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GRAIN FILLING OF DURUM WHEAT THROUGH ASSIMILATE REMOBILISATION UNDER SEMI-ARID CONDITIONS
- K. LATIRI, J. P. LHOMME, D. W. LAWLOR
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- Journal:
- Experimental Agriculture / Volume 49 / Issue 2 / April 2013
- Published online by Cambridge University Press:
- 21 December 2012, pp. 197-211
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In a context of understanding the physiological mechanisms and cultivar traits which could improve durum wheat (Triticum durum) yield in water limited conditions, the paper focuses on the contribution of stored assimilates to grain growth and yield. A conceptual model describing the different fluxes of assimilate during the grain filling period is used together with a dataset from field experiments made in northern Tunisia during two growing seasons and under different conditions of water and nitrogen supply. Three types of behaviour have been encountered in relation to the balance between demand for assimilate and supply. Remobilisation of stored assimilates provides a buffer enabling grain growth to be maintained. Conditions at anthesis play an important role in determining the type of fluxes of assimilates. Grain number also plays a major role in short- or long-term remobilisation and grain number per ear increases short-term remobilisation. In rain-fed conditions, short-term remobilisation allows faster grain growth.
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- The Cambridge Dictionary of Christianity
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- 05 August 2012
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- 20 September 2010, pp xi-xliv
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Growth of spring barley under drought: crop development, photosynthesis, dry-matter accumulation and nutrient content
- D. W. Lawlor, W. Day, A. E. Johnston, B. J. Legg, K. J. Parkinson
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- The Journal of Agricultural Science / Volume 96 / Issue 1 / February 1981
- Published online by Cambridge University Press:
- 27 March 2009, pp. 167-186
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The effects of water deficit on growth of spring barley were analysed under five irrigation treatments. One crop was irrigated at weekly intervals from emergence throughout the growing season, and one was not irrigated at all after emergence. Soil water deficits in the other treatments were allowed to develop early, intermediate or late in the crop's development.
Weekly irrigation produced a crop with a large leaf area index (maximum value 4) and maintained green leaf and awns throughout the grain-filling period. Early drought decreased leaf area index (maximum value 2) by slowing expansion of main-stem leaves and decreasing the number and growth of tiller leaves. Leaf senescence was also increased with drought. Drought late in the development of ears and leaves and during the grain-filling period caused leaves and awns to senesce so that the total photosynthetic areas decreased faster than with irrigation. Photosynthetic rate per unit leaf area was little affected by drought so total dry-matter production was most affected by differences in leaf area.
Early drought gave fewer tillers (550/m2) and fewer grains per ear (18) than did irrigation (760 tillers/m2 and 21 grains per ear). Late irrigation after drought increased the number of grains per ear slightly but not the number of ears/m2. Thus at the start of the grain-filling period crops which had suffered drought early had fewer grains than irrigated (9·5 and 18·8 × 103/m2 respectively) or crops which suffered drought later in development (14 × 103/m2).
During the first 2 weeks of filling, grains grew at almost the same rate in all treatments. Current assimilate supply was probably insufficient to provide this growth in crops which had suffered drought, and stem reserves were mobilized, as shown by the decrease in stem mass during the period. Grains filled for 8 days longer with irrigation and were heavier (36–38 mg) than without irrigation (29–30 mg). Drought throughout the grainfilling period after irrigation earlier in the season resulted in the smallest grains (29 mg).
Grain yield depended on the number of ears, the number of grains per ear and mass per grain. Early drought decreased tillering and tiller ear production and the number of grains that filled in each ear. Late drought affected grain size via the effects on photosynthetic surface area.
Drought decreased the concentrations of phosphorus, potassium and magnesium in the dry matter of crops, and irrigation after drought increased them. Concentration of nitrogen was little affected by treatment. Possible mechanisms by which water deficits and nutrient supply affect crop growth and yield are discussed.
A drought experiment using mobile shelters: the effect of drought on barley yield, water use and nutrient uptake
- W. Day, B. J. Legg, B. K. French, A. E. Johnston, D. W. Lawlor, W. De C. Jeffers
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- The Journal of Agricultural Science / Volume 91 / Issue 3 / December 1978
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- 27 March 2009, pp. 599-623
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Automatic mobile shelters were used to keep rain off a barley crop in a drought experiment. The treatments ranged from no water during the growing season to regular weekly irrigation. This paper reports the effect of drought on the harvest yield and its components, on water use and nutrient uptake.
