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Number of kernels in wheat crops and the influence of solar radiation and temperature

  • R. A. Fischer (a1)

The number of kernels per m2 (K) in well managed and watered wheat crops was studied using results of experiments in Mexico and Australia in which short spring wheat cultivars were subjected to independent variation in radiation, largely via artificial shading, and in temperature. Also crops subjected to differences in weather (year), sowing date and location within Mexico, revealed responses to the natural and simultaneous variation which occurs in radiation and temperature. Responses in K were interpreted in terms of spike dry weight at anthesis (g/m2) and number of kernels per unit of spike weight.

K was linearly and most closely related to incident solar radiation in the 30 days or so preceding anthesis, herein termed the spike growth period; for the cultivar Yecora 70 with full ground cover the slope was 19 kernels/MJ. This response seemed largely due to a linear response of crop growth rate to intercepted solar radiation. The proportion of dry weight increase partitioned to the spike increased somewhat with reduced radiation. Also increasing temperature in the range 14–22 °C during this period reduced K (slope approximately 4% per CC at 15 °C). The cause appeared to be lower spike dry weight due to accelerated development. The number of kernels per unit spike weight at anthesis was little affected by radiation or temperature, and averaged 78±2/g for the cultivar Yecora 70.

With natural variation in radiation and temperature, K was closely and linearly correlated with the ratio of mean daily incident or intercepted radiation to mean temperature above 4·5 °C in the 30 days preceding anthesis. As this ratio, termed the photothermal quotient, increased from 0·5 to 2·0 MJ/m2/day/degree, K increased from 70 to 196 × 102/m2. These responses of K to weather, sowing date and location were closely associated with variation in spike dry weight.

It was concluded that the ratio of solar radiation to temperature could be very useful for estimating K in wheat crop models. Also the analysis of K determination in terms of spike dry weight appeared promising, and suggests that wheat physiologists should place greater emphasis on the growth period immediately before anthesis.

