Wheat root length and not branching is altered in the presence of neighbours, including blackgrass.

The effect of neighbouring plants on crop root system architecture may directly interfere with water and nutrient acquisition, yet this important and interesting aspect of competition remains poorly understood. Here, the effect of the weed blackgrass (Alopecurus myosuroides Huds.) on wheat (Triticum aestivum L.) roots was tested, since a low density of this species (25 plants m-2) can lead to a 10% decrease in wheat yield and herbicide resistance is problematic. We used a simplified growth system based on gelled medium, to grow wheat alongside a neighbour, either another wheat plant, a blackgrass or Brachypodium dystachion individual (a model grass). A detailed analysis of wheat seminal root system architecture showed that the presence of a neighbour principally affected the root length, rather than number or diameter under a high nutrient regime. In particular, the length of first order lateral roots decreased significantly in the presence of blackgrass and Brachypodium. However, this effect was not noted when wheat plants were grown in low nutrient conditions. This suggests that wheat may be less sensitive to the presence of blackgrass when grown in low nutrient conditions. In addition, nutrient availability to the neighbour did not modulate the neighbour effect on wheat root architecture.This work was supported by European Union FP7 Marie Curie International Reintegration Grant, the Gatsby Charitable Foundation, the Broodbank Trust and the Newton Trust University of Cambridge

Seminal root characteristics of wheat grown in LN conditions, in the presence of a different neighbour with a LN or HN patch.

<p>The focal wheat plant was grown in low nutrient (LN) medium while its neighbours (w, wheat; bd, <i>Brachypodium</i>; bg, blackgrass) were grown in a patch of low (LN, black triangles) or high nutrient (HN, white squares) medium. (a) Seminal root length, individual root data (black filled circles) and treatment means (red diamonds). (b) Seminal root number mean ± se. (c) Cumulative length of seminals, mean ± se. (d) Lateral root density in the ramified region, individual root data (black filled circles) and treatment means (red diamonds). Data shown are from three separate experiments, <i>n</i> = 7–10 plants. Significance levels of main factors (N, neighbour, P, patch) and their interactions (N x P) are shown. Significant differences amongst neighbours are indicated below the x-axis,^<b>.</b> <i>p</i> < 0.1, * <i>p</i> < 0.05, <i>n</i>.<i>s</i>., not significant.</p

Experimental setup for investigating the effect of a neighbour on wheat RSA.

<p>(a) Wheat plant grown in homogeneous MS medium with 0.12% (w/v) phytagel alongside a blackgrass individual. (b) Focal wheat plants were grown under different treatments. (c) Wheat roots system extracted from the medium, laid flat on a transparent plate for scanning. (d) Inverted images with dark roots on a white background, and traced using SmartRoot [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0178176#pone.0178176.ref036" target="_blank">36</a>]. (e) Second experimental setup, with the focal (<i>i</i>.<i>e</i>., plant of interest) wheat grown in low nutrient (LN) medium and its neighbour (either w, wheat or bd, <i>Brachypodium</i> or bg, blackgrass) grown in a patch of LN or high nutrient (HN) medium.</p

Description of root system architecture parameters.

<p>Description of root system architecture parameters.</p

Total fresh weight and root to shoot ratio of wheat and neighbours grown in heterogeneous nutrient conditions.

<p>The focal wheat plant was grown in low nutrient (LN) medium while its neighbours (w, wheat; bd, <i>Brachypodium</i>; bg, blackgrass) were grown in a patch of low (LN, black triangles) or high nutrient (HN, white squares) medium. (a) FW and (b) root to shoot ratio of the focal wheat plant grown in different competitive conditions (w, wheat alone; w-w, wheat against wheat; w-bd, wheat against <i>Brachypodium</i>; w-bg, wheat against blackgrass). (c) FW and (d) root to shoot ratio of neighbours. Data shown as mean ± se, <i>n</i> = 7–10 plants from three separate experiments, except for root to shoot ratio of plant of interest where <i>n</i> = 5–10 from two separate experiments. Significance levels of main factors (N, neighbour, P, patch) and their interactions (N x P) are shown. Significant differences amongst neighbours are indicated below the x-axis,^<b>.</b> <i>p</i> < 0.1, * <i>p</i> < 0.05, ** <i>p</i> < 0.01, *** <i>p</i> < 0.001, <i>n</i>.<i>s</i>., not significant.</p

Characteristics of lateral roots of wheat grown in high nutrient conditions and in the presence of different neighbours (w, wheat alone; w-w, wheat against wheat; w-bd, wheat against <i>Brachypodium</i>; w-bg, wheat against blackgrass).

<p>(a) Mean length for first order laterals ± se. (b) Frequency distribution of first order lateral root length. (c) Mean length for second order laterals ± se. (d) Frequency distribution of second order lateral root length. (e) Mean cumulative length of first and second order laterals ± se. Data obtained from 11–12 plants per treatment in three separate experiments;^<b>.</b> <i>p</i> < 0.1, * <i>p</i> < 0.05, ** <i>p</i> < 0.01.</p

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved