Enhancing growth, vitality, and aromatic richness: unveiling the dual magic of silicon dioxide and titanium dioxide nanoparticles in Ocimum tenuiflorum L.

Ocimum tenuiflorum, commonly known as "Holy basil," is renowned for its notable medicinal and aromatic attributes. Its unique fragrance attributes to specific volatile phytochemicals, primarily belonging to terpenoid and/or phenylpropanoid classes, found within their essential oils. The use of nanoparticles (NPs) in agriculture has attracted attention among plant researchers. However, the impact of NPs on the modulation of morpho-physiological aspects and essential oil production in medicinal plants has received limited attention. Consequently, the present study aimed to explore the effect of silicon dioxide (SiO2) and titanium dioxide (TiO2) nanoparticles at various concentrations (viz., DDW (control), Si50+Ti50, Si100+Ti50, Si100+Ti100, Si200+Ti100, Si100+Ti200 and Si200+Ti200 mg L-1) on growth, physiology and essential oil production of O. tenuiflorum at 120 days after planting (DAP). The results demonstrated that the combined application of Si and Ti (Si100+Ti100 mg L-1) exhibited the most favourable outcomes compared to the other combinational treatments. This optimal treatment significantly increased the vegetative growth parameters (root length (33.5%), shoot length (39.2%), fresh weight (62.7%) and dry weight (28.5%)), photosynthetic parameters, enzymatic activities (nitrate reductase and carbonic anhydrase), the overall area of PGTs (peltate glandular trichomes) and essential oil content (172.4%) and yield (323.1%), compared to the control plants. Furthermore, the GCMS analysis showed optimal treatment (Si100+Ti100) significantly improved the content (43.3%) and yield (151.3%) of eugenol, the primary active component of the essential oil. This study uncovers a remarkable and optimal combination of SiO2 and TiO2 nanoparticles that effectively enhances the growth, physiology, and essential oil production in Holy basil. These findings offer valuable insights into maximizing the potential benefits of its use in industrial applications.

Silicon dioxide nanoparticles suppress copper toxicity in Mentha arvensis L. by adjusting ROS homeostasis and antioxidant defense system and improving essential oil production.

Copper (Cu) is an essential micronutrient for plants; however, the excessive accumulation of Cu due to various anthropogenic activities generates progressive pollution of agricultural land and that causes a major constraint for crop production. Excess Cu (80 mg kg-1) in the soil diminished growth and biomass, photosynthetic efficiency and essential oil (EO) content in Mentha arvensis L., while amplifying the antioxidant enzyme's function and reactive oxygen species (ROS) production. Therefore, there is a pressing need to explore effective approaches to overcome Cu toxicity in M. arvensis plants. Thus, the present study unveils the potential of foliar supplementation of two distinct forms of silicon dioxide nanoparticles (SiO2 NPs) i.e., Aerosil 200F and Aerosil 300 to confer Cu stress tolerance attributes to M. arvensis. The experiment demonstrated that applied forms of SiO2 NPs (120 mg L-1), enhanced plants' growth and augmented the photosynthetic efficiency along with the activities of CA (carbonic anhydrase) and NR (nitrate reductase), however, the effects were more accentuated by Aerosil 200F application. Supplementation of SiO2 NPs also exhibited a beneficial effect on the antioxidant machinery of Cu-disturbed plants by raising the level of proline and total phenol as well as the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and glutathione reductase (GR), thereby lowering ROS and electrolytic leakage (EL). Interestingly, SiO2 NPs supplementation upscaled EO production in Cu-stressed plants with more pronounced effects received in the case of Aerosil 200F over Aerosil 300. We concluded that the nano form (Aerosil 200F) of SiO2 proved to be the best in improving the Cu-stress tolerance in plants.

Melatonin supplementation combats nickel-induced phytotoxicity in Trigonella foenum-graecum L. plants through metal accumulation reduction, upregulation of NO generation, antioxidant defence machinery and secondary metabolites.

