’ Buffalograss

Turf colorants effectively enhanced green color of dormant buffalograss. Using a higher application rate or adding a midwinter application helped longevity of color. Colorants increased canopy temperatures more consistently than soil temperatures, which may encourage earlier spring greenup.

Canopy Temperature and Yield Based Selection of Wheat Genotypes for Water Deficit Environment

The experiment was conducted with thirty-five wheat genotypes at the research field of the Department of Agronomy of the Bangabandhu Sheikh Mujibur Rahman Agricultural University from November 2011 to March 2012 to screen out the wheat genotypes for drought tolerance of thirty-five wheat genotypes under water deficit condition. The experiment was carried out in a split-plot design comprising two water regimes in main plot and thirty-five wheat genotypes were placed randomly in sub-plot with three replications. From this experiment, it was found that water deficit condition severely reduced the plant height, number of effective tillers m﹣2, spike length, number of spikelets spike﹣1, number of grains spike﹣1 and thousand grain weight. Based on the percentage of yield reduction, the genotypes BARI Wheat 26, Sourav, BAW 1169 and BAW 1158 were categorized in tolerant group exhibited low yield reduction (>30%) and the genotypes Seri, Pavon, BAW 1166, BAW 1167, BAW 1171 and BAW 1173 were ranked in susceptible group due to very low yielding ability with high yield reduction which ranged from 50.01% to 59.17% in water deficit condition. The maximum increased canopy temperature was recorded in the genotypes BAW 1166, BAW 1167, Seri, Pavon and BARI Wheat 25. The minimum was in the genotypes BARI Wheat 26, BAW 1157, Sourav, BAW 1169 and Gourab. The highest MP, GMP and STI values were recorded in the genotypes BARI Wheat 26, BAW 1158, Sourav, BAW 1169 and BAW 1170. Our results revealed that BARI Wheat 26, BAW 1158, Sourav, BAW 1169 and BAW 1170 were more capable to tolerate water deficit condition.

Effect of Increased Canopy Temperature on Cotton Plant Dry Matter Accumulation and Its Physiological Mechanism

Effect of Increased Canopy Temperature on Cotton Plant Dry Matter Accumulation and Its Physiological Mechanism

Wheat Growth Response to Increased Temperature from Varied Planting Dates and Supplemental Infrared Heating

Possible future increases in atmospheric temperature may threaten wheat (Triticum aestivum L.) production and food security. The purpose of this research is to determine the response of wheat growth to supplemental heating and to seasonal air temperature from an unusually wide range of planting dates. A field study was conducted at Maricopa, AZ, where wheat was planted from September to May over a 2‐yr period for a total of 12 planting dates. Supplemental heating was provided for 6 of the 12 planting dates using infrared heaters placed above the crop which increased canopy temperature by 1.3°C during the day and 2.7°C during the night. Grain yield declined 42 g m−2 (6.9%) per 1°C increase in seasonal temperature above 16.3°C. Supplemental heating had no effect on grain yield for plantings in winter (Dec./Jan.) since temperatures were near optimum (14.9°C). However, in spring (Mar.) plantings where temperature (22.2°C) was above optimum, supplemental heating decreased grain yield from 510 to 368 g m−2. Supplemental heating had the greatest effect in the early fall plantings (Sept./Oct.) when temperature was slightly below optimum (13.8°C) and mid‐season frost limited the yield of unheated plots to only 3 g m−2 whereas yield of heated plots was 435 g m−2. Thus, possible future increases in temperature may decrease wheat yield for late plantings and shift optimum planting windows to earlier dates in areas of the world similar to the desert southwest of the United States.

Drought resistance in an interspecific backcross population of rice ( Oryza spp.) derived from the cross WAB56-104 ( O. sativa) × CG14 ( O. glaberrima)

The ability to identify drought-resistant lines in all seasons would accelerate variety introduction. A total of 202 backcross-inbred lines of rice were subjected to drought during the 2006 and 2007 dry seasons at AfricaRice in Benin. Two irrigation regimes were applied: fully irrigated to maturity and 21 days of drought from 45 days after sowing. Plants were harvested at maturity. Increased canopy temperature under drought as compared to fully irrigated condition was observed. Delays were observed in plant flowering and maturity, with drought susceptibility index reaching 26.8 for flowering. Plant leaves were greener (2.9% increase) under drought than when fully irrigated. Drought negatively affected tiller number, plant height, number of leaves, leaf width and grain yield (16.9%, 13.7%, 6.7%, 14.1% and 26.7% respective reductions). Highly significant ( P ≤ 0.01) correlations were observed between traits measured under fully irrigated and drought conditions ( r between 0.52 and 0.92), except for leaf greenness (SPAD), leaf width and canopy temperature ( r = 0.42 ns, −0.03 ns and −0.30**, respectively). The study identified canopy temperature, SPAD, plant height and leaf number as possible traits that best correlated with grain yield. The performance of these traits under drought was a function of the rice line.