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Angus, J. F., Mackenzie, D. H., Morton, R. & Schafer, C. A. (1981). Phasic development in field crops. II. Thermal and photoperiodic responses of spring wheat. Field Crops Research 4, 269283.
Austin, R. B. & Jones, H. G. (1976). The physiology of wheat. Plant Breeding Institute. Annual Report 1975. pp. 2073.
Borojevic, S. & Williams, W. A. (1982). Genotype × environment interactions for leaf area parameters and yield components and their effects on wheat yields. Crop Science 22, 10201025.
Buck, S. F. (1961). The use of rainfall, temperature, and actual transpiration in some crop-weather investigations. Journal of Agricultural Science, Cambridge 57, 355365.
Cackett, K. E. & Wall, P. C. (1971). The effect of altitude and season length on the growth and yield of wheat (Triticum aestivum) in Rhodesia. Rhodesian Journal of Agricultural Research 9, 107120.
Desjardins, R. L. & Ouellet, C. E. (1980). Determination of the importance of various phases of wheat growth on final yield. Agricultural Meteorology 22, 129136.
Evans, L. T. (1978). The influence of irradiance before and after anthesis on grain yield and its components in microcrops of wheat grown in a constant daylength and temperature regime. Field Crops Research 1, 519.
Fischer, R. A. (1975). Yield potential of dwarf spring wheat and the effect of shading. Crop Science 15, 607613.
Fischer, R. A. (1983). Growth and yield of wheat. In Proceedings Symposium on Potential Productivity of Field Crops under Different Environments, International Rice Research Institute, Los Baños, Philippines, September 1980, pp. 129154.
Fischer, R. A. & Laing, D. R. (1976). Yield potential in a dwarf spring wheat and response to crop thinning. Journal of Agricultural Science, Cambridge 87, 113122.
Fischer, R. A. & Maurer, R. (1976). Crop temperature modification and yield potential in a dwarf spring wheat. Crop Science 16, 855859.
Fischer, R. A. & Stockman, Y. M. (1980). Kernel number–per spike in wheat (Triticum aestivum L.).Responses to preanthesis shading. Australian Journal of Plant Physiology 7, 169180.
Friend, D. J. C., Fisher, J. E. & Helson, V. A. (1963). The effect of light intensity and temperature on floral initiation and inflorescence development in Marquis wheat. Canadian Journal of Botany 41, 16631674.
Gallagher, J. N. (1979). Ear development: processes and prospects. In Crop Physiology and Cereal Breeding. (Proceedings of Eucarpia Workshop, Wageningen, 1978) (ed. Spiertz, J. H. J. and Kramer, Th.), pp. 39.
Gallagher, J. N. & Biscoe, P. V. (1978). Radiation absorption, growth and yield of cereals. Journal of Agricultural Science, Cambridge 91, 4760.
Krenzer, E. G. Jr & Moss, D. N. (1975). Carbon dioxide enrichment effects upon yield and yield components in wheat. Crop Science 15, 7174.
McCree, K. J. (1974). Equations for the rate of dark respiration of white clover and grain sorghum, as functions of dry weight, photosynthetic rate, and temperature. Crop Science 14, 509514.
Michaels, P. J. (1981). The climatic sensitivity of ‘Green Revolution’ wheat culture in Sonora, Mexico. Environmental Conservation 8, 307311.
Midmore, D. M., Cartwright, P. M. & Fischer, R. A. (1982). Wheat in tropical environments. I. Phasic development and spike size. Field Crops Research 5, 185200.
Midmore, D. M., Cartwright, P. M. & Fischer, R. A. (1984). Wheat in tropical environments. II. Crop growth and grain yield. Field Crops Research 8, 207227.
Nix, H. A. (1975). The Australian climate and its effects on grain yield and quality. In Australian Field Crops. Vol. I. Wheat and Other Temperate Cereals (ed. Lazenby, A. and Matheson, E. M.), pp. 183226. Sydney: Angus and Robertson.
Nix, H. A. (1976). Climate and crop productivity in Australia. In Climate and Rice (ed. Yoshida, S.). International Rice Research Institute, Los Baños, The Philippines, pp. 495507.
Pendleton, J. W. & Weibel, R. O. (1965). Shading studies on winter wheat. Agronomy Journal 57, 592593.
Peters, D. B., Pendleton, J. W., Hageman, R. H. & Brown, C. M. (1971). Effect of night air temperature on grain yield of corn, wheat and soybeans. Agronomy Journal 63, 809.
Puckridge, D. W. & Donald, C. M. (1967). Competition among wheat plants sown at a wide range of densities. Australian Journal of Agricultural Research 18, 193211.
Rahman, M. S. (1977). Determination of spikelet number in wheat. Ph.D. thesis, University of Melbourne, 122 pp.
Rawson, H. M. (1970). Spikelet number, its control and relation to yield per ear in wheat. Australian Journal of Biological Sciences 23, 115.
Rawson, H. M. & Bagga, A. K. (1979). Influence of temperature between floral initiation and flag leaf emergence on grain number in wheat. Australian Journal of Plant Physiology 6, 391400.
Richardson, C. W. (1982). Dependence structure of daily temperature and solar radiation. Transactions of the American Society of Agricultural Engineers 25, 735739.
Robertson, G. W. (1968). A biometeorological time scale for a cereal crop involving day and night temperatures and photoperiod. International Journal of Biometeorology 12, 191223.
Saini, H. S. & Aspinall, D. (1982). Sterility in wheat (Triticum aestivum L.) induced by water deficit or high temperature: possible mediation by abscisic acid. Australian Journal of Plant Physiology 9, 529537.
Single, W. V. & Marcellos, H. (1974). Studies of frost injury to wheat. IV. Freezing of ears after emergence from the leaf sheath. Australian Journal of Agricultural Research 25, 679686.
Smika, D. E. & Shawcroft, R. W. (1980). Preliminary study using a wind tunnel to determine the effect of hot wind on a wheat crop. Field Crops Research 3, 129135.
Sofield, I., Evans, L. T., Cook, M. G. & Wardlaw, I. F. (1977). Factors influencing the rate and duration of grain filling in wheat. Australian Journal of Plant Physiology 4, 785797.
Stockman, Y. M., Fischer, R. A. & Brittain, E. G. (1983). Assimilate supply and floret development within the wheat spike. Australian Journal of Plant Physiology 10, 585594.
Takeda, G. (1978). Photosynthesis and dry matter reproduction system in winter cereals. I. Photosynthetic function. Bulletin of the National Institute of Agricultural Sciences Series D. 29, pp. 165.
Thompson, L. M. (1975). Weather variability, climatic change and grain production. Science 188, 525541.
Thorne, G. N. (1974). Physiology of grain yield of wheat and barley. Report Rothamsted Experimental Station for 1973, Part 2, pp. 525.
Wall, P. C. (1979). An analysis of factors limiting grain number and yield of spring wheat in a low latitude environment. Ph.D. thesis, University of Reading.
Wardlaw, I. F. (1970). The effect of temperature on kernel development in cereals. Australian Journal of Agricultural Research 29, 205223.
Warrington, I. J., Dunstone, R. L. & Green, L. M. (1977). Temperature effects at three developmental stages on the yield of the wheat ear. Australian Journal of Agricultural Research 28, 1127.
Welbank, P. J., Witts, K. J. & Thorne, G. N. (1968). Effect of radiation and temperature on efficiency of cereal leaves during grain growth. Annals of Botany 32, 7995.
Willey, R. W. & Holliday, R. (1971). Plant population, shading and thinning studies in wheat. Journal of Agricultural Science, Cambridge 77, 453461.
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