| This experiment used Jingu 21（conventional cultivar）and Zhangzagu 10（hybrids）as test materials.Through potted,field and laboratory experiments,the effects of different concentrations of zinc on the physiological and biochemical indexes,related gene expression,zinc content in different parts of plants,yield and quality of millet in different periods（seedling,booting,flowering and filling stages）were studied.To explore the suitable exogenous zinc spraying period,concentration and optimal zinc-rich combination of millet growth,reveal the effect of zinc on millet growth,photosynthesis mechanism and its role in functional agriculture,and provide theory for the rational application of zinc fertilizer on millet.Based on this,it also provides scientific guidance for the production of zinc-rich millet functional foods.The results are as follows:（1）The photosynthetic characteristics,CA activity,and relative gene expression of different varieties of millet at the seedling stage were studied by spraying Zn solution under pot experiment and indoor culture conditions.Results showed that spraying low-concentration Zn solution(20,40,and 60 mg·L-1)reduced malondialdehyde content and intercellular CO2 concentration（Ci）but increased antioxidant enzyme activity,pigment content,and photosynthetic gas exchange parameters（except for Ci）;meanwhile,spraying high Zn concentration(80 and 100 mg·L-1)exerted opposite effects.The optimal growth of millet was achieved when the Zn concentration was 40 mg·L-1.At this concentration,CA activity increased and β-CA family expression was upregulated,which exerted little or no effect on other CA families.Compared with Zhangza 10,Jingu 21 showed a more significant change.（2）The physiological and photosynthetic characteristics of different cultivars treated with different Zn concentrations at different growth stages were investigated to determine the optimum spraying period and spraying concentration of Zn fertilizer（ZnSO4?7H2O）in foxtail millet plants（Setaria italica L.）throuth pot experiment.Results showed that spraying low Zn concentrations(20,40,and 60 mg·L-1)solutions decreased the malondialdehyde content,Intercellular CO2 concentration（Ci）,and Non-photochemical quenching coefficient（q N）but increased antioxidant enzymatic activities,pigment content,photosynthetic gas exchange parameters（except Ci）,and chlorophyll fluorescence parameters（except q N）.By contrast spraying high Zn concentration(80 and 100 mg·L-1)showed opposite effects.Moreover,?Jingu 21? showed more remarkable variation higher than ?Zhangzagu10’.Thus,low Zn concentration promoted plant growth,while high Zn concentration inhibited plant growth,which was most pronounced during the Millet booting stage.The optimal conditions were booting period and 40 mg·L-1 Zn.（3）Under the field experiment,the zinc content in different parts and the phytic acid content of seeds were determined of millet.The phytic acid/zinc molar ratio was used to evaluate the zinc bioavailability.The results showed that after different exogenous zinc treatment,the grains,leaves,stem-sheath and root zinc content increased gradually with the increase of zinc concentration,namely Zn5 > Zn4 > Zn3 > Zn2 > Zn1 > CK.Although the trend was the same in different varieties and different periods,but the change degree was different.The zinc content in different parts at seedling stage,booting stage,flowering stage and filling stage was mainly shown as: leaves > root > stem-sheath > seed（Zhangzagou 10 at seedling stage and Jingu 21 at filling stage shown as: leaves > root ≈ stem-sheath > seed）.With the increased of zinc concentration,the phytic acid content of millet seeds decreased first and then gradually increased,while the phytic acid/zinc molar ratio decreased significantly.The phytic acid content and phytic acid/zinc molar ratio both changed the most at booting stage.（4）Through two consecutive field experiments,the yield,nutrient quality and cooking quality of different concentrations of zinc fertilizer were measured in different periods of millet.The results showed that application of suitable exogenous zinc(20 to 60 mg·L-1)can improve the millet yield（4.89%-21.16%）,mainly on the influence of the thousand seed weight and grain weight per spike,the ear length had little impact.The content of crude protein,crude fat,soluble total sugar,reducing sugar,starch,vitamin C,amino acids and mineral elements in jingu21 and zhangzao 10 could be increased by spraying zinc solution with appropriate concentration(20-60 mg·L-1)in different periods.The response of nutrient content to different zinc concentrations was Zn2 > Zn3≈Zn1> CK > Zn4 > Zn5.High concentrations of zinc(80-100 mg·L-1)reduced the nutrient quality.Proper zinc concentration can also increased the cooking quality,the alkali spreading value and gel consistency have a certain degree of improvement,high concentrations will inhibit.The two-year trial showed the greatest variation in booting stage. |
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