We investigated the effect of enhanced atmospheric ammonia (NH3) in combination with low and high nitrogen (LN and HN, respectively) growth medium on photosynthetic characteristics of two maize (Zea mays L.) cultivars (NE5 with high- and SD19 with low N-use efficiency) across long-term growth period and their diurnal change patterns exposed to 10 nl l-1 and 1,000 nl l-1 NH3 fumigation in open-top chambers (OTCs). Regardless of the level of N in medium, increased NH3 concentration promoted maximum net photosynthetic rate (Pmax) and apparent quantum yield (AQY) of both cultivars at earlier growth stages, but inhibited Pmax of NE5 from silking to maturity stage and that of SD19 at maturity stage only above the ambient concentration. Greater positive/less negative responses were predominant in the LN than in the HN treatment, especially for SD19. Dark respiration rate (RD) remained more enhanced in the LN than in the HN treatment for SD19 as well as increased in the LN while decreased in the HN treatment for NE5 at their silking stage, following exposure to elevated NH3 concentration. Additionally, enhanced atmospheric NH3 increased net photosynthetic rate (PN) and stomatal conductance (gs) but reduced intercellular CO2 concentration (Ci) of both cultivars with either the LN or HN treatment during the diurnal period at tasseling stage. The diurnal change patterns of PN and gs showed bimodal curve type and those of Ci presented single W-curve type for NE5, when NH3 concentration was enhanced. As for SD19, single-peak curve type was showed for both PN and gs while single V-curve type for Ci. All results supported the hypothesis that appropriately enhanced atmospheric NH3 can increase assimilation of CO2 by improving photosynthesis of maize plant, especially at earlier growth stages and after photosynthetic "noon-break" point. These impacts of elevated NH3 concentration were more beneficial for SD19 as compared to those for NE5, especially in the LN supply environment. and L. X. Zhang ... [et al.].
Effects of high-temperature stress (HTS) and PEG-induced water stress (WS), applied separately or in combination, on the functional activity and ultrastructure of the photosynthetic apparatus (PSA) of maize (Zea mays L.) and sunflower (Helianthus annuus L.) plants were investigated. In maize plant tissues WS provoked the decrease in RWC by 10.9 %, HTS by 7.0 %, and after simultaneous application of the both treatments the decrease was 32.7 % in comparison with control plants. Similar but more expressed changes were observed in sunflower plants. Sunflower was more sensitive to these stresses. Net photosynthetic rate decreased significantly after all treatments, more in sunflower. In mesophyll chloroplasts after separately applied WS and HTS the number of grana and thylakoids was reduced and electron-transparent spaces appeared. At combined stress (WS+HTS) granal and stromal thylakoids were considerably affected and chloroplast envelope in many of them was partially disrupted. and I. Dekov, T. Tsonev, I. Yordanov.
