Impact of Salinity on the Radiation Use Efficiency of Quinoa (Chenopodium quinoa Willd.) in Semi-arid Area in Tunisia

The impact of three level of salinity (T0 = 1.2 dS m-1, T1 = 9.2 dS m-1 and T2 = 18 dS m-1) on photosynthetically active radiation intercepted (PARabs), Radiation Use Efficiency at pre-anthesis and post-anthesis (RUEPR and RUEPS), Radiation Use Efficiency of total dry biomass (RUETDM) and Radiation Use Efficiency of Grain Yield (RUEGY) at quinoa harvest were investigated during the growing season (2015). The RUE pre-anthesis (from transplanting to anthesis) has registered a decrease of 10.8 and 15.8% respectively in T1 (RUEPR = 4.62 g MJ-1) and T2 (RUEPR = 4.36 g MJ-1) compared to the control T0 (RUEPR = 5.18 g MJ-1). Likewise, the RUE post-anthesis was reduced by 8.9 and 32.1% in T1 (RUEPS = 1.23 g MJ-1) and in T2 (RUEPS = 0.91 g MJ-1), dissimilarity to T0 (RUEPS = 1.35 g MJ-1). The maximum RUETDM (3.2 g MJ-1) was manifested in (T0). However, the minimum RUETDM (2.8 g MJ-1) was observed in T2 (S = 18 dS m-1). A decline of 16.1% was observed in RUETDM due to the reduction on TDM from T0 (S = 1.2 dS m-1) to T2 (S = 18 dS m-1). As well, the RUEGY declined when salinity increased. The highest RUEGY (1.24 g MJ-1) was registered in T0. However, the lowest RUEGY (0.62 g MJ-1) was obtained in T2. A decrease of 50% in RUEGY due to the height reduction on yield was observed in the T2.