CO_(2)浓度倍增和土壤盐胁迫对藜麦生理特征及产量的影响

Effects of elevated atmospheric CO_(2) on physiological characteristics and yield of quinoa to salinity stress

利用可精准调控CO_(2)浓度的人工气候室,设置2个CO_(2)浓度(常规组:400μmol/mol和倍增组:800μmol/mol),同时设置2个NaCl胁迫浓度(对照组NaCl浓度为0;盐胁迫组400 mmol/L NaCl),探讨CO_(2)浓度倍增和土壤盐胁迫对藜麦生长、生理、叶片离子含量、叶片光合特性和内禀水分利用效率的影响。结果表明,在盐胁迫下,CO_(2)浓度倍增显著提升藜麦光合速率、降低藜麦气孔导度,提高藜麦内禀水分利用效率,从而增加藜麦产量。但是,在CO_(2)浓度倍增处理下,随着藜麦生长,光合速率提升幅度逐渐缩小,藜麦产生光合适应现象。此外,在盐胁迫下,与CO_(2)浓度常规组相比,CO_(2)浓度倍增最终(63d)降低藜麦叶片Na^(+)浓度达42%,增加藜麦叶片K^(+)浓度达26%,有效调控藜麦叶片中离子平衡,表现出明显的吸K^(+)排Na^(+)的现象。同时,CO_(2)浓度倍增促进藜麦渗透调节,有效调控藜麦叶片水分运动,增加细胞含水率,降低叶片溶质势和水势,提高压力势,维持细胞正常的生理功能。此外,藜麦内禀水分利用效率与藜麦叶水势、溶质势,光合速率和K^(+)浓度呈显著正相关。研究结果有助于深入理解CO_(2)浓度倍增调控作物耐盐性的生理机制,为应对大气CO_(2)浓度升高背景下土壤盐碱化问题,维护生态系统稳定性,保障粮食安全提供参考。

Since the beginning of industrial revolution,atmospheric CO_(2) concentration has increased from 310μmol/mol to approximately 400μmol/mol,and is expected to double at the end of the 21 st century.Soil salinity is a prime abiotic stress that limits agriculture productivity worldwide.A pot experiment was conducted in climate chambers to investigate the response of quinoa(Chenopodium quinoa Willd)to salt stress under ambient(400μmol/mol)and elevated(800μmol/mol)atmospheric CO_(2) concentration.In this study,seeds of quinoa were surface sterilized and sown in peat-filled plastic trays in a greenhouse at ambient temperature.Four weeks after sowing,one seedling was transplanted to each plastic pot(the height of 25 cm and the diameter of 20 cm)containing 5 kg mixture of peat and sand and then placed in climate chambers with different CO_(2) concentrations.Plants at the five-leaf stage were irrigated with 0 mmol/L NaCl(non-saline)and 400 mmol/L Na Cl(saline)solutions,respectively.During the experiment,leaf photosynthesis,stomatal conductance,intrinsic water use efficiency,ions concentrations,water potential,osmotic potential and pressure potential were determined.In addition,the plant height,shoot biomass,root biomass,100-grain weight and grain yield were measured.The results showed that leaf photosynthesis rate and stomatal conductance were significantly reduced while intrinsic water use efficiency was significantly increased under salinity stress compared with control treatment without NaCl addition.The elevated atmospheric CO_(2) concentration enhanced stomatal conductance but decreased photosynthesis rate.In addition,the elevated atmospheric CO_(2) concentration significantly mitigated the negative effects of salt stress on quinoa and increased photosynthesis rate by 39.4%accompanied by decreasing stomatal conductance by 11.5%resulting in enhancing plant height,shoot biomass,root biomass,100-grain weight and grain yield of quinoa by 8%,20%,82%,19%and 34%,respectively.However,the fluctuation of quinoa photosynthesis rate and stomatal conductance gradually decreased with quinoa growth,resulting in photosynthetic acclimation.The rapid development of the root system under elevated atmospheric CO_(2) concentrations greatly increased the root-to-shoot ratio.Thus,it could improve the plant water absorption capacity and mitigate the dehydration of leaf cells induced by salt stress.Moreover,elevated atmospheric CO_(2) concentrations could regulate the hormone levels in plants and thus affect Na^(+)uptake and adjust water balance in cells.The significant difference wasn’t found in leaf potential and osmotic potential under both ambient and elevated atmospheric CO_(2) concentration with non-saline irrigation at the same sampling time.However,elevated atmospheric CO_(2) concentrations significantly decreased leaf potential and osmotic potential than ambient atmospheric CO_(2) concentration with saline irrigation.This phenomenon effectively maintained pressure potential and alleviated water shortage in plant cells.Additionally,compared with ambient atmospheric CO_(2) concentrations,elevated atmospheric CO_(2) concentrations significantly improved plant water relations,decreased Na^(+)by 42%and improved K^(+)retention by 26%under salinity stress.Improved growth,physiology and yield performance were linked with better plant water(osmotic and water potential)and gas relations(leaf photosynthesis rate,stomatal conductance),low Na^(+)and high K^(+)contents in leaves.The results are helpful for understanding the physiological mechanism of salt tolerance in quinoa under elevated atmospheric CO_(2) concentrations.In addition,these findings also provide information for dealing with soil salinization,maintaining ecosystem stability and ensuring food security under the background of elevated atmospheric CO_(2).