Sink strength may be the key to growth and nitrogen responses in N-deficient wheat at elevated CO2

G. S. Rogers*, P. J. Milham, M. Gillings, J. P. Conroy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

133 Citations (Scopus)

Abstract

The influence of elevated CO2 (350, 550 and 900 μL L-1) and N supplies ranging from deficient to excess (0-133 mg N kg-1 soil week-1) on the leaf N concentration and shoot growth of wheat (Triticum aeslivum L.), cultivar Hartog, was investigated. Shoot growth was 30 % greater at 550 μL L-1 compared to ambient CO2 at all levels of N supply. When the CO2 concentration was increased to 900 μL L-1, there was no increase in shoot growth at low N supply but it more than doubled at high N supply (67 mg N kg-1 soil week-1). Growth effects were closely matched by changes in sink development, suggesting that sink strength, mediated through N supply controlled the shoot growth response to elevated CO2. The shoot N concentration was lower at each level of CO2 enrichment and the greatest effect (30% reduction) occurred at 900 μL CO2 L-1, 33 mg N kg-1 soil week-1. The effect of high CO2 on shoot N concentration diminished as N supply increased and, at the highest N addition rate, there was only a 7% reduction. Changes in foliar N concentration due to CO2 enrichment were closely correlated with lower soluble protein concentration, accounting for 58 % of the total leaf N reduction. Ribulose1,5-bisphosphate carboxylase/oxygenase (Rubisco) levels were also reduced at high CO2 and N was allocated away from Rubisco and into other soluble proteins at high CCL when N supply was low. Nonstructural carbohydrate concentration (dry weight basis) was greatest at 900 μL CO2 L-1 and low N supply and may have reduced Rubisco concentration via a feed-back response. Critical foliar N concentrations (N concentration at 90 % of maximum shoot growth) were reduced from 43 mg g-1 at ambient CO2 to 39 and 38 mg g-1 at 550 and 900 μL CO2 L-1, respectively. Elevated CO2, at N supplies of 0-17 mg N kg-1 soil week , reduced flour protein concentration by 9-13 %.

Original languageEnglish
Pages (from-to)253-264
Number of pages12
JournalAustralian Journal of Plant Physiology
Volume23
Issue number3
Publication statusPublished - 1996
Externally publishedYes

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