Showing papers by "Paul Hadley published in 1998"

Yield and partitioning in crops of contrasting cultivars of winter wheat in response to CO2 and temperature in field studies using temperature gradient tunnels

Abstract: Diverse cultivars of winter wheat (Triticum aestivum L.) were grown in the field in 1993/94 and 1994/95 at Reading UK in temperature gradient tunnels at normal atmospheric (c. 370) or elevated CO2 concentration (c. 700 μmol CO2 mol−1 air). In 1993/94, grain yield of cv. Avalon was insensitive to mean temperature (between 8·8 and 10·9°C), while elevated CO2 increased yield by 1·3 t ha−1 (12·6%). In all other cultivars, warming reduced grain yield and CO2 increased grain yield. In 1993/94, in cvs Galahad and Mercia the effects of CO2 and temperature on yield were additive. However, for cv. Hereward in both years and for cv. Soissons in 1994/95, there were negative interactions between the effects of CO2 and temperature on yield: the maximum benefit of doubling CO2 to grain yield, 4·5 and 2·7 t ha−1 (65 and 29%) respectively, occurred at cooler temperatures; there was no benefit from doubling CO2 (i.e. 0%) once the temperature had increased above the seasonal mean by 2·2–2·6°C in cv. Hereward and by 1·3°C in cv. Soissons. The beneficial effect of doubling CO2 on grain yield in cvs Galahad, Hereward, Mercia and Soissons was negated by an increase in mean seasonal temperature of only 0·7–2·0°C. Warming decreased root dry mass at anthesis in 1994/95 while it increased at elevated CO2 (49 and 186%, coolest and warmest regime, respectively). Carbon partitioned to roots declined progressively with warming, while at elevated CO2 there was an average of 56% increase in allocation to roots. The relative impacts of both CO2 and temperature were greater on root dry mass than on either grain yield or total above-ground biomass, while the effects on grain and biomass yield varied considerably between cultivars, suggesting that the impact of rising CO2 and temperature are likely to be dependent on cultivar.

Recovery of Photosynthesis after Environmental Stress in Soybean Grown under Elevated CO2

Abstract: Episodes of high temperature and water deficit may be more frequent under predicted future climates of warmer mean temperatures and elevated CO 2 . This study investigated whether the effects of an episode of high air temperature (HT, 43°C as a daily maximum), water deficit (WD), or both, had the same effect on the recovery of photosynthesis and on leaf water relations of soybean [Glycine max (L.) Merr., cv. Fiskeby V] grown at ambient CO 2 (aCO 2 ) or elevated CO 2 (eCO 2 ). An 8-d period of HT, WD, or both (HTWD) were imposed during early seed filling of soybean grown in glasshouses at either 362 or 685 μmol mol -1 CO 2 . Photosynthesis (Amax), stomatal conductance (g s ), and water relations were measured in fully expanded upper-canopy leaves. Immediately after the 8-d treatments at 60 d after sowing (DAS), Amax was reduced by 31, 48, and 64% in aCO 2 and by 28, 39, and 49% in eCO 2 under HT, WD, and HTWD, respectively, but no significant interactions were detected. At 60 DAS, g s was reduced by WD and HTWD in aCO 2 but not by HT while there was little change in g s by WD, HT, and HTWD under eCO 2 . Amar fully recovered under WD in eCO 2 by 66 DAS, while Amax remained reduced under WD in aCO 2 . Under each CO 2 concentration, almost full recovery of Amax occurred under HT by 75 DAS but under HTWD Amax never attained control values. At 60 DAS, early morning leaf water potential (Ψ) was lower after HT, WD, and HTWD and Amax was a negative function of Ψ, at each CO 2 concentration. The results suggest that full recovery of Amax from WD was only possible under eCO 2 , because at aCO 2 , immediately after the stress episode, Ψ was below the threshold for chloroplast damage.

The Development of Solid Spectral Filters for the Regulation of Plant Growth

Abstract: Phthalocyanine derivatives have been prepared and incorporated into polymer films for use as spectral filters for the modification of plant growth. The unusual absorption characteristics of phthalocyanines, notably the narrow absorption band in the visible region of the electromagnetic spectrum, allows the selective filtering of wavelengths necessary for excitation of either of the two isomeric phytochrome species. The resulting change in the photostationary state for the phytochrome is shown to have a marked effect on the growth characteristics of both chrysanthemums and antirrhinums. Chrysanthemums (short-day plants) grown under a far-red-absorbing film showed a reduction in height (∼14%) and internodal length compared to those grown under a red-absorbing film or a control with no absorption in the visible part of the spectrum; both leaf number and time to flowering were not affected by the presence of the spectral filter. For antirrhinums (long-day plants) both a reduction in height and a substantial increase in leaf area (70%) of the plants grown under the far-red-absorbing film were observed, although flowering was delayed. The potential of these filters as replacements for chemical plant growth regulators is discussed.

