Deep soil exploration vs. topsoil exploitation: distinctive rooting strategies between wheat landraces and wild relatives

Aims Diversity of root systems among genetic resources can contribute to optimize water and nutrient uptake. Topsoil exploitation vs. deep soil exploration represent two contrasting ideotypes in relation to resource use. Our study reveals how rooting patterns changed between wheat wild progenitors and landraces in regard to these ideotypes. Methods Root (partitioning, morphology, distribution, elongation, anatomy) and shoot traits (dry-matter, leaf area, assimilation) of durum landraces, wild emmer and wild einkorn from Iran, Syria, Turkey and Lebanon were phenotyped using the GrowScreen-Rhizo platform. Distinctive rooting patterns were identified via principal component analysis and relations with collection site characteristics analyzed. Results Shoot trait differentiation was strongly driven by seed weight, leading to superior early vigor of landraces. Wild progenitors formed superficial root systems with a higher contribution of lateral and early-emerging nodal axes to total root length. Durum landraces had a root system dominated by seminal axes allocated evenly over depth. Xylem anatomy was the trait most affected by the environmental influence of the collection site. Conclusions The durum landrace root system approximated a deep soil exploration ideotype which would optimize subsoil water uptake, while monococcum-type wild einkorn was most similar to a topsoil exploiting strategy with potential competitive advantages for subsistence in natural vegetation.

Conifer Root Proliferation after 20 Years of Soil Compaction

Soil compaction is known to limit plant growth by reducing soil macroporosity and restricting gas, water, and root movement. Recent evidence from study sites across the United States and Canada, however, suggests that tree growth is not universally affected by soil compaction from forest harvesting practices. Our observational study examined rooting patterns in mixed conifer plantations in the central Sierra Nevada of California to determine whether tree roots use continuous pathways or channels to overcome the physical restrictions of compacted soil. Replicate plots were established 20–25 years earlier to compare compacted and uncompacted treatments after clearcut harvesting. Fine and lateral root counts were taken at multiple depths in soil trenches. Rooting was extensive in compacted plots despite consistently high soil strength values (~3 MPa). No differences in rooting patterns or in fine or lateral root numbers were detected between compaction treatments. The results indicated long-term tolerance by conifer roots to soil compaction without clear use of preferential channels or uncompacted zones.