Plants are frequently exposed to a plethora of unfavorable or even adverse environmental conditions, termed as abiotic stresses (such as salinity, drought, heat, cold, flooding, heavy metals, ozone, UV radiation, etc.) and thus they pose serious threats to the sustainability of crop yield. Soil salinity, one of the most severe abiotic stresses, limits the production of about 6 % of the world’s total land and 20 % of irrigated land (17 % of total cultivated areas) and negatively affects crop production worldwide. On the other hand, increased salinity of agricultural land is expected to have destructive global effects, resulting in up to 50 % land loss by the next couple of decades. The adverse effects of salinity have been ascribed mainly to an increase in sodium (Na+) and chloride (Cl–) ions and hence these ions produce the critical conditions for plant survival by intercepting different plant mechanisms. Both Na+ and Cl– produce many physiological disorders in plants but Cl– is the most dangerous. A plant’s response to salt stress depends on the genotype, developmental stage, as well as the intensity and duration of the stress. Increased salinity has diverse effects on the physiology of plants grown in saline conditions and in response to major factors like osmotic stress, ion-specificity, nutritional and hormonal imbalance, and oxidative damage. In addition to upper plant parts, salinity also affects root growth and physiology and their function in nutrient uptake. The outcome of these effects may cause the disorganization of cellular membranes, inhibit photosynthesis, generate toxic metabolites and decline nutrient absorption, ultimately leading to plant death. In recent decades, exogenous protectants such as osmoprotectants, phytohormones, signaling molecules, polyamines, antioxidants and various trace elements have been found effective in plants in mitigating the salt induced damages. These protectants showed the capacity to enhance the plants’ growth, yield as well as stress tolerance under salinity. In this chapter we attempt to summarize differential responses of plants to salinity with special reference to growth, physiology and yield. Further, we have discussed the progress made in using exogenous protectants to mitigate salt-induced damages in plants.

https://www.springer.com/cda/content/document/cda_downloaddocument/9781461447467-c1.pdf

Plant Response to Salt Stress and Role of Exogenous Protectants to Mitigate Salt-Induced Damages

In this study, a comprehensive review focusing on key strategies of energy saving and climate control technologies for greenhouses is presented. Following the brief and concise assessment of existing greenhouse systems in terms of their role in total energy consumption; cost-effective, energy-efficient and environmentally friendly technologies are analyzed in detail for potential utilization in greenhouses for notable reductions in energy consumption and emission levels. The technologies considered within the scope of this research are mainly renewable and sustainable based solutions such as photovoltaic (PV) modules, solar thermal (T) collectors, hybrid PV/T collectors and systems, phase change material (PCM) and underground based heat storage techniques, energy-efficient heat pumps, alternative facade materials for better thermal insulation and power generation (heat insulation solar glass, PV glazing, aerogel and vacuum insulation panel, polycarbonate sandwich panels), innovative ventilation technologies using pre-heating and cooling (high performance windcatchers) and efficient lighting systems. The findings from the research clearly reveal that up to 80% energy saving can be achieved through appropriate retrofit of conventional greenhouses with a payback period of 4–8 years depending on climatic conditions and crop type.

Renewable and sustainable energy saving strategies for greenhouse systems: A comprehensive review

The aim of this review is to present the progress in preparing phosphorescent particles based on the reported research. We highlight the recent progress on SrAl 2 O 4 : Eu, Dy particles by describing the advantages and disadvantages of the different synthesis methods. This long-lasting material combines several favorable attributes: is stable, efficient, and less toxic that their predecessors. For that, large attention has been paid to the development of an efficient preparation method of SrAl 2 O 4 doped powders, including sol-gel method, hydrothermal synthesis, laser synthesis, combustion synthesis and solid state reaction. However, many of these techniques are not compatible with large-scale production and with the principles of sustainability. Industrial processing of highly crystalline powders usually requires high synthesis temperatures, typically between 1300 and 1900 °C, with long processing times, especially for solid state reaction. As a result, the average particle size is typically within the 20–100 µm range. This large particle size is limiting for current applications that demand sub-micron particles. The microstructure and size which are controlled through adjusting the experimental conditions have a great influence in the final photoluminescence response. Therefore, much effort has been devoted to exploring new strategies to obtain sub–micrometric particles, avoiding stringent, intricate, tedious, costly, or inefficient preparation steps and intrinsic toxicity or elemental scarcity. Moreover, persistent luminescent nanomaterials have attracted great interest to their potential application in solar cells, biological labeling and imaging and security encode. In addition, we describe the challenges and future of phosphorescent materials in regard to their synthesis, properties and applications. Finally, some further suggestions have been also addressed to enhance its photoluminescence response from the perspective of the synthesis. We believe that such a review can accelerate the developments of SrAl 2 O 4 -based materials.

