title: Effects of shading on the photosynthetic characteristics and mesophyll cell ultrastructure of summer maize.
abstract: A field experiment was conducted to study the effects of shading on the photosynthetic characteristics and mesophyll cell ultrastructure of two summer maize hybrids Denghai605 (DH605) and Zhengdan958 (ZD958). The ambient sunlight treatment was used as control (CK) and shading treatments (40 % of ambient sunlight) were applied at different growth stages from silking (R1) to physiological maturity (R6) (S1), from the sixth leaf stage (V6) to R1 (S2), and from seeding to R6 (S3), respectively. The net photosynthetic rate (P n) was significantly decreased after shading. The greatest reduction of P n was found at S3 treatment, followed by S1 and S2 treatments. P n of S3 was decreased by 59 and 48 % for DH605, and 39 and 43 % for ZD958 at tasseling and milk-ripe stages, respectively, compared to that of CK. Additionally, leaf area index (LAI) and chlorophyll content decreased after shading. In terms of mesophyll cell ultrastructure, chloroplast configuration of mesophyll cells dispersed, and part of chloroplast swelled and became circular. Meanwhile, the major characteristics of chloroplasts showed poorly developed thylakoid structure at the early growth stage, blurry lamellar structure, loose grana, and a large gap between slices and warping granum. Then, plasmolysis occurred in mesophyll cells and the endomembrane system was destroyed, which resulted in the dissolution of cell membrane, karyotheca, mitochondria, and some membrane structures. The damaged mesophyll cell ultrastructure led to the decrease of photosynthetic capacity, and thus resulted in significant yield reduction by 45, 11, and 84 % in S1, S2, and S3 treatments, respectively, compared to that of CK.
authors.affiliation: State Key Laboratory of Crop Biology and College of Agronomy, Shandong Agricultural University, Taian, Shandong, 271018, People's Republic of China.
authors.forename: Baizhao
authors.initials: B
authors.lastname: Ren
authors.affiliation: State Key Laboratory of Crop Biology and College of Agronomy, Shandong Agricultural University, Taian, Shandong, 271018, People's Republic of China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Cui
authors.affiliation: Department of Agronomy, Purdue University, West Lafayette, IN, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Camberato
authors.affiliation: State Key Laboratory of Crop Biology and College of Agronomy, Shandong Agricultural University, Taian, Shandong, 271018, 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, Shandong, 271018, 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, Shandong, 271018, People's Republic of China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Crop Biology and College of Agronomy, Shandong Agricultural University, Taian, Shandong, 271018, People's Republic of China. jwzhang@sdau.edu.cn.
authors.forename: Jiwang
authors.initials: J
authors.lastname: Zhang
mesh_terms: D002736:Chloroplasts / Q000528:radiation effects / Q000648:ultrastructure; D058503:Mesophyll Cells / Q000528:radiation effects / Q000648:ultrastructure*; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D018515:Plant Leaves / Q000166:cytology / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D013472:Sunlight; D003313:Zea mays / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects* / Q000648:ultrastructure
keywords: Leaf ultrastructure; Mitochondria; Photosynthetic characteristics; Shading; Summer maize (Zea mays L.)