The influence of root assimilated inorganic carbon on nitrogen acquisition/assimilation and carbon partitioning

Abstract

Summary• Understanding of the influences of root-zone CO 2 concentration on nitrogen (N) metabolism is limited.• The influences of root-zone CO 2 concentration on growth, N uptake, N metabolism and the partitioning of root assimilated 14 C were determined in tomato ( Lycopersicon esculentum ).• Root, but not leaf, nitrate reductase activity was increased in plants supplied with increased root-zone CO 2 . Root phosphoenolpyruvate carboxylase activity was lower with NO 3 --than with NH 4 + -nutrition, and in the latter, was also suppressed by increased root-zone CO 2 . Increased growth rate in NO 3 --fed plants with elevated root-zone CO 2 concentrations was associated with transfer of root-derived organic acids to the shoot and conversion to carbohydrates. With NH 4 + -fed plants, growth and total N were not altered by elevated root-zone CO 2 concentrations, although 14 C partitioning to amino acid synthesis was increased.• Effects of root-zone CO 2 concentration on N uptake and metabolism over longer periods (> 1 d) were probably limited by feedback inhibition. Root-derived organic acids contributed to the carbon budget of the leaves through decarboxylation of the organic acids and photosynthetic refixation of released CO 2 .

CO 2 enrichment modulates ammonium nutrition in tomato adjusting carbon and nitrogen metabolism to stomatal conductance

“…In fact, the drainage of carbon from the TCA cycle under ammonium nutrition at ambient CO 2 could be replenished in a coordinated way via PEPC, supplying OAA, which is reduced to malate, and NADP-ME, which is responsible for malate decarboxylation in order to provide pyruvate for the TCA cycle. Similar results showing a higher PEPC activity in ammonium-fed plants with respect to nitrate-fed plants have been previously reported in the literature [15,16]. Also, a positive response of PEPC activity to the increasing NH 4 + content in tomato root has been recently described by Setién et al [29].…”

“…In this sense, the growth of plants under high irradiance led to increased photosynthetic carbon assimilation and alleviated the toxic effects of high external ammonium concentrations both in pea [13] and wheat plants [8]. Overall, improvement of N status occurs in parallel to TCA anaplerotic enzymes induction; and this induction has been shown to be higher under ammonium nutrition compared to nitrate nutrition [14][15][16]. According to this, Setién et al [8] observed that the beneficial effect of high irradiance for ammonium-fed wheat plants was correlated with an improvement in TCA anaplerotic metabolic pathways.…”

Co-localization of Carbonic Anhydrase and Phosphoenol-pyruvate Carboxylase and Localization of Pyruvate Kinase in Roots and Hypocotyls of Etiolated Glycine max Seedlings

“…Furthermore, the in vitro rates of CA activity found in tomato roots were higher than the in vitro rates of PEPC activity [34] agreeing with the in vivo results in maize root tips [27]. …”

Nitrogen acquisition, PEP carboxylase, and cellular pH homeostasis: new views on old paradigms

“…2002; Norici et al . 2002; Viktor & Cramer 2005). This most likely reflects the higher GS activities, glutamine contents, glutamine : glutamate ratios, and higher rates of amino acid synthesis that are often observed in NH 4 + ‐grown plants (Yemm & Willis 1956; van Beusichem et al .…”