An appraisal of the use of reciprocal transfer experiments : assessing the stages of photoperiod sensitivity in chrysanthemum cv. snowdon (Chrysanthemum morifolium Ramat.)

Abstract: Reciprocal transfer experiments can be used to describe the stages of photoperiod sensitivity in day-length-sensitive plants. However, there are inconsistencies in the literature concerning the techniques used and, more importantly, the assumptions made when analysing such data sets. This paper appraises the use of reciprocal transfer experiments, with chrysanthemum as a model (short day) plant. Experiments showed little evidence to suggest that axillary meristems were incapable of responding to a floral stimulus when released from apical dominance by pinching (even though the apex appeared vegetative). Five short days given after pinching resulted in sufficient induction to initiate an inflorescence, although seven short days were required to commit a plant to flower with a leaf number similar to plants grown in continuous short days. Floral initiation was then visible at the apex after nine short days. Once the inflorescence had been initiated, long days delayed the early stages of flower development. The results are discussed with reference to reciprocal transfer experiments in general, and specifically in relation to problems that arise when the length of a 'juvenile' phase is confounded with the number of inductive cycles for flower commitment.

Canopy development and tillering of field-grown crops of two contrasting cultivars of winter wheat (Triticum aestivum) in response to CO2 and temperature

Abstract: Elevated CO 2 (691 cf. 371 μmol CO 2 mol -1 air) and warmer temperatures (over the range 1.0°C below to 1.6°C above ambient) increased light interception by crops of two contrasting cultivars (Hereward and Soissons) of winter wheat (Triticum aestivum L.) during winter growth in the field. The fractional interception of light by the canopy increased more rapidly initially in Soissons than in Hereward, but Hereward showed a much greater response to CO 2 (35% increase in Hereward but only 7% in Soissons) at 500°Cd after sowing. By terminal spikelet formation, in contrast, fractional interception was greater in Hereward than in Soissons, while the effect of CO 2 was the same in both cultivars (9%). Thus, although differences in the relative response of canopy development to CO 2 were detected between cultivars initially, differences were negligible during later development. The greater interception of light by the canopy in elevated CO 2 , at any one temperature, resulted from increased tillering. The number of tillers plant -1 at terminal spikelet was a linear function of main stem dry mass at this developmental stage but with a greater response in elevated CO 2 , viz 2.3 and 3.8 tillers g -1 main stem dry mass at 371 and 691 μmol CO 2 mol -1 air, respectively; these relations were unaffected by cultivar.

Postharvest sprouting of onion bulbs grown in different temperature and C02 environments in the UK

Abstract: SummaryThe effects of different mean growing season temperatures and C02 concentrations during bulb production on postharvest bulb sprouting in a common storage environment at Reading, UK, was examined in two cultivars of the Rijnsburger type of onion (Allium cepa L.). Crops were grown in the field in temperature gradient tunnels maintained at either 374 or 532 ppm C02. At crop maturity, cohorts of bulbs were harvested, transferred to a constant temperature room (at an average of 11.6°C) and the subsequent duration to sprouting recorded. The duration to the onset of sprouting (expressed as days in storage until the first bulb sprouted) was not affected by cultivar, mean growing season temperature or CO2 concentration, and was 165 d. The subsequent rate of sprouting (expressed as bulbs per day) was a positive linear function of mean growing season temperature, but no effects of CO2 or cultivar were detected. Mean rate of sprouting increased from an average of 0.036 bulbs per day at 12.3°C to 0.093 bulbs pe...

Inflorescence commitment and subsequent development differ in their responses to temperature and photoperiod in Osteospermum jucundum

Abstract: Although Osteospermum is a species which is known to require a period of chilling to induce flowering, the precise form of the relationships between temperature and photoperiod on the phases of flowering has not been quantified. This study aimed to investigate the effects of temperature and photoperiod on time to inflorescence commitment and on the rate of subsequent floral development in Osteospermum jucundum cv. Zulu. To assess how temperature and photoperiod affected the number of days needed for inflorescence commitment, plants were transferred from a range of photothermal environments to a non-inductive environment. The effect of temperature and photoperiod on subsequent inflorescence development was examined by transferring plants with initiated inflorescences to a range of photothermal environments. Inflorescence commitment occurred first in plants grown at a low average diurnal temperature (10.6°C), but no evidence was found to suggest that photoperiod affected the duration of this phase. Once initiated, high temperatures and long days hastened inflorescence development. The rate of progress to flowering from initiation increased linearly with photoperiod and temperature (up to an optimum of 23.5°C).