Wl. Pan et al., ALTERING SOURCE-SINK RELATIONSHIPS IN PROLIFIC MAIZE HYBRIDS - CONSEQUENCES FOR NITROGEN UPTAKE AND REMOBILIZATION, Crop science, 35(3), 1995, pp. 836-845
Competition between grain and roots for photoassimilates may reduce po
st-anthesis N uptake (N-a), thereby limiting grain production of proli
fic maize (Zea mays L.). Field experiments were conducted to determine
if this competition was minimized during the selection for new high-y
ielding prolific lines, providing a plausible physiological explanatio
n for the improved grain yields. The dry matter (DM) and N accumulatio
n and partitioning of two high-yielding and three low-yielding prolifi
cs were compared under full pollination, limited pollination of the ap
ical 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 weig
ht (G(w)) than low-yielding hybrids. A high-yielding hybrid produced 7
1% more G(w) under full pollination than with apical ears only pollina
ted, while limiting pollination had little effect on low-yielding hybr
ids. Greater contributions of subapical ears in new prolifics were att
ributed to greater kernel weight and number, which were positively cor
related with post-anthesis DM accumulation (T-wa). The DM partitioning
to vegetative tissue [T-wa - G(w)] is an indicator of photosynthate a
vailability 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 N-a during multiple ea
r development. These results suggest N-a is regulated by the ear sink
size relative to photosynthate supply.