Root exudation and rhizosphere acidification by two lines of Medicago ciliaris in response to lime-induced iron deficiency

Abstract

The main objective of this work was to compare the tolerance to lime-induced Fe deficiency of two lines of Medicago ciliaris (TN11.11 and TN8.7). We studied the effects of Fe deficiency on:(1) root biomass and rhizosphere acidification, (2) accumulation in the roots and the exudation into the rhizosphere of organic compounds (citric acid, malic acid and phenols), (3) changes under Fe deficient conditions in the activities of two enzymes, the first related to organic acid metabolism (malate dehydrogenase: MDH) and the other to proton extrusion (H + -ATPase activity). After a pre-treatment of one week, plants were transferred into hydroponic culture under three treatments: +Fe, −Fe and +Fe +lime. Iron deficiency led to 40% increase in root biomass in TN11.11 line in the presence of lime. Both the omission of Fe and the addition of lime to the nutrient solution increased the H + -ATPase activity more in TN11.11 than in TN8.7. In addition, Fe deficiency increased accumulation of organic acids as well as phenols in roots, and stimulated the MDH activity more in TN11.11 than in TN8.7 (+75% and +41% in TN11.11 and TN8.7, respectively). Iron deficiency also increased the amounts of citrate, malate and phenols in root exudates. Our data allowed us to note that the TN11.11 line is more effective in overcoming Fe deficiency than TN8.7.

Iron Deficiency Tolerance at Leaf Level in <i>Medicago ciliaris</i> Plants

“…Our results showed that the photosynthetic parameters, leaf Fe content and antioxidant system of the sensitive line TN8.7 were more affected than those of the tolerant TN11.11 line by Fe starvation. These recent findings reinforced our previous work focused in root responses of the same Medicago ciliaris lines [10].…”

“…In previous works [8]- [10], we found that Fe deficiency tolerance in Medicago ciliaris line TN 11.11 is mainly associated with the activation of root plasma membrane H + -ATPase and Fe (III) reductase. In the present study, we investigate some possible mechanisms responsible for Fe deficiency tolerance at leaf level in two Medicago ciliaris lines in order to identify leaf parameters useful for rapid screening of genotypes.…”

“…The genotype TN11.11 is native of a calcareous soil, characterized by its high pH causing Fe deficiency, and is known for its ability to deal with such severe conditions. The genotype TN8.7, colonizing a soil poor in lime content where the pH is lower, is considered to be more sensitive and less efficient in responding to Fe deficiency [10].…”

“…Three-day-old seedlings were transferred to a half strength aerated hydroponic nutrient solution for 7 days and then similar sized seedlings were selected and cultured as groups of 10 plants in 10 Two treatments were applied: −Fe (0 mM) and +Fe (0.03 mM). Both media have a pH around 6.2.…”

Genotypic variation in phosphorus acquisition from sparingly soluble P sources is related to root morphology and root exudates in Brassica napus

“…At the same time, the capacity of the roots to release protons and their H + -ATPase activity were determined by the methods of M'Sehli et al [22] and Shen et al [23], respectively. An in situ visualization technology, as described by Li et al [24] and Yan et al [16], was used to estimate the difference in rhizosphere acidification of both genotypes.…”