Plant Spacing and Reflected Far‐Red Light Effects on Phytochrome‐Regulated Photosynthate Allocation in Corn Seedlings

Allocation of photosynthate among leaves, stems, and roots is critical in seedling establishment. Corn (Zea mays L.) seedlings were grown in different spacing patterns in a field and with different reflected far‐red (FR) to red (R) light ratios to test the effects of a modified FR/R ratio on photoassimilate allocation. Green leaves absorbed most of the R and reflected much of the FR. Therefore, close‐spaced plants received more reflected FR and higher FR/R ratios. Seedlings that received the higher FRJR ratios developed longer and narrower leaves, longer stems, and less massive roots. Stem elongation was an early response to increased FR/R ratio even though fight did not impinge directly on the stems, which were initially at or below the soil surface and covered by several layers of leaves. Row orientation did not significantly alter FR/R ratio or seedling morphology because corn leaves are not heliotropic and did not function as directional FR reflectors, as was observed for soybean [Glycine max (L.) Merr.] in a previous study. An increase in the FR/R ratio reflected up to seedlings from the soil surface also resulted in increased shoot size and shoot/root biomass ratio. Early morphological responses of corn seedlings to FR/R ratio in reflected light are relevant to seedling establishment and are not dependent on the cause of the altered ratio.