Expression quantitative trait loci (eQTL) analyses were applied in order to identify genetic factors that are relevant to the expression of a β-isoform Rubisco activase gene in maize, namely ZmRCAβ, in this study. During two years, a maize recombinant inbred line population was measured for ZmRCAβ expression levels at the grain filling stage. Based on a genetic map containing 916 molecular markers, we detected five eQTLs, namely qRCA2.1 on chromosome 2, and qRCA4.1, qRCA4.2, qRCA4.3, and qRCA4.4 on chromosome 4. These eQTLs explained the phenotypic variation ranging from 6.14% to 7.50% with the logarithm of the odd values ranging from 3.11 to 4.96. Based on the position of the eQTLs and ZmRCAβ on the chromosome, qRCA4.2 was inferred as a cis-eQTL and the remaining as a trans-eQTL, suggesting that a combination of both cis- and trans-acting elements might control ZmRCAβ expression. qRCA4.2, qRCA4.3, and qRCA4.4 were repeatedly detected during two years., Q. Sun, Y. Zhang, B. Chen, B. Jia, Z. L. Zhang, M. Cui, X. Kan, H. B. Shi, D. X. Deng, Z. T. Yin., and Obsahuje bibliografii
Intercropping, a traditional and worldwide cropping practice, has been considered as a paradigm of sustainable agriculture based on complementary mechanisms among different crop species. Soybean (Glycine max) is widely relay intercropped about 60 days before maize (Zea mays) harvest in Southwest China. However, shade caused by tall maize plants may be a limiting factor for soybean growth at a seedling stage. In field research, we studied the ecophysiological responses of two widely cultivated soybean varieties [Gongqiudou494-1 (GQD) and Gongxuan 1 (GX)] to maize shading in a relay intercropping system (RI) compared with monocropped soybean plants (M). Our results showed that soybean seedlings intercropped with maize exhibited significantly downregulated net photosynthetic rate (PN) (-38.3%), transpiration rate (-42.7%), and stomatal conductance (-55.4%) due to low available light. The insignificant changes in intercellular CO2 concentration and the maximum efficiency of PSII photochemistry suggested that the maize shading-induced depressions in PN were probably caused by the deficiency of energy for carbon assimilation. The significantly increased total chlorophyll (Chl) content (+27.4%) and Chl b content (+52.2%), with lowered Chl a/b ratios (-20.5%) indicated soybean plants adjusted their light-harvesting efficiency under maize shading condition. Biomass and leaf area index (LAI) of seedlings under RI decreased significantly (-78.7 and -71%, respectively) in comparison with M. Correlation analysis indicated the relative reduction in biomass accumulation was caused by the decline in LAI rather than PN, it affected negatively the final yields of soybean (32.8%). Cultivar-specific responses to maize shading were observed in respects of LAI, biomass, and grain yield. It indicated that GX might be a better cultivar for relay intercropping with maize in Southwest China., B. Y. Su, Y. X. Song, C. Song, L. Cui, T. W. Yong, W. Y. Yang., and Obsahuje bibliografii
Plant response to the combination of two or more abiotic stresses is different than its response to the same stresses singly. The response of maize (Zea mays L.) photosynthesis, growth, and development processes were examined under sunlit plant growth chambers at three levels of each day/night temperatures (24/16°C, 30/22°C, and 36/28°C) and UV-B radiation levels (0, 5, and 10 kJ m-2 d-1) and their interaction from 4 d after emergence to 43 d. An increase in plant height, leaf area, node number, and dry mass was observed as temperature increased. However, UV-B radiation negatively affected these processes by reducing the rates of stem elongation, leaf area expansion, and biomass accumulation. UV-B radiation affected leaf photosynthesis mostly at early stage of growth and tended to be temperature-dependent. For instance, UV-B radiation caused 3-15% decrease of photosynthetic rate (PN) on the uppermost, fully expanded leaves at 24/16°C and 36/28°C, but stimulated P N about 5-18% at 30/22°C temperature. Moreover, the observed UV-B protection mechanisms, such as accumulation of phenolics and waxes, exhibited a significant interaction among the treatments where these compounds were relatively less responsive (phenolics) or more responsive (waxes) to UV-B radiation at higher temperature treatments or vice versa. Plants exposed to UV-B radiation produced more leaf waxes except at 24/16°C treatment. The detrimental effect of UV-B radiation was greater on plant growth compared to the photosynthetic processes. Results suggest that maize growth and development, especially stem elongation, is highly sensitive to current and projected UV-B radiation levels, and temperature plays an important role in the magnitude and direction of the UV-B mediated responses., S. K. Singh, K. R. Reddy, V. R. Reddy, W. Gao., and Obsahuje bibliografii
