Changes inδ¹³C of dark respired CO₂and organic matter of different organs during early ontogeny in peanut plants

Abstract

Carbon isotope composition in respired CO2 and organic matter of individual organs were measured on peanut seedlings during early ontogeny in order to compare fractionation during heterotrophic growth and transition to autotrophy in a species with lipid seed reserves with earlier results obtained on beans. Despite a high lipid content in peanut seeds (48%) compared with bean seeds (1.5%), the isotope composition of leaf- and root-respired CO2 as well as its changes during ontogeny were similar to already published data on bean seedlings: leaf-respired CO2 became (13)C-enriched reaching -21.5‰, while root-respired CO2 became (13)C-depleted reaching around -31‰ at the four-leaf stage. The opposite respiratory fractionation in leaves vs. roots already reported for C3 herbs was thus confirmed for peanuts. However, contrarily to beans, the peanut cotyledon-respired CO2 was markedly (13)C-enriched, and its (13)C-depletion was noted from the two-leaf stage onwards only. Carbohydrate amounts being very low in peanut seeds, this cannot be attributed solely to their use as respiratory substrate. The potential role of isotope fractionation during glyoxylate cycle and/or gluconeogenesis on the (13)C-enriched cotyledon-respired CO2 is discussed.

Effects of Ontogeny on δ13C of Plant- and Soil-Respired CO2 and on Respiratory Carbon Fractionation in C3 Herbaceous Species

“…The magnitude of change due to both ontogeny and species identity effects on the δ 13 C signal of respired CO 2 was up to 7‰, and the associated respiratory fractionation reached up to 7‰ in Δ Rphloem-leaf . This is in agreement with the 6‰ increase in δ 13 C of leaf-respired CO 2 during the first 22 days of growth of French beans and peanuts, documented in the–to our knowledge–only other studies about the impact of ontogeny on δ 13 C CO2 [ 3 , 17 , 18 ]. These values thus span a similar range as changes in the δ 13 C of leaf-respired CO 2 resulting from changes in environmental conditions (e.g., about 8‰ in [ 40 ]).…”

Quantitative Proteomics and Relative Enzymatic Activities Reveal Different Mechanisms in Two Peanut Cultivars (Arachis hypogaea L.) Under Waterlogging Conditions

“…Excessive water in the soil will reduce the rate of gas exchange between the soil and the atmosphere, thus affecting plant growth and development ( Andrade et al, 2018 ; Garcia et al, 2020 ). Under waterlogging conditions, the oxygen level continues to decrease, but CO 2 , H 2 S, CH 4 , and ethylene continue to accumulate ( Kögel-Knabner et al, 2010 ), which seriously breaks the gas balance and causes a hypoxic or even anoxic environment, reducing the soil reduction potential and affecting the conversion of mineral elements ( Ghashghaie et al, 2015 ). For example, an anoxic environment inhibits aerobic nitrification and nitrifying bacterial activity, resulting in the reduction of nitrate to N 2 and nutrient loss ( Walker et al, 2018 ).…”

Special Issue dedicated to Professor Hanns-Ludwig Schmidt on the occasion of his 85th birthday

“…H.-L. Schmidt and his students and co-workers have contributed many fundamental findings to several fields of basic and applied stable isotope research, in plant biochemistry, human and animal physiology and ecology, environmental science, archaeology, paleoscience, forensics and food authenticity proofing. That diversity is also reflected in the contributions to this Special Issue by colleagues and by former students and co-workers [2][3][4][5][6][7][8][9][10][11][12][13]. Schmidt's own work included early studies on photosynthetic carbon isotope discrimination [14,15], which provides clues on the affiliation of plant species to photosynthetic types, and on limitations of discrete steps in the transfer of CO 2 from the air to RuBisCO in both C 3 and C 4 plants, and on the enzymatic mechanisms underlying post-photosynthetic carbon isotope discrimination phenomena.…”

“…One such finding with wide implications was the heterogeneous carbon isotope pattern in glucose [22] with a 13 C enrichment in the positions C-3 and C-4 which is caused by an equilibrium isotope effect on the aldolase reaction [23]. This pattern, also detectable in leaf soluble sugars and transitory starch [24], is responsible for the 13 C depletion of acetogenic lipids and the relationship between δ 13 C values of the fermentation products ethanol or acetic acid and that of the source sugar ( [10] and literature cited therein), and contributes to the 13 C enrichment of dark-respired CO 2 in plants ([25, see also [9,11]) and in connection with further isotope effects (e.g. [26]) to inter-and intra-molecular diversity of carbon isotope composition in plants (e.g.…”