Regulation of Grain Yield by Photosynthesis in Maize Subjected to a Water Deficiency1
- H. G. McPherson and
- J. S. Boyer2
Since the physiological mechanisms responsible for yield losses under dry conditions are unknown, especially for grain crops, we attempted to identify them in maize (Zea mays L.) subjected" to a water deficiency during most of the grain filling period. The plants were grown in a controlled environment capable of providing yields comparable to the field. Grain yield, dry weights of shoots and roots, apparent photosynthesis, and leaf water potentials (Ψw) were determined. Shortly after tasseling, water was withheld from the soil of half the plants until Ψw had decreased to −18 to −20 bars, where Ψw remained until maturity. Apparent photosynthesis became virtually zero at these Ψw. However, grain yield was 47 to 69% of the control yield. At low Ψw, the grain developed partly at the expense of photosynthate accumulated prior to the desiccation period. Since grain development is dependent entirely on translocation in maize, this indicated that translocation continued despite the cessation of apparent photosynthesis. The parameter most closely related to yield was dry matter accumulated during the entire growing season rather than that accumulated during grain fill alone. We conclude that translocation it less inhibited than photosynthesis during drought, and that the total photosynthetic accumulation for the growing season controls yield during a drought that does not disrupt the flowering process.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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