Responses of canopy and soil climate in a six year free-air CO 2 enrichment study with spring crops

Besides increased growth, plants cultivated under elevated carbon dioxide (CO 2) show reduced transpiration and improved water use efficiency due to decreased stomatal conductances. While growth profits from the longer availability of soil water under CO 2 enrichment, increased canopy temperature may counteract these positive effects. Here we report on time series of soil temperatures and moistures from six years in which spring crops were cultivated in free-air CO 2 enrichment (Mini-FACE) experiments. Besides air and soil climate, temperature and relative humidity were determined in wheat canopies. Measurements rested on five replicates per treatment, representing a control (CON), an ambient air (AMB) and a FACE treatment. While the CON and AMB plots did not receive additional CO 2, concentrations were moderately elevated by 150 μl l −1 in the FACE plots. Plant growth differed among years due to the different climate and duration of individual experiments. Total biomass production was increased in the FACE treatments but significant effects were found only in one out of six years. In most of the years, soil temperatures tended to be reduced and soil moistures remained higher under elevated CO 2. Because the observed differences recurred during the growing season, we conclude that CO 2 enrichment was responsible for changes of the soil microclimate. At the same time vapour pressure deficit in the canopy significantly differed between the treatments for some days. While canopy heating due to CO 2 enrichment occurred in the early growing season these effects disappeared later suggesting that the stronger increase in leaf area index in the FACE treatments mitigated heating effects over time. The results support the supposed effects of CO 2 enrichment on the canopy climate and indicate a ‘microclimatic paradox’ with higher soil water availability due to the reduced transpiration and stronger canopy heating in FACE plots at least early in the season.

Measurement and modelling ozone fluxes over a cut and fertilized grassland

Abstract. During the GRAMINAE Integrated Experiment between 20 May and 15 June 2000, the ozone flux was measured by the eddy covariance method above intensively managed grassland in Braunschweig, northern Germany. Three different phases of vegetation were covered during the measuring campaign: tall grass canopy before cut (29 May 2000), short grass after cut, and re-growing vegetation after fertilization (5 June 2000). Results show that beside weather conditions, the agricultural activities significantly influenced the O3 fluxes. After the cut the daytime average of the deposition velocity (vd) decreased from 0.44 cm s−1 to 0.26 cm s−1 and increased again to 0.32 cm s−1 during the third period. Detailed model calculations were carried out to estimate deposition velocity and ozone flux. The model captures the general diurnal patter of deposition, with vd daytime values of 0.52, 0.24, and 0.35 cm s−1 in the first, second and third period, respectively. Thus the model predicts a stronger response to the cut than the measurements, which is nevertheless smaller than expected on the basis of change in leaf area. The results show that both cut and fertilization have complex impacts on fluxes. Reduction of vegetation by cutting decreased the stomatal flux initially greatly, but the stomatal flux recovered to 80% of its original value within a week. At the same time, the non-stomatal flux appears to have increased directly after the cut, which the model partially explains by an increase in the deposition to the soil. A missing sink after the cut may be the chemical interaction with biogenic volatile organic compounds released after the cut and exposed senescent plant parts, or the increase in soil NO emissions after fertilization. Increased canopy temperatures may also have promoted ozone destruction on leaf surfaces. These results demonstrate the importance of canopy structure and non-stomatal pathways on O3 fluxes.

Elevated CO2 significantly delays reproductive development of soybean under Free-Air Concentration Enrichment (FACE)

The effect of rising atmospheric concentration of carbon dioxide [CO(2)] on the reproductive development of soybean (Glycine max. Merr) has not been evaluated under open-air field conditions. Soybeans grown under Free-Air CO(2) Enrichment (FACE) exhibit warmer canopies due to decreased latent heat loss because of decreased stomatal conductance. According to development models based on accumulated thermal time, or growing degree days ( degrees Cd), increased canopy temperature should accelerate development. The SoyFACE research facility (Champaign, Illinois, USA) was used to test the hypothesis that development is accelerated in soybean when grown in [CO(2)] elevated to 548 micromol mol(-1). Canopy temperature was measured continuously with infrared thermometry, and used in turn to calculate GDD. Opposite to expectation, elevated [CO(2)], while increasing canopy temperature, delayed reproductive development by up to 3 days (P <0.05). Soybean grown in elevated [CO(2)] required approximately 49 degrees Cd more GDD (P <0.05) to complete full bloom stage (R2) and approximately 52 degrees Cd more GDD (P <0.05) to complete the beginning seed (R5) stage, but needed approximately 46 degrees Cd fewer GDD (P <0.05) to complete seed filling (R6). Soybeans grown in elevated [CO(2)] produced significantly more nodes (P <0.01) on the main stem than those grown under current [CO(2)]. This may explain the delay in completion of reproductive development and final maturation of the crop under elevated [CO(2)]. These results show a direct effect of rising [CO(2)] on plant development that will affect both projections of grain supply and may be significant to other species including those in natural communities.

Understorey management increases grape quality, yield and resistance to Botrytis cinerea

A bare ground control was compared with four mulch types (anaerobically and aerobically fermented marc (grape pressings), inter-row grass clippings and shredded office paper) which were applied in winter under 10-year-old Riesling vines in a 10-replicate randomized block design in New Zealand, over 2 consecutive years. Functional soil biological activity, as measured by Biolog Ecoplates and bait lamina probes, was increased 2–4 times in the two marc and paper treatments, compared with the control, an effect relating to the elevated soil moisture and reduced temperature fluctuations under these mulches. Nutrient levels and the C:N ratio were also affected in these treatments. The mulched paper lowered vine canopy density by up to 1.4 times that of the other treatments, an effect which probably led to elevated light penetration into the canopy and consequently increased canopy temperature and photosynthesis and lowered canopy humidity. These changes to soil and vine characteristics increased grape skin strength by up to 10% in the paper treatment and sugar concentrations by 1.2–1.4 °Brix in the two marc and paper treatments. The severity of Botrytis cinerea infections in the anaerobic marc, aerobic marc and paper treatments were reduced to 12, 3 and 2.2% of the control, respectively, in field assessments averaged over two consecutive harvests.