scholarly journals Acclimation of C4 metabolism to low light in mature maize leaves could limit energetic losses during progressive shading in a crop canopy

2014 ◽  
Vol 65 (13) ◽  
pp. 3725-3736 ◽  
Author(s):  
Chandra Bellasio ◽  
Howard Griffiths
Keyword(s):  
Crop Canopy ◽  
Low Light ◽  
C4 Metabolism ◽  
Maize Leaves

Respiration in the light measured by 12CO 2 emission in 13CO 2 atmosphere in maize leaves

2001 ◽  
Vol 28 (11) ◽  
pp. 1103 ◽  
Author(s):  
Francesco Loreto ◽  
Violeta Velikova ◽  
Giorgio Di Marco
Keyword(s):  
Gas Exchange ◽  
Mitochondrial Respiration ◽  
Bundle Sheath ◽  
Gas Exchange Parameters ◽  
Low Light ◽  
Light Intensities ◽  
Wide Range ◽  
Bundle Sheath Cells ◽  
Maize Leaves ◽  
Exchange Parameters

The mitochondrial respiration during photosynthesis is difficult to measure and is indirectly estimated mainly in C 3 plants. Loreto et al. [(1999) Australian Journal of Plant Physiology 26, 733–736] have shown that the emission of 12 CO 2 from illuminated leaves exposed to air containing 13 CO 2 measures photorespiration and mitochondrial respiration in C 3 leaves. This method was used to measure the mitochondrial respiration in illuminated maize leaves. The 12 CO 2 emission was steady after 30 s, a time sufficient to label the CO 2 leakage from bundle sheath cells with 13 CO 2 , but not the mitochondrial respiration in the light. The emission was low (0.1–0.4 ppm or 0.2–0.4 µmol m –2 s –1 ) in a wide range of leaf temperatures and light intensities, but increased at light intensities below 200 µmol m –2 s –1 and at temperatures above 42°C. At 120 s after labelling, the leaf was darkened and the emission rapidly matched the mitochondrial respiration measured by gas exchange. The emission of 12 CO 2 in the light was inversely correlated with photosynthesis. This suggested that most of the respiratory CO 2 was refixed by photosynthesis. The amount of refixed intercellular 12 CO 2 was calculated from gas-exchange parameters. It was 60 to 90% of the tota l12 CO 2 in leaves illuminated and exposed to temperatures below 42°C. In leaves with reduced photosynthesis because of exposure to higher temperatures or low light, the 12 CO 2 refixation decreased. The sum of refixed and emitted 12 CO 2 was close to the mitochondrial respiration in the dark. This suggested that in these leaves the mitochondrial respiration was not inhibited in the light. In salt- and water-stressed leaves, however, the sum of refixed and emitted 12 CO 2 was lower than mitochondrial respiration in the dark, suggesting that the mitochondrial respiration may be inhibited in the light.

scholarly journals Structural and photosynthetic re-acclimation to low light in C4 maize leaves that developed under high light

2019 ◽  
Vol 124 (3) ◽  
pp. 437-445 ◽  
Author(s):  
Takayuki Yabiku ◽  
Osamu Ueno
Keyword(s):  
High Light ◽  
Energetic Cost ◽  
C3 Plants ◽  
Leaf Mass Per Area ◽  
Low Light ◽  
Chlorophyll Contents ◽  
Kranz Anatomy ◽  
Mature Leaves ◽  
Maize Leaves ◽  
Shade Leaves

