Abstract
The appropriate increase of planting densities is the key to the obtainment of high-yield maize (Zea mays L.). However, lodging is a major constraint to limit grain yield under increased planting density in present maize production. Effects of population density on stalk lodging and agronomic traits were investigated using two maize cultivars Denghai 618 (DH618, low stalk with low spike height) and Xianyu335 (XY335, high stalk with high spike height). Four levels of density treatment were imposed by 1.5, 6.0, 7.5, and 9.0 × 104 plants ha−1. Results showed that bending strength, rind penetration strength, maximum bending strength, dry weight, and internode diameter of maize were significantly decreased with the increase of planting density. The change range of XY335 with the increase of planting density was significantly larger than that of DH618, showing a high sensitivity to planting density. In addition, the thickness of cortex and vascular bundle sclerenchyma cells was significantly reduced with the increase of planting density. Compared with 1.5 × 104 plants ha−1, the thickness of the above-ground third internode stem cortex was decreased by 9.64%, 12.72%, and 20.77% for DH618, and 19.26%, 30.49%, and 37.45% for XY335 at 6.0, 7.5, and 9.0 × 104 plants ha−1, respectively. The thickness of vascular bundle sclerenchyma cells at 1.5 × 104 plants ha−1 was decreased by 7.75%, 12.44%%, and 17.89% for DH618, 10.18%, 15.21%, and 24.73% for XY335, compared to those at 6.0, 7.5, and 9.0 × 104 plants ha−1, respectively. Visibly, with the increase of planting density, the thickness of cortex and vascular bundle sclerenchyma cells, and the number of vascular bundles were all significantly decreased, resulting in the increase of lodging rate. However, the extent of variation in these parameters for short-plant height hybrid was less than those for high-plant height hybrid, and the yield of short-plant height hybrid was greater than that of high-plant height hybrid, indicating that short-plant height hybrid has better resistance to lodging with higher yield at higher planting density. Therefore, lodging resistance and yield can be improved through selection and breeding strategies that achieving synergistic development of diameter, dry weight per unit, and cortex thickness in maize basal internodes.
Highlights
Maize (Zea mays L.) is one of the most important food and economic crops cultivated worldwide, with the development of social production, the demand for maize will greatly increase
The maximum lodging resistance of four densities of DH618 increased in varying degrees, while that of XY335 at 15,000 plants ha−1 and 60,000 plants ha−1 increased as growth proceeded
At low density (15,000 plants ha−1), XY335 was significantly higher than DH618, and the maximum resistance to reverse folding of XY335 was significantly lower than that of DH618 after the density increased to 60,000 plants ha−1 (Table 1)
Summary
Maize (Zea mays L.) is one of the most important food and economic crops cultivated worldwide, with the development of social production, the demand for maize will greatly increase. With the increase of planting density, population quality was greatly affected, and lodging has become one of the important limiting factors for the increase of summer maize yield in this region [3,4]. Planting density and lodging resistant is the key to high and stable yield of maize. One of the important ways to achieve a high-yield breakthrough is to select and breed maize hybrids with high density planting resistant in China. Compared with the evolution and development of maize production technology in the world and China, it is shown that increasing planting density is one of the key cultivation measures to increase maize yield in the past 50 years [6,9]. It is important to find out the mechanism of stalk lodging for high-yield maize at high plant density
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