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Covering Middle Leaves and Ears Reveals Differential Regulatory Roles of Vegetative and Reproductive Organs in Root Growth and Nitrogen Uptake in Maize


This article in CS

  1. Vol. 51 No. 1, p. 265-272
    Received: Mar 29, 2010

    * Corresponding author(s): lichj@cau.edu.cn
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  1. Huifeng Yana,
  2. Aixin Shangb,
  3. Yunfeng Penga,
  4. Peng Yua and
  5. Chunjian Li *a
  1. a The Key Lab. of Plant Nutrition, Ministry of Agriculture, Dep. of Plant Nutrition, China Agricultural Univ., Beijing 100193, China
    b Laiwu Vocational and Technical College, Laiwu 271100, China


Root growth and mineral nutrient uptake are two closely related physiological processes regulated by shoot growth and development. To date, little attention has been paid to the effects of leaves and ears on root growth and mineral nutrient uptake. To unravel this physiological puzzle, we treated inbred and hybrid maize (Zea mays L.) plants by shading middle leaves or covering ears from silking onward in two growing seasons under field conditions. We found that shading middle leaves reduced photosynthetic capacity and assimilate allocation to roots and, thus, decreased root growth. However, there was relatively less reduction in total N content of whole plants than that of the root dry wt. of all genotypes, implying that roots of these plants had a higher N uptake rate per unit root dry wt. than the control. In contrast, covering ears suppressed grain development, allowing more assimilate relocation into roots to promote root growth. On the other hand, removal of substantial sink demand (grain filling) directly caused decrease in total N uptake, and the decrease in N content in the shoot was significant in four out of seven genotypes, although the cob and husks could partially substitute for developing grains as a nutrient sink to influence nutrient (N) uptake by roots. Our results suggested that root growth and nutrient uptake (N in this study) were nonsynchronous due to differential regulation primarily by assimilate allocation and shoot demand, respectively.

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