Functioning of potassium and magnesium in photosynthesis, photosynthate translocation and photoprotection

Abstract

Potassium (K) and magnesium (Mg) are mineral nutrients that are required in large quantities by plants. Both elements critically contribute to the process of photosynthesis and the subsequent long-distance transport of photoassimilates. If K or Mg is not present in sufficient quantities in photosynthetic tissues, complex interactions of anatomical, physiological and biochemical responses result in a reduction of photosynthetic carbon assimilation. As a consequence, excessive production of reactive oxygen species causes photo-oxidation of the photosynthetic apparatus and causes an up-regulation of photoprotective mechanisms. In this article, we review the functioning of K and Mg in processes directly or indirectly associated with photosynthesis. Focus is given to chloroplast ultrastructure, light-dependent and -independent reactions of photosynthesis and the diffusion of CO - a major substrate for photosynthesis - into chloroplasts. We further emphasize their contribution to phloem-loading and long-distance transport of photoassimilates and to the photoprotection of the photosynthetic apparatus.

The Influence of Taxonomy and Environment on Leaf Trait Variation Along Tropical Abiotic Gradients

“…Sampled leaves were chosen from individuals that corresponded to the most dominant species in each plot. To determine target species, we ranked and selected species contributing to up to 80% of the total basal area of the plot using data from the most recent plot census (2012)(2013) (Taiz and Zeiger, 2006;Tränkner et al, 2018), [K] is also essential for plant osmotic processes and plays a critical role in long-distance water transport (Wang et al, 2013), and [Ca] is an important constituent of cell walls (Taiz and Zeiger, 2006).…”

Diagnosis of Nitrogen Nutrition in Rice Leaves Influenced by Potassium Levels

“…According to Pettigrew (2008), a deficiency in K decreased the transport of photosynthetic assimilates out of leaves, which may lead to the increase in SLW. Tränkner et al (2018) also reported that a deficiency in K restricted the phloem loading of sucrose resulting in an accumulation of sucrose in source tissues. Zhao et al (2001) reported that K-deficient cotton leaves had less intercellular air space than that supplied with sufficient K. Sims et al (1998) showed that increased N levels could improve leaf thickness by increasing the mesophyll cell layer with only small changes in total epidermal thickness.…”

“…Our results indicated that with the increase in K, leaf K concentrations increased while the N and Mg concentrations decreased. As both N and Mg are structural elements of chlorophyll, they have substantial effects on chlorophyll synthesis (Xiong et al, 2015;Ceylan et al, 2016;Tränkner et al, 2018). Approximately 50% of leaf N invested in the form of photosynthetic proteins, including for the important components in involved in light harvesting, such as chlorophylls (Xiong et al, 2015).…”

Differential effects of varied potassium and magnesium nutrition on production and partitioning of photoassimilates in potato plants

“…Potassium acts as the main osmoticum to maintain cell growth and turgor pressure (Mengel and Arneke , Anschütz et al ), hydraulic conductance (Oddo et al , Chen et al ), leaf expansion (Jordan‐Meille and Pellerin ), root elongation (Song et al ), transport of photoassimilates between source and sink organs (Cakmak et al , Hu et al ) and regulation of stomatal guard cells (Raschke ). Additionally, K is crucial for maintaining photosynthesis (Tränkner et al ) by facilitating CO 2 diffusion through the leaf mesophyll (Jákli et al ). Magnesium is important for the energy metabolism, light harvesting (Verbruggen and Hermans ) and photoassimilate allocation (Cakmak et al ).…”