De. Mccullough et al., INFLUENCE OF N-SUPPLY ON DEVELOPMENT AND DRY-MATTER ACCUMULATION OF AN OLD AND A NEW MAIZE HYBRID, Canadian Journal of Plant Science, 74(3), 1994, pp. 471-477
The response of an old and a new maize (Zea mays L.) hybrid to N suppl
y was evaluated under controlled-environment conditions. An old hybrid
(Pride 5) and a new hybrid (Pioneer 3902) were grown at three N level
s (15, 2.5, and 0.5 mM N), and development and dry matter accumulation
were measured at the 4-, 8-, and 12-leaf stage. Leaf chlorophyll was
monitored from the 8- to 12-leaf stage, and leaf photosynthesis, stoma
tal conductance, and leaf chlorophyll fluorescence were measured at th
e 12-leaf stage. Rate of dry matter accumulation decreased with declin
ing N supply. fn contrast, decreasing N supply progressively increased
the duration of the 4- to 8-leaf phase and the 8- to la-leaf phase. A
s a consequence, total dry matter at the 12-leaf stage did not differ
among N levels. The rate of leaf appearance of the old hybrid (Pride 5
) was proportionately more reduced under low N than that of the new hy
brid (Pioneer 3902). Similarly, the reduction in crop growth rate duri
ng the 8- to 12-leaf stage at the lowest N level was 46% for Pride 5 a
nd 24% for Pioneer 3902. Leaf chlorophyll content was higher for Pride
5 than for Pioneer 3902 at high N levels, but leaf chlorophyll conten
t declined significantly more rapidly in Pride 5 than in Pioneer 3902
when N stress increased. Leaf carbon assimilation rates were 4-27% hig
her for the new hybrid, with the largest differences occurring at low
N levels. Collectively, results of this study show that the old hybrid
(Pride 5) was more sensitive to N stress during early development tha
n the new hybrid (Pioneer 3902).