In China, narrow-wide row planting pattern has been advocated for maize (Zea mays L.) production. However, no previous study has clearly elucidated the complexity of factors affecting maize canopy such as the microclimatic factors, and the effect of photosynthesis in narrow-wide row planting pattern. The current study was undertaken to identify the planting patterns that influence microclimatic conditions and photosynthesis of two maize cultivars (Beiyu288 and Xianyu335) grown 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 (3) uniform row of 65 cm (CK, conventional row as control, 6.4 plants m-2). Light interception, temperature, relative humidity (RH), CO2 concentration, and leaf photosynthesis within the canopy were measured in each planting treatment at the grain-filling stage. The net photosynthetic rate
(PN), intercellular CO2 concentration (Ci), stomatal conductance
(gs), transpiration rate (E), and temperature of the narrow-wide row exceeded that of the conventional row. The CO2 concentration and RH of the narrow-wide row were lower than CK by 50 cm strata. The narrow-wide row had a more uniform light intercepted at the whole canopy profile. The results of the current study suggest that
narrow-wide row-planting pattern has a positive effect on canopy microclimate factors and promotes photosynthesis., T. D. Liu, F. B. Song., and Obsahuje bibliografii
The herbicides diuron, fluridone, or sulcotrione differently reduced chlorophyll (Chl) and carotenoid (Car) contents. Four days after herbicide treatment, application of sulcotrione resulted in a Chl/Car ratio of 5.88, similar as in untreated controls; diuron resulted in ratio of 5.24, while fluridone induced a greater diminution in Car contents and yielded a final ratio of 7.02. Sulcotrione induced a more rapid decrease than fluridone did in the quantum yield of photosystem 2 (PS2) as monitored by Chl fluorescence. Measurements of DPIP reduction with isolated thylakoids indicated that sulcotrione was a more effective inhibitor of the Hill reaction in cucumber, a herbicide sensitive species, than in maize, a herbicide-insensitive species. These results are consistent with the view that inhibition of electron transport via reduction in plastoquinone contents in plants leads to the major herbicidal effect of sulcotrione in mature green tissues. and J.-S. Kim ... [et al.].
Current research on the effect of increased UV-B radiation on crop production has been limited to exposing plants to improbable UV-B dose or growth condition. The objective of this study was to test the effects of short-term modulated increased UV-B radiation on maize (Zea mays L.) growth, grain yield, and quality under field conditions for three years. A modulated irradiance system was used to maintain UV-B radiation at 30% above the ambient level and was applied daily between the elongation and silking stages of maize. The result indicated that increased UV-B radiation adversely affected maize growth and yield, especially on plant height when UV-B was enhanced at the elongation stage and on yield when UV-B was enhanced near the silking stage. Yield reduction that induced by enhanced UV-B radiation was associated with reductions in number of kernels per row and kernel mass. Protein content of grains was increased with enhanced UV-B radiation, but oil and starch contents were not affected. This study confirmed the sensitivity of maize to increased UV-B radiation under the field condition, and contributed to understand the full negative and positive effects of increased UV-B radiation on crop production., L. N. Yin, S. W. Wang., and Obsahuje bibliografii
