Relationships between stable isotope natural abundances (δ13C and δ15N) and water use efficiency in rice under alternate wetting and drying irrigation in soils with high clay contents

Zhenchang Wang; Jinjing Liu; Yaosheng Wang; Evgenios Agathokleous; Yousef Alhaj Hamoud; Rangjian Qiu; Cheng Hong; Minghao Tian; Hiba Shaghaleh; Xiangping Guo

doi:10.3389/fpls.2022.1077152

Relationships between stable isotope natural abundances (δ¹³C and δ¹⁵N) and water use efficiency in rice under alternate wetting and drying irrigation in soils with high clay contents

Front Plant Sci. 2022 Dec 2:13:1077152. doi: 10.3389/fpls.2022.1077152. eCollection 2022.

Authors

Zhenchang Wang^{1

2}, Jinjing Liu^{1

2}, Yaosheng Wang³, Evgenios Agathokleous⁴, Yousef Alhaj Hamoud^{1

5}, Rangjian Qiu⁶, Cheng Hong^{1

2}, Minghao Tian^{1

2}, Hiba Shaghaleh⁷, Xiangping Guo^{1

2}

Affiliations

¹ College of Agricultural Science and Engineering, Hohai University, Nanjing, China.
² Jiangsu Province Engineering Research Center for Agricultural Soil-Water Efficient Utilization, Carbon Sequestration and Emission Reduction, Nanjing, China.
³ Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing, China.
⁴ School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing, China.
⁵ Department of Soil and Land Reclamation, Aleppo University, Aleppo, Syria.
⁶ State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, China.
⁷ College of Environment, Hohai University, Nanjing, China.

Abstract

Natural abundance of the stable isotope (δ¹³C and δ¹⁵N) in plants is widely used to indicate water use efficiency (WUE). However, soil water and texture properties may affect this relationship, which remains largely elusive. Therefore, the purpose of this study was to evaluate δ¹³C as affected by different combinations of alternate wetting and drying irrigation (AWD) with varied soil clay contents in different organs and whole plant and assess the feasibility of using δ¹³C and δ¹⁵N as a physiological indicator of whole-plant water use efficiency (WUE_whole-plant). Three AWD regimes, I₁₀₀ (30 mm flooded when soil reached 100% saturation), I₉₀ (30 mm flooded when reached 90% saturation) and I₇₀ (30 mm flooded when reached 70% saturation) and three soil clay contents, 40% (S₄₀), 50% (S₅₀), and 60% (S₆₀), were included. Observed variations in WUE_whole-plant did not conform to theoretical expectations of the organs δ¹³C (δ¹³C_organs) of plant biomass based on pooled data from all treatments. However, a positive relationship between δ¹³C_leaf and WUE_ET (dry biomass/evapotranspiration) was observed under I₉₀ regime, whereas there were no significant relationships between δ¹³C_organs and WUE_ET under I₁₀₀ or I₇₀ regimes. Under I₁₀₀, weak relationships between δ¹³C_organs and WUE_ET could be explained by (i) variation in C allocation patterns under different clay content, and (ii) relatively higher rate of panicle water loss, which was independent of stomatal regulation and photosynthesis. Under I₇₀, weak relationships between δ¹³C_organs and WUE_ET could be ascribed to (i) bigger cracks induced by water-limited irrigation regime and high clay content soil, and (ii) damage caused by severe drought. In addition, a negative relationship was observed between WUE_whole-plant and shoot δ¹⁵N (δ¹⁵N_shoot) across the three irrigation treatments, indicating that WUE_whole-plant is tightly associated with N metabolism and N isotope discrimination in rice. Therefore, δ¹³C should be used cautiously as an indicator of rice WUE_whole-plant at different AWD regimes with high clay content, whereas δ¹⁵N could be considered an effective indicator of WUE_whole-plant.

Keywords: Oryza sativa L; alternate wetting and drying irrigation; soil clay content; water use efficiency; δ13C; δ15N.