Root foraging and yield components underlying limited effects of Partial Root-zone Drying on oilseed rape, a crop with an indeterminate growth habit

Abstract

We report on two experiments with oilseed rape (Brassica napus L.) to test if partial root-zone drying techniques improve yield in a crop in which vegetative and reproductive growth overlap (indeterminate growth habit), and to investigate what plant morphological responses contribute to the yield that is realized. Deficit irrigation resulted in smaller plants with smaller yields but larger seeds compared to treatments with shallow groundwater (first experiment) and with fully watered conditions (second experiment). Different partial root-zone drying treatments (water supply patterns) under deficit irrigation, however, had little effect on plant growth and yield components (number of branches, branch lengths, number of pods, etc.). Our results suggest that partial root-zone drying doesn't work well with oilseed rape. Detailed measurements of soil water contents and root distribution indicate that roots were extremely plastic, effectively foraging for water, and these root responses may have overwhelmed physiological effects of partial root drying on the shoot. Furthermore, in crops with indeterminate growth with a short vegetative growth phase, partial root-zone drying may be ineffective in enhancing the major yield components. Further reasons for the lack of success are discussed.

Contrasting root behaviour in two grass species: a test of functionality in dynamic heterogeneous conditions

“…Patch dynamics, simulated by switching the patches halfway the experiment affected root distribution belowground significantly, but had no consequences for growth aboveground. Morphological responses, probably combined with rapid physiological changes seem to result in an apparent homeostasis aboveground, as also observed in other studies (Jansen et al 2006;Wang et al 2009). …”

Regulated deficit irrigation for crop production under drought stress. A review

“…For example, partial root-zone irrigation has no effect on root growth in oilseed rape (Wang et al 2009). The tap and lateral rooting nature of oilseed allows the plants to root vertically and horizontally in response to water availability in the soil.…”

Oilseed rape (Brassica napus) as a resource for farmland insect pollinators: quantifying floral traits in conventional varieties and breeding systems

“…For example, beekeepers have noted concern that varieties of OSR with high glucose nectars result in crystallized honey stores in the hive that cannot easily be exploited and used by bees in the colony and produce rapidly granulating, lower value honeys (Calder, 1986). The growth, development and function of floral characters may be resource limited in plants (Diggle, 1997;Galen, 1999); indeed, B. napus plants, which exhibit an indeterminate growth habit (Wang et al, 2009), adjust the number, but not the size, of flowers they produce according to planting density (Cresswell et al, 2001) and visitation by insects (Mesquida et al, 1988b). However, there may be additional, inherent constraints on the number and size of flowers due to variety or breeding system.…”