The Response of Root/Shoot Partitioning and Root Morphology to Light Reduction in Maize Genotypes

摘要

In maize (Zea mays L.), increasing sowing density in early maturing genotypes modifies the root/shoot ratio, which generates more frequent lodging. The effects of available light on root emergence and biomass were thus studied to investigate the genetic variation and its interaction with light in traits related to root lodging. Isolated plants of eight hybrids of contrasting maturities and lodging resistance were grown in pots in outdoor conditions, in full sunlight and under neutral shading which captured 61% of the incident light. Plants were harvested at four sampling dates for root and shoot dry matter determination and measurement of some major traits involved in the architecture of the adventitious root system. The partitioning of biomass between root and shoot varied among genotypes. Biomass allocation was significantly affected by light treatment, and the effects varied among genotypes. Some genotypes seemed better able to maintain biomass allocation to the shoot, without major effects on root morphology, than were others. At silking, the final number of emerged roots from the first six internodes was similar across treatments. On the other internodes, the number of roots was lower in the shaded treatment, but the reduction observed (between 8 and 26%) depended on genotype and earliness. In addition, some genotypes with similar root biomass clearly differed in root morphology (58% variation in the average weight of root primary axes under shading), indicating a variation in the structure of the root system. The relationships between root biomass and root number indicated significant interactions between genotypes and shading, with possible consequences on root lodging resistance in the field.