Habib-ur-Rehman Athar

Growth of plants is severely reduced due to water stress by affecting photosynthesis including photosystem II (PSII) activity and electron transport. This study emphasised on comparative and priority targeted changes in PSII activity due to progressive drought in seven populations of Panicum antidotale (P. antidotale) collected from Cholistan Desert and non-Cholistan regions. Tillers of equal growth of seven populations of P. antidotale grown in plastic pots filled with soil were subjected progressive drought by withholding water irrigation for three weeks. Progressive drought reduced the soil moisture content, leaf relative water content, photosynthetic pigments and fresh and dry biomass of shoots in all seven populations. Populations from Dingarh Fort, Dingarh Grassland and Haiderwali had higher growth than those of other populations. Cholistani populations especially in Dingarh Grassland and Haiderwali had greater ability of osmotic adjustment as reflected by osmotic potential and greater accumulation of total soluble proteins. Maximum H2O2 under water stress was observed in populations from Muzaffargarh and Khanewal but these were intermediate in MDA content. Under water stress, populations from Muzaffargarh and Dingarh Fort had greater K+ accumulation in their leaves. During progressive drought, non-Cholistani populations showed complete leaf rolling after 23 days of drought, and these populations could not withstand with more water stress condition while Cholistani populations tolerated more water stress condition for 31 days. Moreover, progressive drought caused PSII damages after 19 days and it became severe after …

Salt stress limits photosynthetic capacity of plants by disturbing thylakoidal reactions. Chlorophyll fluorescence measurements help in measuring the extent of photosystem-II (PSII) photodamage. Panicum antidotale (P. antidotale) and Panicum turgidum (P. turgidum) are potential fodder grasses, adapted to a variety of environmental stresses like salinity and drought. In the present study, photosynthetic performance was assessed by chlorophyll a fluorescence kinetic analysis of excised leaves of these two grass species immersed in varying concentration of NaCl (0, 250, 500 and 1000 mM NaCl) after 24 hours. Salt stress decreased chlorophyll fluorescence at J, I and P steps indicating reduced efficiency of electron transfer at PSII and from PSII to PSI. In addition, salt induced increase in Fo (11% in P. antidotale; 29% in P. turgidum) along with reduction in Fm indicated PSII photoinhibition at the donor end. Performance index (PIABS) and quantum yield of PSII were decreased in excised leaves of both Panicum species with increasing salt levels. However, P. antidotale had greater PIABS (1.08) and quantum yield of PSII (0.72) than in P. turgidum (0.47 and 0.57 respectively), which is associated with better management in absorption (0.84% as compared to 12.4% in P. turgidum), trapping and electron transport or better management of PSII excitation pressure under salt stress. Activity of PSII measured as PIABS and some related JIP-test parameters can be used as potential indicators of salt tolerance. So increasing salinity stress affected primary photochemistry of PSII in excised leaves of both grass species but adverse effect of salt stress on PSII …

Improvements in crop yields have been a challenge for breeders and biotechnologists as multiple attributes must be considered simultaneously for successful breeding. These attributes include morphological, physiological, biochemical and molecular features. In addition, they are closely associated with the photosynthetic efficiency of crops. In recent years, there has been tremendous advancement in studies related to morphological, physiological and biochemical attributes capable of improving photosynthetic efficiency through manipulation. However, there is limited information on the molecular processes that can potentially have a similar effect on crops. Furthermore, the use of nanotechnology for the improvement of crops has been scarcely studied. In this chapter, we present metabolic engineering as a molecular approach that enhances cell membrane thermostability and photosynthetic efficiency. We also consider nanoformulation as a growing nanotechnology approach. Nanoformulation involves the use of nanoparticles for the delivery of abiotic stress tolerance traits capable of improving photosynthetic efficiency. Finally, the analytical platforms that have been used in the metabolic characterisation of higher crops, which can be used in the assessment of the metabolic profiles of nanoformulated crops, are discussed. Overall, this chapter provides molecular and nanotechnology crop-specific information that will enable breeders and biotechnologists in the journey to successful breeding.