Abstract Background and Aims C4 plants have higher photosynthetic capacity than C3 plants, but this advantage comes at an energetic cost that is problematic under low light. In the crop canopy, lower leaves first develop under high light but later experience low light because of mutual shading. To explore the re-acclimation of C4 leaves to low light, we investigated the structural and physiological changes of the leaves of maize plants grown in shaded pots. Methods Plants were first grown under high light, and then some of them were shaded (20 % of sunlight) for 3 weeks. Four types of leaves were examined: new leaves that developed under low light during shading (L), new leaves that developed under high light (H), mature leaves that developed under high light before shading and were then subjected to low light (H–L) and mature leaves that always experienced high light (H–H). Key Results The leaf mass per area, nitrogen and chlorophyll contents per unit leaf area, chlorophyll a/b ratio and activities of C3 and C4 photosynthetic enzymes were lower in H–L than in H–H leaves and in L than in H leaves. Unlike L leaves, H–L leaves maintained the thickness and framework of the Kranz anatomy of H leaves, but chloroplast contents in H–L leaves were reduced. This reduction of chloroplast contents was achieved mainly by reducing the size of chloroplasts. Although grana of mesophyll chloroplasts were more developed in L leaves than in H leaves, there were no differences between H–L and H–H leaves. The light curves of photosynthesis in H–L and L leaves were very similar and showed traits of shade leaves. Conclusions Mature maize leaves that developed under high light re-acclimate to low-light environments by adjusting their biochemical traits and chloroplast contents to resemble shade leaves but maintain the anatomical framework of sun leaves.

Software pattern recognition applied to nanodiffraction patterns from a STEM instrument

1986 ◽  
Vol 44 ◽  
pp. 694-695
Author(s):  
G.Y. Fan ◽  
J.M. Cowley
Keyword(s):  
Image Processing ◽  
Pattern Recognition ◽  
Computer Software ◽  
Processing System ◽  
Light Level ◽  
Host Computer ◽  
Low Light ◽  
Image Processing System ◽  
Recent Developments ◽  
On Line

In recent developments, the ASU HB5 has been modified so that the timing, positioning, and scanning of the finely focused electron probe can be entirely controlled by a host computer. This made the asynchronized handshake possible between the HB5 STEM and the image processing system which consists of host computer (PDP 11/34), DeAnza image processor (IP 5000) which is interfaced with a low-light level TV camera, array processor (AP 400) and various peripheral devices. This greatly facilitates the pattern recognition technique initiated by Monosmith and Cowley. Software called NANHB5 is under development which, instead of employing a set of photo-diodes to detect strong spots on a TV screen, uses various software techniques including on-line fast Fourier transform (FFT) to recognize patterns of greater complexity, taking advantage of the sophistication of our image processing system and the flexibility of computer software.

Low-light-level three-dimensional video microscope with long working distance objective lenses

1994 ◽  
Vol 52 ◽  
pp. 226-227
Author(s):  
W. Lin ◽  
J. Gregorio ◽  
T.J. Holmes ◽  
D. H. Szarowski ◽  
J.N. Turner
Keyword(s):  
Three Dimensional ◽  
Light Level ◽  
Stereo Pair ◽  
Light Illumination ◽  
Initial Image ◽  
Low Light ◽  
Image Recording ◽  
Depth Discrimination ◽  
Video Microscope ◽  
Working Distance

A low-light level video microscope with long working distance objective lenses has been built as part of our integrated three-dimensional (3-D) light microscopy workstation (Fig. 1). It allows the observation of living specimens under sufficiently low light illumination that no significant photobleaching or alternation of specimen physiology is produced. The improved image quality, depth discrimination and 3-D reconstruction provides a versatile intermediate resolution system that replaces the commonly used dissection microscope for initial image recording and positioning of microelectrodes for neurobiology. A 3-D image is displayed on-line to guide the execution of complex experiments. An image composed of 40 optical sections requires 7 minutes to process and display a stereo pair.The low-light level video microscope utilizes long working distance objective lenses from Mitutoyo (10X, 0.28NA, 37 mm working distance; 20X, 0.42NA, 20 mm working distance; 50X, 0.42NA, 20 mm working distance). They provide enough working distance to allow the placement of microelectrodes in the specimen.