Nickel (Ni) at a toxic level (80 mg kg-1 of soil) adversely affects the crop performance of fenugreek (Trigonella foenum-graecum L.). Melatonin (MEL), a potent plant growth regulator, is ascribed to offer promising roles in heavy metal stress alleviation. In this study, different doses viz. 0, 25, 50, 75 and 100 µM of MEL were administered to plants through foliage under normal and Ni-stress conditions. The experiment unveiled positive roles of MEL in enhancing root-shoot lengths, fresh-dry weights, seed yield and restoring photosynthetic efficiency assessed in terms of higher Fv/Fm, YII, qP, and lower NPQ values in plants exposed to Ni (80 mg kg-1). MEL supplementation (at 75 µM) effectively restricted Ni accumulation and regulated oxidative stress via modulation of MDA, O2-, H2O2 and NO generation, most prominently. Besides, MEL at 75 µM more conspicuously perked up the activities of antioxidant enzymes like SOD, POX, CAT and APX by 15.7, 20.0, 14.5 and 16.5% higher than the Ni-exposed plants for effective ROS scavenging. Likewise, MEL at 75 µM also efficiently counteracted Ni-generated osmotic stress, through an upscaled accumulation of proline (19.6%) along with the enhancement in the concentration of total phenols (13.6%), total tannins (11.2%), total flavonoids (25.5%) and total alkaloids (19.2%) in plant's leaves. Furthermore, under 80 mg kg-1 Ni stress, MEL at 75 µM improved the seed's trigonelline content by 40.1% higher compared to Ni-disturbed plants, upgrading the pharmacological actions of the plant. Thus, the present study deciphers the envisaged roles of MEL in the alleviation of Ni stress in plants to enhance overall crop productivity.

Silicon nanoparticles (SiNPs) restore photosynthesis and essential oil content by upgrading enzymatic antioxidant metabolism in lemongrass (Cymbopogon flexuosus) under salt stress.

Lemongrass (Cymbopogon flexuosus) has great relevance considering the substantial commercial potential of its essential oil. Nevertheless, the increasing soil salinity poses an imminent threat to lemongrass cultivation given its moderate salt-sensitivity. For this, we used silicon nanoparticles (SiNPs) to stimulate salt tolerance in lemongrass considering SiNPs special relevance to stress settings. Five foliar sprays of SiNPs 150 mg L-1 were applied weekly to NaCl 160 and 240 mM-stressed plants. The data indicated that SiNPs minimised oxidative stress markers (lipid peroxidation, H2O2 content) while triggering a general activation of growth, photosynthetic performance, enzymatic antioxidant system including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), and osmolyte proline (PRO). SiNPs amplified stomatal conductance and photosynthetic CO2 assimilation rate by about 24% and 21% in NaCl 160 mM-stressed plants. Associated benefits contributed to pronounced plant phenotype over their stressed counterparts, as we found. Foliar SiNPs sprays assuaged plant height by 30% and 64%, dry weight by 31% and 59%, and leaf area by 31% and 50% under NaCl 160 and 240 mM concentrations, respectively. SiNPs relieved enzymatic antioxidants (SOD, CAT, POD) and osmolyte (PRO) in lemongrass plants stressed with NaCl 160 mM (9%, 11%, 9%, and 12%, respectively) and NaCl 240 mM (13%, 18%, 15%, and 23%, respectively). The same treatment supported the oil biosynthesis improving essential oil content by 22% and 44% during 160 and 240 mM salt stress, respectively. We found SiNPs can completely overcome NaCl 160 mM stress while significantly palliating NaCl 240 mM stress. Thus, we propose that SiNPs can be a useful biotechnological tool to palliate salinity stress in lemongrass and related crops.

Involvement of abscisic acid in silicon-mediated enhancement of copper stress tolerance in Artemisia annua.

Heavy metal (HM) toxicity is a well-known hazard which causes deleterious impact on the growth and development of plants. The impact of abscisic acid (ABA) in presence of silicon (Si) on plant development and quality traits has largely gone unexplored. The effects of ABA and Si on the growth, yield, and quality characteristics of Artemisia annua L. plants growing under copper (Cu) stress (20 and 40 mg kg-1) were investigated in a pot experiment. During this investigation, Cu stress caused severe damage to the plants but exogenous administration of Si and ABA ameliorated the harmful effects of Cu toxicity, and the plants displayed higher biomass and improved physio-biochemical attributes. Copper accumulated in the roots and shoots and its toxicity caused oxidative stress as demonstrated by the increased 2-thiobarbituric acid reactive substance (TBARS) content. It also resulted in the increased activity of antioxidant enzymes, however, the exogenous Si and ABA supplementation decreased the buildup of reactive oxygen species (ROS) and lipid peroxidation, alleviating the oxidative damage produced by HM stress. Copper toxicity had a considerable negative impact on glandular trichome density, ultrastructure as well as artemisinin production. However, combined Si and ABA enhanced the size and density of glandular trichomes, resulting in higher artemisinin production. Taken together, our results demonstrated that exogenous ABA and Si supplementation protect A. annua plants against Cu toxicity by improving photosynthetic characteristics, enhancing antioxidant enzyme activity, protecting leaf structure and integrity, avoiding excess Cu deposition in shoot and root tissues, and helping in enhanced artemisinin biosynthesis. Our results indicate that the combined application of Si and ABA improved the overall growth of plants and may thus be used as an effective approach for the improvement of growth and yield of A. annua in Cu-contaminated soils.

