https://www.cell.com/trends/plant-science/pdf/S1360-1385(10)00211-6.pdf

Photoprotection in plants: a new light on photosystem II damage

The process of photosynthesis is initiated by the capture of sunlight by a network of light-absorbing molecules (chromophores), which are also responsible for the subsequent funneling of the excitation energy to the reaction centers. Through evolution, genetic drift, and speciation, photosynthetic organisms have discovered many solutions for light harvesting. In this review, we describe the underlying photophysical principles by which this energy is absorbed, as well as the mechanisms of electronic excitation energy transfer (EET). First, optical properties of the individual pigment chromophores present in light-harvesting antenna complexes are introduced, and then we examine the collective behavior of pigment−pigment and pigment−protein interactions. The description of energy transfer, in particular multichromophoric antenna structures, is shown to vary depending on the spatial and energetic landscape, which dictates the relative coupling strength between constituent pigment molecules. In the latter half...

Light Absorption and Energy Transfer in the Antenna Complexes of Photosynthetic Organisms.

The aim of this educational review is to provide practical information on the hardware, methodology, and the hands on application of chlorophyll (Chl) a fluorescence technology. We present the paper in a question and answer format like frequently asked questions. Although nearly all information on the application of Chl a fluorescence can be found in the literature, it is not always easily accessible. This paper is primarily aimed at scientists who have some experience with the application of Chl a fluorescence but are still in the process of discovering what it all means and how it can be used. Topics discussed are (among other things) the kind of information that can be obtained using different fluorescence techniques, the interpretation of Chl a fluorescence signals, specific applications of these techniques, and practical advice on different subjects, such as on the length of dark adaptation before measurement of the Chl a fluorescence transient. The paper also provides the physiological background for some of the applied procedures. It also serves as a source of reference for experienced scientists.

https://link.springer.com/content/pdf/10.1007%2Fs11120-014-0024-6.pdf

Frequently asked questions about in vivo chlorophyll fluorescence: Practical issues

Rubisco is a large enzyme with a molecular mass of approximately 550 kD. The maximum rate of CO2 fixation (i.e. ribulose-1,5-bisphosphate [RuBP] carboxylation) at CO2 saturation is only 15 to 30 mol CO2 mol−1 Rubisco protein s−1 at 25°C. Affinity to CO2 is also low, and the K m, K c, at 25°C

/pdf/leaf-functional-anatomy-in-relation-to-photosynthesis-3pjha67dny.pdf

Leaf Functional Anatomy in Relation to Photosynthesis

Multiple functional roles of anthocyanins in plant-environment interactions.

The literature and our present examinations indicate that the intra-leaf light absorption profile is in most cases steeper than the photosynthetic capacity profile. In strong white light, therefore, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. Because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than would additional red or blue light. Based on the assessment of effects of the additional monochromatic light on leaf photosynthesis, we developed the differential quantum yield method that quantifies efficiency of any monochromatic light in white light. Application of this method to sunflower leaves clearly showed that, in moderate to strong white light, green light drove photosynthesis more effectively than red light. The green leaf should have a considerable volume of chloroplasts to accommodate the inefficient carboxylation enzyme, Rubisco, and deliver appropriate light to all the chloroplasts. By using chlorophylls that absorb green light weakly, modifying mesophyll structure and adjusting the Rubisco/chlorophyll ratio, the leaf appears to satisfy two somewhat conflicting requirements: to increase the absorptance of photosynthetically active radiation, and to drive photosynthesis efficiently in all the chloroplasts. We also discuss some serious problems that are caused by neglecting these intra-leaf profiles when estimating whole leaf electron transport rates and assessing photoinhibition by fluorescence techniques.

/pdf/green-light-drives-leaf-photosynthesis-more-efficiently-than-1mazbqk4cf.pdf

Green light drives leaf photosynthesis more efficiently than red light in strong white light: revisiting the enigmatic question of why leaves are green.

