Planting pattern affects canopy structure of crops and influences other physiological characteristics such as light interception and radiation use efficiency. In the current paper, the effects of planting patterns on the canopy structure, light interception, and photosynthetic characteristics at silking stage of two maize (Zea mays L.) cultivars (Beiyu288 and Xianyu 335) were examined in three planting patterns narrow-wide rows of (1) 30 cm + 170 cm (P1, 6.4 plants m -2 ), and (2) 40 cm+90 cm (P2, 6.4 plants m -2 ), and uniform row of 65 cm (control, i.e. CK, 6.4 plants m -2 ). The ratio of leaves perpendicular to rows was highest in P1 and the leaf orientation value in P1 was constant and slightly lower in P2 compared with that in CK. Although a decrease in the total intercepted photosynthetically active radiation (IPAR) of P1 was found in the two cultivars, more incoming PAR was detected at the middle-low canopy strata of P1. The apparent quantum yield and the net photosynthesis rate (P N ) in P1 and P2 were significantly higher than those in CK. The P N and stomatal conductance (g s ) values in P1 were significantly higher than those in CK, and the intercellular CO 2 concentration decreased with an increase in P N . These results indicated that narrow-wide row planting patterns improved the canopy structure, allowed more IPAR to reach the middle-low strata of the canopy, and enhanced the leaf photosynthetic characteristics of maize crops at silking stage compared with CK.Additional key words: intercellular CO 2 concentration; net photosynthesis rate; stomatal conductance; Zea mays L. ResumenEstructura de la cubierta vegetal, intercepción de luz y características fotosintéticas en el cultivo de maíz en floración bajo diferentes patrones espaciales de las plantas El patrón espacial de las plantas puede afectar a la estructura de la cubierta vegetal de los cultivos y a diversas características fisiológicas. En este trabajo se analizó el efecto del patrón espacial sobre la estructura del cultivo, la intercepción de luz, y la capacidad fotosintética en dos híbridos de maíz (Beiyu288 y Xianyu335). Estos se sembraron siguiendo tres patrones espaciales: en hileras estrechas y anchas de 30 cm+170 cm (P1), 40 cm+90 cm (P2) y en hileras a 65 cm (CK), con una densidad de siembra de 6,4 plantas m -2 . El patrón espacial de las plantas no afectó al índice del área foliar, pero si afectó a su distribución espacial: en P1 se registró la mayor proporción de hojas perpendiculares a la hilera de siembra y las hojas presentaron una angulación uniforme con respecto al tallo; en P2 presentaron menor ángulo que en CK. La captura de luz resultó menor en P1, y una mayor cantidad de luz alcanzó a los estratos inferiores de la cubierta vegetal. Con todos los patrones espaciales, al incrementar la P N se redujeron tanto la tasa de fotosíntesis neta (P N ) como la conductancia estomática (g s ) y la concentración de CO 2 intracelular (C i ). Sin embargo, la P N y la g s fueron mayores en P1 que en CK. Los resultados indican que e...

In a field experiment, two winter wheat (Triticum aestivum L.) cultivars, Tainong 18 (a large-spike cultivar) and Jinan 17 (a multiple-spike cultivar), were treated with 78% (S1), 50% (S2), and 10% (S3) of full sunshine (S0, control) from anthesis to maturity to determine the responses of photosynthetic characteristics and antioxidative enzyme activities in a flag leaf. Compared with S0 treatment, the chlorophyll (Chl) content and maximal efficiency of photosystem II (PSII) photochemistry (F v /F m ) of flag leaves were enhanced in treatments S1 and S2. From 0 to 7 d post flowering, the Chl content and F v /F m in S3 were also higher than those in S0, but significantly lower than those in controls, respectively. With the increase of shading intensity, the effective quantum yield of PSII (Φ PSII ) was promoted; whereas, the ratio of Chl a/b declined. Compared with S0, treatments S2 and S3 significantly suppressed the activities of superoxide dismutase (SOD) and peroxidase (POD), net photosynthetic rate (P N ), and contents of total soluble sugar, nevertheless, S1 treatment showed positive effects on the above parameters. Under the same shading condition, Jinan 17 had larger Chl content and higher activities of PSII and antioxidative enzymes, but lower malondialdehyde (MDA) content than Tainong 18. The results indicated that multiple-spike cultivar was more advantageous for the Huang-Huai-Hai Plain, where shading problem occurs later during the growth period, than the large-spike cultivar, because of the lesser damage in a flag leaf and better photosynthetic function of the former one. Wheat plants under S1 shading condition had relatively high activities of antioxidative enzymes and a low degree of membrane lipid peroxidation, which was in favor of stress resistance, maintaining high P N duration, and accumulation of photosynthates in wheat plants.