Long lasting phosphors: SrAl2O4:Eu, Dy as the most studied material

The conduction of the experiment on plant photosynthetic efficiency has been made possible by a stay of FO within the Department of Plant Sciences, Wageningen, financed by a grant of the C. T. de Wit Graduate School for Production Ecology and Resource Conservation (PE&RC) of Wageningen University. We acknowledge Dr. E. Kaiser (WUR) and V. Jalink (Phenovation B.V., Wageningen) for their support in the implementation of the experiment on PSII quantum efficiency. We are also grateful to Prof. M. T. Rodriguez-Estrada, Dr. V. Cardenia, and Mr. S. Savioli for their technical support in GC-MS analysis.

/pdf/unraveling-the-role-of-red-blue-led-lights-on-resource-use-5aius1hzc1.pdf

Unraveling the Role of Red:Blue LED Lights on Resource Use Efficiency and Nutritional Properties of Indoor Grown Sweet Basil.

Salt stress is one of the major abiotic stresses limiting crop production especially in arid and semi-arid regions. It is reported that about 7 % of the total earths land and 20 % of the total arable area are affected by high salt contents. Reclamation of salt affected soils is necessary as the salt is engulfing the cultivable land day by day. The earliest response of plants to salt stress is reduction in the rate of leaf surface expansion followed by cessation of expansion as the stress intensifies but growth resumes when the stress is relieved. Metabolic processes like photosynthesis, protein synthesis and lipid metabolisms are affected due to salt stress. Salinity is responsible for different types of stresses like, osmotic stress, ionic stress, oxidative stress and hormonal imbalances. The osmotic stress is caused by the excess of Na+ and Cl− ions in the soil that decrease the osmotic potential and hampers the water uptake and nutrients. Low molecular mass compounds known as compatible solutes is accumulated under salt stress. These compatible solutes include proline, glycinebetaine, sugars, proteins, polyols, etc. They do not interfere with the normal biochemical reactions and helps the plants in building the resistance against the stress.

Salt Stress: Causes, Types and Responses of Plants

Light energy is an important factor for plant growth. In regions where the natural light source (solar radiation) is not sufficient for growth optimization, additional light sources are being used. Traditional light sources such as high pressure sodium lamps and other metal halide lamps are not very efficient and generate high radiant heat. Therefore, new sustainable solutions should be developed for energy efficient greenhouse lighting. Recent developments in the field of light source technologies have opened up new perspectives for sustainable and highly efficient light sources in the form of LEDs (light-emitting diodes) for greenhouse lighting. This review focuses on the potential of LEDs to replace traditional light sources in the greenhouse. In a comparative economic analysis of traditional vs. LED lighting, we show that the introduction of LEDs allows reduction of the production cost of vegetables in the long-run (several years), due to the LEDs׳ high energy efficiency, low maintenance cost and longevity. In order to evaluate LEDs as an alternative to current lighting sources, species specific plant response to different wavelengths is discussed in a comparative study. However, more detailed scientific studies are necessary to understand the effect of different spectra (using LEDs) on plants physiology. Technical innovations are required to design and realize an energy efficient light source with a spectrum tailored for optimal plant growth in specific plant species.

LEDs for energy efficient greenhouse lighting

Tomato cultivar PKM 1 were subjected to 25, 50, 100, 150 and 200 mM NaCl stress and response of tomato plant to saltstress were determined by assessing the variability of different biochemical parameters In this present study endogenouscontent of growth hormones IAA and ABA in leaves, proline and mineral (Na+ and K+) content in leaves and maturefruits were estimated Leaf area and dry matter content of tomato fruits under salt stress were determined to study theeffect of salinity on photosynthetic yield Results showed that leaf area and dry matter content of tomato fruits decreasedwith application of elevated salt stress, however endogenous content of IAA, ABA and proline was found to beincreasing with increase in salt treatment Application of NaCl caused increase in Na+ content, while K+ content andK+/Na+ ratio decreased with increase in salt stress Another striking point is that increase in proline and Na+ contentwas more in leaves than fruits, which suggests that leaves are more sensitive than fruitsKeyword: Salt stress, IAA, ABA, Proline, Na+, dry matter

http://www.thejaps.org.pk/docs/v-22-1/25.pdf

The effect of salinity on growth, hormones and mineral elements in leaf and fruit of tomato cultivar PKM1.