Morphogenetic machines revealed: Microscopy of living cells in the embryo of the frog, Xenopus laevis

1993 ◽  
Vol 51 ◽  
pp. 172-173
Author(s):  
Ray Keller
Keyword(s):  
Image Processing ◽  
Fluorescent Dyes ◽  
Cell Movement ◽  
Living Cells ◽  
Ease Of Use ◽  
Low Light ◽  
Amphibian Embryo ◽  
Large Populations ◽  
Light Fluorescence ◽  
Video Image Processing

The amphibian embryo offers advantages of size, availability, and ease of use with both microsurgical and molecular methods in the analysis of fundamental developmental and cell biological problems. However, conventional wisdom holds that the opacity of this embryo limits the use of methods in optical microscopy to resolve the cell motility underlying the major shape-generating processes in early development.These difficulties have been circumvented by refining and adapting several methods. First, methods of explanting and culturing tissues were developed that expose the deep, nonepithelial cells, as well as the superficial epithelial cells, to the view of the microscope. Second, low angle epi-illumination with video image processing and recording was used to follow patterns of cell movement in large populations of cells. Lastly, cells were labeled with vital, fluorescent dyes, and their behavior recorded, using low-light, fluorescence microscopy and image processing. Using these methods, the details of the cellular protrusive activity that drives the powerful convergence (narrowing)

Interaction of divalent metal ions with the NADP+-malic enzyme from maize leaves

1991 ◽  
Vol 81 (4) ◽  
pp. 462-466 ◽  
Author(s):  
Maria Fabiana Drincovich ◽  
Alberto A. Iglesias ◽  
Carlos S. Andreo
Keyword(s):  
Metal Ions ◽  
Malic Enzyme ◽  
Divalent Metal ◽  
Divalent Metal Ions ◽  
Maize Leaves

Challenges of Aircraft and Drone Spray Applications

2020 ◽  
Vol 31 (2) ◽  
pp. 83-88 ◽  
Author(s):  
Fernando K. Carvalho ◽  
Rodolfo G. Chechetto ◽  
Alisson A. B. Mota ◽  
Ulisses R. Antuniassi
Keyword(s):  
Smallholder Farmers ◽  
Crop Protection ◽  
Crop Canopy ◽  
Target Species ◽  
Buffer Zones ◽  
Correct Dose ◽  
Knapsack Sprayer ◽  
Water Courses ◽  
Low Toxicity ◽  
Heavy Loads

Crop protection on major crops is now required to follow the principles of integrated pest management so the timing and accuracy of any application of a pesticide or biopesticide has to be more precise to minimize adverse effects on non-target species. The development of UAVs (unmanned aerial vehicles) provides a means of providing a more targeted application of the correct dose, especially by using formulations that are more persistent, thus minimizing loss of spray in areas subject to rain. Avoiding use of too high a dosage allows greater survival of natural enemies and reduces the selection pressure for pests becoming resistant to specific modes of action. The downward flow of air from a UAV should also provide better distribution and impaction of droplets within a crop canopy, reduce soil impaction caused by taking heavy loads of spray applied with 200 l ha–1 of water, and allow treatments when fields are too wet to access with ground equipment. In Asia, many smallholder farmers are using a drone in preference to using a knapsack sprayer. According to Matthews, it has been shown that ULV spraying can be effective, but it needs a narrow droplet spectrum with the droplets remaining stable and not shrinking to become too small. Formulation research can reduce the volatility of the spray, hence the success of oil-based sprays. However, instead of petroleum-based oils, there is a chance to develop vegetable oil carriers with micro-sized particle suspensions to deliver low toxicity pesticides in droplets that can be deposited within the crop and not drift beyond the crop boundary. Oil deposits will be less prone to loss after rain so less should be lost in neighbouring ditches and water courses, especially as rainfall patterns are forecast to change. More studies are needed to evaluate the swath for deposition, buffer zones, formulation, nozzle selection, to guide future specific legislation for UAV applications.

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