Leaf Age, Canopy Position, and Habitat Affect the Carbon Isotope Discrimination and Water-Use Efficiency in Three C3 Leguminous Prosopis Species from a Hyper-Arid Climate.

M. Iftikhar Hussain,Ali El-Keblawy,François Mitterand Tsombou

doi:10.3390/plants8100402

M. Iftikhar Hussain, Ali El-Keblawy + Show 1 more

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https://doi.org/10.3390/plants8100402

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Abstract

The present study involved measurements of the stable carbon isotope composition (δ13C) and intrinsic water-use efficiency (iWUE) of three C3 leguminous Prosopis spp. (P. juliflora, P. cineraria, and P. pallida) foliage at different canopy positions (east and west) from saline (SLH) and non-saline habitats (NSH). Integrated measurements of the stable carbon isotope composition (δ13C) of plant tissue were broadly used to study iWUE, taking into consideration the effect of leaf age and canopy position on C isotope discrimination. Mature foliage of P. pallida from an SLH with a west canopy position had significantly higher δ13C (less negative) than that from NSH. On the west side, Δ13C values ranged from 17.8‰ (P. pallida) to 22.31‰ (P. juliflora) for a west canopy position, while they varied from 18.05‰ (P. pallida) to 22.4‰ (P. cineraria) on the east canopy side. Because the patterns are similar for the three Prosopis species, the difference in carbon isotope discrimination (Δ13C) between the canopy position (west and east) is relatively consistent among species and sites, ranging between 17.8 ± 4.43‰ for the young foliage in the west and 18.05 ± 4.35‰ for the east canopy position. The iWUE of P. pallida was twice that of P. cineraria. The iWUE of P. juliflora was higher from NSH than SLH. Mature leaves possessed a higher iWUE than the young leaves. We concluded that exotic P. juliflora and P. pallida have higher iWUE values than the native P. cineraria, which might be due to the rapid below-ground development of plant roots in the Arabian deserts of the United Arab Emirates (UAE). This could enable the alien species access to deeper humid soil layers or water resources.

Highlights

The element carbon possesses three naturally occurring isotopes: C, C, and C
In non-saline habitats (NSH), the carbon (C%) in both young and mature leaves of P. juliflora was higher for the east than the west canopy position, while it remained unaffected in saline habitats (SLH) (Figure 1a)
There was a significant reduction in N% in young foliage on the east side compared to the west canopy position in NSH

Summary

Introduction

The element carbon possesses three naturally occurring isotopes: C, C, and C. The focus is on the first two carbon forms, which are stable isotopes (12 C and 13 C), because they are differently fractionated by photosynthetic pathways. A difference in isotope assimilation into the plant structure is mainly attributed to a difference in the diffusion rates of 12 CO2 and 13 CO2 during the photosynthetic assimilation of CO2 , in conjunction with carboxylation enzyme preference for one isotopic form of carbon dioxide over another [1]. The study of the stable isotopes of carbon, nitrogen, and oxygen composition provides further understanding of the biogeochemical cycle of plant ecosystems. The plant water-use efficiency can be measured at different levels, such as the leaf, whole plant, and ecosystem levels [1]. It is more precisely referred to as “intrinsic water-use efficiency”,

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