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
Periodic drought fluctuation is a common phenomenon in Northwest China. We analyzed the response of Chinese dwarf cherry (Cerasus humilis) seedlings, a dwarf shrub species with considerably strong adaptabilities, exposed to water stress (WS) by withholding water for 21 d, and subsequent recovery of 7 d. Leaf relative water content (LRWC), net photosynthetic rate (PN), maximal quantum yield of PSII photochemistry (Fv/Fm), and effective quantum yield of PSII photochemistry (ΦPSII) decreased with increasing water deficit. In contrast, the nonphotochemical quenching of Chl fluorescence (NPQ) significantly increased, as well as the amounts of violaxanthin (V) + antheraxanthin (A) + zeaxanthin (Z). In the whole levels, the photosynthetic pigment composition did not display significant changes in WS seedlings. However, the de-epoxidation state of xanthophyll cycle pigments [(Z+0.5A)/VAZ ] generally exhibited higher values in WS seedlings. The significant inhibition of de-epoxidation by dithiothreitol (DTT) and negligible changes of epoxidation of Z by glucosamine (Gla) were both observed; the slight but stably upregulated transcript level of violaxanthin de-epoxidase (VDE) and downregulated zeaxanthin epoxidase (ZEP) expression profile were found during WS period, indicating that they were regulated on post-transcript levels. VDE activity, via the accumulation of Z and A, which confers a greater capacity of photoprotection, appears to contribute to the survival of severely stressed plants. and X. S. Song ... [et al.].
Mutants with altered leaf morphology are useful as markers for the study of genetic systems and for probing the leaf differentiation process. One such mutant with deficient greening and altered development of the leaf mesophyll appeared in an inbred line of sunflower (Helianthus annuus L.). The objectives of the present study were to determine the inheritance of the mutant leaf trait and its morphological characterisation. The mutation, named mesophyll cell defective1 (mcd1), has pleiotropic effects and it is inherited as a monogenic recessive. The structure and tissue organization of mcd1 leaves are disrupted. In mcd1 leaves, the mesophyll has prominent intercellular spaces, and palisade and spongy tissues are not properly shaped. The mutant palisade cells also appear to be more vacuolated and with a reduced number of chloroplasts than the wild type leaves of equivalent developmental stage. The lamina thickness of mcd1 leaves is greatly variable and in some areas no mesophyll cells are present between the adaxial and abaxial epidermis. The leaf area of the mcd1 mutant is extremely reduced as well as the stem height. A deficient accumulation of photosynthetic pigments characterizes both cotyledons and leaves of the mutant. In mcd1 leaves, chlorophyll (Chl) fluorescence imaging evidences a spatial heterogeneity of leaf photosynthetic performance. Little black points, which correspond to photosystem II (PSII) maximum efficiency (Fv/Fm) values close to zero, characterize the mcd1 leaves. Similarly, the lightadapted quantum efficiency (ΦPSII) values show a homogeneous distribution over wild type leaf lamina, while the damaged areas in mcd1 leaves, represented by yellow zones, are prominent. In conclusion, the loss of function of the MCD1 gene in Helianthus annuus is correlated with a variegated leaf phenotype characterized by a localized destruction of mesophyll morphogenesis and defeat of PSII activity. and M. Fambrini ... [et al.].
Accurate and nondestructive methods to determine individual leaf areas of plants are a useful tool in physiological and agronomic research. Determining the individual leaf area (LA) of rose (Rosa hybrida L.) involves measurements of leaf parameters such as length (L) and width (W), or some combinations of these parameters. Two-year investigation was carried out during 2007 (on thirteen cultivars) and 2008 (on one cultivar) under greenhouse conditions, respectively, to test whether a model could be developed to estimate LA of rose across cultivars. Regression analysis of LA vs. L and W revealed several models that could be used for estimating the area of individual rose leaves. A linear model having L×W as the independent variable provided the most accurate estimate (highest r2, smallest MSE, and the smallest PRESS) of LA in rose. Validation of the model having L×W of leaves measured in the 2008 experiment coming from other cultivars of rose showed that the correlation between calculated and measured rose LA was very high. Therefore, this model can estimate accurately and in large quantities the LA of rose plants in many experimental comparisons without the use of any expensive instruments. and Y. Rouphael ... [et al.].
