| Nitrogen?N?and iron?Fe?is one of the essential macro-and micro-nutrients for crop growth and development,respectively,which greatly affects crop's yield and quality.Quinoa?Chenopodium quinoa Willd.?is an annual herbaceous crop belonging toChenopodiaceae.Its seeds are rich in amino acids,high protein and mineral elements.The purposes of this study were to investigate the effects of different combinations of N and Fe on the growth and physiological characteristics of different varieties of quinoa.The responsesand underlying physiological mechanisms between different quinoa varieties will provide the practical evidence for their cultivation in the field.In these experiments,seedlings of several dominant commercial quinoa varieties were used,and the sandy culture experiment was carried out with Hoagland nutrient solution.Two research contents were done here.1.Effects of N and Fe on the seedling growth characteristics of 3 quinoa varieties?red,black and white?under four different concentrations of Fe(10,50,100,300?mol·L-1)and N(4,8,12 mmol·L-1)contents.The results showed that N was the key factor to promote plant growth and other morphological indices,but Fe had a minor effect.Based on the growth traits,the combined applications of N and Fe had a significant effect on the accumulation of total biomass.It was found that the effect of N application on leaf morphology indexwas greater than that of Fe.Leaf area of red and white quinoa was larger than that of black variety.The supply of N was negatively correlated with SLA.Compared to other varieties,leaf water content of red and white quinoa was the lowest.Red and white quinoa had the highest growth potential?i.e.,biomass?,whilst the black one had the lowest.2.The growth,chlorophyll content,MDA content and antioxidant enzymes?SOD,APX,CAT?in seedlings of 2 quinoa varieties?red and black?were studied under the combined effects of three Fe(10,100,300?mol L-1)and two N(4,12mmol·L-1)contents.The variables ofosmotic substances?proline,protein and soluble sugars?,ferric reductase?FeR?,total N,total Fe,total amino acids and their components were studied.The results were as follows:?1?Appropriate combination of N and Fe was beneficial to inhibit the degradation of chlorophyll content in leaves of quinoa seedlings.N supply affected MDA content.The expression of the major protective enzymes occurred in leaves,rather than in roots.With the increase of nitrogen supply,oxidative damage of cell membrane in leaves and roots of quinoa increased significantly,approximatingthat of proline.The antioxidant enzymes and soluble proteins showed dynamic changes with the prolongation of stress time.At less days under N and Fe nutrition?12 days?,leaves of quinoa seedlings stimulated its protective system to secrete a large amount of enzymes and protect soluble protein from oxidative injury.With the prolongation of stress time?20 days?,antioxidant system by a certain degree of damage in its activity is reduced.But under a long-time stress,quinoa through their own physiological regulation,synergistic antioxidant enzymes,osmoregulation,can effectively alleviate to some extent the oxidative damage caused by nitrogen and iron stress,improve the activity of enzyme to enhance its resistance.?2?Compared to black variety,the red variety had higher FeRactivity in roots.Total Fe content of two varieties was higher in roots than leaves,while total nitrogen content was higher in leaves than in roots.The total iron content in red quinoa reached the maximum when the supply of medium concentration Fe and high concentration N?Fe2N2?,while black quinoa reached the maximum value when suppliedwith high Fe and low N contents?Fe3N1?.The total nitrogen content of red quinoa reached the maximum at low content of Fe and high content of N?Fe1N2?,while that of black quinoa reached the maximum at medium contents of Fe and high contents of N?Fe2N2?.Thecontent of each component of the amino acids showed a consistent response to the N and Fe treatments.But under nitrogen and iron nutrition,total amino acids in leaves were higher in red than black variety.The contents of 17 amino acids were higher in high N condition than low N condition.Whereas,across the two N supply conditions,total amino acids under the different Fe supply of red quinoa showed the order of medium Fe>low Fe>high Fe?Fe2>Fe1>Fe3?.Black quinoa showed an increased trendwith the increase of Fe supply under low Ncondition,but decreased with the increase of Fe supply under low Ncondition.Under different N and Fe nutrition,the contents of total N and total Fe,amino acids in quinoa plants may be differentially related to plant genotype,physiological statusand exogenous nutrition enhancement.The migration of iron was mainly accumulated in the roots;but nitrogen in plants is easy to transport,and leaf nitrogen content was higher.Compared to black variety,the seedlings of red variety had higher N and Fe requirements and had higher growth rate. |
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