Plants interact with a wide variety of microorganisms that exist belowground in the rhizosphere and aboveground in the phyllosphere in their surrounding environment. The rhizosphere is a soil zone near the plant roots that is home to various organisms, primarily arbuscular mycorrhizal fungi (AMF) and rhizobacteria. Some plant-microbial associations, including antagonistic, amensalism, parasitism, and symbiotic, defend host plants from harmful microbial and nonmicrobial invaders and provide essential nutrients, whereas others negatively impact plants. These interactions have considerable effects on the biomass development of both belowground and aboveground plants, and thus, they play a vital role in plant survival. Understanding microbial association in the rhizosphere and phyllosphere is therefore critical to sustainable agriculture at the field level. Strigolactones (SLs) are a class of phytohormones that play …

Multiplex genome editing techniques are newly designed powerful and flexible biotechnological tools for precisely modifying multiple targets in a genome. These genome editing techniques have increased the possibility of making desired modifications to a target genome at various nucleotide levels. Multiplex genome editing tools based on the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system permit the simultaneous creation of mutations at different loci in multiple genes or a single gene at the same time. Multiplex CRISPR-based genome editing is advancing the basic and applied research in modern crop breeding because it was previously impossible to edit genomes so precisely using earlier genome editing techniques such as zinc-finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs). Many cereal crops, including rice, maize, wheat, cotton, and …

Disputes about the probable availability of safe water and the efficacy of processed wastewater are key issues that necessitate a suitable solution to enhance the quality of clean water. The current research emphasizes the synthesis of ZnSe-reduced graphene oxide nanocomposites (ZnSe:rGO) with different weight ratios of rGO (represented as X = 0.6, 1 and 1.6 g)via one-step hydrothermal method. The photocatalytic performance for the degradation of methyl violet (MV) dye was investigated under visible light irradiation by varying the reaction parameters. The crystal structure, elemental composition, surface functionality and morphology of the synthesized ZnSe-XrGO nanocomposites were estimated by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopic (SEM) techniques. UV–visible spectroscopy was …

Plant salt tolerance is controlled by various physiological processes such as water and ion homeostasis, photosynthesis, and cellular redox balance, which are in turn controlled by gene expression. In the present study, plants of six canola cultivars (DGL, Dunkled, Faisal Canola, Cyclone, Legend, and Oscar) were evaluated for salt tolerance by subjecting them to 0 or 200 mM NaCl stress. Based on growth, cultivars DGL, Dunkled, and Faisal Canola were ranked as salt tolerant, while cultivars Cyclone, Legend, and Oscar were ranked as salt-sensitive ones. Differential salt tolerance in these canola cultivars was found to be associated with a relatively lower accumulation of Na+ and greater accumulation of K+ in the leaves, lower oxidative damage (MDA), and better antioxidative defense system (Superoxide dismutase, SOD; peroxidase, POD, and catalase, CAT). Cultivar Oscar was the poorest to discriminate Na+ and K+ uptake and accumulation in leaves and had poor antioxidant potential to scavenge ROS. Salt stress did not affect the structural stability of photosystem-II (PSII) till three weeks, thereafter it caused a significant decrease. Salt stress increased the performance index (PIABS) by increasing the density of active reaction centers in Oscar. Salt stress decreased the antenna size thereby lowering the absorption and trapping energy flux, and maintaining the electron transport with an increase in heat dissipation. This may represent a potential mechanism to cope with salt stress. Transcriptome analysis of salt-sensitive cultivar Oscar further revealed that salt stress down-regulated DEGs related to hormonal signal transduction pathways …

Chlorophyll a fluorescence (CF) is an effective tool to measure the photosynthetic efficiency, functional capacity and structural stability of photosystem-II and the overall health status of plants in normal or stress environment. The present study was designed to investigate the response of PSII through CF in pearl millet (Pennisetum glaucum L.) grown under saline stress (200 mM NaCl). In first round, eighteen varieties were screened for salinity tolerance at vegetative stage. The relative rate of reduction in biomass, pigments, Na+ and K+ indicated YBS-93, YBS-94 and YDR-8-1 varieties as tolerant and the YBS-98, YCMP-19 and YCMP-34 varieties as salt sensitive varieties. While the chlorophyll-a fluorescence transient analysis, raw OJIP induction curves, Fo and Fm normalised curves exhibited that substantial variation in CF occurred at the O, J, I and P steps in salt sensitive varieties. The comprehensive investigation of JIP test attributes proposed that salinity stress triggered photoinhibition of PSII via disturbance in absorption of light from reaction centres (ABS), low electron transport and photochemical fluxes (ETo, ψ0 & ɸEo) and increased dissipation fluxes (DIo & ɸDo). However, increased dissipation energy (DIO/RC) under salinity stress acts as a preventative control to protect PSII from photooxidative damage in the thylakoid membrane. While photoinhibition of PSII resulted in decrease in quantum yield of PSII (Fv/Fm) and performance index (Pi) under salinity stress. These findings provided important understanding of the salinity tolerance in pearl millet and have opened avenues to further explore the molecular signalling pathways involved in …