The effect of soil compaction on wheat during early tillering: III. Fate of carbon transported to the roots


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Wheat (Triticum aestivum L. cv. Eradu) was grown in the field or glasshouse on a deep loamy sand which had either a compact soil layer (compact soil) between 10 and 55 cm depth or a deep‐tilled profile (loosened soil). The pattern of assimilate transport to the roots was investigated. Previously reported growth rates and solute concentrations of the seminal root axes were coupled with rates of O2 uptake measured in the field to give estimates of dry weight import into the ethanol‐insoluble (structural), ethanol‐soluble (osmotic) and respiratory pools. The calculated daily import of dry weight was 28% less in mechanically impeded than unrestricted apices. However, the dry weight required to produce 1 cm of root was twice as high for axes in compact soil. In these roots, a greater proportion of imported substrates went into ethanol‐insoluble matter, probably cell walls. Non‐respired 14C lost from root systems into the rhizosphere was measured in the glasshouse and found to be less than 4% of the 14C fixed 72 h earlier, even in compact soil. The partitioning of 14C‐labelled assimilate in plants from the two treatments was compared. The proportion of 14C in the ethanol‐soluble fraction was hardly affected by tissue age or soil strength. Furthermore, 62–82% of the soluble 14C was in the neutral (sugar) fraction in the roots. However, the 14C concentration (dry‐weight basis) in apices of seminal root axes was substantially greater when the roots grew in loosened soil. The greater sink strength of seminal root? growing in loosened soil was reflected in a 3‐fold larger incorporation of 14C into each gram of new ethanol‐insoluble material formed. In contrast, concentrations of 14C were similar in mature root tissues, nodal roots and shoots taken from both soil treatments.

Original languageEnglish
Pages (from-to)43-49
Number of pages7
JournalNew Phytologist
Issue number1
Publication statusPublished - 1990
Externally publishedYes


  • Assimilates
  • compaction
  • soil strength
  • Triticum
  • wheat


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