Different Sensitivity to Red-Far Red Ratio Perceived by Plants within Maize Canopy Determines the Early Established Plant-to-Plant Variability.

In maize crops with an even seedling emergence and a similar initial plant growth, plant-to-plant variability of aerial plant biomass is early established. The development of these hierarchies (i.e. dominant and dominated plant types) takes place well before the start of the critical period for kernel number determination, and has a pronounced effect on final kernel set. We have demonstrated that light environment (i.e. light intensity and light quality) early perceived by each plant resulted similar. Hence, the increased coefficient of variation (CV) of plant biomass early detected could be related to a different sensitivity among plants of a stand in response to a same stimulus (e.g. low red-far red ratio; R/FR). This plausible speculation arises from evidences of different sensitivity thresholds in plant hormone action among individuals of the same species. In this work, we have analyzed the existence of genotypic variability at a population level in the response of aerial plant biomass and root-shoot ratio (R/S) to R/FR. Individuals plants of two hybrids, previously described by their different plant-to-plant variability at field conditions (low and high plant-to-plant variability for the DK752 and DK765; respectively), were cultivated in pots with a randomized design, with ca. 30 replicates. Mirrors reflecting different R/FR (0.3; 0.6 and 1) were placed close to plants to simulate the presence of neighbors in the field. From the four ligulated leaf stage and onwards, the CV of aerial plant biomass was increased in response to low R/FR, with the DK765 yielding the high CV values. For this hybrid, distribution of aerial plant biomass (mean and standard deviation) was different among R/FR treatments, but those of R/S were similar. Contrarily, distribution of aerial plant biomass of DK752 was similar among the different R/FR treatments, but mean R/S decreased in response to low R/FR.