title: Effects of plant density on the photosynthetic and chloroplast characteristics of maize under high-yielding conditions.
abstract: Plant density has been recognized as a major factor determining the grain yield. The photosynthetic performance changes as the density increases. The main objective of this research was to evaluate responses of photosynthetic performance and chloroplast ultrastructure to planting densities in two summer maize (Zea mays L.) hybrids Denghai661 (DH661) and Nongda108 (ND108). DH661 was planted at densities of 30,000, 45,000, 60,000, 75,000, 90,000, 105,000, 120,000, or 135,000 plants ha-1. ND108 was planted at densities of 30,000, 45,000, 60,000, 75,000, or 90,000 plants ha-1. Research variables included leaf area, grain yield, chlorophyll content, leaf gas exchange parameters, number of chloroplasts, and chloroplast ultrastructure. As plant density increased, chlorophyll a and b content significantly decreased; carotenoids initially decreased and then increased; the net photosynthetic rate during each growth period significantly decreased; the membrane structure of mesophyll cells was gradually damaged; the number of chloroplasts significantly decreased; the external form of chloroplasts shifted from long and oval to elliptical or circular; the number of grana significantly decreased, while the number of grana lamellae increased; grana gradually became hypogenetic and eventually dissolved; plot yield increased; and yield per plant significantly decreased. The yield per plant of DH661 at 135,000 plants ha-1and that of ND108 at 90,000 plants ha-1decreased by 65.8 and 42.5%, respectively, compared with those at 30,000 plants ha-1.
authors.affiliation: State Key Laboratory of Crop Biology and College of Agronomy, Shandong Agricultural University, Taian, 271018, Shandong, People's Republic of China.
authors.forename: Baizhao
authors.initials: B
authors.lastname: Ren
authors.affiliation: Yantai Academy of Agricultural Science, Yan tai, 265599, Shandong, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Crop Biology and College of Agronomy, Shandong Agricultural University, Taian, 271018, Shandong, People's Republic of China. jwzhang@sdau.edu.cn.
authors.forename: Jiwang
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Crop Biology and College of Agronomy, Shandong Agricultural University, Taian, 271018, Shandong, People's Republic of China.
authors.forename: Shuting
authors.initials: S
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Crop Biology and College of Agronomy, Shandong Agricultural University, Taian, 271018, Shandong, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Crop Biology and College of Agronomy, Shandong Agricultural University, Taian, 271018, Shandong, People's Republic of China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhao
mesh_terms: D002734:Chlorophyll / Q000032:analysis; D002736:Chloroplasts / Q000737:chemistry / Q000648:ultrastructure*; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves / Q000033:anatomy & histology; D011156:Population Density; D012621:Seasons; D012639:Seeds / Q000033:anatomy & histology; D003313:Zea mays / Q000033:anatomy & histology / Q000502:physiology* / Q000648:ultrastructure*
chemical_list: D002734:Chlorophyll
keywords: Chloroplast; Plant density; Summer maize; Ultrastructure