Vol.:(0123456789) 1 3 Planta https://doi.org/10.1007/s00425-019-03253-9 ORIGINAL ARTICLE Ionic selectivity and coordinated transport of Na + and K + in fag leaves render diferential salt tolerance in rice at the reproductive stage Koushik Chakraborty 1  · Krishnendu Chattaopadhyay 1  · Lopamudra Nayak 1  · Soham Ray 1  · Lucina Yeasmin 1  · Priyanka Jena 1  · Sunanda Gupta 1  · Sangram K. Mohanty 1  · Padmini Swain 1  · Ramani K. Sarkar 1 Received: 21 February 2019 / Accepted: 1 August 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Main conclusion The present study shows that salt tolerance in the reproductive stage of rice is primarily governed by the selective Na + and K + transport from the root to upper plant parts. Ionic discrimination at the flag leaf, gov- erned by differential expression of Na + - and K + -specific transporters/ion pumps, is associated with reduced spikelet sterility and reproductive stage salt tolerance. Abstract Reproductive stage salt tolerance is crucial in rice to guarantee yield under saline condition. In the present study, diferential ionic selectivity and the coordinated transport (from root to fag leaf) of Na + and K + were investigated to assess their impact on reproductive stage salt tolerance. Four rice genotypes having diferential salt sensitivity were subjected to reproductive stage salinity stress in pots. The selective Na + and K + transport from the root to upper plant parts was observed in tolerant genotypes. We noticed that prolonged salt exposure did not alter fag leaf greenness even up to 6 weeks; how- ever, it had a detrimental efect on panicle development especially in the salt-susceptible genotype Sabita. But more precise chlorophyll fuorescence imaging analysis revealed salinity-induced damages in Sabita. The salt-tolerant genotype Pokkali (AC41585), a potential Na + excluder, managed to sequester higher Na + load in the roots with little upward transport as evident from greater expression of HKT1 and HKT2 transporters. In contrast, the moderately salt-tolerant Lunidhan was less selective in Na + transport, but possessed a higher capacity to Na + sequestration in leaves. Higher K + uptake and tissue- specifc redistribution mediated by HAK and AKT transporters showed robust control in selective K + movement from the root to fag leaf and developing panicles. On the contrary, expressions of Na + -specifc transporters in developing panicles were either down-regulated or unafected in tolerant and moderately tolerant genotypes. Yet, in the panicles of the susceptible genotype Sabita, some of the Na + -specifc transporter genes (SOS1, HKT1;5, HKT2;4) were upregulated. Apart from the ionic regulation strategy, cellular energy balance mediated by diferent plasma-membrane and tonoplastic H + -pumps were also associated with the reproductive stage salt tolerance in rice. Keywords Chlorophyll fuorescence imaging · Flowering stage · Ion channels · Ion pumps · Salinity · Transporter Abbreviations ChlF Chlorophyll fuorescence HKT High-afnity potassium transporter SOS Salt overly sensitive SSI Stress stability index V-PPase Vacuolar pyrophosphatase V-ATPase Vacuolar type H + ATPase YSI Yield stability index Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00425-019-03253-9) contains supplementary material, which is available to authorized users. * Koushik Chakraborty Koushik.Chakraborty@icar.gov.in; koushikiari@gmail.com * Krishnendu Chattaopadhyay Krishnendu.Chattopadhyay@icar.gov.in; krishnenducrri@gmail.com 1 ICAR, National Rice Research Institute, Cuttack, Odisha 753006, India