Drought caused large decreases in yield, and affected each component of the grain yield. The magnitude of each component varied by up to 25% between treatments, and much of the variation could be accounted for by linear regression against the mean soil water deficit in one of three periods. For the number of grains per ear, the relevant period included tillering and ear formation; for the number of ears per unit ground area, the period included stem extension and tiller death; for grain mass, the period included grain filling.
The harvest yields were linearly related to water use, with no indication of a critical period of drought sensitivity. The relation of grain yield to the maximum potential soil water deficit did show that a prolonged early drought had an exceptionally large effect on both yield and water use.
Two unsheltered irrigation experiments, also on barley, were made in the same year on a nearby site. The effects of drought on yield in these experiments were in good agreement with the effects observed on the mobile shelter site.
When fully irrigated, the small plots under the mobile shelters used water 11% faster than larger areas of crop, because of advection. The maximum depth from which water was extracted was unaffected by the drought treatment. When 50% of the available soil water had been used the uptake rate decreased, but the maximum depth of uptake continued to increase.
Measurements of crop nutrients at harvest showed that nitrogen uptake was large, because of site history, and that phosphate uptake was decreased by drought to such an extent that phosphate shortage may have limited yield.
The effects of sowing date and other factors on growth, yield and nitrogen uptake, and on the incidence of pests and diseases, of winter barley at rothamsted from 1981 to 1983
- F. V. Widdowson, R. J. Darby, A. M. Dewar, J. P. Jenkyn, B. R. Kerry, D. W. Lawlor, R. T. Plumb, G. J. S. Ross, G. C. Scott, A. D. Todd, D. W. Wood
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- The Journal of Agricultural Science / Volume 106 / Issue 3 / June 1986
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- 27 March 2009, pp. 551-574
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Multifactorial experiments on winter barley cv. Igri grown after potatoes were made from 1981 to 1983 on silty clay loam soils at Rothamsted. All tested combinations of seven factors, each at two levels: with and without autumn pesticide (aldicarb), two sowing dates (September or October), with and without a fungicidal seed treatment (‘Baytan’), with and without spring and summer fungicides, two amounts of nitrogen, two times of applying nitrogen and with and without a growth regulator (‘Terpal’). Growth, development, yield, nitrogen uptake, pests and diseases were monitored. Sowing in September, fungicide sprays in spring and summer, and the growth regulator had the largest mean benefits on grain yield (+0·80, +0·56 and +0·34 t/ha respectively). Some factors interacted with sowing date; thus aldicarb, the fungicide sprays in spring and summer and the later timing of N all increased yield more on the September-than on the October-sown barley. The larger yields on the September-sown plots were associated with more ears/m2 (978 v. 744) and, in spite of fewer grains per ear (17·8 v. 20·1), more grains per m2 (17·6 v. 14·7 × 103), but lighter grains (39·2 v. 42·3 mg). The largest yields each year (ca. 8.0–8.5 t/ha) were obtained from September-sown barley fully protected from pests and from pathogens in spring and summer and given N in April rather than in March.
The aphid vectors of barley yellow dwarf virus were sufficiently common and infective in two of the three autumns to infect the September-sown barley sufficiently that their control by aldicar b enhanced yield. Nematodes, slugs and dipterous stem borers were not numerous enough to be damaging in any year. Mildew in autumn was controlled by the seed treatment, but effects on yield were inconsistent. Mildew in spring and summer was more abundant on the October-than on the September-sown barley; it was controlled by fungicide sprays, which increased yield significantly each year. Leaf blotch was more abundant on the September-sown barley.
The effects of drought on barley: soil and plant water relations
- W. Day, D. W. Lawlor, B. J. Legg
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- The Journal of Agricultural Science / Volume 96 / Issue 1 / February 1981
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- 27 March 2009, pp. 61-77
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In a field experiment on the effects of drought on spring barley, the crop was protected from rainfall by automatic rain shelters; a range of drought treatments was achieved by irrigating various plots according to a predetermined schedule. There were 12 treatments which ranged from no irrigation to full irrigation from emergence to harvest; results from seven treatments are discussed in this paper.
