Soil salinity effect on carbon isotope composition of plant biomass

Abstract

The analysis of the carbon isotopic data available from the literature evidences in favor of the significant effect of salinity on plant and photosynthesizing alga biomass. The nature of this effect is explained in terms of oscillation model of carbon isotope fractionation in photosynthesis. The data interpretation and conclusions are compared with those obtained from commonly adopted steadystate model of carbon isotope fractionation in photosynthesis. It is shown that the first model gives a new explanation and substantiation on the causes of different response of carbon isotope ratio of glycophyte (salt-sensitive plants) and halophyte (salt tolerant) plant biomass to salinity change. A new explanation for inversion of carbon isotope effect sign in C 4-plants in response to salt stress is given. Under salt stress due to the increase of CO 2 leakage from bundle sheath back to mesophyll cells the isotope fractionation in C 4-plants becomes similar to that in C 3-plants, i.e. the contribution of isotope fractionation in RuBP carboxylation grows up and results in 12 C-enrichment of biomass and inversion of isotope effect sign as well.

Global Photosynthesis and its Regulatory Role in Natural Carbon Cycle

“…Natural observations and in vitro experiments showed that the carbon isotopic variations depending on CO 2 concentrations in the environment may achieve 25%o [20]. It was also found [21] that the 12 C enrichment of biomass turned out to be much less than the carbon isotope effects of RuBP carboxylation on the enzymes isolated from the biomass of these organisms. The effects were about 60-65%o.…”

“…CO 2 assimilation results in enrichment of total biomass in 12 C isotope whereas photorespiration leads to accumulation in biomass of 13 …”

“…This leads to a natural redistribution of carbon isotopes between fractions. The lipid fraction of biomass turns to be 3-5%o "lighter" than other factions (lignin, protein and carbohydrate) [12]. This is a result of a specific way of biosynthesis of lipid components in a cell that occurs through structural C 2 -fragments and is accompanied by a carbon isotope effect [13,14].…”

“…This is clearly manifested in the shift of the isotopic composition of organic matter relative to the source of carbon of biogenic material. At all stages of sedimentation and digenesis there was a steady enrichment of organic matter in 12 C, which indicates an increase in the relative proportion of total carbon of the lipid component [15,16]. But it doesn't mean structural and chemical stability of the lipid fraction components.…”

Prediction of Salt Tolerance in Rice (Oryza Sativa) Based on Shoot Ion Content under Non-Stressed Conditions

“…Our CID data are in agreement with the salt tolerance of the standard lines and confirmed their classes as tolerant, moderately tolerant and susceptible. For more information on the use CID as a surrogate for salt tolerance, the reader is referred to recent publications [46][47][48]. Here we focus on the ability to screen for salt tolerance using element composition in non-stressed conditions.…”