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Photosynthesis

About: Photosynthesis is a research topic. Over the lifetime, 19789 publications have been published within this topic receiving 895197 citations.


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Journal ArticleDOI
H Hori1, S Osawa
TL;DR: A phylogenetic tree of most of the major groups of organisms has been constructed from the 352 5S ribosomal RNA sequences now available, and suggests that there are several majorgroups of eubacteria that diverged during the early stages of their evolution.
Abstract: A phylogenetic tree of most of the major groups of organisms has been constructed from the 352 5S ribosomal RNA sequences now available. The tree suggests that there are several major groups of eubacteria that diverged during the early stages of their evolution. Metabacteria (= archaebacteria) and eukaryotes separated after the emergence of eubacteria. Among eukaryotes, red algae emerged first; and, later, thraustochytrids (a Proctista group), ascomycetes (yeast), green plants (green algae and land plants), "yellow algae" (brown algae, diatoms, and chrysophyte algae), basidiomycetes (mushrooms and rusts), slime- and water molds, various protozoans, and animals emerged, approximately in that order. Three major types of photosynthetic eukaryotes--i.e., red algae (= Chlorophyll a group), green plants (Chl. a + b group) and yellow algae (Chl. a + c)--are remotely related to one another. Other photosynthetic unicellular protozoans--such as Cyanophora (Chl. a), Euglenophyta (Chl. a + b), Cryptophyta (Chl. a + c), and Dinophyta (Chl. a + c)--seem to have separated shortly after the emergence of the yellow algae.

261 citations

Journal ArticleDOI
TL;DR: Phytoplankton respond to variations in light intensity as they are mixed through the water column to modulate the rate of photosynthesis in situ, which influences light harvesting and Calvin cycle activity.

261 citations

Journal ArticleDOI
TL;DR: There was a 1.5-fold enhancement in the rate of CO2 assimilation in plants grown in 64 Pa CO2, there was, however, some evidence to suggest that the activities of other metabolic pathways in the plants were not stimulated to the same extent by the enriched CO2 atmosphere.
Abstract: Cotton plants were grown in late spring under full sunlight in glasshouses containing normal ambient partial pressure of CO2 (32±2Pa) and enriched partial pressure of CO2 (64±1.5Pa) and at four levels of nitrogen nutrition. Thirty-five days after planting, the total dry weights of high CO2-grown plants were 2- to 3.5-fold greater than plants grown in normal ambient CO2 partial pressure. Depending on nitrogen nutrition level, non-structural carbohydrate content (mainly starch) in the leaves of plants grown in normal CO2 was between 4 and 37% of the total leaf dry weight compared to 39 to 52% in the leaves of high CO2-grown plants. Specific leaf weight calculated using total dry weight was 1.6- to 2-fold greater than that based on structural dry weight. In high CO2-grown plants the amount of non-structural carbohydrate translocated from the leaves at night was between 10 and 20% of the level at the end of the photoperiod. This suggests that the plant was unable to utilize all the carbohydrate it assimilated in elevated CO2 atmosphere. While there was a 1.5-fold enhancement in the rate of CO2 assimilation in plants grown in 64 Pa CO2, there was, however, some evidence to suggest that the activities of other metabolic pathways in the plants were not stimulated to the same extent by the enriched CO2 atmosphere. This resulted in massive accumulation of non-structural carbohydrate, particularly at low level of nitrogen nutrition.

261 citations

Journal ArticleDOI
TL;DR: The usefulness of increasing photosynthetic capacity can be maximised through changes in management practices and manipulation of other genetic traits to optimise the conditions under which increased photosynthesis can lead to maximal growth increases.
Abstract: Plants typically convert only 2-4% of the available energy in radiation into new plant growth. This low efficiency has provided an impetus for trying to genetically manipulate plants in order to achieve greater efficiencies. But to what extent can increased photosynthesis be expected to increase plant growth? This question is addressed by treating plant responses to elevated CO2 as an analogue to increasing photosynthesis through plant breeding or genetic manipulations. For plants grown optimal growth conditions and elevated CO2, photosynthetic rates can be more than 50% higher than for plants grown under normal CO2 concentrations. This reduces to 40% higher for plants grown under the average of optimal and sub-optimal conditions, and over the course of a full day, average photosynthetic enhancements under elevated CO2 are estimated to be about 30%. The 30% enhancement in photosynthesis is reported to increase relative growth rate by only about 10%. This discrepancy is probably due to enhanced carbohydrate availability exceeding many plant9s ability to fully utilise it due to nutrient or inherent internal growth limitations. Consequently, growth responses to elevated CO2 increase with plant9s sink capacity and nutrient status. However, even a 10% enhancement in relative growth rate can translate into absolute growth enhancements of up to 50% during the exponential growth phase of plants. When space constraints and self-shading force an end to exponential growth, on-going growth enhancements are likely to be closer to the enhancement of relative growth rate. The growth response to elevated CO2 suggests that increases in photosynthesis almost invariably increase growth, but that growth response is numerically much smaller than the initial photosynthetic enhancement. This lends partial support to the usefulness of breeding plants with greater photosynthetic capacity, but dramatic growth stimulation should not be expected. The usefulness of increasing photosynthetic capacity can be maximised through changes in management practices and manipulation of other genetic traits to optimise the conditions under which increased photosynthesis can lead to maximal growth increases.

261 citations

Journal ArticleDOI
TL;DR: The results support the roles of alternative electron sinks (either from PSII or PSI) and cyclic electron flow in photoprotection of PSII and PSI in drought stress conditions and analyses of the partitioning of absorbed energy between photosystems are needed for interpreting flux through linear electron flow, PSI cyclic electrons flow, along withAlternative electron sinks.
Abstract: The photosynthetic responses of wheat (Triticum aestivum L.) leaves to different levels of drought stress were analyzed in potted plants cultivated in growth chamber under moderate light. Low-to-medium drought stress was induced by limiting irrigation, maintaining 20 % of soil water holding capacity for 14 days followed by 3 days without water supply to induce severe stress. Measurements of CO2 exchange and photosystem II (PSII) yield (by chlorophyll fluorescence) were followed by simultaneous measurements of yield of PSI (by P700 absorbance changes) and that of PSII. Drought stress gradually decreased PSII electron transport, but the capacity for nonphotochemical quenching increased more slowly until there was a large decrease in leaf relative water content (where the photosynthetic rate had decreased by half or more). We identified a substantial part of PSII electron transport, which was not used by carbon assimilation or by photorespiration, which clearly indicates activities of alternative electron sinks. Decreasing the fraction of light absorbed by PSII and increasing the fraction absorbed by PSI with increasing drought stress (rather than assuming equal absorption by the two photosystems) support a proposed function of PSI cyclic electron flow to generate a proton-motive force to activate nonphotochemical dissipation of energy, and it is consistent with the observed accumulation of oxidized P700 which causes a decrease in PSI electron acceptors. Our results support the roles of alternative electron sinks (either from PSII or PSI) and cyclic electron flow in photoprotection of PSII and PSI in drought stress conditions. In future studies on plant stress, analyses of the partitioning of absorbed energy between photosystems are needed for interpreting flux through linear electron flow, PSI cyclic electron flow, along with alternative electron sinks.

260 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20242
20232,453
20225,090
2021738
2020732
2019616