Photosynthesis holds the key to life; it is the process by which green plants use the light of the sun to synthesize nutrients from carbon dioxide and water and generate oxygen as a by-product. Without it, life on our planet would be all but impossible and to fully understand how photosynthesis works means to understand life.
A technique that is used to study photosynthesis is the thermoluminescence technique, which allows the user to study charge recombination reactions in photosystem II. Though used by a relatively small number of scientists, it has advantages over the more widely used fluorescence decay kinetics. The thermoluminescence technique can be used to, for example, characterize photosynthetic electron transport in detail and study the way plants respond to different physiological conditions. The technique has also been shown to be applicable in a wide range of photosynthetic organisms, from higher plants to cyanobacteria.
The February Special Issue of Physiologia Plantarum is a tribute to Jean-Marc Ducruet for his contribution to thermoluminescence and photosynthesis research. An avid advocate of the thermoluminescence technique, Jean-Marc Ducruet travelled around the world to help young scientists and construct thermoluminescence devices. All the papers in this Special issue are a testament to the potential and broad range of thermoluminescence as a method of research. To mark this release, we have created an overview of the different species that were used in the papers of this issue. We will be releasing highlights on three of these articles.
Highlight I: The effects of putrescine pre-treatment on osmotic stress responses in drought-tolerant and drought-sensitive wheat seedlings (Doneva et al., 2020)
Drought has a detrimental effect on plants and causes a serious worldwide reduction in crop yield. It is estimated that three-quarters of the land used to cultivate the major crops are experiencing drought-induced yield losses. Water deficit induces stomatal closure, a plant’s attempt to reduce water loss through transpiration. This results in a reduction of photosynthesis, ultimately leading to a lessening of productivity. The article by Doneva et al., (2020) looked into the effects of drought stress in two wheat varieties, the drought-tolerant Katya and drought-sensitive Zora cultivars.
The authors found the drought-resistant variety to have higher photosynthetic ability, stable charge separation in PSII and higher proline accumulation and antioxidant activity. They further investigated a possible positive effect of putrescine pre-treatment and showed that it led to a significant increase in photosynthetic activity, stomatal conductance and transpiration, albeit more prominent in the already drought-resistant variety. The authors conclude that the putrescine pre-treatment might be a promising and beneficial agricultural practice to increase the stress resistance of crops. Click here to read the full article.
Highlight II: Identification of the AG afterglow thermoluminescence band in the cyanobacterium Synechocystis PCC 6803 (Kodru et al., 2020)
The organism believed to be responsible for the oxygenation of the earth’s atmosphere and the origin of plastids in green plants and algae, cyanobacteria, have truly made the earth a wholly different place. Despite ultimately being responsible for a plant’s ability to photosynthesize, there are some distinct differences between observing photosynthesis in plants and cyanobacteria.
The thermoluminescence technique has proven to be a useful technique to study PSII activity in intact photosynthetic systems. A luminescence emission that can be detected by the thermoluminescence technique is the afterglow band, an indicator of the NADH dehydrogenase-like (NDH) complex-mediated cyclic electron flow. Proposed as a simple tool to study for example the chloroplast’s energetic state, the afterglow band has so far only been characterized in algae and plants. Kodru et al., (2020) show, by optimizing the far-red light illumination, the presence of the afterglow band in cyanobacteria Synechocystis PCC 6803 for the first time. Would you like to know more? Click here.
Highlight III: Luminescence imaging of leaf damage induced by lipid peroxidation products and its modulation by b-cyclocitral (Rac et al., 2020)
Plants are subjected to a plethora of biotic and abiotic stresses. One of these, high light intensity, can cause photooxidative damage in the form of, among others, lipid peroxidation. Lipid peroxidation can result in an accumulation of reactive carbonyl species (RCS) that can react with proteins and DNA, ultimately leading to cell death. The article by Rac et al., (2020) shows the usefulness of autoluminescence imaging to monitor oxidative degradation of leaf tissues, even in an early stage of degradation when visual symptoms such as leaf necroses are hardly visible. The authors further show that a SCARECROW-LIKE 14 detoxification pathway can be triggered by the application of the signaling apocarotenoid β-CC. This detoxification then mitigates the effect of the application of a particularly reactive and harmful RCS. Would you like to read the whole paper? Click here.