Relationship Between Anatomic Structure Of Maize Vegetative Organs And Yields Under Different Planting Densities

The differences in vegetative organ structures of maize were studied grown under high, medium and low planting density conditions. The correlation between structure, density and yield were analysed by the SPSS software. The results are listed as follows:First, with the increase of the planting density, the root number of individual plant and the overall diameter and stele diameter of root obviously reduced, but the ratio of stele to root diameter reduced slightly. Moreover, the numbers and diameters of protoxylem and metaxylem vessels were significantly reduced, and the total element numbers of phloem and phloem of roots in cross-section reduced. The data analysis indicated that all root parameters mentioned above has a remarkably negative correlation with the density, but positive correlation with yield.Second, the effect of planting density on the thickness of mechanical tissues in ear node and the first node below ear is not obvious. However, density affects greatly the number and size of vascular bundles (on cross section) in the two nodes. The number and size of vascular bundles was notably lower at the planting density of 5000-6000 plants/mu than that at 4000 plants/mu. The total number and size of vascular bundles had a remarkably negative correlation with the density, but positive correlation with yield. In particular, the effect of density is more visible in phloem compared to xylem, and both phloem area and sieve number negatively correlated with density, positively correlated with yield.Finally, with the increase of planting density, the area of whole leaves of a single plant decreases, the length of ear five-leaf increases and width decreases, the leaf shape tends to become slender. The size of epidermis cell is almost unchanged and the thickness of mesophyll is greatest under the density of 5000 plants /mu. Both the distances among veins and the sizes of veins are not obviously changed, compared to the visible alteration in the xylem area of leaf vein, which becomes lower with the increase of planting density. The density of stomata reduces with planting density increase, but the length and width of single stomata become a lit larger. The leaf area, the vein structure and the density of stomata has a remarkable negative correlation with density, and remarkable positive correlation with the yield indexes.In summary, the results in the present thesis indicate that the effect of high density on roots is greater than on stems and leaf, the effect on phloem of the ear node and the first node below ear is greater than xylem, the effect on the leaf structure is only a little bit.