Plant Vacuolar Trafficking Occurs through Distinctly Regulated Pathways

RAB5 GTPases act as molecular switches that regulate various endosomal functions in animal cells, including homotypic fusion of early endosomes, endosomal motility, endosomal signaling, and subcompartmentalization of the endosomal membrane. RAB5 proteins fulfill these diverse functions through interactions with downstream effector molecules. Two canonical RAB5 members, ARA7 and RAB HOMOLOG1 (RHA1), are encoded in the Arabidopsis thaliana genome. ARA7 and RHA1 play crucial roles in endocytic and vacuolar trafficking pathways. Plant RAB5 GTPases function via interactions with effector molecules, whose identities and functions are currently unclear. In this study, we searched for canonical RAB5 effector molecules of Arabidopsis and identified a candidate, which we called ENDOSOMAL RAB EFFECTOR WITH PX-DOMAIN (EREX). The intimate genetic interaction between EREX and RAB5 members, the results from subcellular colocalization experiments, and the direct interaction observed in an in vitro pull-down assay strongly suggest that EREX is a genuine effector of canonical RAB5s in Arabidopsis. We further found that close homologs of EREX play partially redundant functions with EREX in the transport of seed storage proteins. Our results indicate that canonical plant RAB5s acquired distinct effector molecules from those of non-plant systems to fulfill their functions.

ENDOSOMAL RAB EFFECTOR WITH PX-DOMAIN, an interacting partner of RAB5 GTPases, regulates membrane trafficking to protein storage vacuoles in Arabidopsis

Rab GTPases regulate the tethering and fusion of transport vesicles to target membranes in membrane trafficking by acting as a molecular switch, cycling between GDP- and GTP-bound states. RAB5 is a member of the Rab GTPase family, the members of which have been shown to perform various functions in the endocytic pathway, including the regulation of endosomal fusion and motility in animal cells. RAB5-mediated endosomal trafficking has also been found to play important roles in various higher order plant functions, which include the regulation of the polar transport of auxin and responses to environmental conditions. The regulatory mechanisms and functions of plant RAB5 have also been investigated at the molecular and cellular levels. However, the significance of RAB5 activity at the tissue and organ levels has hardly been investigated thus far. In the present study, we examined the effect of a mutation in VPS9a, which encodes the sole guanine nucleotide exchange factor for all RAB5s in the vegetative stages of Arabidopsis thaliana. We found that multiple developmental processes were impaired in the mutant plants, including the growth and pattern formation of the roots and establishment of auxin maxima. Our results indicate that RAB5 plays distinctive pivotal roles in the development of plants.

RAB5 Activation is Required for Multiple Steps in Arabidopsis thaliana Root Development

PROBLEM TO BE SOLVED: To reduce manufacturing costs of an exhaust emission control system by making a piping distance of a bypass passage 32 bypassing selective catalyst reduction devices 34, 35 as short as possible.SOLUTION: An exhaust emission control system includes: as an exhaust passage 30 of an engine 25 mounted on a ship 1, a main passage 31 communicating with outside; a bypass passage 32 branching off from a halfway part of the main passage 31; and a composite casing 33 linking both the main passage 31 and bypass passage 32 to each other. Selective catalyst reduction devices 34, 35 are housed in the composite casing 33 at the side of the main passage 31. Route switching members 37, 38 which switch an exhaust emission moving direction are arranged at a branch part 53 between the main passage 31 and the bypass passage 32. A reductant injection body 61 is arranged in the main passage 31 between the route switching member 37 and the composite casing 33.

Takeshi Inoue

Papers

Green light drives leaf photosynthesis more efficiently than red light in strong white light: revisiting the enigmatic question of why leaves are green.

Plant Vacuolar Trafficking Occurs through Distinctly Regulated Pathways

ENDOSOMAL RAB EFFECTOR WITH PX-DOMAIN, an interacting partner of RAB5 GTPases, regulates membrane trafficking to protein storage vacuoles in Arabidopsis

RAB5 Activation is Required for Multiple Steps in Arabidopsis thaliana Root Development

Exhaust emission control system and ship equipped with the same