Exogenous Strigolactone (GR24) Positively Regulates Growth, Photosynthesis, and Improves Glandular Trichome Attributes for Enhanced Artemisinin Production in Artemisia annua.

Artemisia annua is a medicinal plant particularly known for the production of a sesquiterpene lactone artemisinin; a specialty metabolite known for its efficacy in the treatment of malaria by killing different strains of Plasmodium falciparum due to radicals released upon the cleavage of its endoperoxide motif. Considering these facts and the immense medicinal value of artemisinin, the enhancement of in planta production of artemisinin is highly desirable. As strigolactones are known to regulate various aspects of plant growth and development, the effects of foliar spray of different concentrations of synthetic strigolactone analog GR24 (0, 0.5, 1, 2, 4, and 8 µM) on A. annua were studied. As compared to the control group, the foliar application of GR24 had a positive impact on general growth, photosynthesis, and other physiological indices with 4 µM GR24 showing the best results. The results indicate that GR24 application increased the plant biomass and various attributes related to photosynthesis, like total chlorophyll content, chlorophyll fluorescence, stomatal conductance, internal CO2, and net photosynthetic rate. Moreover, the activity of various enzymes related to photosynthesis like carbonic anhydrase, nitrate reductase, and RuBisCO was escalated. The GR24 also improved certain attributes related to glandular trichomes, with a significant enhancement in content and yield of artemisinin as compared to untreated plants.

Exogenous abscisic acid mediates ROS homeostasis and maintains glandular trichome to enhance artemisinin biosynthesis in Artemisia annua under copper toxicity.

One of the major abiotic stresses that cause environmental pollution is heavy metal stress. In the present investigation, copper (Cu) toxicity caused morphological and cellular damages to the Artemisia annua L. plants but supplementation of abscisic acid (ABA) ameliorated the damaging effect of Cu. Copper toxicity significantly reduced the shoot and root lengths; fresh and dry weights of shoot. However, exogenous application of ABA to Cu-treated plants significantly attenuated the damaging effects on plants caused by Cu toxicity. Copper stress also reduced the physiological and biochemical parameters, but ABA application ameliorated the negative effects of Cu in the affected plant. Accumulation of Cu in plant tissues significantly increased the membrane damage and oxidative enzyme activities such as catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD). Further, the impact of high concentration of Cu on density, area and ultrastructure of glandular trichomes and artemisinin content was studied. Moreover, the foliar application of ABA improved the area, density of glandular trichomes and secured the plant cells from Cu toxicity. Therefore, this investigation indicated that the exogenous application of ABA protects A. annua plant by increasing antioxidant enzymes activity, which helps in maintaining cell integrity of leaves and results in increased artemisinin production.

Oligomers of carrageenan regulate functional activities and artemisinin production in Artemisia annua L. exposed to arsenic stress.

Recently, a promising technique has come forward in field of radiation-agriculture in which the natural polysaccharides are modified into useful oligomers after depolymerization. Ionizing radiation technology is a simple, pioneering, eco-friendly, and single step degradation process which is used in exploiting the efficiency of the natural polysaccharides as plant growth promoters. Arsenic (As) is a noxious and toxic to growth and development of medicinal plants. Artemisinin is obtained from the leaves of Artemisia annua L., which is effective in the treatment of malaria. The present study was undertaken to find out possible role of oligomers of irradiated carrageenan (IC) on two varieties viz. 'CIM-Arogya' (As-tolerant) and 'Jeevan Raksha' (As-sensitive) of A. annua exposed to As. The treatments applied were 0 (control), 40 IC (40 mg L-1 IC), 80 IC (80 mg L-1 IC), 45 As (45 mg kg-1 soil As), 40 IC + 45 As (40 mg L-1 IC + 45 mg kg-1 soil As), and 80 IC + 45 As (80 mg L-1 IC + 45 mg kg-1 soil As). The present study was based on various parameters namely plant fresh weight (FW), dry weight (DW), leaf area index (LAI), leaf yield (LY), chlorophyll and carotenoid content, net photosynthetic rate (PN), stomatal conductance (Gs), carbonic anhydrase activity (CA), proline content (PRO), lipid peroxidation (TBARS), endogenous ROS production (H2O2 content), catalase activity (CAT), peroxidase activity (POX), superoxide dismutase activity (SOD), ascorbate peroxidase activity (APX), As content, and artemisinin content in leaves. Plant growth and other physiological and biochemical parameters including enzymatic activities, photosynthetic activity, and its related pigments were negatively affected under As stress. Leaf-applied IC overcame oxidative stress generated due to As in plants by activating antioxidant machinery. Interestingly, leaf-applied IC enhanced the production (content and yield) of artemisinin under high As stress regardless of varieties. The oligomers of IC and As were found to be responsible for the production of endogenous H2O2 which has a pivotal role in the biosynthesis of artemisinin in A. annua.

