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Enhanced accumulation of gibberellins rendered rice seedlings sensitive to ammonium toxicity.

ABSTRACT: Ammonium (NH4+) phytotoxicity is a worldwide phenomenon, but the primary toxic mechanisms are still controversial. In the present study, we investigated the physiological function of gibberellins (GAs) in the response of rice plants to NH4+ toxicity and polyamine accumulation using GA biosynthesis-related rice mutants. Exposure to NH4+ significantly decreased GA4 production in shoots of wild-type (WT) plants. Both exogenous GA application to the WT and increases in endogenous GA levels in eui1 mutants rendered them more sensitive to NH4+ toxicity. In contrast, growth of sd1 GA-deficient mutants was more tolerant to NH4+ toxicity than that of their WT counterparts. The role of polyamines in GA-mediated NH4+ toxicity was evaluated using WT rice plants and their GA-related mutants. The eui1 mutants with GA overproduction displayed a higher endogenous putrescine (Put) accumulation than WT plants, leading to an enhanced Put/[spermidine (Spd)+spermine (Spm)] ratio in their shoots. In contrast, mutation of the SD1 gene encoding a defective enzyme in GA biosynthesis resulted in a significant increase in Spd and Spm production, and reduction in the Put/(Spd+Spm) ratio when exposed to a high NH4+ medium. Exogenous application of Put exacerbated symptoms associated with NH4+ toxicity in rice shoots, while the symptoms were alleviated by an inhibitor of Put biosynthesis. These findings highlight the involvement of GAs in NH4+ toxicity, and that GA-induced Put accumulation is responsible for the increased sensitivity to NH4+ toxicity in rice plants.

SUBMITTER: Wang B

PROVIDER: S-EPMC7031073 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Enhanced accumulation of gibberellins rendered rice seedlings sensitive to ammonium toxicity.

Wang Baolan B Wei Haifang H Zhang Hui H Zhang Wen-Hao WH

Journal of experimental botany 20200201 4

Ammonium (NH4+) phytotoxicity is a worldwide phenomenon, but the primary toxic mechanisms are still controversial. In the present study, we investigated the physiological function of gibberellins (GAs) in the response of rice plants to NH4+ toxicity and polyamine accumulation using GA biosynthesis-related rice mutants. Exposure to NH4+ significantly decreased GA4 production in shoots of wild-type (WT) plants. Both exogenous GA application to the WT and increases in endogenous GA levels in eui1 m ...[more]

PMID: 31667503

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Project description:Nitrogen deficiency and toxicity, primarily in its ammonium form (NH4+), can suppress plant growth and development. The use of silicon (Si) or salicylic acid (SA) may be an alternative to minimize the harmful effects of nutrient imbalances caused by NH4+, thereby improving the photosynthetic efficiency of plants. The aim of the present study was to assess the action of fertigation-applied Si and SA foliar spraying in mitigating NH4+ toxicity and deficiency in eucalyptus clonal seedlings. Two experiments were performed with eucalyptus clonal seedlings (Eucalyptus urophylla x Eucalyptus grandis), in a greenhouse. Both were carried out using a 4x2 factorial design and four concentrations of NH4+ (5, 15, 30 and 60 mmol L-1), in the absence and presence of Si (2 mmol L-1), in experiment I; or with and without SA foliar application (10-2 mmol L-1), in experiment II, with six repetitions. Nitrogen content rose as a result of increasing N-NH4+ concentration in the nutrient solution, and Si supplied via the nutrient solution was efficient in increasing the Si content in eucalyptus seedlings. The rise in N-NH4+ concentration favored the maintenance of the photosynthetic apparatus, but high N-NH4+ concentration increased energy loss through fluorescence and decreased the efficiency of photosystem II. The addition of Si to the nutrient solution proved to be beneficial to the photosynthetic apparatus by decreasing F0 at 15 and 30 mmol L-1 of NH4+; and Fm at all NH4+ concentrations studied. In addition, the beneficial element also increases Fv/Fm at all NH4+ concentrations studied. SA foliar application was also efficient in reducing photosynthetic energy losses by decreasing F0 and Fm at all NH4+ concentrations studied. However, SA only increased the Fv/Fm at the high concentrations studied (30 and 60 mmol L-1 of NH4+). Nitrogen disorder by deficiency or N-NH4+ toxicity reduced shoot dry mass production. The addition of Si to the nutrient solution and SA foliar application increased shoot dry mass production at all N-NH4+ concentrations studied, and benefitted the photosynthetic apparatus by decreasing fluorescence and improving the quantum efficiency of photosystem II as well as dry mass production.

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Enhanced accumulation of gibberellins rendered rice seedlings sensitive to ammonium toxicity.

Publications

Enhanced accumulation of gibberellins rendered rice seedlings sensitive to ammonium toxicity.

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