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This article in AJ

  1. Vol. 90 No. 3, p. 324-328
    Received: Feb 10, 1997

    * Corresponding author(s): mikeb@mv.pi.csiro.au
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Temperature and Sowing Date Affect the Linear Increase of Sunflower Harvest Index

  1. Michael P. Bange ,
  2. Graeme L. Hammer and
  3. Kenneth G. Rickert
  1. C SIRO Div. of Plant Industry, Cotton Res. Unit, Locked Bag 59, Narrabri, NSW 2390, Australia
    Q ueensland Dep. of Primary Industries, Agricultural Production Systems Research Unit (APSRU), 203 Tor St., P.O. Box 102, Toowoomba, QLD 4350, Austrilia
    P lant Production Dep., Univ. of Queensland Gatton College, Australia



The linearity of daily linear harvest index (HI) increase can provide a simple means to predict grain growth and yield in field crops. However, the stability of the rate of increase across genotypes and environments is uncertain. Data from three field experiments were collated to investigate the phase of linear HI increase of sunflower (Helianthus annuus L.) across environments by changing genotypes, sowing time, N level, and solar irradiation level. Linear increase in HI was similar among different genotypes, N levels, and radiation treatments (mean 0.0125 d−1), but significant differences occurred between sowings. The linear increase in HI was not stable at very low temperatures (down to 9°C) during grain filling, due to possible limitations to biomass accumulation and translocation (mean 0.0091 d−1). Using the linear increase in HI to predict grain yield requires predictions of the duration from anthesis to the onset of linear HI increase (lag phase) and the cessation of linear HI increase. These studies showed that the lag phase differed, and the linear HI increase ceased when 91% of the anthesis to physiological maturity period had been completed.

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