The rate of water uptake was determined for four soil horizons centred at 0·15, 0·50, 0·80 and 1·10 m. For all treatments, the rate of uptake in each horizon decreased as the soil dried, and although there were large differences in root density between horizons, maximum rates of uptake were similar in all horizons down to 0·80 m. Treatment effects showed that prolonged drought decreased the rate of uptake from the 0·80 and 1·10 m horizons: root density at and below 1·0 m probably differed between treatments.
Differences between treatments in leaf water potential (ψL) and osmotic potential (πL) were small, and there was no evidence that osmotic adjustment contributed to the drought response of this crop. Near anthesis, pre-dawn ψL was near zero for irrigated treatments and between – 3 and – 5 bar for unirrigated. During the day, ψL decreased to a minimum of – 15 to – 18 bar for irrigated plants, and was generally 3 bar lower for unirrigated. For all treatments, ψL was greater than π for the major part of the day, i.e. positive turgor was maintained; however, turgor was usually greater for irrigated than for unirrigated plants. The relationship, for leaf 8, between ψL and transpiration flux density was markedly non-linear, and was of a similar form for irrigated and vinirrigated plants. As the form of this relationship was independent of treatment, the non-linearity could not have been caused by variations in soil water potential through the profile.
Stomatal resistance differed markedly between treatments. A detailed analysis is presented, relating measured resistance for leaf 8 to ψL and to environmental variables: irradiance (I), water vapour pressure deficit (vpd), and temperature (T). The analysis showed no significant dependence of resistance on ψL or T, but marked dependence on I and vpd; a mathematical model combining a hyperbolic response function for I and an exponential function for vpd fitted the data well. The responses of abaxial and adaxial surface resistances to vpd were similar, but their light responses differed because of their different exposures to incident irradiance.
The effects of drought on barley growth: models and measurements showing the relative importance of leaf area and photosynthetic rate
- B. J. Legg, W. Day, D. W. Lawlor, K. J. Parkinson
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- The Journal of Agricultural Science / Volume 92 / Issue 3 / June 1979
- Published online by Cambridge University Press:
- 27 March 2009, pp. 703-716
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In a field experiment on the effects of drought on spring barley the crop was protected from rain by automatic rain shelters. Various plots received irrigation at different times to give a range of drought treatments from full irrigation to no irrigation between emergence and harvest. The foliage area, light interception, stomatal resistance and leaf photosynthesis rate of five treatments were measured throughout the growing season, and a mathematical model has related the computed whole canopy photosynthesis to the measured total dry-matter yields at harvest. Hence, it was possible to estimate tha independent influences of drought on radiation interception, efficiency of use of intercepted radiation, and respiration. The analysis shows that for all treatments the decrease of intercepted radiation was the major factor in reducing yield, and it accounted for a loss of 30–40% for treatments that were stressed from the beginning of the season, and of 10–20% for treatments that were stressed after mid-May. Stomatal closure caused a reduction of up to 11% in daily photosynthesis, and the maximum effect was on plants that acquired a large leaf area before being stressed. However, the effect of stomatal closure integrated over the whole season was only 6% or less. Our measurements of internal resistance to carbon dioxide transfer were not precise enough to show significant differences between treatments; but increases of internal resistance, caused by stress, may have contributed to loss of yield.
Redesigning Rice Photosynthesis to Increase Yield (Studies in Plant Science, 7). Proceedings of the workshop on the Quest to Reduce Hunger: Redesigning Rice Photosynthesis, held in Los Banos, Philippines, 30 November to 3 December 1999. Edited by J. E. SHEEHY, P. L. MITCHELL & B. HARDY. vi+293 pp. Amsterdam: Elsevier Science B.V./International Rice Research Institute, Los Banos, Philippines (2000). Eur 129.33 (US$149) (hardback). ISBN 0 444 50610 1.
- D. W. LAWLOR
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- Journal:
- The Journal of Agricultural Science / Volume 139 / Issue 2 / September 2002
- Published online by Cambridge University Press:
- 27 January 2003, pp. 227-230
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