Research On Screening Of Maize Resistance Variety To Low Iron And Physiological Mechanism

Study the influence of different Fe3+ levels on corn seedling to screen the optimum iron concentration for corn seedling. Then 23 maize cultivars were cultured in low and regular iron supply conditions, low iron tolerance comparative values of morphological and physiological indexes of seedings were evaluated by the principal component analysis, subordinate function analysis and clustering analysis to evaluate their ability of resistance to low iron. Selected the two representative varieties from them, Zhenghong2 which is resisted to low iron and Chuandan 418 which is not resisted to low iron for the light, medium and heavy degree of low iron stress and studying maize seeding plants growth, photosynthetic characteristics, iron metabolism, resistibility and root physiological characteristics of this two varieties of maize, which is to reveal the resistance to low iron stress response mechanism in maize seeding stage. The results were as follows:(1)Low concentration of Fe3+ nutrient solution inhibits the growth of the shoot and the high significantly inhibits the growth of the root. The most suitable Fe3+ concentration for Maize-Zhenghong505 is 100 μmol/L.10 μmol/L Fe3+ can be used as low iron stress concentration. The active Fe and chlorophyll content were increased with the increase of iron concentration. The correlationship between them was significant at 1% level, and the correlation with both for iron concentration conforms to the logistic function model, and to the growth of the plant state (plant height, stem diameter, leaf area, leaf weight, etc.) also reached significant level. So the active Fe and chlorophyll content can be used as integrated indicators to predict Fe-deficiency of maize early development stage.(2)The tolerance to low iron stress among 23 cultivars were markedly different, and Fangyul, Fukangyu909, Zhengda619, Zhenghong102, Fude2 and Zhenghong2 had strong resistance to low iron. Comparative values of expanded leaf number, leaf area, root length, root dry weight and iron accumulation could be considered as low iron-resistance selection indexes in maize seedling stage. The regression equation D= (-384.23+2.71X4+2.50X5+3.22X6+1.70X9+4.86X14)×10-3, can be used to predict the low iron-resistance ability of maize cultivars in seedling stage.(3)Low iron stress caused maize seedling’s height, stem diameter, visible leaf, expanded leaf, root length, root volume and leaf area reduced. In general, the influence of low iron stress on aboveground growth is relatively smaller than underground part and the effect on Zhenghong2 is relatively smaller than Chuandan418.(4) Low iron stress not only reduce the leaf area of corn seedling stage, will also reduce the leaf chlorophyll content and photosynthetic rate, and thus affect the accumulation of dry matter. Dry weight per plant and iron concentration was significantly positive correlation.Compared with Chuandan418, dry weight of Zhenghong2 per plant (y) is affected by concentration of iron (x) is small, and the slope of the linear regression equation of iron concentration is low.(5) With the reduction of iron concentration, the corn seedling root activity and soluble iron per capacity (megan acid secretion) is reduced, lead to the ground and underground part of iron content and accumulation is reduced, but the iron element to aboveground distribution, physiological efficiency of iron element are enhanced, this may be a important physiological mechanism of corn adapt to low iron stress. Compared with Chuandan418, Iron accumulation of Zhenghong2 is higher, less affected by the concentration of iron, and physiological efficiency of iron absorption is higher under the condition, this is why Zhonghong2 has strong capability of resistance to low iron.(6)Under low iron stress, POD enzyme changed indistinctively, but the CAT enzyme activity was significantly suppressed, which makes the active oxygen removal ability and corn membrane system damage, and the more serious with low iron stress increase, but at the same time, soluble protein content increased dramatically, to a certain extent to ensure the balance of cell osmotic potential. The Zhenghong2’s CAT enzyme activity and soluble protein content were higher than Chuandan418;it shows that Zhenghong2 has the strong ability of active oxygen removal and osmotic regulation, stronger adaptability to the low iron stress.