Effects Of Different Concentrations Of Calcium Nitrate On Quinoa Under Salt Stress

Crop growth are affected by external biotic factors and abiotic factorss.Salt stress is one of major abiotic stresses,which leads to drastic changes in plant growth and development.High concentrations of NaCl(the main salt in the soil)inhibits plant growth for two reasons: osmotic stress and ionic stress.With the develpoment of the regulation mechanism of Ca2+ on ion homeostasis under salt stress,more and more attention has been paid to alleviationof adverse effects of salt stress by exogenous application of calcium.In view of the harm of soid salinization,improving plant salt tolerance is an effective measure to improve crop yield in China.one of the most promising crops — Quinoa(Chenopodium quinoa Willd.)is a natural Andean crop that was called "the mother of food" by the ancient Incas.As a kind of monomeric species,quinoa is a food that can basically meet the basic nutritional needs of the human body.It is recognized by more and more people,and has important theoretical and practical perspectives.At present,many studies on quinoa mainly focus on the physiological mechanism of stress resistance.The purpose of this study was to investigate the effects of exogenous application of calcium nitrate on the growth and physiological status of quinoa under salt stress,and discuss the alleviation mechanism of exogenous application of Ca2+ on the adverse effects of salt stress.It is a effective mean to improve salt tolerance.In this study,quinoa was used as a research material to explore the physiological mechanisms of its vegetative growth stage under different treatments.The seedlings were randomly divided into 8 groups,four groups were used as non-salt stress treatments,and four groups were salt stress(200 m M NaCl)treatments.Different concentrations of Ca(NO3)2(0,5,20,150 m M)were applied separately in the non-salt stress treatmentand the salt stress treatment.The physiological indexes were as follows: growth parameters,photosynthetic parameters,the activity of antioxidant enzymes,osmotic potential and osmotic adjustment substance content and other physiological indicators.Effects of salt stress on quinoa: as a halophyte,the growth and development of quinoa were inhibited under 200 m M NaCl.The photosynthetic rate of quinoa was decreased significantly due to stomatal limitation.The production of active oxygen had adverse effects cell membrane is relatively permeable.The ion selective absorption was unbalanced,causing ion toxicity.Water deficit lead to increase in the content of osmotic adjustment substances(such as organic acid and proline).Effect of calcium nitrate on quinoa under salt stress: A certain concentration of exogenous calcium nitrate can effectively alleviate the salt stress damage caused by 200 m MNaCl.The treatment with combinations of 5m M Ca(NO3)2 and 200 m M NaCl improved effectively the stomatal conductance of quinoa,enhanced the photosynthetic pigments and water use efficiency,increased its photosynthetic rate,effectively reduced the reactive oxygen species caused by salt stress.Under the treatment with combinations of 20 m M Ca(NO3)2 and 200 m M NaCl,the growth and development of the seedlings were significantly improved,the relative growth rate and relative water content were optimal.Under the stress condition,the inhibition of K+ and Ca2+ absorption was significantly relieved.The ion content reached a relative equilibrium state.Although the proline content did not reach the minimum,it decreased significantly compared with salt stress.Under 200 m M NaCl treatment,the seedlings of quinoa were affected by salt stress.The growth index was reduced,and physiological metabolism waa weakened.Exogenous application of Ca(NO3)2 had a certain alleviation effect on the growth and physiological metabolism of quinoa,and the optimal Ca(NO3)2 concentration was 20 m M.Once the concentration wasbeyond 150 m M,it would further inhibit the growth and physiological activities of quinoa.