Abstract
Magnesium (Mg) is essential for many biological processes in plant cells, and its deficiency causes yield reduction in crop systems. Low Mg status reportedly affects photosynthesis, sucrose partitioning and biomass allocation. However, earlier physiological responses to Mg deficiency are scarcely described. Here, we report that Mg deficiency in Arabidopsis thaliana first modified the mineral profile in mature leaves within 1 or 2 days, then affected sucrose partitioning after 4 days, and net photosynthesis and biomass production after 6 days. The short-term Mg deficiency reduced the contents of phosphorus (P), potassium, manganese, zinc and molybdenum in mature but not in expanding (young) leaves. While P content decreased in mature leaves, P transport from roots to mature leaves was not affected, indicating that Mg deficiency triggered retranslocation of the mineral nutrients from mature leaves. A global transcriptome analysis revealed that Mg deficiency triggered the expression of genes involved in defence response in young leaves.
Highlights
The magnesium ion (Mg2+) is the second most abundant cation in plant cells after potassium (Marschner, 1995) and is engaged in crucial biological functions for plants, such as stabilisation of chlorophyll (Strouse, 1974) and ribosome (Akanuma et al, 2014) structures and the regulation of enzymatic activities (Clarkson and Hanson, 1980; Cowan, 2002)
In Mg-deficient plants, the biomass production was affected on day 6, when the fresh weight of the whole shoot and expanding leaves were 13% (p < 0.05) and 44% (p < 0.01) lower, respectively, compared to the control plants (Figure 2A)
As the alternative counter cation of SO42−, Na+ was selected over K+ to permit the examination of the effect of Mg deficiency on the K profile
Summary
The magnesium ion (Mg2+) is the second most abundant cation in plant cells after potassium (Marschner, 1995) and is engaged in crucial biological functions for plants, such as stabilisation of chlorophyll (Strouse, 1974) and ribosome (Akanuma et al, 2014) structures and the regulation of enzymatic activities (Clarkson and Hanson, 1980; Cowan, 2002). Crop fertilisation most often focuses on nitrogen (N), phosphorus (P) and potassium (K), but ignores Mg (Fageria et al, 2008). Mg deficiency affects the productivity of various crops (cereals, potatoes, sugar beets, etc.) and fruits (Gerendás and Führs, 2013). The apparent symptom of Mg deficiency is interveinal chlorosis as a result of chlorophyll degradation (Marschner, 1995; Tanoi and Kobayashi, 2015). One of the earliest reported physiological symptoms is accumulation of sucrose and starch
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