Effect of irradiated sodium alginate and phosphorus on biomass and artemisinin production in Artemisia annua.

It is now being realized that irradiation products of natural bioactive agents can also be beneficially utilized to impart value addition in agriculture by converting these bioactive agents into more useful form. Polysaccharides, such as sodium alginate, have proven to be wonderful growth promoting substances in their depolymerized form for various plants. Artemisinin has been increasingly popular as an effective and safe alternative therapy against malaria; also proved effective against the highly adaptable malaria parasite, which has already become resistant to many other drugs. The drug artemisinin can be extracted from the leafy tissues of Artemisia annua. Therefore, experiments were conducted with an aim to evaluate artemisinin production and overall plant development though depolymerized sodium alginate application and nutrient supply. In the present study, sodium alginate, irradiated by Co-60 gamma rays together with various phosphorus doses, was used to study their effect on growth, physiological and biochemical processes and production of artemisinin in A. annua. Among various applied doses of phosphorus fertilizer, P40 (40 kg Pha(-1)) together with ISA80 (80 mg L(-1)) significantly improved all the parameters studied. Increase in plant height as well as weight was noted at this treatment. Dry leaf yield, artemisinin concentration in leaves and artemisinin yield was also significantly enhanced by the treatment.

Depolymerized carrageenan ameliorates growth, physiological attributes, essential oil yield and active constituents of Foeniculum vulgare Mill.

Irradiated carrageenan (IC) elicits an array of plant defense responses and biological activities in plants. An experiment was carried out in the naturally illuminated conditions of net house in order to assess the effects of foliar spray of IC on agricultural performance of fennel (Foeniculum vulgare Mill.), which is a high-value essential oil bearing medicinal crop used in pharmaceutical, food and cosmetic industries. There were applied four IC concentrations (40, 60, 80 and 100 mg L(-1)) as foliar sprays. Application of IC significantly improved the growth attributes, physiological and biochemical parameters, essential oil yield and the contents of main components of essential oil of fennel. IC applied at 80 mg L(-1) enhanced these parameters maximally. Unirradiated carrageenan and deionized water had no effect on the attributes studied. Moreover, GLC analysis revealed a significant increase in the components of essential oil, viz. fenchone (4.48-7.82%) and anethole (78.38-86.08%) compared to the control.

Calcium ameliorates photosynthetic capacity, nitrate reductase, carbonic anhydrase, nitrogen assimilation, yield and quality of Cassia sophera L. - a medicinal legume.

Plant biological yield appears to be comparatively low in calcium deficient soils of Aligarh, Western Uttar Pradesh, India. Here, Ca deficiency poses a serious yield and quality limitation for several crops, including various medicinal legumes in this region of India. Cassia sophera L. is an important medicinal herb of great therapeutic value and is used in the modern as well as traditional systems of medicine. In view of the medicinal importance of Cassia sophera L., a hypothesis was designed to determine whether calcium application through soil could enhance the photosynthetic efficiency, enzymatic activities, nitrogen assimilation, yield and quality attributes. The plants were grown in pots containing soil supplied with five levels of calcium, viz. 0, 40, 80, 120 and 160 mg Ca kg(-1) soil (Ca0, Ca1, Ca2, Ca3 and Ca4, respectively) applied as calcium chloride (CaCl2). The performance of the crop was assessed in terms of various growth, physiological, biochemical, yield and quality attributes at 120, 150, 180 and 210 days after sowing. Calcium application proved significantly effective on most of the attributes studied. Of the five calcium levels, Ca3 showed the best results that significantly stimulated most of the attributes studied at the three growth stages.