Impaired electron transfer accounts for the photosynthesis inhibition in wheat seedlings (Triticum aestivum L.) subjected to ammonium stress

Feng Wang, Jingwen Gao, Songmei Shi, Xinhua He, Tingbo Dai

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16 Citations (Scopus)

Abstract

No single mechanism can provide an adequate explanation for the inhibition of photosynthesis when plants are supplied with ammonium (NH4 +) as the sole nitrogen (N) source. We performed a hydroponic experiment using two N sources [5 mM NH4 + and 5 mM nitrate (NO3 )] to investigate the effects of NH4 + stress on the photosynthetic capacities of two wheat cultivars (NH4 +-sensitive AK58 and NH4 +-tolerant XM25). NH4 + significantly inhibited the growth and light-saturated photosynthesis (Asat) of both cultivars, but the extent of such inhibition was greater in the NH4 +-sensitive AK58. The CO2 concentration did not limit CO2 assimilation under NH4 + nutrition; though both stomatal and mesophyll conductance were significantly suppressed. Carboxylation efficiency (CE), light-saturated potential rate of electron transport (Jmax), the quantum efficiency of PSII (ΦPSII), electron transport rate through PSII [Je(PSII)], and Fv/Fm were significantly reduced by NH4 +. As a result, NH4 + nutrition resulted in a significant increase in the production of hydrogen peroxide (H2O2) and superoxide anion radicals (O2 •−), but these symptoms were less severe in the NH4 +-tolerant XM25, which had a higher capacity of removing elevated reactive oxygen species (ROS). Thus, NH4 + N sources might decreased electron transport efficiency and increased the production of ROS, exacerbating damage to the electron transport chain, leading to a reduced plant photosynthetic capacity.

Original languageEnglish
Pages (from-to)159-172
Number of pages14
JournalPhysiologia Plantarum
Volume167
Issue number2
DOIs
Publication statusPublished - 1 Oct 2019

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