Control of Kernel Weight in Maize by Post-Flowering Source-Sink Ratio and Kernel Water Status

BORRÁS, L.; WESTGATE, M.E.; OTEGUI, M.E.

ANNALS OF BOTANY

Oxford University Press

Año: 2003 vol. 91 p. 857 - 867

0305-7364

The maize (Zea mays L.) kernel undergoes large changes in water content during its development. Whether such changes might regulate the pattern of kernel development or are simply a consequence of it has not been established because other factors, such as assimilate supply, also can limit the rate and duration of kernel growth. This study was conducted to determine how kernel water status and assimilate supply might interact to control the pattern of kernel growth in maize. Two commercial hybrids were sown at three contrasting stand densities (1, 8 and 18 pl m-2), and kernel numbers were restricted by hand pollination to control the post-flowering source-sink ratio within each stand density. Kernel development and water status [water content, water potential (øw), osmotic potential (øs), turgor] were monitored throughout the entire grain-filling period. Source-sink ratio treatments altered final KW in both genotypes due to alterations in kernel growth rate (r2: 0.91; p<0.001) and not the duration of grain-filling. Variation in final KW in response to altered source-sink ratio was closely correlated with maximum kernel water content (r2: 0.95; p<0.001) achieved during rapid dry matter accumulation. Variation in KW, however, was not reflected in other kernel water status parameters, which remained fairly stable in response  to assimilate availability treatments. These results indicate that maximum water content is a good indicator of kernel sink capacity in maize. Other kernel water status parameters may determine the duration of grain-filling, but have no discernible impact on kernel growth rate.