a1_Shallow ponds with rapidly photosynthesising cyanobacteria or eukaryotic algae are used for growing biotechnology feedstock and have been proposed for biofuel production but a credible model to predict the productivity of a column of phytoplankton in such ponds is lacking. Oxygen electrodes and Pulse Amplitude Modulation (PAM) fluorometer technology were used to measure gross photosynthesis (PG) vs. irradiance (E) curves (PG vs. E curves) in Chlorella (chlorophyta), Dunaliella salina (chlorophyta) and Phaeodactylum (bacillariophyta). PG vs. E curves were fitted to the waiting-in-line function [PG = (PGmax × E/Eopt) × exp(1 — E/Eopt)]. Attenuation of incident light with depth could then be used to model PG vs. E curves to describe PG vs. depth in pond cultures of uniformly distributed planktonic algae. Respiratory data (by
O2-electrode) allowed net photosynthesis (PN) of algal ponds to be modelled with depth. Photoinhibition of photosynthesis at the pond surface reduced PN of the water column. Calculated optimum depths for the algal ponds were: Phaeodactylum, 63 mm; Dunaliella, 71 mm and Chlorella, 87 mm. Irradiance at this depth is ≈ 5 to 10 μmol m-2 s-1 photosynthetic photon flux density (PPFD). This knowledge can then be used to optimise the pond depth. The total net P N [μmol(O2) m-2 s-1] were: Chlorella, ≈ 12.6 ± 0.76; Dunaliella, ≈ 6.5 ± 0.41; Phaeodactylum ≈ 6.1 ± 0.35. Snell’s and Fresnel’s laws were used to correct irradiance for reflection and refraction and thus estimate the time course of PN over the course of a day taking into account respiration during the day and at night. The optimum PN of a pond adjusted to be of optimal depth (0.1-0.5 m) should be approximately constant because increasing the cell density will proportionally reduce the optimum depth of the pond and vice versa., a2_Net photosynthesis for an optimised pond located at the tropic of Cancer would be [in t(C) ha-1 y-1]: Chlorella, ≈ 14.1 ± 0.66; Dunaliella, ≈ 5.48 ± 0.39; Phaeodactylum, ≈ 6.58 ± 0.42 but such calculations do not take weather, such as cloud cover, and temperature, into account., R. J. Ritchie, A. W. D. Larkum., and Obsahuje bibliografii a dodatky
Irradiance data software developed by the NREL Solar Radiation Laboratory (Simple Model of Atmospheric Radiative Transfer of Sunshine, SMARTS) has been used for modelling photosynthesis. Spectra and total irradiance were expressed in terms of quanta [mol m-2 s-1, photosynthetic photon flux density, PPFD (400-700 nm)]. Using the SMARTS software it is possible to (1) calculate the solar spectrum for a planar surface for any given solar elevation angle, allowing for the attenuating effects of the atmosphere on extraterrestrial irradiance at each wavelength in the 400-700 nm range and for the thickness of atmosphere the light must pass through during the course of a day, (2) calculate PPFD vs. solar time for any latitude and date and (3) estimate total daily irradiance for any latitude and date and hence calculate the total photon irradiance for a whole year or for a growing season. Models of photosynthetic activity vs. PPFD are discussed. Gross photosynthesis (Pg) vs. photosynthetic photon flux density (PPFD) (Pg vs. I) characteristics of single leaves compared to that of a canopy of leaves are different. It is shown that that the optimum irradiance for a leaf (Iopt) is the half-saturation irradiance for a battery of leaves in series. A C3 plant, with leaves having an optimum photosynthetic rate at 700 μmol m-2 s-1 PPFD, was used as a realistic worked example. The model gives good estimates of gross photosynthesis (Pg) for a given date and latitude. Seasonal and annual estimates of Pg can be made. Taking cloudiness into account, the model predicts maximum Pg rates of about 10 g(C) m-2 d-1, which is close to the maximum reported Pg experimental measurements. and R. J. Ritchie.
Chlorophyll fluorescence measurements showed that plasticity to salinity in stems of Salicornia ramosissima is expressed at a modular level, so intraplant variation should be considered in further studies. and S. Redondo-Gómez ... [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
We investigated the effect of moderate Cu2+ and Cd2+ stress by applying chlorophyll (Chl) fluorescence and P700 absorbance measurements to monitor the photosynthetic electron transport activity of 3-week-old Pisum sativum L. cv. Petit Provençal plants grown in a modified Hoagland solution containing 50 μM CuSO4 or 5 μM CdCl2. Both heavy metals caused a slight inhibition in PSII photochemistry as indicated by the decrease in the effective quantum efficiency of PSII (ΦPSII), the maximum electron transport capacity (ETRmax), and the maximum quantum yield for electron transport (α). PSI photochemistry was also affected by these heavy metals. Cu2+ and Cd2+ decreased the quantum efficiency of PSI (ΦPSI) as well as the number of electrons in the intersystem chain, and the Cu2+ treatment significantly reduced the number of electrons from stromal donors available for PSI. These results indicate that PSII and PSI photochemistry of pea plants are both sensitive to moderate Cu2+ and Cd2+ stress, which in turn is easily detected and monitored by Chl fluorescence and P700 absorbance measurements. Therefore, monitoring the photochemistry of pea plants with these noninvasive, yet sensitive techniques offers a promising strategy to study heavy metal toxicity in the environment., B. Wodala ... [et al.]., and Obsahuje bibliografii
Athyrium pachyphlebium C. is a popular ornamental fern with considerable shade tolerance. The aim of this study was to investigate how the mature sporophytes acclimate to different light levels and to obtain an optimal light environment for their growth both in natural forest canopy and in urban landscapes. Plant growth and morphology, photosynthetic light-response curves and chlorophyll (Chl) fluorescence were measured at four different light levels (45% full sunlight, 30%, 20% and 8%). As the light intensities declined from 45% to 20%, seedling height, crown growth, foliage number and plant lifespan increased significantly. Seedlings grown at 20% light level were vigorous with great ornamental value. Plants grown in deep shade (8% light) showed severe symptoms of lodging and in 45% full sun, the plants showed highlight-stress symptoms. Seedlings in high light levels exhibited a higher
light-saturated photosynthetic rate (P max), light compensation point (LCP), light saturation point (LSP) and a reduced ability for nonphotochemical quenching (NPQ) of excess light than those in low light levels. However, seedlings in low light exhibited greater efficiency in absorbing and utilizing light energy, characterized by higher chlorophyll b (Chl b) and electron transport rate (ETR). These results indicated that a light level of about 20% full sun appeared to be optimal for A. pachyphlebium when both physiological and morphological performance in the landscape were considered. and D. Huang ... [et al.].