The rainy season affects the development of maize in Liaoning Province in China. Continuous, rainy weather and scant sunlight result in poor pollination, bald tips, and in an abnormally high, barren stalk. Field studies were conducted at the kernel formation stage (3-11 d after silking). Paired, near-isogenic lines of nonbarren stalk (Shennong 98B) and barren stalk (Shennong 98A) were exposed to 38, 60, and 75% shading to investigate changes in photosynthesis and chlorophyll (Chl) fluorescence characteristics under different light intensities. Net photosynthetic rate (PN), leaf maximum photochemical efficiency of PSII (Fv/Fm), photochemical quenching of Chl fluorescence (qP), and actual photochemical efficiency of PSII (ΦPSII) of Shennong 98B were always higher than those of Shennong 98A under natural light, contrary to nonphotochemical quenching (NPQ). Fv/Fm, ΦPSII, and qP increased, while PN and electron transport rate (ETR) decreased after shading, and this was aggravated with increasing shade intensity. PN, qP, ΦPSII, and ETR were lower than the values in natural light condition after seven days of shading. NPQ, Fv/Fm, ΦPSII, qP, and ETR recovered, when shading was removed. The PN of two inbred lines returned soon to the control levels after 38% shade. Under shade and natural light conditions, the PN and Chl fluorescence characteristics of Shennong 98A were both lower than those of Shennong 98B. We suggest that a poor adaptability to low light is an important physiological reason for inducing barren stalk in low light-sensitive maize., X. M. Zhong, Z.S. Shi, F.H. Li, H.J. Huang., and Obsahuje bibliografii
Soil compaction in agricultural areas inhibits plant root growth through increased mechanical resistance, altered water and nutrient supply. The main objective of this study was to evaluate spatial distribution of roots and its effect on water uptake of maize grown on field with subsoil compaction. Two treatments were examined: complex melioration consisting of deep loosening in combination with drainage and control without applied meliorations. Root observations were conducted on vertical and superposed horizontal planes covered with a 2 cm grid short after silking. Root distributions expressed as index of density and/or dry mass density were estimated down to 1m soil depth and with a distance to a plant base. For analysis of root distribution pattern on the horizontal planes, a Variance to Mean Ratio (VMR) test was applied. Soil water monitoring were conducted during the vegetation period. On the vertical planes, root densities were similar in the topsoil of both treatments, but the results were significantly higher in the subsoil of the meliorated one showing deeper allocation of root density. In contrast, the control had more squares with lots of roots (i.e. higher indexes) just at the top- subsoil boundary owing to bunching of roots in macropores. The horizontal planes in the control generally consisted larger areas without visible roots and thus great distances for water and nutrient transmission, especially in the subsoil. The estimated VMR also pointed toward different levels of root clustering. Consequently, an inhibited water extraction from the subsoil in the control, a delay in crop ontogenesis and a less biomass production was established during the observed period. and Zhutnenie poľnohospodárskej pôdy bráni rastu koreňov; je to spôsobené zvýšeným mechanickým odporom pôdy, a zníženým prítokom vody a živín. Cieľom tejto štúdie je zhodnotenie priestorovej variability koreňov, ich vplyvu na odber vody koreňmi kukurice na poli so zhutnenou podorničnou vrstvou. Boli hodnotené dva spôsoby obrábania: komplexná meliorácia pozostávajúca z hlbokého podrývania v kombinácii s drenážou a obrábanie (kontrola) bez melioračných zásahov. Identifikácia rozdelenia koreňov bola vykonaná vo vertikálnych a horizontálnych rovinách s 2-cm sieťou, krátko po metaní. Rozdelenie koreňov bolo vyjadrené ako index hustoty alebo ako hustota suchej biomasy koreňov do hĺbky 1 m; v horizontálnom smere až k susedným rastlinám. Bol použitý test ''Variance to Mean Ratio'' (VMR) na určenie rozdelenia koreňov v horizontálnom smere počas vegetačného obdobia. Hustota koreňov vrchnej vrstvy pôdy vo vertikálnej rovine bola podobná pre obidve varianty, ale pre meliorovanú pôdu boli hodnoty hustoty koreňov v podloží podstatne vyššie a korene zasahovali hlbšie. Ako protiklad, na kontrolnom pozemku bolo viac štvorcov s mnohými koreňmi (t.j. vyššie indexy) práve na hranici orničnej a podorničnej vrstvy, pre enormný rast koreňov v makropóroch. V horizontálnej rovine tento kontrolný pozemok obsahoval veľké oblasti bez viditeľných koreňov, a to znamená veľké vzdialenosti pre prenos vody a živín v podorničnej vrstve. Výsledky aplikácie VMR naznačujú tiež rozdielne úrovne zhlukov koreňov. Z toho vyplýva znížený odber vody koreňmi rastlín na kontrolnom pozemku, ako aj pomalšia ontogenéza a nižšia produkcia biomasy, ktorá bola identifikovaná počas sledovaného obdobia.