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Altering Source-Sink Relationships in Prolific Maize Hybrids: Consequences for Nitrogen Uptake and Remobilization

Dep. of Crop and Soil Sciences, Washington State Univ., Pullman, WA 99164-6420
Clemson Univ., Rt. 1 Box 531, Florence, SC 29501
Dep. of Genetics, North Carolina State Univ., Raleigh, NC 27695-7614

E. J. Kamprath and W. A. Jackson

Dep. of Soil Science, North Carolina State Univ., Raleigh, NC 27695-7619

^* Corresponding author (pan{at}wsuvm1.wsu.csc.edu).

Competition between grain and roots for photoassimilates may reduce post-anthesis N uptake (N_a), thereby limiting grain production of prolific maize (Zea mays L.). Field experiments were conducted to determine if this competition was minimized during the selection for new high-yielding prolific lines, providing a plausible physiological explanation for the improved grain yields. The dry matter (DM) and N accumulation and partitioning of two high-yielding and three low-yielding prolifics were compared under full pollination, limited pollination of the apical ear, or no pollination. The following year, one high-yielding and one low-yielding hybrid were grown at 34 000 and 45 000 plants ha^–1. Fully pollinated, high-yielding hybrids averaged 74% more grain weight (G_w) than low-yielding hybrids. A highyielding hybrid produced 71% more G_w under full pollination than with apical ears only pollinated, while limiting pollination had little effect on low-yielding hybrids. Greater contributions of subapical ears in new prolifics were attributed to greater kernel weight and number, which were positively correlated with post-anthesis DM accumulation (T_wa). The DM partitioning to vegetative tissue [T_wa – G_w] is indicator of photosynthate availability for plant functions during grain-filling. Greater [T_wa – G_w] occurred at the low plant density and with limited pollination, and this was positively related to N_a while inversely related to N_r. The high-yielding hybrids maintained T_wa and Na during multiple ear development. These results suggest N_a is regulated by the ear sink size relative to photosynthate supply.

Received for publication June 13, 1994.

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