Maize seed and stem roots differ in response to neighbouring weeds

Abstract

Afifi M & Swanton C (2011). Maize seed and stem roots differ in response to neighbouring weeds. Weed Research51, 442–450.SummaryLight signals such as the red to far‐red ratio (R/FR) reflected from stem and leaf surfaces of neighbouring weeds can trigger a shade avoidance response in maize seedlings, resulting in a reduction in root biomass. In this experiment, we tested the hypothesis that maize roots originating from seed or stem tissue differed in their response to the R/FR ratio reflected from neighbouring weeds. Laboratory experiments were conducted under conditions of non‐limiting resources using perennial ryegrass as a model weed species. The above‐ground reduction in the R/FR ratio reflected from neighbouring weeds delayed the emergence of the root radicle and reduced the root relative growth rate from emergence until the fourth leaf tip stage of maize. At this leaf stage, no effect was observed on root length or surface area of the root radicle or seminal roots. In contrast, crown root length, diameter, surface area and number were all reduced, compared with crown roots grown under weed‐free conditions. These changes accounted for the observed reduction in total root biomass and volume. This is the first study to report that maize roots originating from seed or stem tissue differ in their response to the proximity of neighbouring weeds.