| The veins are distributed regularly in mesophyll tissues and play a role in transport and support.The internal structure of the vein varies with the size of the veins.Maize is a typical gramineous plant with obvious parallel veins sequence.The mid-vein in the middle part of the leaf blade contains multiple vascular bundles,and the mesophyll tissues on both sides of the mid-vein are distributed with different thicknesses.According to the thickness can be divided into 1st-level lateral veins,2nd-level lateral veins,3rd-level lateral veins,and 4th level lateral veins.In this study,the leaves of two maize inbred lines Zheng 58,Chang 7-2 and their hybrid offspring Zheng 58 × Chang 7-2(Zhengdan 958,Chang 7-2 × Zheng 58)were used as materials.The relationship of leaf size,the number of lateral veins,the relationship between lateral veins and leaf width and the differences of leaf vein parameters were compared.The main results are as follows:1)In total,2220 groups of vein data were collected from the four maize materials.The leaf length increased gradually to the maximum and then decreased,and the maximum was at the 10-13 th leaf stage.The leaf width was similar,and the maximum value was 6-10 th leaf stage.The ratio of length to width of the two hybrid offspring in the early growing stage of maize was similar to that of Zheng58 and Zheng58 and the ratio of length to width of the two hybrid combinations was more similar to that of Chang 7-2.The leaf size of hybrid offspring was larger than that of Chang 7-2,showing heterosis.2)A total of 1083 samples were collected from four maize materials.The ratio of the number of primary lateral veins to leaf width was proportional to the growth and development stage of maize.From 11 th leaf stage to 13 th leaf stage,the number of primary lateral veins was the most,which began to decrease gradually after 13 th leaves.The number of unilateral pulses can be expressed by formula n+2.The leaf width was positively correlated with the number of lateral veins.3)The diameter of the 1st-level lateral vein was in direct proportion to the distance and width of the first lateral vein.The diameter of each lateral vein increased steadily from the 3rd leaf stage to the 12-14 th leaf stage and reached the maximum value,and then decreased.The leaf veins density was stable after 13 th leaf stages in the late stage of leaf growth and development.Analysis of leaf vein parameters showed that hybrid offspring were more similar to their female parents.4)The microscopy showed that the leaf veins of hybrid offspring were more similar to their female parents.It was found that the structure of mid-vein region,the number of primary lateral veins and the number of cells in mid-vein region of hybrid offspring were more similar to those of female parents,and the area of mid-vein region of Zheng58 and Zheng 58 × Chang 7-2 was larger than that of female parent.The staining results showed that there was more lignin in the mid-vein region of Chang 7-2 and Zheng 58 × Chang 7-2,which indicated that its leaf vein had stronger supporting power.5)The study of photosynthetic rate showed that the photosynthetic rate of two hybrid offspring was higher than that of inbred lines,while the leaf vein was responsible for the transport of photosynthetic products,which reflected the positive correlation between photosynthetic rate and leaf veins parameters.There was a positive correlation between photosynthetic rate and leaf size.In this study,the leaf size,leaf vein number,leaf vein parameters,leaf vein morphology and anatomy were compared and analyzed between hybrids and their parents.The results showed that the size and number of hybrid combinations were more similar to those of their female parents.The size and number of cells in the mid-vein region were further verified,and the results were in accordance with the above results.This study will provide new data for analyzing the mechanism of maize heterosis. |
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