Ethylene is enough to indicate soil compaction
It is difficult to drive a shovel through compacted soil, and it seems that plant roots have the same problem when growing in compacted soil. Pandey et al. found, however, that the problem is not a physical resistance, but rather the inhibition of growth by means of a signaling pathway. The volatile plant hormone ethylene is distributed through aerated soils, but compacted soils reduce such distribution and increase the concentration of ethylene near root tissues. The cellular signal waterfall caused by too much ethylene stops root growth. Therefore, gas diffusion serves as a reading of soil compaction for plant roots growing in search of productive nutrition.
Science, this issue p. 276
Abstract
Soil compaction is a major challenge for modern agriculture. Compaction is thought to reduce root growth by limiting the ability of roots to penetrate harder soil. We report that root growth in compacted soil is actively suppressed by the volatile hormone ethylene. We found the mutant Arabidopsis and rice roots that were not sensitive to ethylene penetrated compaction soil more effectively than wild-type roots. Our results suggest that soil compaction reduces gas diffusion through a reduction in air-filled pores, which causes ethylene to accumulate in root tissues and cause growth-limiting hormone responses. We suggest that ethylene serves as an early warning signal for roots to avoid compacted soils, which would be relevant for research on the cultivation of crops resistant to soil compaction.