Rising sea levels and salinization of groundwater due to global climate change result in fast-dwindling sources of freshwater. Therefore, it is important to find alternatives to grow food crops and vegetables. Halophytes are naturally evolved salt-tolerant plants that are adapted to grow in environments that inhibit the growth of most glycophytic crop plants substantially. Members of the Salicornioideae are promising candidates for saline agriculture due to their high tolerance to salinity. Our aim was to develop genetically characterized lines of Salicornia and Sarcocornia for further breeding and to determine optimal cultivation conditions. To obtain a large and diverse genetic pool, seeds were collected from different countries and ecological conditions. The external transcribed spacer (ETS) sequence of 62 Salicornia and Sarcocornia accessions was analysed: ETS sequence data showed a clear distinction between the two genera and between different Salicornia taxa. However, in some cases the ETS was not sufficiently variable to resolve morphologically distinct species. For the determination of optimal cultivation conditions, experiments on germination, seedling establishment and growth to a harvestable size were performed using different accessions of Salicornia spp. Experiments revealed that the percentage germination was greatest at lower salinities and with temperatures of 20/10 °C (day/night). Salicornia spp. produced more harvestable biomass in hydroponic culture than in sand culture, but the nutrient concentration requires optimization as hydroponically grown plants showed symptoms of stress. Salicornia ramosissima produced more harvestable biomass than Salicornia dolichostachya in artificial sea water containing 257 mM NaCl. Based on preliminary tests on ease of cultivation, gain in biomass, morphology and taste, S. dolichostachya was investigated in more detail, and the optimal salinity for seedling establishment was found to be 100 mM. Harvesting of S. dolichostachya twice in a growing season was successful, but the interval between the harvests needs to be optimized to maximize biomass production.

/pdf/salicornia-as-a-crop-plant-in-temperate-regions-selection-of-5cbnps4h2w.pdf

Salicornia as a crop plant in temperate regions: selection of genetically characterized ecotypes and optimization of their cultivation conditions

SPECIAL ISSUE: Physiology and Ecology of Halophytes—Plants Living in Salt-Rich Environments Salicornia as a crop plant in temperate regions: selection of genetically characterized ecotypes and optimization of their cultivation conditions

Carotenoids, the naturally occurring isoprenoids form essential components of photosynthetic antenna and reaction centre complexes. Thus they play a significant role in absorption, dissipation and transfer of light energy for the process of photosynthesis. The effects of salt stress on carotenoid gene expression in tomato leaves were studied. For that tomato plants were subjected to different concentration of salt water. Morphological characters such as plant height, no. of fruits per plant, chlorophyll content and expression of four major carotenoid pathway genes such as phytoene synthase, phytoene desaturase, zeta carotene desaturase and lycopene beta cyclase were analysed. The quantitative expression analysis using real time PCR has shown a decrease in the expression of all the studied genes as the salt concentration increased. Among the different concentrations of NaCl used for the experiment, it was seen that 200 mM was most detrimental for the carotenoid gene expression. Lycopene beta cyclase, the enzyme that converts lycopene to beta carotene was seen to be highly affected compared to other genes studied showing a 1.87 fold inhibition in its expression at 200 mM NaCl.

/pdf/effect-of-salt-stress-on-expression-of-carotenoid-pathway-xb0gp419hj.pdf

Devesh Singh

Papers

LEDs for energy efficient greenhouse lighting

The effect of salinity on growth, hormones and mineral elements in leaf and fruit of tomato cultivar PKM1.

Salicornia as a crop plant in temperate regions: selection of genetically characterized ecotypes and optimization of their cultivation conditions

SPECIAL ISSUE: Physiology and Ecology of Halophytes—Plants Living in Salt-Rich Environments Salicornia as a crop plant in temperate regions: selection of genetically characterized ecotypes and optimization of their cultivation conditions

Effect of salt stress on expression of carotenoid pathway genes in tomato