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Changes in yield attributes and K allocation in wheat as affected by K deficiency and elevated CO2

Asif, Muhammad, Tunc, CevzaEsin, Ozturk, Levent
Plant and soil 2018 v.426 no.1-2 pp. 153-162
C3 plants, additive effect, biomass production, carbon dioxide, carbon dioxide enrichment, environmental factors, grain yield, growth chambers, harvest index, leaves, nutrient deficiencies, nutrient use efficiency, nutritional status, peduncle, photosynthesis, plant growth, potassium, ribulose-bisphosphate carboxylase, soil, straw, water use efficiency, wheat
BACKGROUND: Elevated carbon dioxide enhances biomass production and final crop yield of C₃ species as a consequence of increased photosynthesis, water use efficiency and RuBisCO saturation. However, this enhancement is limited by environmental conditions such as nutrient deficiencies. This study evaluates the interactive effects of K supply (deficient or adequate) and atmospheric CO₂ (ambient or elevated) on grain yield and yield related attributes along with allocation of K in different shoot parts (i.e. grains, leaves, stem and peduncle) in bread wheat. METHODS: Bread wheat (T. aestivum cv. Tahirova) was cultivated in soil fertilized with adequate or deficient K in pots under ambient (420 μmol mol⁻¹) or elevated (700 μmol mol⁻¹) atmospheric CO₂ conditions in dedicated plant growth chambers. At full maturity, plants were harvested and grain yield and yield attributes along with K status of grains, peduncle, leaves and stem parts were determined. RESULTS: While K deficiency severely reduced grain yield and yield attributes under both ambient (a-CO₂) and elevated (e-CO₂) CO₂ conditions, e-CO₂ significantly enhanced grain yield even in K-deficient plants through maintaining a greater harvest index, spikes per plant and grain weight and thus increased overall K use efficiency. Deficient-K treatment significantly increased grain K concentration as a consequence of “concentration effect”. On the contrary, K concentration in leaf, stem and peduncle was severely decreased whereas e-CO₂ had an additive effect on the decrease in K concentrations. Consequently, in deficient-K plants K content (total K accumulated/taken up) in all shoot parts including grains was reduced to only a fraction of adequate-K plants. Moreover, deficient-K plants tended to allocate a greater portion of K in grains as compared to other shoot parts. Elevated CO₂ also enhanced K allocation into grains particularly in deficient-K plants. CONCLUSION: Potassium deficiency severely reduces grain yield and biomass production in bread wheat in both a-CO₂ and e-CO₂ environments, however e-CO₂ partly alleviates the detrimental effect of K deficiency on grain yield, but not straw yield. Plants under K deficiency stress allocated a greater portion of K in the grains and e-CO₂ augmented this effect. In wheat, any one of peduncle, leaf or stem K concentration is a better measure of overall plant K nutritional status as compared to grain K, which may be severely biased due to “concentration effect” in K-deficient plants.